A client asked me to do this configuration because they did not have the resources to it themselves. No problem. I have been working with LoRa and Kerlinks for a while now doing a consultancy job for another client (a big telco). They did not want to connect the Kerlink to their local network for security reasons. They wanted to add their gateway to TheThingsNetwork.org (TTN), a global open crowdsourced Internet of Things data network that started in The Netherlands. Reading the forums, I noticed that many trying to do the same have run into issues. The documentation is sometimes incomplete and scattered so it takes a bit of effort to get it to work.

IoT lab at the home office
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The task at hand:

Configure a Kerlink IoT station to use its GPRS/3G modem as its uplink path and connect it to TheThingsNetwork.org. The SIM provided was a PukData M2M SIM which uses the KPN mobile network in The Netherlands.
Normally, the Kerlink will use its  ethernet (eth0) uplink as its default path. The basic idea here is that, if configured correctly, an autoconnect mechanism will trigger the GPRS bearer, establishes a PPP connection and set a default route and DNS.
I had already installed the TTN firmware with the polypacket forwarder on the Kerlink and got it to work using the ethernet uplink. I used a LoRaMote to check if packets actually showed up in the TTN api. For the next step, I basically followed the GPRS/3G guide on the TTN Wiki  which boils down to:

• Set the GPRS options to match your SIM and telco’s APN settings (i.e. APN name, pincode, username and password).
• Configure auto connect in the knet monitor.
• Set the bearers priority.
• Because no username/password is set for this APN, and empty username/password fields trigger a bug, I also installed the patched GPRS init script.

 
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I ran into a couple of things so these considerations may be useful:

• If your SIM comes with a pin code (usually 0000), set it with ‘GPRSPIN=<your pin here>’.
• If your APN username and password are to be left empty, replace the GPRS init script with the patched version as mentioned at the bottom of the guide.
• Carefully choose your ip_link address in /knet/knetd.xml depending on your requirements. This address is pinged periodically to determine if the GPRS auto connect needs to be activated. In my case I wanted one that is only reachable over the GPRS APN (e.g. for KPN use their DNS server: 194.151.228.34) to force it to bring up the ppp0 interface whenever possible. If you’re using GPRS as a backup path this should be different (I guess an address only reachable via eth0 but make sure the PPP session is terminated as soon as the primary path becomes available again). Use tcpdump (e.g. tcpdump -i ppp0 -n -v port 1700 or icmp) to check if it is pinging the correct address and if status updates are sent.
• I chose not to use peerdns (GPRSDNS=no) because the default DNS servers are not restored in case of a GPRS connection failure, thus breaking eth0 as a fallback path. I used the Google public DNS servers in stead as they work on both paths. This could also be fixed in /etc/ppp/ip-down.
• Remember that your default gateway will be set to the ppp0 interface whenever that interface comes up. You may want to be able to connect through eth0 for maintenance…
• The (poly) packet forwarder needs to be restarted whenever there is an interface change to make sure it binds to the right source address. If it isn’t you will see packets going out the ppp0 interface with the eth0 source address (or vice versa). I added ‘/usr/bin/killall poly_pkt_fwd’ to /etc/ppp/ip-up and /etc/ppp/ip-down.
• The firewall is not enabled by default. Make sure to edit /etc/init.d/firewall to your needs and turn it on in /etc/sysconfig/network (FIREWALL=yes). Don’t forget IPv6 although dropbear for instance does not listen on a v6 socket.

Tests to do to make sure it all works:

• Check if the gateway is still active (is sending status updates) and node messages are received in the TTN API after unplugging the ethernet uplink cable. If you’re using an ethernet power injector, make sure to unplug the cable going into the injector rather than the one going out to the Kerlink. Duh! 😉 Remember that you can’t log in to the gateway anymore, assuming access to the GPRS/3G address is blocked.
• Plug the ethernet cable back in and see if you can log in again. Then check if updates/messages are still being sent over the ppp0 interface using tcpdump.
• Power cycle the Kerlink while leaving the ethernet uplink cable unplugged. This will make sure the Kerlink will boot successfully in stand-alone mode, which was the whole purpose of this exercise.

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Configuration:

/etc/sysconfig/network:

 # Selector operator APN
 GPRSAPN=internet.access.nl
 # Enter pin code if activated
 GPRSPIN=0000
 # Update /etc/resolv.conf to get dns facilities
 GPRSDNS=no
 # PAP authentication
 GPRSUSER=
 GPRSPASSWORD=
 # Bearers priority order
 BEARERS_PRIORITY="ppp0,eth0,eth1"

/knet/knetd.xml:

<!-- ############## connection parameters ############## -->
<!-- nb of second to retry to connect to server if connection failed-->
<CONNECT retry_timeout="10" />
<!-- port nunmber for local application kms connection -->
<CONNECT kms_port="35035" />
<CONNECT auto_connection="YES" />
<!-- frequency of connection monitoring -ping- (in seconds) -->
<CONNECT link_timeout="30"/>
<!-- DNS servers will be pinged if commented or deleted. Some operators can block the ping on there DNS servers -->
<CONNECT ip_link="194.151.228.34"/>

Questions?

Don’t hesitate to leave a comment below or send a message.

The post How to configure the Kerlink IoT Station for GPRS/3G uplink connectivity appeared first on IPv6.net.

After some of these examples, output from a packet sniffer demonstrates the changes to the packet headers. The book finishes with mechanisms for implementing mixed IPv4 and IPv6 environments and approaches to transitioning from IPv4 to IPv6. Additional references and notes point the reader to more details or topics not covered by the book. Overall I certainly recommend this book as a starting point into IPv6 if the reader has some IPv4 and routing experience. I believe for the novice an additional more general book on networking should be digested first.
The book covers the Internet history and the motivation of IPv6. The IPv6 headers and Extension headers are presented in (again) a straightforward explanation with plenty of diagrams and tables. This explanation includes the specific differences between IPv4 and IPv6 headers. A nice overview of IPSec headers includes authentication, transport, and tunneling modes. Chapter four outlines the multitude of unicast, multicast, and anycast address types. The Neighborhood Discovery Protocol is a new feature of Internet Control Message Protocol version 6 (ICMPv6). Graziani shows ICMPv6 with its enhancements is an important change in how IP hosts identify themselves and others hosts and routers on the network.
The middle of the book discusses IPv6 configuration and routing. Initially, a router is configured from scratch with the various address types. The same example configuration and network is nicely used through the middle of the book. This method is useful for continuity and context. Building on this initial configuration static routes and routing tables are built. The old and new RIPng, EIGRP, and OSPF are compared and contrasted in Chapter 8. The middle ends with Dynamic Host Configuration Protocol version 6 (DHCPv6). The new features such as stateless & stateful DHCP and relay agents are covered. Some interesting differences in Domain Name Service (DNS), TCP, and UDP are explained.
The book ends with mixed IPv4 and IPv6 environments. Graziani shows dual stack allows for parallel IPv4 and IPv6 networks. He covers tunneling methods such as 6to4 and ISATAP that allow for IPv6 packets to be encapsulated in IPv4 packets and routed through an IPv4 network. He shows this allows for a smooth transition from IPv4. Finally Network Address Translation IPv6 to IPv4 (NAT64) is walked through. He shows this allows and IPv4 address to be mapped to a IPv6 address and vice versa to allow coexisting IPv4 and IPv6 networks to communicate.
 
One of the most substantial changes from IPv4 to IPv6 is the addresses and their types. After introducing hexadecimal and the address format short hands, Graziani explains well the structure of the new 128-bit address: prefix, subnet, and interface id.
After trying others – THIS is THE BOOK!
By John Scott on March 22, 2013
The review written by Cosmic Traveler says it well. I purchased 2 other books before this one and they both ended up on the bottom shelf of my bookshelf. I ordered this one and I couldn’t put it down. If the mere thought of a 128-bit address represented in hexadecimal format makes your hair stand up, you need to order this book and then go have a glass of wine – or a cold beer.
IPv6
By Matthew Petersen on February 14, 2014
To support future business continuity, growth, and innovation, organizations must transition to IPv6, the next generation protocol for defining how computers communicate over networks. IPv6 Fundamentals provides a thorough yet easy-to-understand introduction to the new knowledge and skills network professionals and students need to deploy and manage IPv6 networks.
Excellent book, highly recommended!
By MSG causes migraines on October 15, 2013
Even though I have been a CCIE since the 1990s and have dealt with IPv6 successfully on the re-certification exams, this book added a lot of needed clarity on the context and usage of IPv6 so the concepts are more readily absorbed and made intuitive. For those network engineers not yet exposed to IPv6 due to their individual customer/employer situations, it is a near-term reality everyone is going to have to deal with as the IPv4 private addressing RFC 1918 (and the updated IPv4 content in RFC 6761) cannot eliminate the reality that IPv4 is nearing address depletion.
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UNDERSTANDING IPV6!!!
By COSMIC TRAVELER on November 17, 2012
Are you a network engineer; network designer; network technician; part of the technical staff; and, networking student, including those of the Cisco Networking Academy; who are seeking a solid understanding of the fundamentals of IPv6? If you are, then this book is for you! Author Rick Graziani, has done an outstanding job of writing a book that focuses on the basics of IPv6.
Author Graziani, begins by discussing how the Internet of today requires a new network layer protocol, Ipv6, to meet the demands of its users. Then, the author examines the Ipv6 protocol and its fields. Next, he introduces IPv6 addressing and address types. The author continues by examining the different types of IPv6 addresses in detail. Then, he examines ICMPv6. The author then illustrates the configuration of IPv6, addressing the use of a common topology. Next, he examines the IPv6 routing table and changes in the configurations pertaining to IPv6. The author continues by discussing three routing protocols: RIPng, EIGRP for IPv6 and OSPFv3. Then, he examines DHCP for IPv6 or DHCPv6. The author then covers two of three strategies for IPv4 and IPv6 integration and coexistence: dual-stack and tunneling. Finally, he discusses the third technique for transition from IPv4 and IPv6: Network Address Translation or NAT.
This most excellent book provides a thorough yet easy-to-understand introduction to IPv6. More importantly, this great book is also intended to provide a foundation in IPv6 that will allow you to build on it.
Great book to begin IPv6 study
By Cord Scott on March 22, 2013
Really like this book. Information is accurate and concise and concentrates on the protocol and not just how to configure Cisco gear for IPv6, which is what too many people look for. Not a whole lot on migration but Cisco Press has another book that deals with that.
Everyone should start IPv6 with this book
By Andras Dosztal on May 13, 2013
Detailed but still easy to understand, having a good balance of theory and practical knowledge. Up to date, covers all topics needed for someone who’s getting familiar with IPv6. Having prior IPv4 and routing knowledge is recommended.

The post Book review – IPv6 Fundamentals: A Straightforward Approach to Understanding IPv6 appeared first on IPv6.net.

Assigned Numbers: RFC 1700 is Replaced by an On-line Database

Status of this Memo
   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.
Copyright Notice
   Copyright (C) The Internet Society (2002).  All Rights Reserved.
Abstract
   This memo obsoletes RFC 1700 (STD 2) "Assigned Numbers", which
   contained an October 1994 snapshot of assigned Internet protocol
   parameters.
Description
   From November 1977 through October 1994, the Internet Assigned
   Numbers Authority (IANA) periodically published tables of the
   Internet protocol parameter assignments in RFCs entitled, "Assigned
   Numbers".  The most current of these Assigned Numbers RFCs had
   Standard status and carried the designation: STD 2.  At this time,
   the latest STD 2 is RFC 1700.
   Since 1994, this sequence of RFCs have been replaced by an online
   database accessible through a web page (currently, www.iana.org).
   The purpose of the present RFC is to note this fact and to officially
   obsolete RFC 1700, whose status changes to Historic.  RFC 1700 is
   obsolete, and its values are incomplete and in some cases may be
   wrong.
   We expect this series to be revived in the future by the new IANA
   organization.
Security Considerations
   This memo does not affect the technical security of the Internet.
Reynolds                     Informational                      [Page 1]

 
RFC 3232         RFC 1700 Replaced by On-line Database      January 2002
Author's Address
   Joyce K. Reynolds
   RFC Editor
   4676 Admiralty Way
   Marina del Rey, CA  90292
   USA
   EMail: rfc-editor@rfc-editor.org

The post RFC 3232 – Assigned Numbers: RFC 1700 is Replaced by an On-line Database appeared first on IPv6.net.

The post 6RD – IPv6 Rapid Deployment appeared first on IPv6.net.

The post IPv6 Can No Longer Be Ignored appeared first on IPv6.net.

The post NAT64 and DNS64 in 30 minutes appeared first on IPv6.net.

The post RFC 2464 – Transmission of IPv6 Packets over Ethernet Networks appeared first on IPv6.net.

Network Working Group             A. Conta, Digital Equipment Corporation
Request for Comments: 1885                         S. Deering, Xerox PARC
Category: Standards Track                                   December 1995

               Internet Control Message Protocol (ICMPv6)
               for the Internet Protocol Version 6 (IPv6)
                             Specification

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Abstract

   This document specifies a set of Internet Control Message Protocol
   (ICMP) messages for use with version 6 of the Internet Protocol
   (IPv6).  The Internet Group Management Protocol (IGMP) messages
   specified in STD 5, RFC 1112 have been merged into ICMP, for IPv6,
   and are included in this document.

Table of Contents

   1. Introduction........................................3

   2. ICMPv6 (ICMP for IPv6)..............................3

         2.1 Message General Format.......................3

         2.2 Message Source Address Determination.........4

         2.3 Message Checksum Calculation.................5

         2.4 Message Processing Rules.....................5

   3. ICMPv6 Error Messages...............................8

         3.1 Destination Unreachable Message..............8

         3.2 Packet Too Big Message......................10

         3.3 Time Exceeded Message.......................11

         3.4 Parameter Problem Message...................12

   4. ICMPv6 Informational Messages......................14

         4.1 Echo Request Message........................14

         4.2 Echo Reply Message..........................15

         4.3 Group Membership Messages...................17

   5. References.........................................19

   6. Acknowledgements...................................19

   7. Security Considerations............................19

   Authors' Addresses....................................20

1. Introduction

   The Internet Protocol, version 6 (IPv6) is a new version of IP.  IPv6
   uses the Internet Control Message Protocol (ICMP) as defined for IPv4
   [RFC-792], with a number of changes.  The Internet Group Membership
   Protocol (IGMP) specified for IPv4 [RFC-1112] has also been revised
   and has been absorbed into ICMP for IPv6. The resulting protocol is
   called ICMPv6, and has an IPv6 Next Header value of 58.

   This document describes the format of a set of control messages used
   in ICMPv6.  It does not describe the procedures for using these
   messages to achieve functions like Path MTU discovery or multicast
   group membership maintenance; such procedures are described in other
   documents (e.g., [RFC-1112, RFC-1191]).  Other documents may also
   introduce additional ICMPv6 message types, such as Neighbor Discovery
   messages [IPv6-DISC], subject to the general rules for ICMPv6
   messages given in section 2 of this document.

   Terminology defined in the IPv6 specification [IPv6] and the IPv6
   Routing and Addressing specification [IPv6-ADDR] applies to this
   document as well.

2. ICMPv6 (ICMP for IPv6)

   ICMPv6 is used by IPv6 nodes to report errors encountered in
   processing packets, and to perform other internet-layer functions,
   such as diagnostics (ICMPv6 "ping") and multicast membership
   reporting.  ICMPv6 is an integral part of IPv6 and MUST be fully
   implemented by every IPv6 node.

2.1 Message General Format

   ICMPv6 messages are grouped into two classes: error messages and
   informational messages.  Error messages are identified as such by
   having a zero in the high-order bit of their message Type field
   values.  Thus, error messages have message Types from 0 to 127;
   informational messages have message Types from 128 to 255.

   This document defines the message formats for the following ICMPv6
   messages:

        ICMPv6 error messages:

             1    Destination Unreachable      (see section 3.1)
             2    Packet Too Big               (see section 3.2)
             3    Time Exceeded                (see section 3.3)
             4    Parameter Problem            (see section 3.4)

        ICMPv6 informational messages:

             128  Echo Request                 (see section 4.1)
             129  Echo Reply                   (see section 4.2)
             130  Group Membership Query       (see section 4.3)
             131  Group Membership Report      (see section 4.3)
             132  Group Membership Reduction   (see section 4.3)

   Every ICMPv6 message is preceded by an IPv6 header and zero or more
   IPv6 extension headers. The ICMPv6 header is identified by a Next
   Header value of 58 in the immediately preceding header.  (NOTE: this
   is different than the value used to identify ICMP for IPv4.)

   The ICMPv6 messages have the following general format:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |     Code      |          Checksum             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                         Message Body                          +
      |                                                               |

   The type field indicates the type of the message. Its value
   determines the format of the remaining data.

   The code field depends on the message type. It is used to create an
   additional level of message granularity.

   The checksum field is used to detect data corruption in the ICMPv6
   message and parts of the IPv6 header.

2.2 Message Source Address Determination

   A node that sends an ICMPv6 message has to determine both the Source
   and Destination IPv6 Addresses in the IPv6 header before calculating
   the checksum.  If the node has more than one unicast address, it must
   choose the Source Address of the message as follows:

    (a) If the message is a response to a message sent to one of the
        node's unicast addresses, the Source Address of the reply must
        be that same address.

    (b) If the message is a response to a message sent to a multicast or
        anycast group in which the node is a member, the Source Address
        of the reply must be a unicast address belonging to the
        interface on which the multicast or anycast packet was received.

    (c) If the message is a response to a message sent to an address
        that does not belong to the node, the Source Address should be
        that unicast address belonging to the node that will be most
        helpful in diagnosing the error. For example, if the message is
        a response to a packet forwarding action that cannot complete
        successfully, the Source Address should be a unicast address
        belo
nging to the interface on which the packet forwarding
        failed.

    (d) Otherwise, the node's routing table must be examined to
        determine which interface will be used to transmit the message
        to its destination, and a unicast address belonging to that
        interface must be used as the Source Address of the message.

2.3 Message Checksum Calculation

   The checksum is the 16-bit one's complement of the one's complement
   sum of the entire ICMPv6 message starting with the ICMPv6 message
   type field, prepended with a "pseudo-header" of IPv6 header fields,
   as specified in [IPv6, section 8.1].  The Next Header value used in
   the pseudo-header is 58.  (NOTE: the inclusion of a pseudo-header in
   the ICMPv6 checksum is a change from IPv4; see [IPv6] for the
   rationale for this change.)

   For computing the checksum, the checksum field is set to zero.

2.4 Message Processing Rules

   Implementations MUST observe the following rules when processing
   ICMPv6 messages (from [RFC-1122]):

    (a) If an ICMPv6 error message of unknown type is received, it MUST
        be passed to the upper layer.

    (b) If an ICMPv6 informational message of unknown type is received,
        it MUST be silently discarded.

    (c) Every ICMPv6 error message (type < 128) includes as much of the
        IPv6 offending (invoking) packet (the packet that caused the
        error) as will fit without making the error message packet
        exceed 576 octets.

    (d) In those cases where the internet-layer protocol is required to
        pass an ICMPv6 error message to the upper-layer protocol, the
        upper-layer protocol type is extracted from the original packet
        (contained in the body of the ICMPv6 error message) and used to
        select the appropriate upper-layer protocol entity to handle the
        error.

        If the original packet had an unusually large amount of
        extension headers, it is possible that the upper-layer protocol
        type may not be present in the ICMPv6 message, due to truncation
        of the original packet to meet the 576-octet limit.  In that
        case, the error message is silently dropped after any IPv6-layer
        processing.

    (e) An ICMPv6 error message MUST NOT be sent as a result of
        receiving:

         (e.1) an ICMPv6 error message, or

         (e.2) a packet destined to an IPv6 multicast address (there are
               two exceptions to this rule: (1) the Packet Too Big
               Message - Section 3.2 - to allow Path MTU discovery to
               work for IPv6 multicast, and (2) the Parameter Problem
               Message, Code 2 - Section 3.4 - reporting an unrecognized
               IPv6 option that has the Option Type highest-order two
               bits set to 10), or

         (e.3) a packet sent as a link-layer multicast, (the exception
               from e.2 applies to this case too), or

         (e.4) a packet sent as a link-layer broadcast, (the exception
               from e.2 applies to this case too), or

         (e.5) a packet whose source address does not uniquely identify
               a single node -- e.g., the IPv6 Unspecified Address, an
               IPv6 multicast address, or an address known by the ICMP
               message sender to be an IPv6 anycast address.

    (f) Finally, to each sender of an erroneous data packet, an IPv6
        node MUST limit the rate of ICMPv6 error messages sent, in order
        to limit the bandwidth and forwarding costs incurred by the
        error messages when a generator of erroneous packets does not
        respond to those error messages by ceasing its transmissions.

        There are a variety of ways of implementing the rate-limiting
        function, for example:

         (f.1) Timer-based - for example, limiting the rate of
               transmission of error messages to a given source, or to
               any source, to at most once every T milliseconds.

         (f.2)  Bandwidth-based - for example, limiting the rate at
               which error messages are sent from a particular interface
               to some fraction F of the attached link's bandwidth.

        The limit parameters (e.g., T or F in the above examples) MUST
        be configurable for the node, with a conservative default value
        (e.g., T = 1 second, NOT 0 seconds, or F = 2 percent, NOT 100
        percent).

   The following sections describe the message formats for the above
   ICMPv6 messages.

3. ICMPv6 Error Messages

3.1 Destination Unreachable Message

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |     Code      |          Checksum             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             Unused                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    As much of invoking packet                 |
      +                as will fit without the ICMPv6 packet          +
      |                       exceeding 576 octets                    |

   IPv6 Fields:

   Destination Address

                  Copied from the Source Address field of the invoking
                  packet.

   ICMPv6 Fields:

   Type           1

   Code           0 - no route to destination
                  1 - communication with destination
                        administratively prohibited
                  2 - not a neighbor
                  3 - address unreachable
                  4 - port unreachable

   Unused         This field is unused for all code values.
                  It must be initialized to zero by the sender
                  and ignored by the receiver.
   Description

   A Destination Unreachable message SHOULD be generated by a router, or
   by the IPv6 layer in the originating node, in response to a packet
   that cannot be delivered to its destination address for reasons other
   than congestion.  (An ICMPv6 message MUST NOT be generated if a
   packet is dropped due to congestion.)

   If the reason for the failure to deliver is lack of a matching entry
   in the forwarding node's routing table, the Code field is set to 0
   (NOTE: this error can occur only in nodes that do not hold a "default
   route" in their routing tables).

   If the reason for the failure to deliver is administrative
   prohibition, e.g., a "firewall filter", the Code field is set to 1.

   If the reason for the failure to deliver is that the next destination
   address in the Routing header is not a neighbor of the processing
   node but the "strict" bit is set for that address, then the Code
   field is set to 2.

   If there is any other reason for the failure to deliver, e.g.,
   inability to resolve the IPv6 destination address into a
   corresponding link address, or a link-specific problem of some sort,
   then the Code field is set to 3.

   A destination node SHOULD send a Destination Unreachable message with
   Code 4 in response to a packet for which the transport protocol
   (e.g., UDP) has no listener, if that transport protocol has no
   alternative means to infor
m the sender.

   Upper layer notification

   A node receiving the ICMPv6 Destination Unreachable message MUST
   notify the upper-layer protocol.

3.2 Packet Too Big Message

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |     Code      |          Checksum             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             MTU                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    As much of invoking packet                 |
      +               as will fit without the ICMPv6 packet           +
      |                       exceeding 576 octets                    |

   IPv6 Fields:

   Destination Address

                  Copied from the Source Address field of the invoking
                  packet.

   ICMPv6 Fields:

   Type           2

   Code           0

   MTU            The Maximum Transmission Unit of the next-hop link.

   Description

   A Packet Too Big MUST be sent by a router in response to a packet
   that it cannot forward because the packet is larger than the MTU of
   the outgoing link.  The information in this message is used as part
   of the Path MTU Discovery process [RFC-1191].

   Sending a Packet Too Big Message makes an exception to one of the
   rules of when to send an ICMPv6 error message, in that unlike other
   messages, it is sent in response to a packet received with an IPv6
   multicast destination address, or a link-layer multicast or link-
   layer broadcast address.

   Upper layer notification

   An incoming Packet Too Big message MUST be passed to the upper-layer
   protocol.

3.3 Time Exceeded Message

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |     Code      |          Checksum             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                             Unused                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    As much of invoking packet                 |
      +               as will fit without the ICMPv6 packet           +
      |                       exceeding 576 octets                    |

   IPv6 Fields:

   Destination Address
                  Copied from the Source Address field of the invoking
                  packet.

   ICMPv6 Fields:

   Type           3

   Code           0 - hop limit exceeded in transit

                  1 - fragment reassembly time exceeded

   Unused         This field is unused for all code values.
                  It must be initialized to zero by the sender
                  and ignored by the receiver.

   Description

   If a router receives a packet with a Hop Limit of zero, or a router
   decrements a packet's Hop Limit to zero, it MUST discard the packet
   and send an ICMPv6 Time Exceeded message with Code 0 to the source of
   the packet.  This indicates either a routing loop or too small an
   initial Hop Limit value.

   The router sending an ICMPv6 Time Exceeded message with Code 0 SHOULD
   consider the receiving interface of the packet as the interface on
   which the packet forwarding failed in following rule (d) for
   selecting the Source Address of the message.

   Upper layer notification

   An incoming Time Exceeded message MUST be passed to the upper-layer
   protocol.

3.4 Parameter Problem Message

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |     Code      |          Checksum             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                            Pointer                            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                    As much of invoking packet                 |
      +               as will fit without the ICMPv6 packet           +
      |                       exceeding 576 octets                    |

   IPv6 Fields:

   Destination Address

                  Copied from the Source Address field of the invoking
                  packet.

   ICMPv6 Fields:

   Type           4

   Code           0 - erroneous header field encountered

                  1 - unrecognized Next Header type encountered

                  2 - unrecognized IPv6 option encountered

   Pointer        Identifies the octet offset within the
                  invoking packet where the error was detected.

                  The pointer will point beyond the end of the ICMPv6
                  packet if the field in error is beyond what can fit
                  in the 576-byte limit of an ICMPv6 error message.

   Description

   If an IPv6 node processing a packet finds a problem with a field in
   the IPv6 header or extension headers such that it cannot complete
   processing the packet, it MUST discard the packet and SHOULD send an
   ICMPv6 Parameter Problem message to the packet's source, indicating
   the type and location of the problem.

   The pointer identifies the octet of the original packet's header
   where the error was detected. For example, an ICMPv6 message with
   Type field = 4, Code field = 1, and Pointer field = 40 would indicate

   that the IPv6 extension header following the IPv6 header of the
   original packet holds an unrecognized Next Header field value.

   Upper layer notification

   A node receiving this ICMPv6 message MUST notify the upper-layer
   protocol.

4. ICMPv6 Informational Messages

4.1 Echo Request Message

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |     Code      |          Checksum             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Identifier          |        Sequence Number        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Data ...
      +-+-+-+-+-

   IPv6 Fields:

   Destination Address

                  Any legal IPv6 address.

   ICMPv6 Fields:

   Type           128

   Code           0

   Identifier     An identifier to aid in matching Echo Replies
                  to this Echo Request.  May be zero.

   Sequence Number

                  A sequence number to aid in matching Echo Replies
                  to this Echo Request.  May be zero.

   Data           Zero or more octets of arbitrary data.

   Description

   Every node MUST implement an ICMPv6 Echo responder function that
   receives Echo Requests and sends correspond
ing Echo Replies.  A node
   SHOULD also implement an application-layer interface for sending Echo
   Requests and receiving Echo Replies, for diagnostic purposes.

   Upper layer notification

   A node receiving this ICMPv6 message MAY notify the upper-layer
   protocol.

4.2 Echo Reply Message

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |     Code      |          Checksum             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Identifier          |        Sequence Number        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Data ...
      +-+-+-+-+-

   IPv6 Fields:

   Destination Address

                  Copied from the Source Address field of the invoking
                  Echo Request packet.

   ICMPv6 Fields:

   Type           129

   Code           0

   Identifier     The identifier from the invoking Echo Request message.

   Sequence       The sequence number from the invoking Echo Request
   Number         message.

   Data           The data from the invoking Echo Request message.

   Description

   Every node MUST implement an ICMPv6 Echo responder function that
   receives Echo Requests and sends corresponding Echo Replies.  A node
   SHOULD also implement an application-layer interface for sending Echo
   Requests and receiving Echo Replies, for diagnostic purposes.

   The source address of an Echo Reply sent in response to a unicast
   Echo Request message MUST be the same as the destination address of
   that Echo Request message.

   An Echo Reply SHOULD be sent in response to an Echo Request message
   sent to an IPv6 multicast address.  The source address of the reply
   MUST be a unicast address belonging to the interface on which the
   multicast Echo Request message was received.

   The data received in the ICMPv6 Echo Request message MUST be returned
   entirely and unmodified in the ICMPv6 Echo Reply message, unless the
   Echo Reply would exceed the MTU of the path back to the Echo
   requester, in which case the data is truncated to fit that path MTU.

   Upper layer notification

   Echo Reply messages MUST be passed to the ICMPv6 user interface,
   unless the corresponding Echo Request originated in the IP layer.

4.3 Group Membership Messages

   The ICMPv6 Group Membership Messages have the following format:

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Type      |     Code      |          Checksum             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |     Maximum Response Delay    |          Unused               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      +                                                               +
      |                          Multicast                            |
      +                                                               +
      |                           Address                             |
      +                                                               +
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   IPv6 Fields:

   Destination Address

                  In a Group Membership Query message, the multicast
                  address of the group being queried, or the Link-Local
                  All-Nodes multicast address.

                  In a Group Membership Report or a Group Membership
                  Reduction message, the multicast address of the
                  group being reported or terminated.

   Hop Limit      1

   ICMPv6 Fields:

   Type           130 - Group Membership Query
                  131 - Group Membership Report
                  132 - Group Membership Reduction

   Code           0

   Maximum Response Delay

                  In Query messages, the maximum time that responding
                  Report messages may be delayed, in milliseconds.

                  In Report and Reduction messages, this field is
                  is initialized to zero by the sender and ignored by
                  receivers.

   Unused         Initialized to zero by the sender; ignored by receivers.

   Multicast Address

                  The address of the multicast group about which the
                  message is being sent.  In Query messages, the Multicast
                  Address field may be zero, implying a query for all
                  groups.

   Description

   The ICMPv6 Group Membership messages are used to convey information
   about multicast group membership from nodes to their neighboring
   routers.  The details of their usage is given in [RFC-1112].

5. References

   [IPv6]       Deering, S., and R. Hinden, "Internet Protocol, Version
                6, Specification", RFC 1883, Xerox PARC, Ipsilon
                Networks, December 1995.

   [IPv6-ADDR]  Hinden, R., and S. Deering, Editors, "IP Version 6
                Addressing Architecture", RFC 1884, Ipsilon Networks,
                Xerox PARC, December 1995.

   [IPv6-DISC]  Narten, T., Nordmark, E., and W. Simpson, "Neighbor
                Discovery for IP Version 6 (IPv6)", Work in Progress.

   [RFC-792]    Postel, J., "Internet Control Message Protocol", STD 5,
                RFC 792, USC/Information Sciences Institute, September
                1981.

   [RFC-1112]   Deering, S., "Host Extensions for IP Multicasting", STD
                5, RFC 1112, Stanford University, August 1989.

   [RFC-1122]   Braden, R., "Requirements for Internet Hosts -
                Communication Layers", STD 3, RFC 1122, USC/Information
                Sciences Institute, October 1989.

   [RFC-1191]   Mogul, J., and S. Deering, "Path MTU Discovery", RFC
                1191, DECWRL, Stanford University, November 1990.

6. Acknowledgements

   The document is derived from previous ICMP drafts of the SIPP and
   IPng working group.

   The IPng working group and particularly Robert Elz, Jim Bound, Bill
   Simpson, Thomas Narten, Charlie Lynn, Bill Fink, and Scott Bradner
   (in chronological order) provided extensive review information and
   feedback.

7. Security Considerations

   Security issues are not discussed in this memo.

Authors' Addresses:

   Alex Conta                            Stephen Deering
   Digital Equipment Corporation         Xerox Palo Alto Research Center
   110 Spitbrook Rd                      3333 Coyote Hill Road
   Nashua, NH 03062                      Palo Alto, CA 94304

   Phone: +1-603-881-0744                Phone: +1-415-812-4839
   EMail: conta@zk3.dec.com              EMail: deering@parc.xerox.com

The post RFC 1885 – Internet Control Message Protocol (ICMPv6) for IPv6 (OBSOLETE) appeared first on IPv6.net.

Network Working Group                                        R. Hinden
Request for Comments: 2373                                       Nokia
Obsoletes: 1884                                             S. Deering
Category: Standards Track                                Cisco Systems
							     July 1998

                  IP Version 6 Addressing Architecture

Status of this Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

Abstract

   This specification defines the addressing architecture of the IP
   Version 6 protocol [IPV6].  The document includes the IPv6 addressing
   model, text representations of IPv6 addresses, definition of IPv6
   unicast addresses, anycast addresses, and multicast addresses, and an
   IPv6 node's required addresses.

Table of Contents

   1. Introduction.................................................2
   2. IPv6 Addressing..............................................2
      2.1 Addressing Model.........................................3
      2.2 Text Representation of Addresses.........................3
      2.3 Text Representation of Address Prefixes..................5
      2.4 Address Type Representation..............................6
      2.5 Unicast Addresses........................................7
        2.5.1 Interface Identifiers................................8
        2.5.2 The Unspecified Address..............................9
        2.5.3 The Loopback Address.................................9
        2.5.4 IPv6 Addresses with Embedded IPv4 Addresses.........10
        2.5.5 NSAP Addresses......................................10
        2.5.6 IPX Addresses.......................................10
        2.5.7 Aggregatable Global Unicast Addresses...............11
        2.5.8 Local-use IPv6 Unicast Addresses....................11
      2.6 Anycast Addresses.......................................12
        2.6.1 Required Anycast Address............................13
      2.7 Multicast Addresses.....................................14

        2.7.1 Pre-Defined Multicast Addresses.....................15
        2.7.2 Assignment of New IPv6 Multicast Addresses..........17
      2.8 A Node's Required Addresses.............................17
   3. Security Considerations.....................................18
   APPENDIX A: Creating EUI-64 based Interface Identifiers........19
   APPENDIX B: ABNF Description of Text Representations...........22
   APPENDIX C: CHANGES FROM RFC-1884..............................23
   REFERENCES.....................................................24
   AUTHORS' ADDRESSES.............................................25
   FULL COPYRIGHT STATEMENT.......................................26

1.0 INTRODUCTION

   This specification defines the addressing architecture of the IP
   Version 6 protocol.  It includes a detailed description of the
   currently defined address formats for IPv6 [IPV6].

   The authors would like to acknowledge the contributions of Paul
   Francis, Scott Bradner, Jim Bound, Brian Carpenter, Matt Crawford,
   Deborah Estrin, Roger Fajman, Bob Fink, Peter Ford, Bob Gilligan,
   Dimitry Haskin, Tom Harsch, Christian Huitema, Tony Li, Greg
   Minshall, Thomas Narten, Erik Nordmark, Yakov Rekhter, Bill Simpson,
   and Sue Thomson.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC 2119].

2.0 IPv6 ADDRESSING

   IPv6 addresses are 128-bit identifiers for interfaces and sets of
   interfaces.  There are three types of addresses:

     Unicast:   An identifier for a single interface.  A packet sent to
                a unicast address is delivered to the interface
                identified by that address.

     Anycast:   An identifier for a set of interfaces (typically
                belonging to different nodes).  A packet sent to an
                anycast address is delivered to one of the interfaces
                identified by that address (the "nearest" one, according
                to the routing protocols' measure of distance).

     Multicast: An identifier for a set of interfaces (typically
                belonging to different nodes).  A packet sent to a
                multicast address is delivered to all interfaces
                identified by that address.

   There are no broadcast addresses in IPv6, their function being
   superseded by multicast addresses.

   In this document, fields in addresses are given a specific name, for
   example "subscriber".  When this name is used with the term "ID" for
   identifier after the name (e.g., "subscriber ID"), it refers to the
   contents of the named field.  When it is used with the term "prefix"
   (e.g.  "subscriber prefix") it refers to all of the address up to and
   including this field.

   In IPv6, all zeros and all ones are legal values for any field,
   unless specifically excluded.  Specifically, prefixes may contain
   zero-valued fields or end in zeros.

2.1 Addressing Model

   IPv6 addresses of all types are assigned to interfaces, not nodes.
   An IPv6 unicast address refers to a single interface.  Since each
   interface belongs to a single node, any of that node's interfaces'
   unicast addresses may be used as an identifier for the node.

   All interfaces are required to have at least one link-local unicast
   address (see section 2.8 for additional required addresses).  A
   single interface may also be assigned multiple IPv6 addresses of any
   type (unicast, anycast, and multicast) or scope.  Unicast addresses
   with scope greater than link-scope are not needed for interfaces that
   are not used as the origin or destination of any IPv6 packets to or
   from non-neighbors.  This is sometimes convenient for point-to-point
   interfaces.  There is one exception to this addressing model:

     An unicast address or a set of unicast addresses may be assigned to
     multiple physical interfaces if the implementation treats the
     multiple physical interfaces as one interface when presenting it to
     the internet layer.  This is useful for load-sharing over multiple
     physical interfaces.

   Currently IPv6 continues the IPv4 model that a subnet prefix is
   associated with one link.  Multiple subnet prefixes may be assigned
   to the same link.

2.2 Text Representation of Addresses

   There are three conventional forms for representing IPv6 addresses as
   text strings:

   1. The preferred form is x:x:x:x:x:x:x:x, where the 'x's are the
      hexadecimal values of the eight 16-bit pieces of the address.
      Examples:

         FEDC:BA98:7654:3210:FEDC:BA98:7654:3210

         1080:0:0:0:8:800:200C:417A

      Note that it is not necessary to write the leading zeros in an
      individual field, but there must be at least one numeral in every
      field (except for the case described in 2.).

   2. Due to some methods of allocating certain styles of IPv6
      addresses, it will be common for addresses to contain long strings
      of zero bits.  In order to make writing addresses containing zero
      bits easier a special syntax is available to compress the zeros.
      The use of "::" indicates multiple groups of 16-bits of zeros.
      The "::" can only appear once in an address.  The "::" can also be
      used to compress the leading and/or trailing zeros in an address.

      For example the following addresses:

         1080:0:0:0:8:800:200C:417A  a unicast address
         FF01:0:0:0:0:0:0:101        a multicast address
         0:0:0:0:0:0:0:1             the loopback address
         0:0:0:0:0:0:0:0             the unspecified addresses

      may be represented as:

         1080::8:800:200C:417A       a unicast address
         FF01::101                   a multicast address
         ::1                         the loopback address
         ::                          the unspecified addresses

   3. An alternative form that is sometimes more convenient when dealing
      with a mixed environment of IPv4 and IPv6 nodes is
      x:x:x:x:x:x:d.d.d.d, where the 'x's are the hexadecimal values of
      the six high-order 16-bit pieces of the address, and the 'd's are
      the decimal values of the four low-order 8-bit pieces of the
      address (standard IPv4 representation).  Examples:

         0:0:0:0:0:0:13.1.68.3

         0:0:0:0:0:FFFF:129.144.52.38

      or in compressed form:

         ::13.1.68.3

         ::FFFF:129.144.52.38

2.3 Text Representation of Address Prefixes

   The text representation of IPv6 address prefixes is similar to the
   way IPv4 addresses prefixes are written in CIDR notation.  An IPv6
   address prefix is represented by the notation:

      ipv6-address/prefix-length

   where

      ipv6-address    is an IPv6 address in any of the notations listed
                      in section 2.2.

      prefix-length   is a decimal value specifying how many of the
                      leftmost contiguous bits of the address comprise
                      the prefix.

   For example, the following are legal representations of the 60-bit
   prefix 12AB00000000CD3 (hexadecimal):

      12AB:0000:0000:CD30:0000:0000:0000:0000/60
      12AB::CD30:0:0:0:0/60
      12AB:0:0:CD30::/60

   The following are NOT legal representations of the above prefix:

      12AB:0:0:CD3/60   may drop leading zeros, but not trailing zeros,
                        within any 16-bit chunk of the address

      12AB::CD30/60     address to left of "/" expands to
                        12AB:0000:0000:0000:0000:000:0000:CD30

      12AB::CD3/60      address to left of "/" expands to
                        12AB:0000:0000:0000:0000:000:0000:0CD3

   When writing both a node address and a prefix of that node address
   (e.g., the node's subnet prefix), the two can combined as follows:

      the node address      12AB:0:0:CD30:123:4567:89AB:CDEF
      and its subnet number 12AB:0:0:CD30::/60

      can be abbreviated as 12AB:0:0:CD30:123:4567:89AB:CDEF/60

2.4 Address Type Representation

   The specific type of an IPv6 address is indicated by the leading bits
   in the address.  The variable-length field comprising these leading
   bits is called the Format Prefix (FP).  The initial allocation of
   these prefixes is as follows:

    Allocation                            Prefix         Fraction of
                                          (binary)       Address Space
    -----------------------------------   --------       -------------
    Reserved                              0000 0000      1/256
    Unassigned                            0000 0001      1/256

    Reserved for NSAP Allocation          0000 001       1/128
    Reserved for IPX Allocation           0000 010       1/128

    Unassigned                            0000 011       1/128
    Unassigned                            0000 1         1/32
    Unassigned                            0001           1/16

    Aggregatable Global Unicast Addresses 001            1/8
    Unassigned                            010            1/8
    Unassigned                            011            1/8
    Unassigned                            100            1/8
    Unassigned                            101            1/8
    Unassigned                            110            1/8

    Unassigned                            1110           1/16
    Unassigned                            1111 0         1/32
    Unassigned                            1111 10        1/64
    Unassigned                            1111 110       1/128
    Unassigned                            1111 1110 0    1/512

    Link-Local Unicast Addresses          1111 1110 10   1/1024
    Site-Local Unicast Addresses          1111 1110 11   1/1024

    Multicast Addresses                   1111 1111      1/256

    Notes:

      (1) The "unspecified address" (see section 2.5.2), the loopback
          address (see section 2.5.3), and the IPv6 Addresses with
          Embedded IPv4 Addresses (see section 2.5.4), are assigned out
          of the 0000 0000 format prefix space.

      (2) The format prefixes 001 through 111, except for Multicast
          Addresses (1111 1111), are all required to have to have 64-bit
          interface identifiers in EUI-64 format.  See section 2.5.1 for
          definitions.

   This allocation supports the direct allocation of aggregation
   addresses, local use addresses, and multicast addresses.  Space is
   reserved for NSAP addresses and IPX addresses.  The remainder of the
   address space is unassigned for future use.  This can be used for
   expansion of existing use (e.g., additional aggregatable addresses,
   etc.) or new uses (e.g., separate locators and identifiers).  Fifteen
   percent of the address space is initially allocated.  The remaining
   85% is reserved for future use.

   Unicast addresses are distinguished from multicast addresses by the
   value of the high-order octet of the addresses: a value of FF
   (11111111) identifies an address as a multicast address; any other
   value identifies an address as a unicast address.  Anycast addresses
   are taken from the unicast address space, and are not syntactically
   distinguishable from unicast addresses.

2.5 Unicast Addresses

   IPv6 unicast addresses are aggregatable with contiguous bit-wise
   masks similar to IPv4 addresses under Class-less Interdomain Routing
   [CIDR].

   There are several forms of unicast address assignment in IPv6,
   including the global aggregatable global unicast address, the NSAP
   address, the IPX hierarchical address, the site-local address, the
   link-local address, and the IPv4-capable host address.  Additional
   address types can be defined in the future.

   IPv6 nodes may have considerable or little knowledge of the internal
   structure of the IPv6 address, depending on the role the node plays
   (for instance, host versus router).  At a minimum, a node may
   consider that unicast addresses (including its own) have no internal
   structure:

   |                           128 bits                              |
   +-----------------------------------------------------------------+
   |                          node addre
ss                           |
   +-----------------------------------------------------------------+

   A slightly sophisticated host (but still rather simple) may
   additionally be aware of subnet prefix(es) for the link(s) it is
   attached to, where different addresses may have different values for
   n:

   |                         n bits                 |   128-n bits   |
   +------------------------------------------------+----------------+
   |                   subnet prefix                | interface ID   |
   +------------------------------------------------+----------------+

   Still more sophisticated hosts may be aware of other hierarchical
   boundaries in the unicast address.  Though a very simple router may
   have no knowledge of the internal structure of IPv6 unicast
   addresses, routers will more generally have knowledge of one or more
   of the hierarchical boundaries for the operation of routing
   protocols.  The known boundaries will differ from router to router,
   depending on what positions the router holds in the routing
   hierarchy.

2.5.1 Interface Identifiers

   Interface identifiers in IPv6 unicast addresses are used to identify
   interfaces on a link.  They are required to be unique on that link.
   They may also be unique over a broader scope.  In many cases an
   interface's identifier will be the same as that interface's link-
   layer address.  The same interface identifier may be used on multiple
   interfaces on a single node.

   Note that the use of the same interface identifier on multiple
   interfaces of a single node does not affect the interface
   identifier's global uniqueness or each IPv6 addresses global
   uniqueness created using that interface identifier.

   In a number of the format prefixes (see section 2.4) Interface IDs
   are required to be 64 bits long and to be constructed in IEEE EUI-64
   format [EUI64].  EUI-64 based Interface identifiers may have global
   scope when a global token is available (e.g., IEEE 48bit MAC) or may
   have local scope where a global token is not available (e.g., serial
   links, tunnel end-points, etc.).  It is required that the "u" bit
   (universal/local bit in IEEE EUI-64 terminology) be inverted when
   forming the interface identifier from the EUI-64.  The "u" bit is set
   to one (1) to indicate global scope, and it is set to zero (0) to
   indicate local scope.  The first three octets in binary of an EUI-64
   identifier are as follows:

       0       0 0       1 1       2
      |0       7 8       5 6       3|
      +----+----+----+----+----+----+
      |cccc|ccug|cccc|cccc|cccc|cccc|
      +----+----+----+----+----+----+

   written in Internet standard bit-order , where "u" is the
   universal/local bit, "g" is the individual/group bit, and "c" are the
   bits of the company_id.  Appendix A: "Creating EUI-64 based Interface
   Identifiers" provides examples on the creation of different EUI-64
   based interface identifiers.

   The motivation for inverting the "u" bit when forming the interface
   identifier is to make it easy for system administrators to hand
   configure local scope identifiers when hardware tokens are not
   available.  This is expected to be case for serial links, tunnel end-
   points, etc.  The alternative would have been for these to be of the
   form 0200:0:0:1, 0200:0:0:2, etc., instead of the much simpler ::1,
   ::2, etc.

   The use of the universal/local bit in the IEEE EUI-64 identifier is
   to allow development of future technology that can take advantage of
   interface identifiers with global scope.

   The details of forming interface identifiers are defined in the
   appropriate "IPv6 over <link>" specification such as "IPv6 over
   Ethernet" [ETHER], "IPv6 over FDDI" [FDDI], etc.

2.5.2 The Unspecified Address

   The address 0:0:0:0:0:0:0:0 is called the unspecified address.  It
   must never be assigned to any node.  It indicates the absence of an
   address.  One example of its use is in the Source Address field of
   any IPv6 packets sent by an initializing host before it has learned
   its own address.

   The unspecified address must not be used as the destination address
   of IPv6 packets or in IPv6 Routing Headers.

2.5.3 The Loopback Address

   The unicast address 0:0:0:0:0:0:0:1 is called the loopback address.
   It may be used by a node to send an IPv6 packet to itself.  It may
   never be assigned to any physical interface.  It may be thought of as
   being associated with a virtual interface (e.g., the loopback
   interface).

   The loopback address must not be used as the source address in IPv6
   packets that are sent outside of a single node.  An IPv6 packet with
   a destination address of loopback must never be sent outside of a
   single node and must never be forwarded by an IPv6 router.

2.5.4 IPv6 Addresses with Embedded IPv4 Addresses

   The IPv6 transition mechanisms [TRAN] include a technique for hosts
   and routers to dynamically tunnel IPv6 packets over IPv4 routing
   infrastructure.  IPv6 nodes that utilize this technique are assigned
   special IPv6 unicast addresses that carry an IPv4 address in the low-
   order 32-bits.  This type of address is termed an "IPv4-compatible
   IPv6 address" and has the format:

   |                80 bits               | 16 |      32 bits        |
   +--------------------------------------+--------------------------+
   |0000..............................0000|0000|    IPv4 address     |
   +--------------------------------------+----+---------------------+

   A second type of IPv6 address which holds an embedded IPv4 address is
   also defined.  This address is used to represent the addresses of
   IPv4-only nodes (those that *do not* support IPv6) as IPv6 addresses.
   This type of address is termed an "IPv4-mapped IPv6 address" and has
   the format:

   |                80 bits               | 16 |      32 bits        |
   +--------------------------------------+--------------------------+
   |0000..............................0000|FFFF|    IPv4 address     |
   +--------------------------------------+----+---------------------+

2.5.5 NSAP Addresses

   This mapping of NSAP address into IPv6 addresses is defined in
   [NSAP].  This document recommends that network implementors who have
   planned or deployed an OSI NSAP addressing plan, and who wish to
   deploy or transition to IPv6, should redesign a native IPv6
   addressing plan to meet their needs.  However, it also defines a set
   of mechanisms for the support of OSI NSAP addressing in an IPv6
   network.  These mechanisms are the ones that must be used if such
   support is required.  This document also defines a mapping of IPv6
   addresses within the OSI address format, should this be required.

2.5.6 IPX Addresses

   This mapping of IPX address into IPv6 addresses is as follows:

   |   7   |                   121 bits                              |
   +-------+---------------------------------------------------------+
   |0000010|                 to be defined                           |
   +-------+---------------------------------------------------------+

   The draft definition, motivation, and usage are under study.

2.5.7 Aggregatable Global Unicast Addresses

   The global aggregatable global unicast address is defined in [AGGR].
   This address format is designed to support both the current provider
   based aggregation and a new type of aggregation called exchanges.
   The combination will allow efficient routing aggregation for both
   sites which connect directly to providers and who connect to
   exchanges.  Sites will have the choice to connect to either type of
   aggregation point.

   The IPv6 aggregatable global unicast address format is as follows:

   | 3|  13 | 8 |   24   |   16   |          64 bits               |
   +--+-----+---+--------+--------+--------------------------------+
   |FP| TLA |RES|  NLA   |  SLA   |         Interface ID           |
   |  | ID  |   |  ID    |  ID    |                                |
   +--+-----+---+--------+--------+--------------------------------+

   Where

      001          Format Prefix (3 bit) for Aggregatable Global
                   Unicast Addresses
      TLA ID       Top-Level Aggregation Identifier
      RES          Reserved for future use
      NLA ID       Next-Level Aggregation Identifier
      SLA ID       Site-Level Aggregation Identifier
      INTERFACE ID Interface Identifier

   The contents, field sizes, and assignment rules are defined in
   [AGGR].

2.5.8 Local-Use IPv6 Unicast Addresses

   There are two types of local-use unicast addresses defined.  These
   are Link-Local and Site-Local.  The Link-Local is for use on a single
   link and the Site-Local is for use in a single site.  Link-Local
   addresses have the following format:

   |   10     |
   |  bits    |        54 bits          |          64 bits           |
   +----------+-------------------------+----------------------------+
   |1111111010|           0             |       interface ID         |
   +----------+-------------------------+----------------------------+

   Link-Local addresses are designed to be used for addressing on a
   single link for purposes such as auto-address configuration, neighbor
   discovery, or when no routers are present.

   Routers must not forward any packets with link-local source or
   destination addresses to other links.

   Site-Local addresses have the following format:

   |   10     |
   |  bits    |   38 bits   |  16 bits  |         64 bits            |
   +----------+-------------+-----------+----------------------------+
   |1111111011|    0        | subnet ID |       interface ID         |
   +----------+-------------+-----------+----------------------------+

   Site-Local addresses are designed to be used for addressing inside of
   a site without the need for a global prefix.

   Routers must not forward any packets with site-local source or
   destination addresses outside of the site.

2.6 Anycast Addresses

   An IPv6 anycast address is an address that is assigned to more than
   one interface (typically belonging to different nodes), with the
   property that a packet sent to an anycast address is routed to the
   "nearest" interface having that address, according to the routing
   protocols' measure of distance.

   Anycast addresses are allocated from the unicast address space, using
   any of the defined unicast address formats.  Thus, anycast addresses
   are syntactically indistinguishable from unicast addresses.  When a
   unicast address is assigned to more than one interface, thus turning
   it into an anycast address, the nodes to which the address is
   assigned must be explicitly configured to know that it is an anycast
   address.

   For any assigned anycast address, there is a longest address prefix P
   that identifies the topological region in which all interfaces
   belonging to that anycast address reside.  Within the region
   identified by P, each member of the anycast set must be advertised as
   a separate entry in the routing system (commonly referred to as a
   "host route"); outside the region identified by P, the anycast
   address may be aggregated into the routing advertisement for prefix
   P.

   Note that in, the worst case, the prefix P of an anycast set may be
   the null prefix, i.e., the members of the set may have no topological
   locality.  In that case, the anycast address must be advertised as a
   separate routing entry throughout the entire internet, which presents

   a severe scaling limit on how many such "global" anycast sets may be
   supported.  Therefore, it is expected that support for global anycast
   sets may be unavailable or very restricted.

   One expected use of anycast addresses is to identify the set of
   routers belonging to an organization providing internet service.
   Such addresses could be used as intermediate addresses in an IPv6
   Routing header, to cause a packet to be delivered via a particular
   aggregation or sequence of aggregations.  Some other possible uses
   are to identify the set of routers attached to a particular subnet,
   or the set of routers providing entry into a particular routing
   domain.

   There is little experience with widespread, arbitrary use of internet
   anycast addresses, and some known complications and hazards when
   using them in their full generality [ANYCST].  Until more experience
   has been gained and solutions agreed upon for those problems, the
   following restrictions are imposed on IPv6 anycast addresses:

      o An anycast address must not be used as the source address of an
        IPv6 packet.

      o An anycast address must not be assigned to an IPv6 host, that
        is, it may be assigned to an IPv6 router only.

2.6.1 Required Anycast Address

   The Subnet-Router anycast address is predefined.  Its format is as
   follows:

   |                         n bits                 |   128-n bits   |
   +------------------------------------------------+----------------+
   |                   subnet prefix                | 00000000000000 |
   +------------------------------------------------+----------------+

   The "subnet prefix" in an anycast address is the prefix which
   identifies a specific link.  This anycast address is syntactically
   the same as a unicast address for an interface on the link with the
   interface identifier set to zero.

   Packets sent to the Subnet-Router anycast address will be delivered
   to one router on the subnet.  All routers are required to support the
   Subnet-Router anycast addresses for the subnets which they have
   interfaces.

   The subnet-router anycast address is intended to be used for
   applications where a node needs to communicate with one of a set of
   routers on a remote subnet.  For example when a mobile host needs to
   communicate with one of the mobile agents on its "home" subnet.

2.7 Multicast Addresses

   An IPv6 multicast address is an identifier for a group of nodes.  A
   node may belong to any number of multicast groups.  Multicast
   addresses have the following format:

   |   8    |  4 |  4 |                  112 bits                   |
   +------ -+----+----+---------------------------------------------+
   |11111111|flgs|scop|                  group ID                   |
   +--------+----+----+---------------------------------------------+

      11111111 at the start of the address identifies the address as
      being a multicast address.

                                    +-+-+-+-+
      flgs is a set of 4 flags:     |0|0|0|T|
                                    +-+-+-+-+

         The high-order 3 flags are reserved, and must be initialized to
         0.
         T = 0 indicates a permanently-assigned ("well-known") multicast
         address, assigned by the global internet numbering authority.

         T = 1 indicates a non-permanently-assigned ("transient")
         multicast address.

      scop is a 4-bit multicast scope value used to limit the scope of
      the multicast group.  The values are:

         0  reserved
         1  node-local scope
         2  link-local scope
         3  (unassigned)
         4  (unassigned)
         5  site-local scope
         6  (unassigned)
         7  (unassigned)
         8  organization-local scope
         9  (unassigned)
         A  (unassigned)
         B  (unassigned)
         C  (unassigned)

         D  (unassigned)
         E  global scope
         F  reserved

      group ID identifies the multicast group, either permanent or
      transient, within the given scope.

   The "meaning" of a permanently-assigned multicast address is
   independent of the scope value.  For example, if the "NTP servers
   group" is assigned a permanent multicast address with a group ID of
   101 (hex), then:

      FF01:0:0:0:0:0:0:101 means all NTP servers on the same node as the
      sender.

      FF02:0:0:0:0:0:0:101 means all NTP servers on the same link as the
      sender.

      FF05:0:0:0:0:0:0:101 means all NTP servers at the same site as the
      sender.

      FF0E:0:0:0:0:0:0:101 means all NTP servers in the internet.

   Non-permanently-assigned multicast addresses are meaningful only
   within a given scope.  For example, a group identified by the non-
   permanent, site-local multicast address FF15:0:0:0:0:0:0:101 at one
   site bears no relationship to a group using the same address at a
   different site, nor to a non-permanent group using the same group ID
   with different scope, nor to a permanent group with the same group
   ID.

   Multicast addresses must not be used as source addresses in IPv6
   packets or appear in any routing header.

2.7.1 Pre-Defined Multicast Addresses

   The following well-known multicast addresses are pre-defined:

      Reserved Multicast Addresses:   FF00:0:0:0:0:0:0:0
                                      FF01:0:0:0:0:0:0:0
                                      FF02:0:0:0:0:0:0:0
                                      FF03:0:0:0:0:0:0:0
                                      FF04:0:0:0:0:0:0:0
                                      FF05:0:0:0:0:0:0:0
                                      FF06:0:0:0:0:0:0:0
                                      FF07:0:0:0:0:0:0:0
                                      FF08:0:0:0:0:0:0:0
                                      FF09:0:0:0:0:0:0:0

                                      FF0A:0:0:0:0:0:0:0
                                      FF0B:0:0:0:0:0:0:0
                                      FF0C:0:0:0:0:0:0:0
                                      FF0D:0:0:0:0:0:0:0
                                      FF0E:0:0:0:0:0:0:0
                                      FF0F:0:0:0:0:0:0:0

   The above multicast addresses are reserved and shall never be
   assigned to any multicast group.

      All Nodes Addresses:    FF01:0:0:0:0:0:0:1
                              FF02:0:0:0:0:0:0:1

   The above multicast addresses identify the group of all IPv6 nodes,
   within scope 1 (node-local) or 2 (link-local).

      All Routers Addresses:   FF01:0:0:0:0:0:0:2
                               FF02:0:0:0:0:0:0:2
                               FF05:0:0:0:0:0:0:2

   The above multicast addresses identify the group of all IPv6 routers,
   within scope 1 (node-local), 2 (link-local), or 5 (site-local).

      Solicited-Node Address:  FF02:0:0:0:0:1:FFXX:XXXX

   The above multicast address is computed as a function of a node's
   unicast and anycast addresses.  The solicited-node multicast address
   is formed by taking the low-order 24 bits of the address (unicast or
   anycast) and appending those bits to the prefix
   FF02:0:0:0:0:1:FF00::/104 resulting in a multicast address in the
   range

      FF02:0:0:0:0:1:FF00:0000

   to

      FF02:0:0:0:0:1:FFFF:FFFF

   For example, the solicited node multicast address corresponding to
   the IPv6 address 4037::01:800:200E:8C6C is FF02::1:FF0E:8C6C.  IPv6
   addresses that differ only in the high-order bits, e.g. due to
   multiple high-order prefixes associated with different aggregations,
   will map to the same solicited-node address thereby reducing the
   number of multicast addresses a node must join.

   A node is required to compute and join the associated Solicited-Node
   multicast addresses for every unicast and anycast address it is
   assigned.

2.7.2 Assignment of New IPv6 Multicast Addresses

   The current approach [ETHER] to map IPv6 multicast addresses into
   IEEE 802 MAC addresses takes the low order 32 bits of the IPv6
   multicast address and uses it to create a MAC address.  Note that
   Token Ring networks are handled differently.  This is defined in
   [TOKEN].  Group ID's less than or equal to 32 bits will generate
   unique MAC addresses.  Due to this new IPv6 multicast addresses
   should be assigned so that the group identifier is always in the low
   order 32 bits as shown in the following:

   |   8    |  4 |  4 |          80 bits          |     32 bits     |
   +------ -+----+----+---------------------------+-----------------+
   |11111111|flgs|scop|   reserved must be zero   |    group ID     |
   +--------+----+----+---------------------------+-----------------+

   While this limits the number of permanent IPv6 multicast groups to
   2^32 this is unlikely to be a limitation in the future.  If it
   becomes necessary to exceed this limit in the future multicast will
   still work but the processing will be sightly slower.

   Additional IPv6 multicast addresses are defined and registered by the
   IANA [MASGN].

2.8 A Node's Required Addresses

   A host is required to recognize the following addresses as
   identifying itself:

      o Its Link-Local Address for each interface
      o Assigned Unicast Addresses
      o Loopback Address
      o All-Nodes Multicast Addresses
      o Solicited-Node Multicast Address for each of its assigned
        unicast and anycast addresses
      o Multicast Addresses of all other groups to which the host
        belongs.

   A router is required to recognize all addresses that a host is
   required to recognize, plus the following addresses as identifying
   itself:

      o The Subnet-Router anycast addresses for the interfaces it is
        configured to act as a router on.
      o All other Anycast addresses with which the router has been
        configured.
      o All-Routers Multicast Addresses

      o Multicast Addresses of all other groups to which the router
        belongs.

   The only address prefixes which should be predefined in an
   implementation are the:

      o Unspecified Address
      o Loopback Address
      o Multicast Prefix (FF)
      o Local-Use Prefixes (Link-Local and Site-Local)
      o Pre-Defined Multicast Addresses
      o IPv4-Compatible Prefixes

   Implementations should assume all other addresses are unicast unless
   specifically configured (e.g., anycast addresses).

3. Security Considerations

   IPv6 addre
ssing documents do not have any direct impact on Internet
   infrastructure security.  Authentication of IPv6 packets is defined
   in [AUTH].

APPENDIX A : Creating EUI-64 based Interface Identifiers
--------------------------------------------------------

   Depending on the characteristics of a specific link or node there are
   a number of approaches for creating EUI-64 based interface
   identifiers.  This appendix describes some of these approaches.

Links or Nodes with EUI-64 Identifiers

   The only change needed to transform an EUI-64 identifier to an
   interface identifier is to invert the "u" (universal/local) bit.  For
   example, a globally unique EUI-64 identifier of the form:

   |0              1|1              3|3              4|4              6|
   |0              5|6              1|2              7|8              3|
   +----------------+----------------+----------------+----------------+
   |cccccc0gcccccccc|ccccccccmmmmmmmm|mmmmmmmmmmmmmmmm|mmmmmmmmmmmmmmmm|
   +----------------+----------------+----------------+----------------+

   where "c" are the bits of the assigned company_id, "0" is the value
   of the universal/local bit to indicate global scope, "g" is
   individual/group bit, and "m" are the bits of the manufacturer-
   selected extension identifier.  The IPv6 interface identifier would
   be of the form:

   |0              1|1              3|3              4|4              6|
   |0              5|6              1|2              7|8              3|
   +----------------+----------------+----------------+----------------+
   |cccccc1gcccccccc|ccccccccmmmmmmmm|mmmmmmmmmmmmmmmm|mmmmmmmmmmmmmmmm|
   +----------------+----------------+----------------+----------------+

   The only change is inverting the value of the universal/local bit.

Links or Nodes with IEEE 802 48 bit MAC's

   [EUI64] defines a method to create a EUI-64 identifier from an IEEE
   48bit MAC identifier.  This is to insert two octets, with hexadecimal
   values of 0xFF and 0xFE, in the middle of the 48 bit MAC (between the
   company_id and vendor supplied id).  For example the 48 bit MAC with
   global scope:

   |0              1|1              3|3              4|
   |0              5|6              1|2              7|
   +----------------+----------------+----------------+
   |cccccc0gcccccccc|ccccccccmmmmmmmm|mmmmmmmmmmmmmmmm|
   +----------------+----------------+----------------+

   where "c" are the bits of the assigned company_id, "0" is the value
   of the universal/local bit to indicate global scope, "g" is
   individual/group bit, and "m" are the bits of the manufacturer-
   selected extension identifier.  The interface identifier would be of
   the form:

   |0              1|1              3|3              4|4              6|
   |0              5|6              1|2              7|8              3|
   +----------------+----------------+----------------+----------------+
   |cccccc1gcccccccc|cccccccc11111111|11111110mmmmmmmm|mmmmmmmmmmmmmmmm|
   +----------------+----------------+----------------+----------------+

   When IEEE 802 48bit MAC addresses are available (on an interface or a
   node), an implementation should use them to create interface
   identifiers due to their availability and uniqueness properties.

Links with Non-Global Identifiers

   There are a number of types of links that, while multi-access, do not
   have globally unique link identifiers.  Examples include LocalTalk
   and Arcnet.  The method to create an EUI-64 formatted identifier is
   to take the link identifier (e.g., the LocalTalk 8 bit node
   identifier) and zero fill it to the left.  For example a LocalTalk 8
   bit node identifier of hexadecimal value 0x4F results in the
   following interface identifier:

   |0              1|1              3|3              4|4              6|
   |0              5|6              1|2              7|8              3|
   +----------------+----------------+----------------+----------------+
   |0000000000000000|0000000000000000|0000000000000000|0000000001001111|
   +----------------+----------------+----------------+----------------+

   Note that this results in the universal/local bit set to "0" to
   indicate local scope.

Links without Identifiers

   There are a number of links that do not have any type of built-in
   identifier.  The most common of these are serial links and configured
   tunnels.  Interface identifiers must be chosen that are unique for
   the link.

   When no built-in identifier is available on a link the preferred
   approach is to use a global interface identifier from another
   interface or one which is assigned to the node itself.  To use this
   approach no other interface connecting the same node to the same link
   may use the same identifier.

   If there is no global interface identifier available for use on the
   link the implementation needs to create a local scope interface
   identifier.  The only requirement is that it be unique on the link.
   There are many possible approaches to select a link-unique interface
   identifier.  They include:

      Manual Configuration
      Generated Random Number
      Node Serial Number (or other node-specific token)

   The link-unique interface identifier should be generated in a manner
   that it does not change after a reboot of a node or if interfaces are
   added or deleted from the node.

   The selection of the appropriate algorithm is link and implementation
   dependent.  The details on forming interface identifiers are defined
   in the appropriate "IPv6 over <link>" specification.  It is strongly
   recommended that a collision detection algorithm be implemented as
   part of any automatic algorithm.

APPENDIX B: ABNF Description of Text Representations
----------------------------------------------------

   This appendix defines the text representation of IPv6 addresses and
   prefixes in Augmented BNF [ABNF] for reference purposes.

      IPv6address = hexpart [ ":" IPv4address ]
      IPv4address = 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT "." 1*3DIGIT

      IPv6prefix  = hexpart "/" 1*2DIGIT

      hexpart = hexseq | hexseq "::" [ hexseq ] | "::" [ hexseq ]
      hexseq  = hex4 *( ":" hex4)
      hex4    = 1*4HEXDIG

APPENDIX C: CHANGES FROM RFC-1884
---------------------------------

   The following changes were made from RFC-1884 "IP Version 6
   Addressing Architecture":

      - Added an appendix providing a ABNF description of text
        representations.
      - Clarification that link unique identifiers not change after
        reboot or other interface reconfigurations.
      - Clarification of Address Model based on comments.
      - Changed aggregation format terminology to be consistent with
        aggregation draft.
      - Added text to allow interface identifier to be used on more than
        one interface on same node.
      - Added rules for defining new multicast addresses.
      - Added appendix describing procedures for creating EUI-64 based
        interface ID's.
      - Added notation for defining IPv6 prefixes.
      - Changed solicited node multicast definition to use a longer
        prefix.
      - Added site scope all routers multicast address.
      - Defined Aggregatable Global Unicast Addresses to use "001" Format
        Prefix.
      - Changed "010" (Provider-Based Unicast) and "100" (Reserved for

      Geographic) Format Prefixes to Unassigned.
      - Added section on Interface ID definition for unicast addresses.
        Requires use of EUI-64 in range of format prefixes and rules for
        setting global/local scope bit in EUI-64.
      - Updated NSAP text to reflect working in RFC1888.
      - Removed protocol specific IPv6 multicast addresses (e.g., DHCP)
        and referenced the IANA definitions.
      - Removed section "Unicast Address Example".  Had become OBE.
      - Added new and updated references.
      - Minor text clarifications and improvements.

REFERENCES

   [ABNF]    Crocker, D., and P. Overell, "Augmented BNF for
             Syntax Specifications: ABNF", RFC 2234, November 1997.

   [AGGR]    Hinden, R., O'Dell, M., and S. Deering, "An
             Aggregatable Global Unicast Address Format", RFC 2374, July
             1998.

   [AUTH]    Atkinson, R., "IP Authentication Header", RFC 1826, August
             1995.

   [ANYCST]  Partridge, C., Mendez, T., and W. Milliken, "Host
             Anycasting Service", RFC 1546, November 1993.

   [CIDR]    Fuller, V., Li, T., Yu, J., and K. Varadhan, "Classless
             Inter-Domain Routing (CIDR): An Address Assignment and
             Aggregation Strategy", RFC 1519, September 1993.

   [ETHER]   Crawford, M., "Transmission of IPv6 Pacekts over Ethernet
             Networks", Work in Progress.

   [EUI64]   IEEE, "Guidelines for 64-bit Global Identifier (EUI-64)
             Registration Authority",
             http://standards.ieee.org/db/oui/tutorials/EUI64.html,
             March 1997.

   [FDDI]    Crawford, M., "Transmission of IPv6 Packets over FDDI
             Networks", Work in Progress.

   [IPV6]    Deering, S., and R. Hinden, Editors, "Internet Protocol,
             Version 6 (IPv6) Specification", RFC 1883, December 1995.

   [MASGN]   Hinden, R., and S. Deering, "IPv6 Multicast Address
             Assignments", RFC 2375, July 1998.

   [NSAP]    Bound, J., Carpenter, B., Harrington, D., Houldsworth, J.,
             and A. Lloyd, "OSI NSAPs and IPv6", RFC 1888, August 1996.

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, March 1997.

   [TOKEN]   Thomas, S., "Transmission of IPv6 Packets over Token Ring
             Networks", Work in Progress.

   [TRAN]    Gilligan, R., and E. Nordmark, "Transition Mechanisms for
             IPv6 Hosts and Routers", RFC 1993, April 1996.

AUTHORS' ADDRESSES

   Robert M. Hinden
   Nokia
   232 Java Drive
   Sunnyvale, CA 94089
   USA

   Phone: +1 408 990-2004
   Fax:   +1 408 743-5677
   EMail: hinden@iprg.nokia.com

   Stephen E. Deering
   Cisco Systems, Inc.
   170 West Tasman Drive
   San Jose, CA 95134-1706
   USA

   Phone: +1 408 527-8213
   Fax:   +1 408 527-8254
   EMail: deering@cisco.com

Full Copyright Statement

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