Internet R. Bonica Internet-Draft D. Gan Expires: December 10, 2006 Juniper Networks P. Nikander Ericsson Research Nomadic Lab D. Tappan C. Pignataro Cisco Systems, Inc. June 8, 2006 Modifying ICMP to Support Multi-part Messages draft-bonica-internet-icmp-05 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on December 10, 2006. Copyright Notice Copyright (C) The Internet Society (2006). Abstract This document redefines selected ICMPv4 messages to support multi- part operation. A multi-part ICMP message carries all of the information that ICMP messages carried previously, as well as Bonica, et al. Expires December 10, 2006 [Page 1] Internet-Draft Multi-part ICMP Messages June 2006 additional information that applications may require. Multi-part messages are supported by an ICMP extension structure. The extension structure is situated at the end of the ICMP message. It includes an extension header followed by one or more extension objects. Each extension object contains an object header and object payload. All object headers share a common format. This document further redefines a subset of the above mentioned ICMP messages by specifying a length attribute. Many of the ICMP messages to which an extension structure can be appended include and "original datagram" field. The "original datagram" field contains the initial octets of the datagram to which the ICMP message is a response. Although the original datagram field is of variable length, the ICMP message does not include a field that specifies its length. Therefore, in order to facilitate message parsing, this draft allocates eight previously reserved bits to reflect the length of the "original datagram" field. The proposed modifications change the requirements for ICMPv4 compliance. The impact of these changes on compliant implementations is discussed, and new requirements for future implementations are presented. Bonica, et al. Expires December 10, 2006 [Page 2] Internet-Draft Multi-part ICMP Messages June 2006 Table of Contents 1. Conventions Used In This Document . . . . . . . . . . . . . . 4 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Summary of Changes to ICMP . . . . . . . . . . . . . . . . . . 5 4. ICMP Extensibility . . . . . . . . . . . . . . . . . . . . . . 5 4.1. Destination Unreachable . . . . . . . . . . . . . . . . . 7 4.2. Source Quench . . . . . . . . . . . . . . . . . . . . . . 8 4.3. Time Exceeded . . . . . . . . . . . . . . . . . . . . . . 9 4.4. Parameter Problem . . . . . . . . . . . . . . . . . . . . 9 4.5. ICMP Messages That Cannot Be Extended . . . . . . . . . . 10 5. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 10 5.1. Classic Application Receives ICMP Message With Extensions . . . . . . . . . . . . . . . . . . . . . . . . 12 5.2. Non-compliant Application Receives ICMP Message With No Extensions . . . . . . . . . . . . . . . . . . . . . . 12 5.3. Non-compliant Application Receives ICMP Message With Compliant Extensions . . . . . . . . . . . . . . . . . . . 13 5.4. Compliant Application Receives ICMP Message with No Extensions . . . . . . . . . . . . . . . . . . . . . . . . 13 5.5. Compliant Application Receives ICMP Message with Non-compliant Extensions . . . . . . . . . . . . . . . . . 13 6. The ICMP Extension Structure . . . . . . . . . . . . . . . . . 14 7. ICMP Extension Objects . . . . . . . . . . . . . . . . . . . . 15 8. Security Considerations . . . . . . . . . . . . . . . . . . . 15 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 11.1. Normative References . . . . . . . . . . . . . . . . . . . 16 11.2. Informative References . . . . . . . . . . . . . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 18 Intellectual Property and Copyright Statements . . . . . . . . . . 19 Bonica, et al. Expires December 10, 2006 [Page 3] Internet-Draft Multi-part ICMP Messages June 2006 1. Conventions Used In This Document The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC2119 [1]. 2. Introduction This document redefines selected ICMP [2] messages to include an extension structure and a length attribute. In this document, the term ICMP refers exclusively to ICMPv4. Unless explicitly noted, ICMPv6 is NOT discussed in this memo. The extension structure supports multi-part ICMP operation. Protocol designers can make an ICMP message carry additional information by encoding that information in an extension. This document also addresses a fundamental problem in ICMP extensibility. Many of the ICMP messages addressed by this memo include an "original datagram" field. The "original datagram" field contains the initial octets of the datagram to which the ICMP message is a response. Although the "original datagram" field is of variable length, the ICMP message does not include a field that specifies its length. Application software infers the length of the "original datagram" field from the total length of the ICMP message. If an extension structure were appended to the message without adding a length attribute for the "original datagram" field, the message would become unparsable. Specifically, application software would not be able to determine where the "original datagram" field ends and where the extension structure begins. Therefore, this document proposes a length attribute as well as an extension structure that is appended to the ICMP message. The current memo also addresses backwards compatibility with existing ICMP implementations that either do not implement the extensions defined herein or implement them without adding the required length attributes. In particular, this draft addresses backwards compatibility with certain, widely deployed, MPLS-aware ICMP implementations that send the extensions defined herein without adding the required length attribute. The current memo does not define any ICMP extension objects. It defines only the extension header and a common header that all extension objects share. Reference [5] provides a sample application of the ICMP Extension Object. Bonica, et al. Expires December 10, 2006 [Page 4] Internet-Draft Multi-part ICMP Messages June 2006 3. Summary of Changes to ICMP The following is a summary of changes to ICMP that are proposed by this memo: - An ICMP Extension Structure MAY be appended to any ICMP message except for those excluded below. - The ICMP Extension Structure MUST NOT be appended to the Redirect, Echo Request, Echo Reply and Domain Name Reply messages. - When ICMP Extensions are appended to a message that includes an "original datagram" field, the ICMP message MUST specify a length attribute for the "original datagram" field. - When ICMP Extensions are appended to a message that includes an "original datagram" field, the "original datagram" field MUST include at least 128 octets. If the original datagram did not contain 128 octets, the "original datagram" field MUST be zero padded to 128 octets. - When ICMP Extensions are appended to a message that includes an "original datagram" field, the "original datagram" field MUST be zero padded to the nearest 32-bit boundary. 4. ICMP Extensibility RFC 792 defines the following ICMP message types: - Destination Unreachable - Time Exceeded - Parameter Problem - Source Quench - Redirect - Echo Request/Reply - Timestamp/Timestamp Reply - Information Request/Information Reply RFC 1191 [3] adds a "Next-Hop MTU" field to the Destination Unreachable message. Subsequent RFCs define the following messages: Bonica, et al. Expires December 10, 2006 [Page 5] Internet-Draft Multi-part ICMP Messages June 2006 - Address Mask Request/Reply [6] - Router Solicitation/Advertisement [7] - Traceroute [8] - Domain Name Request/Reply [9] - Security Failure [10] - Experimental Mobility [11] Many ICMP messages are extensible as currently defined. Protocol designers can extend ICMP messages by simply appending fields or data structures to them. The following ICMP messages are not extensible as currently defined: - Destination Unreachable - Source Quench - Time Exceeded - Parameter Problem - Redirect - Echo Request - Echo Reply - Domain Name Reply These ICMP messages contain an "original datagram" field which represents a portion of the original datagram to which the ICMP messages is a response. As originally defined, this field includes the IP header plus the next eight octets of the original datagram. RFC 1812 [4] extends this field to contain as many octets as possible, without exceeding a limit of 576 octets for the entire ICMP message. Unfortunately, the "original datagram" field lacks a length attribute. Application software infers the length of this field from the total length of the ICMP message. If an extension structure were appended to the message without adding a length attribute for the "original datagram" field, the message would become unparsable. Specifically, application software would not be able to determine Bonica, et al. Expires December 10, 2006 [Page 6] Internet-Draft Multi-part ICMP Messages June 2006 where the "original datagram" field ends and where the extension structure begins. In order to solve this problem, this memo introduces an 8-bit length attribute to the following ICMP messages. - Destination Unreachable - Source Quench - Time Exceeded - Parameter Problem The length attribute MUST be specified when the ICMP Extension Structure is appended to the above mentioned ICMP messages. The length attribute represents the length of the "original datagram" field, measured in 32-bit words. When the length attribute is specified, the "original datagram" field MUST be zero padded to the nearest 32-bit boundary. Space for the length attribute is claimed from reserved octets, whose value was previously required to be zero. Because the sixth octet of each of the impacted ICMP messages was reserved for future use, this octet was selected as the location of the length attribute. In order the achieve backwards compatibility, when the ICMP Extension Structure is appended to an ICMP message and that ICMP message contains an "original datagram" field, the "original datagram" field MUST contain at least 128 octets. If the original datagram did not contain 128 octets, the "original datagram" field MUST be zero padded to 128 octets. (See Section 5.1 for rationale.) The following sub-sections depict length attribute as it has been introduced to selected ICMP messages. 4.1. Destination Unreachable Figure 1 depicts the Destination Unreachable Message. Bonica, et al. Expires December 10, 2006 [Page 7] Internet-Draft Multi-part ICMP Messages June 2006 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 | Length | Next-Hop MTU | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Internet Header + leading octets of original datagram | | | | // | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Destination Unreachable The syntax and semantics of all fields are unchanged from RFC 792 and RFC 1191. However, a length attribute is added to the second word. The length attribute represents length of the padded "original datagram" field, measured in 32-bit words. 4.2. Source Quench Figure 2 depicts the 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 | Length | unused | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Internet Header + leading octets of original datagram | | | | // | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Source Quench The syntax and semantics of all fields are unchanged from RFC 792, except for a length attribute which is added to the second word. The length attribute represents length of the padded "original datagram" field, measured in 32-bit words. Bonica, et al. Expires December 10, 2006 [Page 8] Internet-Draft Multi-part ICMP Messages June 2006 4.3. Time Exceeded Figure 3 depicts the 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 | Length | unused | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Internet Header + leading octets of original datagram | | | | // | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: Time Exceeded The syntax and semantics of all fields are unchanged from RFC 792, except for a length attribute which is added to the second word. The length attribute represents length of the padded "original datagram" field, measured in 32-bit words. 4.4. Parameter Problem Figure 4 depicts the 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 | Length | unused | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Internet Header + leading octets of original datagram | | | | // | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Parameter Problem The syntax and semantics of all fields are unchanged from RFC 792, Bonica, et al. Expires December 10, 2006 [Page 9] Internet-Draft Multi-part ICMP Messages June 2006 except for a length attribute which is added to the second word. The length attribute represents length of the padded "original datagram" field, measured in 32-bit words. 4.5. ICMP Messages That Cannot Be Extended The ICMP Extension Structure MAY be appended to any ICMP message listed in Section 4 with the following exceptions. Due to a lack of reserved octets from which to allocate space, a length attribute could not be added to the following ICMP messages: - Redirect - Echo Request - Echo Reply - Domain Name Reply Therefore, the ICMP Extension Structure cannot be used in conjunction with the those ICMP messages. Furthermore, the ICMP Extension Structure cannot be used in conjunction with the Experimental Mobility message, because that message already contains an extensible "options" field. ICMP messages defined in the future SHOULD either support the ICMP Extension Structure or state explicitly that they do not. 5. Backwards Compatibility ICMP messages can be categorized as follows: - Messages that do not include any ICMP extensions - Messages that include non-compliant ICMP extensions - Messages that includes compliant ICMP extensions Any ICMP implementation can send a message that does not include extensions. ICMP implementations produced prior to 1999 are not known to send ICMP extensions. Some ICMP implementations, produced between 1999 and the present, may send a non-compliant version of ICMP extensions described in this memo. Specifically, these implementations may append the ICMP Bonica, et al. Expires December 10, 2006 [Page 10] Internet-Draft Multi-part ICMP Messages June 2006 Extension Structure to the Time Exceeded and Destination Unreachable messages. When they do this, they send exactly 128 octets representing the original datagram, zero padding if required. They also calculate checksums as described in this document. However, they do not specify a length attribute to be associated with the "original datagram" field. It is assumed that ICMP implementations produced in the future will send ICMP extensions that are compliant with this specification. Likewise, applications that consume ICMP messages can be categorized as follows: - Classic applications - Non-compliant applications - Compliant applications Classic applications do not parse extensions defined in this memo. They are insensitive to the length attribute that is associated with the "original datagram" field. Non-compliant implementations parse the extensions defined in this memo, but only in conjunction with the Time Expired and Destination Unreachable messages. They require the "original datagram" field to contain exactly 128 octets and are insensitive to the length attribute that is associated with the "original datagram" field. Non-compliant applications were produced between 1999 and the present. Compliant applications comply fully with the specifications of this document. In order to demonstrate backwards compatibility, Table 1 describes how members of each application category would parse each category of ICMP message. +----------------+----------------+----------------+----------------+ | | No Extensions | Non-compliant | Compliant | | | | Extensions | Extensions | +----------------+----------------+----------------+----------------+ | Classic | - | Section 5.1 | Section 5.1 | | Application | | | | | | | | | | Non-compliant | Section 5.2 | - | Section 5.3 | | Application | | | | | | | | | Bonica, et al. Expires December 10, 2006 [Page 11] Internet-Draft Multi-part ICMP Messages June 2006 | Compliant | Section 5.4 | Section 5.5 | - | | Application | | | | +----------------+----------------+----------------+----------------+ Table 1 In the table above, cells that contain a dash represent the nominal case and require no explanation. In the following sections, we assume that the ICMP message type is "Time Exceeded". 5.1. Classic Application Receives ICMP Message With Extensions When a classic application receives an ICMP message that includes extensions, it will incorrectly interpret those extensions as being part of the "original datagram" field. Fortunately, the extensions are guaranteed to begin at least 128 octets beyond the beginning of the "original datagram" field. So, only those ICMP applications that process the 129th octet of the "original datagram" field will be adversely effected. To date, no such applications have been identified. 5.2. Non-compliant Application Receives ICMP Message With No Extensions When a non-compliant application receives a message that contains no extensions, the application examines the total length of the ICMP message. If the total ICMP message length is less than the length of its IP header plus 144 octets, the application correctly determines that the message does not contain any extensions. The 144 octet sum is derived from 8 octets for the first two words of the ICMP Time Exceeded message, 128 octets for the "original datagram" field, 4 octets for the ICMP Extension Header and 4 octets for a single ICMP Object header. All of these octets would be required if extensions were present. If the ICMP payload contains 144 octets or more, the application must examine the 137th octet to determine whether it represents a valid ICMP Extension Header. In order to represent a valid Extension Header, it must contain a valid version number and checksum. If it does not contain a valid version number and checksum, the application correctly determines that the message does not contain any extensions. Non-compliant applications assume that the ICMP Extension Structure begins on the 137th octet of the Time Exceeded message, after a 128 octet field representing the padded "original datagram" message. It is possible that a non-compliant application will parse an ICMP Bonica, et al. Expires December 10, 2006 [Page 12] Internet-Draft Multi-part ICMP Messages June 2006 message incorrectly under the following conditions: - the message does not contain extensions - the original datagram field contains 144 octets or more - selected octets of the original datagram field represent the correct values for an extension header version number and checksum Although this is possible, it is very unlikely. 5.3. Non-compliant Application Receives ICMP Message With Compliant Extensions When a non-compliant application receives a message that contains compliant ICMP extensions, it will parse those extensions correctly only if the "original datagram" field contains exactly 128 octets. This is because non-compliant applications are insensitive to the length attribute that is associated with the "original datagram" field. (They assume its value to be 128.) Provided that the entire ICMP messages does not exceed 576 octets, there is no upper limit upon the length of the "original datagram" field. However, each vendor will decide how many octets to include. Those wishing to be backward compatible with non-compliant TRACEROUTE implementations will include exactly 128 octets. Those not requiring compatibility with non-compliant TRACEROUTE applications may include more octets. 5.4. Compliant Application Receives ICMP Message with No Extensions When a compliant application receives an ICMP message, it examines the length attribute that is associated with the "original datagram" field. If the length attribute is zero, the compliant application MUST determine that the message contains no extensions. 5.5. Compliant Application Receives ICMP Message with Non-compliant Extensions When a compliant application receives an ICMP message, it examines the length attribute that is associated with the "original datagram" field. If the length attribute is zero, the compliant application MUST determine that the message contains no extensions. In this case, that determination is technically correct, but not backwards compatible with the non-compliant implementation that originated the ICMP message. So, to ease transition yet encourage compliant implementation, Bonica, et al. Expires December 10, 2006 [Page 13] Internet-Draft Multi-part ICMP Messages June 2006 compliant TRACEROUTE implementations MAY include a non-default operation mode to also interpret non-compliant responses. Specifically, when a TRACEROUTE application operating in non- compliant mode receives an ICMP message that contains 144 octets or more in its payload and does not specify a length attribute, it will parse for a valid extension header beginning at octet 137. If the application detects a valid version and checksum, it will treat the following octets as an extension structure. 6. The ICMP Extension Structure This memo proposes an optional ICMP Extension Structure that can be appended to any ICMP message, except for those that are disqualified in Section 4.5 of this document. The Extension Structure contains exactly one Extension Header followed by one or more objects. Having received an ICMP message with extensions, application software MAY process selected objects while ignoring others. The presence of an unrecognized object does not imply that an ICMP message is malformed. As stated in RFC 792, the total length of the ICMP message, including extensions, MUST NOT exceed 576 octets. Figure 5 depicts the ICMP Extension Header. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| (Reserved) | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: ICMP Extension Header The fields of the ICMP Extension Header are as follows: Version: 4 bits ICMP extension version number. This is version 2. Reserved: 12 bits Must be set to 0. Checksum: 16 bits Bonica, et al. Expires December 10, 2006 [Page 14] Internet-Draft Multi-part ICMP Messages June 2006 The one's complement of the one's complement sum of the data structure, with the checksum field replaced by zero for the purpose of computing the checksum. An all-zero value means that no checksum was transmitted. 7. ICMP Extension Objects Each extension object contains one or more 32-bit words, representing an object header and payload. All object headers share a common format. Figure 6 depicts the Object Header and payload. 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 | Class-Num | C-Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | // (Object payload) // | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: Object Header and Payload An object header has the following fields: Length: 16 bits Length of the object, measured in octets, including the object header and object payload. Class-Num: 8 bits Identifies object class. C-Type: 8 bits Identifies object sub-type. 8. Security Considerations Upon receipt of an ICMP message, application software must check it for syntactic correctness. The extension checksum must be verified. Improperly specified length attributes and other syntax problems may result in buffer overruns. Bonica, et al. Expires December 10, 2006 [Page 15] Internet-Draft Multi-part ICMP Messages June 2006 This memo does not define the conditions under which a router sends an ICMP message. Therefore, it does not expose routers to any new denial of service attacks. Routers may need to limit the rate at which ICMP messages are sent. 9. IANA Considerations The ICMP Extension Object header contains two 8-bit fields: The Class-Num identifies the object class, and the C-Type identifies the class sub-type. Sub-type values are defined relative to a specific object class value, and are defined per-class. IANA should establish a registry of ICMP extension objects classes and class sub-types. There are no values assigned within this document to maintain. Object classes 0xF7 - 0xFF are reserved for private use. Object class values are assignable on a first-come- first-serve. The policy for assigning sub-type values should be defined in the document defining new class values. 10. Acknowledgments Thanks to Joe Touch for his comments regarding this draft. 11. References 11.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [2] Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, September 1981. [3] Mogul, J. and S. Deering, "Path MTU discovery", RFC 1191, November 1990. [4] Baker, F., "Requirements for IP Version 4 Routers", RFC 1812, June 1995. 11.2. Informative References [5] Atlas, A., "ICMP Extensions for Unnumbered Interfaces", draft-atlas-icmp-unnumbered-01 (work in progress), March 2006. [6] Mogul, J. and J. Postel, "Internet Standard Subnetting Bonica, et al. Expires December 10, 2006 [Page 16] Internet-Draft Multi-part ICMP Messages June 2006 Procedure", STD 5, RFC 950, August 1985. [7] Deering, S., "ICMP Router Discovery Messages", RFC 1256, September 1991. [8] Malkin, G., "Traceroute Using an IP Option", RFC 1393, January 1993. [9] Simpson, W., "ICMP Domain Name Messages", RFC 1788, April 1995. [10] Karn, P. and W. Simpson, "ICMP Security Failures Messages", RFC 2521, March 1999. [11] Kempf, J., "Instructions for Seamoby and Experimental Mobility Protocol IANA Allocations", RFC 4065, July 2005. Bonica, et al. Expires December 10, 2006 [Page 17] Internet-Draft Multi-part ICMP Messages June 2006 Authors' Addresses Ronald P. Bonica Juniper Networks 2251 Corporate Park Drive Herndon, VA 20171 US Email: rbonica@juniper.net Der-Hwa Gan Juniper Networks 1194 N. Mathilda Ave. Sunnyvale, CA 94089 US Email: dhg@juniper.net Pekka Nikander Ericsson Research Nomadic Lab JORVAS FIN-02420 Finland Email: pekka.nikander@nomadiclab.com Daniel C. Tappan Cisco Systems, Inc. 250 Apollo Drive Chelmsford, MA 01824 US Email: tappan@cisco.com Carlos Pignataro Cisco Systems, Inc. 7025 Kit Creek Road Research Triangle Park, N.C. 27709 US Email: cpignata@cisco.com Bonica, et al. Expires December 10, 2006 [Page 18] Internet-Draft Multi-part ICMP Messages June 2006 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2006). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Bonica, et al. Expires December 10, 2006 [Page 19]