| Internet-Draft | ICMP Node ID | October 2024 |
| Fenner & Thomas | Expires 4 April 2025 | [Page] |
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 a given 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 and/or a textual name for the node, in the case where each node may not have a unique IP address (e.g., a deployment in which all interfaces have IPv6 addresses and all nexthops are IPv6 nexthops, even for IPv4 routes).¶
This note is to be removed before publishing as an RFC.¶
The latest revision of this draft can be found at https://fenner.github.io/icmp-node-id/draft-ietf-intarea-extended-icmp-nodeid.html. Status information for this document may be found at https://datatracker.ietf.org/doc/draft-ietf-intarea-extended-icmp-nodeid/.¶
Discussion of this document takes place on the Internet Area Working Group Working Group mailing list (mailto:int-area@ietf.org), which is archived at https://mailarchive.ietf.org/arch/browse/int-area/. Subscribe at https://www.ietf.org/mailman/listinfo/int-area/.¶
Source for this draft and an issue tracker can be found at https://github.com/fenner/icmp-node-id.¶
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Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved.¶
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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.¶
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.¶
ICMPv4 is used to refer to Internet Control Message Protocol (ICMP) specified in [RFC0792].¶
ICMPv6 is used to refer to Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) specified in [RFC4443].¶
ICMP is used to refer to both ICMPv4 and ICMPv6.¶
This section defines the Node Identification Object, an ICMP Extension Object with a Class-Num (Object Class Value) of 5 (see Section 6).¶
Similar to Section 4 of [RFC5837], this object can be appended to the following messages:¶
ICMPv4 Time Exceeded¶
ICMPv4 Destination Unreachable¶
ICMPv4 Parameter Problem¶
ICMPv6 Time Exceeded¶
ICMPv6 Destination Unreachable¶
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. See Section 5 for suggested configuration regarding including these messages.¶
Similarly to the Interface Identification Object defined in [RFC5837], there are two different pieces of information that can appear in a Node Information Object:¶
An IP Address Sub-Object MAY be included, containing an address of sufficient scope to identify the node within the domain. The IP Address Sub-Object is defined in Section 3.2 of this memo.¶
A Node Name Sub-Object MAY be included, as specified in Section 3.3, containing up to 63 octets of the YANG sys:hostname ([RFC7317]) or another appropriate name uniquely identifying the node.¶
The C-Type contains a bitmask describing what information is included in this Node Identification Object (Figure 1). The fields in this bitmask are chosen so that the IPAddr and name bits overlap with the same bits as defined in [RFC5837], so that an implementation that supports exactly these bits can reuse packet generation and parsing code.¶
Bit 0 1 2 3 4 5 6 7
+-------+-------+-------+-------+-------+-------+-------+-------+
| Reserved | IPAddr| name | Rsvd2 |
+-------+-------+-------+-------+-------+-------+-------+-------+
The following are bit-field definitions for C-Type:¶
Reserved (bits 0-4): These bits are reserved for future use and MUST be set to 0 on transmit and ignored on receipt.¶
IP Addr (bit 5) : When set, a Node IP Address Sub-Object is present. When clear, an IP Address Sub-Object is not present. The Node IP Address Sub-Object is described in Section 3.2 of this memo.¶
Node Name (bit 6): When set, a Node Name Sub-Object is included. When clear, it is not included. The Node Name Sub-Object is described in Section 3.3 of this memo.¶
Rsvd2 (bit 7): This bit is reserved for future use and MUST be set to 0 on transmit and ignored on receipt.¶
The information included does not self-identify, so this specification defines a specific ordering for sending the information that must be followed.¶
If bit 5 (IP Address) is set, a Node IP Address Sub-Object MUST be sent first. If bit 6 (Name) is set, a Node Name Sub-Object MUST be sent next. The information order is thus: IP Address Sub-Object, Node Name Sub-Object. Any or all pieces of information may be present or absent, as indicated by the C-Type. Any data that follows these optional pieces of information MUST be ignored.¶
It is valid (though pointless until additional bits are assigned by IANA) to receive a Node Information Object where bits 5 and 6 are both 0; this MUST NOT generate a warning or error.¶
Bit values SHOULD be assigned from left to right in the diagram above, i.e., starting at zero. The sub-objects associated with each new bit MUST be placed in the packet after the sub-objects defined in this memo. For example, if bit 0 is assigned to the Fooblewomp, a packet with bits 0 and 5 set MUST contain the Node IP Address Sub-Object, followed by the Fooblewomp sub-object.¶
If a bit is set that a receiver does not support, followed by a bit that the receiver does support, the receiver MUST ignore all of the additional data, since the length of the unsupported data is unknown.¶
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 2.¶
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...
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 as follows:¶
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. The length of this field can be derived from the AFI.¶
Figure 3 depicts the Node Name Sub-Object:¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length | Node Name... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The Node Name Sub-Object MUST have a length that is a multiple of 4 octets and MUST NOT exceed 64 octets.¶
The Length field represents the length of the Node Name Sub- Object, including the length and the node name in octets. The maximum valid length is 64 octets. The length is constrained to ensure there is space for the start of the original packet and additional information.¶
The second field contains the human-readable node name. The node name SHOULD be the YANG sys:hostname [RFC7317], if less than 64 octets, or the first 63 octets of the sys:hostname, if the sys:hostname is longer. The node name MAY be some other human-meaningful name of the node. The node name MUST be padded with ASCII NUL characters if the object would not otherwise terminate on a 4-octet boundary.¶
The node name MUST be represented in the UTF-8 charset [RFC3629] using the Default Language [RFC2277].¶
An address translator MAY use this extension when translating an ICMP message listed above to include the pre-translation source address of a packet. When doing so, it MUST include the IP Address Sub-Object, and MUST NOT include the Node Name Sub-Object. If an ICMP Extension Structure is already present in the packet being translated, this Extension Object is appended to the existing ICMP Extension Structure and the checksum is updated. If an ICMP Extension Structure is not present in the packet being translated, one is added using the rules of [RFC4884]. Further details of this mode of operation are outside the scope of this memo.¶
A node name may reveal sensitive information It may not be desirable to allow this information to be sent to an arbitrary receiver. The addition of this information to the ICMP responses listed in Section 3 is configurable, and defaults to off. An implementation may 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. Access control lists (ACLs) may be used to filter the destinations to which this information may be communicated.¶
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.¶
This IANA has allocated the ICMP Extension Object Class value 5 to the extension described above. The corresponding Class Sub-types Registry is as follows:¶
| C-Type (Value) | Description | Reference |
|---|---|---|
| 0-4 | Unallocated - allocatable with Standards Action | [This document] |
| 5 | IP Address Sub-object included | [This document] |
| 6 | Name Sub-object included | [This document] |
| 7 | Unallocated - allocatable with Standards Action | [This document] |
This section is to be removed before publishing as an RFC.¶
Fixed several copy-pasta errors that still referred to interface names instead of node name.¶
Renamed to draft-ietf-intarea-extended-icmp-nodeid-00 to reflect adoption by WG¶
This document derives text heavily from [RFC5837], since the underlying mechanism is identical, and only the semantics of the message differs. Thanks are therefore due to that document's authors: Alia K. Atlas, Ronald P. Bonica, Carlos Pignataro, Naiming Shen, and JR. Rivers.¶
Further thanks are due to the following who have provided valuable contributions to this document: Med Boucadair, Jen Linkova, and David Lamparter.¶