Internet-Draft ICMP System ID February 2024
Fenner Expires 12 August 2024 [Page]
Internet Area Working Group
Intended Status:
Standards Track
B. Fenner
Arista Networks

Extending ICMP for System Identification


RFC5837 describes a mechanism for Extending ICMP for Interface and Next-Hop Identification, which allows providing additional information in an ICMP error that helps identify interfaces participating in the path. This is especially useful in environments where each interface may not have a unique IP address to respond to, e.g., a traceroute.

This document introduces a similar ICMP extension for Node identification. It allows providing a unique IP address or a textual name for the node, in the case where each node may not have a unique IP address (e.g., the IPv6 nexthop deployment case described in draft-chroboczek-intarea-v4-via-v6).

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This Internet-Draft will expire on 12 August 2024.

Table of Contents

1. Introduction

In addition to adding incoming interface information to a traceroute using the mechanisms described in [RFC5837], a network operator may be interested in adding information to identify nodes themselves. [I-D.chroboczek-intarea-v4-via-v6] describes a scenario in which individual nodes do not have unique IPv4 addresses to use to reply to an IPv4 traceroute, so additional information is needed.

2. Conventions and Definitions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

3. Node Identification Object

This section defines the Node Identification Object, an ICMP Extension Object with a Class-Num (Object Class Value) of TBD that can be appended to the following messages:

For reasons described in [RFC4884], this extension cannot be appended to any of the currently defined ICMPv4 or ICMPv6 messages other than those listed above.

The extension defined herein MAY be appended to any of the above listed messages and SHOULD be appended whenever required to identify the node and when local policy or security considerations do not supersede this requirement.

3.1. C-Type Meaning in a Node Identification Object

C-Type values in a Node Identification Object include:

  • 1: Identifies Node by Name

If the Node Identification Object identifies the node by name, the Object Payload contains the configured node name. It is presumed that the operator configures a unique node name for each system that is identified in this manner. If the Object Payload would not otherwise terminate on a 32-bit boundary, it MUST be padded with ASCII NULL characters.

  • 2: Identifies Node by Address

If the Node Identification Object identifies the node by address, the Object Payload contains an address sufficient to identify the node within the appropriate scope - global or as otherwise configured - as depicted in Figure 1.

 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
|              AFI              |            Reserved           |
|                           Address...
Figure 1: Node Identification Object - C-Type 2 Payload

Payload fields are defined as follows:

  • Address Family Identifier (AFI): This 16-bit field identifies the type of address represented by the Address field. Values for this field represent a subset of values found in the IANA registry of Address Family Numbers (available from [IANA.address-family-numbers]). Valid values are 1 (representing a 32-bit IPv4 address) and 2 (representing a 128-bit IPv6 address).

  • Reserved: This field MUST be set to 0 and ignored upon receipt.

  • Address: This variable-length field represents an address of appropriate scope (global, if none other defined) that can be used to identify the node.

4. Security Considerations

It may not be desirable to allow this information to be sent to an arbitrary receiver. The addition of this information SHOULD be configurable, and MUST default to off. An implementation SHOULD determine what objects may be appended to a given message based on the destination IP address of the ICMP message that will contain the objects.

The intended field of use for the extensions defined in this document is administrative debugging and troubleshooting. The extensions herein defined supply additional information in ICMP responses. These mechanisms are not intended to be used in non-debugging applications.

This document does not specify an authentication mechanism for the extension that it defines. Application developers should be aware that ICMP messages and their contents are easily spoofed.

5. IANA Considerations

This document will ask IANA to allocate an ICMP Extension Object Class referred to as TBD above. But for now this document is just for discussion.

6. Normative References

Chroboczek, J., Kumari, W. A., and T. Høiland-Jørgensen, "IPv4 routes with an IPv6 next hop", Work in Progress, Internet-Draft, draft-chroboczek-intarea-v4-via-v6-00, , <>.
IANA, "Address Family Numbers", <>.
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <>.
Bonica, R., Gan, D., Tappan, D., and C. Pignataro, "Extended ICMP to Support Multi-Part Messages", RFC 4884, DOI 10.17487/RFC4884, , <>.
Atlas, A., Ed., Bonica, R., Ed., Pignataro, C., Ed., Shen, N., and JR. Rivers, "Extending ICMP for Interface and Next-Hop Identification", RFC 5837, DOI 10.17487/RFC5837, , <>.
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <>.


This document derives text heavily from [RFC5837], since the underlying mechanism is identical, and only the content of the messages differ.

Author's Address

Bill Fenner
Arista Networks
5453 Great America Parkway
Santa Clara, California 95054
United States of America