6LoWPAN, short for IPv6 over Low-Power Wireless Personal Area Networks, is a protocol that allows IPv6 packets to be transmitted over low-power, low-rate wireless networks. It is specifically designed to address the challenges of connecting resource-constrained IoT devices to the internet, such as sensors, actuators, and other smart devices that operate on limited power sources.

Applications and Examples

Smart Home Automation: 6LoWPAN is widely used in smart home automation systems to connect various IoT devices like smart thermostats, lighting controls, and security cameras to a central hub or the cloud. This enables homeowners to remotely monitor and control their home devices using smartphones or other connected devices.

Industrial IoT (IIoT)

In industrial settings, 6LoWPAN is applied to connect sensors, actuators, and other industrial equipment to a centralized monitoring system. This allows for real-time data collection, analysis, and predictive maintenance, leading to increased operational efficiency and cost savings.

Smart Agriculture

In the agricultural sector, 6LoWPAN is utilized to create smart farming solutions that monitor soil moisture levels, temperature, and other environmental factors. Farmers can use this data to optimize irrigation, crop management, and overall farm productivity.

Healthcare Monitoring

6LoWPAN is employed in healthcare applications for remote patient monitoring, wearable health devices, and medical equipment connectivity. This enables healthcare providers to track patient vitals, deliver personalized care, and respond promptly to critical health events.

Advantages of IPv6 in 6LoWPAN

Scalability: IPv6 provides a vast address space, allowing for the seamless connection of a large number of IoT devices without running out of unique IP addresses.

Energy Efficiency

6LoWPAN reduces the energy consumption of IoT devices by optimizing packet size and transmission protocols, extending the battery life of these devices.

Security

IPv6 includes built-in security features like IPsec, enhancing data encryption and authentication for secure communication between IoT devices and networks.

Interoperability

6LoWPAN ensures interoperability between different IoT devices and networks, enabling seamless communication and data exchange across diverse IoT ecosystems.

Market players and products

Several vendors have adopted the 6LoWPAN protocol in their products across various industries. Here are some examples of vendors and the products where the 6LoWPAN protocol is utilized:

• Nest (Google):
  • Product: Nest Thermostat
  • Application: Smart home automation
  • Description: The Nest Thermostat uses the 6LoWPAN protocol to connect to other smart home devices and the cloud, enabling users to remotely control their home’s temperature and energy usage.
• Philips Hue:
  • Product: Philips Hue Smart Lighting System
  • Application: Smart home lighting
  • Description: The Philips Hue smart lighting system incorporates 6LoWPAN technology to communicate wirelessly with the Hue Bridge, allowing users to control their lighting settings via a mobile app or voice commands.
• Bosch:
  • Product: Bosch XDK Cross Domain Development Kit
  • Application: Industrial IoT (IIoT)
  • Description: The Bosch XDK development kit utilizes the 6LoWPAN protocol to enable connectivity between industrial sensors, actuators, and IoT devices, facilitating data collection and analysis for predictive maintenance and process optimization.
• Libelium:
  • Product: Meshlium Gateway
  • Application: Smart Agriculture
  • Description: The Meshlium Gateway from Libelium integrates 6LoWPAN technology to connect agricultural sensors and monitoring devices, enabling farmers to gather real-time data on soil conditions, weather patterns, and crop health for precision farming.
• Fitbit:
  • Product: Fitbit Wearable Health Devices
  • Application: Healthcare Monitoring
  • Description: Fitbit’s wearable health devices leverage the 6LoWPAN protocol to transmit health data to smartphones or cloud servers, allowing users and healthcare providers to track fitness metrics, monitor heart rate, and manage overall well-being.

These are just a few examples of vendors incorporating the 6LoWPAN protocol in their products to enable seamless connectivity, data exchange, and smart functionalities in smart homes, industries, agriculture, healthcare, and other IoT applications.

Wrap up

In conclusion, the integration of IPv6 in the 6LoWPAN protocol plays a pivotal role in advancing IoT connectivity and efficiency across various industries. By leveraging the scalability, energy efficiency, security, and interoperability of IPv6, 6LoWPAN empowers organizations to harness the full potential of IoT technologies for improved operational processes, enhanced user experiences, and innovative applications in smart homes, industries, agriculture, healthcare, and beyond.

The post Exploring the Role of IPv6 in the 6LoWPAN Protocol: Enhancing IoT Connectivity and Efficiency 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.
[amazon template=add to cart&asin=1587143135]
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 Internet Protocol – IPv4 vs IPv6 as Fast As Possible appeared first on IPv6.net.

The post The beginning of the end appeared first on IPv6.net.

WORLD IPv6 LAUNCH DAY

The post The Future Is Forever appeared first on IPv6.net.

The post IPv6 Can No Longer Be Ignored 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                                          J. Postel
Request for Comments:  792                                           ISI
                                                          September 1981
Updates:  RFCs 777, 760
Updates:  IENs 109, 128
                   INTERNET CONTROL MESSAGE PROTOCOL
                         DARPA INTERNET PROGRAM
                         PROTOCOL SPECIFICATION
Introduction
   The Internet Protocol (IP) [1] is used for host-to-host datagram
   service in a system of interconnected networks called the
   Catenet [2].  The network connecting devices are called Gateways.
   These gateways communicate between themselves for control purposes
   via a Gateway to Gateway Protocol (GGP) [3,4].  Occasionally a
   gateway or destination host will communicate with a source host, for
   example, to report an error in datagram processing.  For such
   purposes this protocol, the Internet Control Message Protocol (ICMP),
   is used.  ICMP, uses the basic support of IP as if it were a higher
   level protocol, however, ICMP is actually an integral part of IP, and
   must be implemented by every IP module.
   ICMP messages are sent in several situations:  for example, when a
   datagram cannot reach its destination, when the gateway does not have
   the buffering capacity to forward a datagram, and when the gateway
   can direct the host to send traffic on a shorter route.
   The Internet Protocol is not designed to be absolutely reliable.  The
   purpose of these control messages is to provide feedback about
   problems in the communication environment, not to make IP reliable.
   There are still no guarantees that a datagram will be delivered or a
   control message will be returned.  Some datagrams may still be
   undelivered without any report of their loss.  The higher level
   protocols that use IP must implement their own reliability procedures
   if reliable communication is required.
   The ICMP messages typically report errors in the processing of
   datagrams.  To avoid the infinite regress of messages about messages
   etc., no ICMP messages are sent about ICMP messages.  Also ICMP
   messages are only sent about errors in handling fragment zero of
   fragemented datagrams.  (Fragment zero has the fragment offeset equal
   zero).
                                                                [Page 1]
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Message Formats
   ICMP messages are sent using the basic IP header.  The first octet of
   the data portion of the datagram is a ICMP type field; the value of
   this field determines the format of the remaining data.  Any field
   labeled "unused" is reserved for later extensions and must be zero
   when sent, but receivers should not use these fields (except to
   include them in the checksum).  Unless otherwise noted under the
   individual format descriptions, the values of the internet header
   fields are as follows:
   Version
      4
   IHL
      Internet header length in 32-bit words.
   Type of Service
      0
   Total Length
      Length of internet header and data in octets.
   Identification, Flags, Fragment Offset
      Used in fragmentation, see [1].
   Time to Live
      Time to live in seconds; as this field is decremented at each
      machine in which the datagram is processed, the value in this
      field should be at least as great as the number of gateways which
      this datagram will traverse.
   Protocol
      ICMP = 1
   Header Checksum
      The 16 bit one's complement of the one's complement sum of all 16
      bit words in the header.  For computing the checksum, the checksum
      field should be zero.  This checksum may be replaced in the
      future.
[Page 2]
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   Source Address
      The address of the gateway or host that composes the ICMP message.
      Unless otherwise noted, this can be any of a gateway's addresses.
   Destination Address
      The address of the gateway or host to which the message should be
      sent.
                                                                [Page 3]
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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                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Internet Header + 64 bits of Original Data Datagram      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   IP Fields:
   Destination Address
      The source network and address from the original datagram's data.
   ICMP Fields:
   Type
      3
   Code
      0 = net unreachable;
      1 = host unreachable;
      2 = protocol unreachable;
      3 = port unreachable;
      4 = fragmentation needed and DF set;
      5 = source route failed.
   Checksum
      The checksum is the 16-bit ones's complement of the one's
      complement sum of the ICMP message starting with the ICMP Type.
      For computing the checksum , the checksum field should be zero.
      This checksum may be replaced in the future.
   Internet Header + 64 bits of Data Datagram
      The internet header plus the first 64 bits of the original
[Page 4]
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      datagram's data.  This data is used by the host to match the
      message to the appropriate process.  If a higher level protocol
      uses port numbers, they are assumed to be in the first 64 data
      bits of the original datagram's data.
   Description
      If, according to the information in the gateway's routing tables,
      the network specified in the internet destination field of a
      datagram is unreachable, e.g., the distance to the network is
      infinity, the gateway may send a destination unreachable message
      to the internet source host of the datagram.  In addition, in some
      networks, the gateway may be able to determine if the internet
      destination host is unreachable.  Gateways in these networks may
      send destination unreachable messages to the source host when the
      destination host is unreachable.
      If, in the destination host, the IP module cannot deliver the
      datagram  because the indicated protocol module or process port is
      not active, the destination host may send a destination
      unreachable message to the source host.
      Another case is when a datagram must be fragmented to be forwarded
      by a gateway yet the Don't Fragment flag is on.  In this case the
      gateway must discard the datagram and may return a destination
      unreachable message.
      Codes 0, 1, 4, and 5 may be received from a gateway.  Codes 2 and
      3 may be received from a host.
                                                                [Page 5]
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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                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Internet Header + 64 bits of Original Data Datagram      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   IP Fields:
   Destination Address
      The source network and address from the original datagram's data.
   ICMP Fields:
   Type
      11
   Code
      0 = time to live exceeded in transit;
      1 = fragment reassembly time exceeded.
   Checksum
      The checksum is the 16-bit ones's complement of the one's
      complement sum of the ICMP message starting with the ICMP Type.
      For computing the checksum , the checksum field should be zero.
      This checksum may be replaced in the future.
   Internet Header + 64 bits of Data Datagram
      The internet header plus the first 64 bits of the original
      datagram's data.  This data is used by the host to match the
      message to the appropriate process.  If a higher level protocol
      uses port numbers, they are assumed to be in the first 64 data
      bits of the original datagram's data.
   Description
      If the gateway processing a datagram finds the time to live field
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      is zero it must discard the datagram.  The gateway may also notify
      the source host via the time exceeded message.
      If a host reassembling a fragmented datagram cannot complete the
      reassembly due to missing fragments within its time limit it
      discards the datagram, and it may send a time exceeded message.
      If fragment zero is not available then no time exceeded need be
      sent at all.
      Code 0 may be received from a gateway.  Code 1 may be received
      from a host.
                                                                [Page 7]
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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    |                   unused                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Internet Header + 64 bits of Original Data Datagram      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   IP Fields:
   Destination Address
      The source network and address from the original datagram's data.
   ICMP Fields:
   Type
      12
   Code
      0 = pointer indicates the error.
   Checksum
      The checksum is the 16-bit ones's complement of the one's
      complement sum of the ICMP message starting with the ICMP Type.
      For computing the checksum , the checksum field should be zero.
      This checksum may be replaced in the future.
   Pointer
      If code = 0, identifies the octet where an error was detected.
   Internet Header + 64 bits of Data Datagram
      The internet header plus the first 64 bits of the original
      datagram's data.  This data is used by the host to match the
      message to the appropriate process.  If a higher level protocol
      uses port numbers, they are assumed to be in the first 64 data
      bits of the original datagram's data.
[Page 8]
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   Description
      If the gateway or host processing a datagram finds a problem with
      the header parameters such that it cannot complete processing the
      datagram it must discard the datagram.  One potential source of
      such a problem is with incorrect arguments in an option.  The
      gateway or host may also notify the source host via the parameter
      problem message.  This message is only sent if the error caused
      the datagram to be discarded.
      The pointer identifies the octet of the original datagram's header
      where the error was detected (it may be in the middle of an
      option).  For example, 1 indicates something is wrong with the
      Type of Service, and (if there are options present) 20 indicates
      something is wrong with the type code of the first option.
      Code 0 may be received from a gateway or a host.
                                                                [Page 9]
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Source Quench 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                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Internet Header + 64 bits of Original Data Datagram      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   IP Fields:
   Destination Address
      The source network and address of the original datagram's data.
   ICMP Fields:
   Type
      4
   Code
      0
   Checksum
      The checksum is the 16-bit ones's complement of the one's
      complement sum of the ICMP message starting with the ICMP Type.
      For computing the checksum , the checksum field should be zero.
      This checksum may be replaced in the future.
   Internet Header + 64 bits of Data Datagram
      The internet header plus the first 64 bits of the original
      datagram's data.  This data is used by the host to match the
      message to the appropriate process.  If a higher level protocol
      uses port numbers, they are assumed to be in the first 64 data
      bits of the original datagram's data.
   Description
      A gateway may discard internet datagrams if it does not have the
      buffer space needed to queue the datagrams for output to the next
      network on the route to the destination network.  If a gateway
[Page 10]
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      discards a datagram, it may send a source quench message to the
      internet source host of the datagram.  A destination host may also
      send a source quench message if datagrams arrive too fast to be
      processed.  The source quench message is a request to the host to
      cut back the rate at which it is sending traffic to the internet
      destination.  The gateway may send a source quench message for
      every message that it discards.  On receipt of a source quench
      message, the source host should cut back the rate at which it is
      sending traffic to the specified destination until it no longer
      receives source quench messages from the gateway.  The source host
      can then gradually increase the rate at which it sends traffic to
      the destination until it again receives source quench messages.
      The gateway or host may send the source quench message when it
      approaches its capacity limit rather than waiting until the
      capacity is exceeded.  This means that the data datagram which
      triggered the source quench message may be delivered.
      Code 0 may be received from a gateway or a host.
                                                               [Page 11]
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Redirect 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             |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                 Gateway Internet Address                      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |      Internet Header + 64 bits of Original Data Datagram      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   IP Fields:
   Destination Address
      The source network and address of the original datagram's data.
   ICMP Fields:
   Type
      5
   Code
      0 = Redirect datagrams for the Network.
      1 = Redirect datagrams for the Host.
      2 = Redirect datagrams for the Type of Service and Network.
      3 = Redirect datagrams for the Type of Service and Host.
   Checksum
      The checksum is the 16-bit ones's complement of the one's
      complement sum of the ICMP message starting with the ICMP Type.
      For computing the checksum , the checksum field should be zero.
      This checksum may be replaced in the future.
   Gateway Internet Address
      Address of the gateway to which traffic for the network specified
      in the internet destination network field of the original
      datagram's data should be sent.
[Page 12]
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   Internet Header + 64 bits of Data Datagram
      The internet header plus the first 64 bits of the original
      datagram's data.  This data is used by the host to match the
      message to the appropriate process.  If a higher level protocol
      uses port numbers, they are assumed to be in the first 64 data
      bits of the original datagram's data.
   Description
      The gateway sends a redirect message to a host in the following
      situation.  A gateway, G1, receives an internet datagram from a
      host on a network to which the gateway is attached.  The gateway,
      G1, checks its routing table and obtains the address of the next
      gateway, G2, on the route to the datagram's internet destination
      network, X.  If G2 and the host identified by the internet source
      address of the datagram are on the same network, a redirect
      message is sent to the host.  The redirect message advises the
      host to send its traffic for network X directly to gateway G2 as
      this is a shorter path to the destination.  The gateway forwards
      the original datagram's data to its internet destination.
      For datagrams with the IP source route options and the gateway
      address in the destination address field, a redirect message is
      not sent even if there is a better route to the ultimate
      destination than the next address in the source route.
      Codes 0, 1, 2, and 3 may be received from a gateway.
                                                               [Page 13]
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Echo or 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 ...
   +-+-+-+-+-
   IP Fields:
   Addresses
      The address of the source in an echo message will be the
      destination of the echo reply message.  To form an echo reply
      message, the source and destination addresses are simply reversed,
      the type code changed to 0, and the checksum recomputed.
   IP Fields:
   Type
      8 for echo message;
      0 for echo reply message.
   Code
      0
   Checksum
      The checksum is the 16-bit ones's complement of the one's
      complement sum of the ICMP message starting with the ICMP Type.
      For computing the checksum , the checksum field should be zero.
      If the total length is odd, the received data is padded with one
      octet of zeros for computing the checksum.  This checksum may be
      replaced in the future.
   Identifier
      If code = 0, an identifier to aid in matching echos and replies,
      may be zero.
   Sequence Number
[Page 14]
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      If code = 0, a sequence number to aid in matching echos and
      replies, may be zero.
   Description
      The data received in the echo message must be returned in the echo
      reply message.
      The identifier and sequence number may be used by the echo sender
      to aid in matching the replies with the echo requests.  For
      example, the identifier might be used like a port in TCP or UDP to
      identify a session, and the sequence number might be incremented
      on each echo request sent.  The echoer returns these same values
      in the echo reply.
      Code 0 may be received from a gateway or a host.
                                                               [Page 15]
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Timestamp or Timestamp 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        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Originate Timestamp                                       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Receive Timestamp                                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Transmit Timestamp                                        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   IP Fields:
   Addresses
      The address of the source in a timestamp message will be the
      destination of the timestamp reply message.  To form a timestamp
      reply message, the source and destination addresses are simply
      reversed, the type code changed to 14, and the checksum
      recomputed.
   IP Fields:
   Type
      13 for timestamp message;
      14 for timestamp reply message.
   Code
      0
   Checksum
      The checksum is the 16-bit ones's complement of the one's
      complement sum of the ICMP message starting with the ICMP Type.
      For computing the checksum , the checksum field should be zero.
      This checksum may be replaced in the future.
   Identifier
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      If code = 0, an identifier to aid in matching timestamp and
      replies, may be zero.
   Sequence Number
      If code = 0, a sequence number to aid in matching timestamp and
      replies, may be zero.
   Description
      The data received (a timestamp) in the message is returned in the
      reply together with an additional timestamp.  The timestamp is 32
      bits of milliseconds since midnight UT.  One use of these
      timestamps is described by Mills [5].
      The Originate Timestamp is the time the sender last touched the
      message before sending it, the Receive Timestamp is the time the
      echoer first touched it on receipt, and the Transmit Timestamp is
      the time the echoer last touched the message on sending it.
      If the time is not available in miliseconds or cannot be provided
      with respect to midnight UT then any time can be inserted in a
      timestamp provided the high order bit of the timestamp is also set
      to indicate this non-standard value.
      The identifier and sequence number may be used by the echo sender
      to aid in matching the replies with the requests.  For example,
      the identifier might be used like a port in TCP or UDP to identify
      a session, and the sequence number might be incremented on each
      request sent.  The destination returns these same values in the
      reply.
      Code 0 may be received from a gateway or a host.
                                                               [Page 17]
                                                          September 1981
RFC 792
Information Request or Information 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        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   IP Fields:
   Addresses
      The address of the source in a information request message will be
      the destination of the information reply message.  To form a
      information reply message, the source and destination addresses
      are simply reversed, the type code changed to 16, and the checksum
      recomputed.
   IP Fields:
   Type
      15 for information request message;
      16 for information reply message.
   Code
      0
   Checksum
      The checksum is the 16-bit ones's complement of the one's
      complement sum of the ICMP message starting with the ICMP Type.
      For computing the checksum , the checksum field should be zero.
      This checksum may be replaced in the future.
   Identifier
      If code = 0, an identifier to aid in matching request and replies,
      may be zero.
   Sequence Number
      If code = 0, a sequence number to aid in matching request and
      replies, may be zero.
[Page 18]
September 1981
RFC 792
   Description
      This message may be sent with the source network in the IP header
      source and destination address fields zero (which means "this"
      network).  The replying IP module should send the reply with the
      addresses fully specified.  This message is a way for a host to
      find out the number of the network it is on.
      The identifier and sequence number may be used by the echo sender
      to aid in matching the replies with the requests.  For example,
      the identifier might be used like a port in TCP or UDP to identify
      a session, and the sequence number might be incremented on each
      request sent.  The destination returns these same values in the
      reply.
      Code 0 may be received from a gateway or a host.
                                                               [Page 19]
                                                          September 1981
RFC 792
Summary of Message Types
    0  Echo Reply
    3  Destination Unreachable
    4  Source Quench
    5  Redirect
    8  Echo
   11  Time Exceeded
   12  Parameter Problem
   13  Timestamp
   14  Timestamp Reply
   15  Information Request
   16  Information Reply
[Page 20]
September 1981
RFC 792
References
   [1]  Postel, J. (ed.), "Internet Protocol - DARPA Internet Program
         Protocol Specification," RFC 791, USC/Information Sciences
         Institute, September 1981.
   [2]   Cerf, V., "The Catenet Model for Internetworking," IEN 48,
         Information Processing Techniques Office, Defense Advanced
         Research Projects Agency, July 1978.
   [3]   Strazisar, V., "Gateway Routing:  An Implementation
         Specification", IEN 30, Bolt Beranek and Newman, April 1979.
   [4]   Strazisar, V., "How to Build a Gateway", IEN 109, Bolt Beranek
         and Newman, August 1979.
   [5]   Mills, D., "DCNET Internet Clock Service," RFC 778, COMSAT
         Laboratories, April 1981.

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