ICMP Query for IP Node Information

This document introduces two new ICMP messages. They are called the ICMP Query Request and the ICMP Query Response. The ICMP Query Request requests information. The ICMP Query Response provides information in response to an ICMP Query Request. Both messages are specified for ICMPv4 and ICMPv6 . Both messages include an ICMP Extension Structure . ICMP Extension Objects in the Query Request message determine which information is requested. ICMP Extension Objects in the Query Response message provide the requested information. To prevent denial of service attacks, the ICMP Query Response message MUST NOT be longer than the corresponding ICMP Query Request message. This document updates .

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 when, and only when, they appear in all capitals, as shown here.

The ICMP Query Request message is defined for both ICMPv4 and ICMPv6. Like any ICMP message, the ICMP Query Request message is encapsulated in an IP header. The ICMPv4 version of the Query Request message is encapsulated in an IPv4 header, while the ICMPv6 version is encapsulated in an IPv6 header. The ICMP Query Request message has the following format:

IP Header fields: Source Address: The Source Address identifies the ICMP Querying node. It MUST be a valid IP unicast address. Destination Address: The Destination Address identifies the ICMP Queried node. It MUST be a valid IP unicast address. ICMP fields: Type: ICMP Query Request. The value is TBD1 for ICMP and TBD2 for ICMPv6. Code: MUST be set to 0 and MUST be ignored upon receipt. Checksum: The same as defined in . Identifier: An Identifier aids in matching ICMP Query Replies to ICMP Query Requests. Sequence Number: A Sequence Number to aid in matching ICMP Query Replies to ICMP Query Requests. Following the ICMP Query Request header, it's an ICMP Extension Structure as specified in Sections 7 and 8 of , continuing to the end of the packet. Nothing can be added after the ICMP Extension Structure.

One or more Query Request Objects MUST be encapsulated in an ICMP Extension Structure of the ICMP Query Request message. Each Query Request Object has the following format:

Object fields: Class-Num: Indicates the class of IP node information to be queried. The value will be requested by a separate document. C-Type: Indicates the sub-type of IP node information to be queried. The value will be requested by a separate document. Length: Length of the object, measured in octets, including the Object Header and payload. Object payload: Following the Query Request Object Header is the Query Request Object Payload, which is used to define the scope of IP node information to be queried. The length of this field is variable. The value will be defined by a separate document.

One or more Pad Objects MAY be encapsulated in an ICMP Extension Structure of the ICMP Query Request message. Each Pad Object has the following format:

Object fields: Class-Num: Indicates that it's a Pad Object. The value is TBD5. C-Type: The value is 0. Length: Length of the object, measured in octets, including the Object Header and payload. Object payload: Following the Pad Object Header is the Pad Object Payload, which SHOULD be filled by a sequence of pseudorandom numbers, or MAY be filled with all zeros. An implementation MUST control the content of the Pad Object Payload field..

One Query Pre-Request Object MUST be encapsulated in an ICMP Extension Structure of the ICMP Query Request message. Query Pre-Request Object has the following format:

Object fields: Class-Num: Indicates that it's a Query Pre-Request Object. The value is TBD6. C-Type: The value is 0. Length: Length of the object, measured in octets, including the Object Header and payload. Object payload: Following the Query Pre-Request Object Header is the Query Pre-Request Object Payload, which is a list of two-tuples (Class-Num and C-Type) used to query what kinds of information are supported by the ICMP Queried node. The length of this field is variable. The value of each two-tuple will be the same as what's assigned by IANA for each Query Request Object, with an IANA request by a separate document.

The ICMP Query Response message is defined for both ICMPv4 and ICMPv6. Like any ICMP message, the ICMP Query Response message is encapsulated in an IP header. The ICMPv4 version of the Query Response message is encapsulated in an IPv4 header, while the ICMPv6 version is encapsulated in an IPv6 header. The ICMP Query Response message has the following format:

IP Header fields: Source Address: Copied from the Destination Address field of the invoking ICMP Query Request packet. Destination Address: Copied from the Source Address field of the invoking ICMP Query Request packet. ICMP fields: Type: ICMP Query Response. The value is TBD3 for ICMPv4 and TBD4 for ICMPv6. Code: The values are (0) No Error, (1) Malformed Query, (2) Unrecognized Query Request Object, and (3) Request Denied. See for details. Checksum: The same as defined in . Identifier: Copied from the Identifier field of the invoking ICMP Query Request message. Sequence Number: Copied from the Sequence Number field of the invoking ICMP Query Request message. Following the ICMP Query Response header, it's an ICMP Extension Structure as specified in Sections 7 and 8 of , continuing to the end of the packet. Nothing can be added after the ICMP Extension Structure.

One or more Query Response Objects MUST be encapsulated in an ICMP Extension Structure of the ICMP Query Response message. Each Query Response Object has the following format:

Object fields: Class-Num: Indicates the class of replied IP node information. The value will be requested by a separate document. C-Type: Indicates the sub-type of replied IP node information. The value will be requested by a separate document. Length: Length of the object, measured in octets, including the Object Header and payload. Object payload: Following the Query Response Object Header is the Query Response Object Payload, which is the replied IP node information. The length of this field is variable. The value will be defined by a separate document.

One Query Pre-Response Object MUST be encapsulated in an ICMP Extension Structure of the ICMP Query Response message. Query Pre-Response Object has the following format:

Object fields: Class-Num: Indicates that it's a Query Pre-Response Object. The value is TBD7. C-Type: The value is 0. Length: Length of the object, measured in octets, including the Object Header and payload. Object payload: Following the Query Pre-Response Object Header is the Query Pre-Response Object Payload, which is a list of two-tuples (Class-Num and C-Type) used to respond the ICMP Querying node what kinds of information are supported by the ICMP Queried node. The length of this field is variable. The value of each two-tuple is copied from the Query Pre-Request Object of the invoking ICMP Query Request message.

The Code field in the ICMP Query Response MUST be set to (1) Malformed Query if any of the following conditions apply: The ICMP Query Request does not include an ICMP Extension Structure. The ICMP Extension Structure checksum is 0 or incorrect. The ICMP Query Request is otherwise malformed. The Code field in the ICMP Query Response MUST be set to (2) Unrecognized Query Request Object if any of the following conditions apply: The ICMP Extension Structure of the ICMP Query Request does not include a Query Request Object. None of the Class-Num of the Query Request Object is recognized. None of the C-Type of the Query Request Object is recognized.

Section 4.6 of provides a list of extensible ICMP messages (i.e., messages that can carry the ICMP Extension Structure). This document adds the ICMP Query Request message and the ICMP Query Response message to that list.

To remove to potential of abusing ICMP Query as a means of attack amplification, Pad Object defined in MAY be included in the ICMP Query Request message, to ensure that the Query Reply message must never be larger than the invoking Query Request message. To ensure the queried information is supported by the Queried node, before sending the ICMP Query Request message containing one or more Query Request Objects, the ICMP Querying node can send first an ICMP Query Request message containing only one Query Pre-Request Object defined in . And once receiving an ICMP Query Request message containing only one Query Pre-Request Object, the ICMP Queried node MUST respond an ICMP Query Response message containing only one Query Pre-Response Object defined in , telling the ICMP Querying node what kinds of information are supported by the ICMP Queried node.

defines an experimental protocol using ICMPv6 type values 139/140. Section 4 of that RFC specifies the two types of Node Information (NI) messages, the NI Query and the NI Reply, which can be used to learn the addresses and names for nodes on the other end of a point-to-point link or nodes on a shared-medium link such as an Ethernet. defines a network diagnostic tool called PROBE using ICMP type values 42/43 and ICMPv6 type values 160/161. Sections 2 and 3 of that document specify the two types of ICMP messages, the Extended Echo Request and the Extended Echo Reply, which can be used to query the status of a probed interface. Whether the NI Query/Reply or the Extended Echo Request/Reply are not designed for a generic ICMP Query, so if reusing their ICMP type values, some backward compatibility issues need to be resolved, which means complexity and redundant fields.

This document requests the following actions from IANA: Add the following ICMPv4 Type to the "ICMP Type Numbers" registry: TBD1 Query Request Add the following Code to the "Type TBD1 - Query Request" subregistry: (0) No Error Add the following ICMPv6 Type to the "ICMPv6 'type' Numbers" registry: TBD2 Query Request As ICMPv6 distinguishes between informational and error messages, and this is an informational message, the value must be assigned from the range 128-255. Add the following Code to the "Type TBD2 - Query Request" subregistry: (0) No Error Add the following ICMPv4 Type to the "ICMP Type Numbers" registry: TBD3 Query Response Add the following Codes to the "Type TBD3 - Query Response" subregistry: (0) No Error (1) Malformed Query (2) Unrecognized Query Request Object (3) Request Denied Add the following ICMPv6 Type to the "ICMPv6 'type' Numbers" registry: TBD4 Query Response As ICMPv6 distinguishes between informational and error messages, and this is an informational message, the value must be assigned from the range 128-255. Add the following Codes to the "Type TBD4 - Query Response" subregistry: (0) No Error (1) Malformed Query (2) Unrecognized Query Request Object (3) Request Denied Add the following Class-Num to the "ICMP Extension Object Classes and Class Sub-types" registry: (TBD5) Pad Object (TBD6) Query Pre-Request Object (TBD7) Query Pre-Response Object Add the following C-type to the "Sub-types - Class TBD5 - Pad Object" subregistry: (0) Reserved Add the following C-type to the "Sub-types - Class TBD6 - Query Pre-Request Object" subregistry: (0) Reserved Add the following C-type to the "Sub-types - Class TBD7 - Query Pre-Response Object" subregistry: (0) Reserved C-Type values are assigned on a First Come First Serve (FCFS) basis with a range of 0-255. All subregistries mentioned above are requested to be newly created by IANA and the subregistries will contain the new codes. All codes mentioned above are assigned on an FCFS basis with a range of 0-255.

Security issues discussed in apply to this document. This document recommends using IP Authentication Header or IP Encapsulating Security Payload Header to provide integrity protection for replied IP node information. This document recommends using IP Encapsulating Security Payload Header to provide privacy protection for replied IP node information. This document recommends that the network operators establish policies that restrict access to ICMP Query functionality. In order to enforce these policies, nodes that support ICMP Query functionality MUST support the following configuration options: Enable/disable ICMP Query functionality. By default, ICMP Query functionality is disabled. Define the prefixes from which ICMP Query Request messages are permitted. In order to protect local resources, implementations SHOULD rate-limit incoming ICMP Query Request messages. To avoid the potential amplification attack, an implementation that supports this specification MUST ensure that the Query Response message must never be larger than the Query Request message.

The authors would like to acknowledge Sebastian Moeller, Paul Vixie, Jen Linkova, and Dave Thaler for their valuable comments.