Internet R. Bonica Internet-Draft D. Gan Expires: March 20, 2006 Juniper Networks P. Nikander Ericsson Research Nomadic Lab D. Tappan Cisco Systems, Inc. September 16, 2005 Extending the Internet Control Message Protocol (ICMP) draft-bonica-internet-icmp-00 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 March 20, 2006. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This document defines a syntax that can be used to extend ICMPv4. The syntax is characterized by an extension structure that is appended to currently defined ICMP messages. The extension structure contains an extension header followed by one or more objects. Each Bonica, et al. Expires March 20, 2006 [Page 1] Internet-Draft Extending ICMP September 2005 object contains an object header and a payload. All object headers share a common format. Table of Contents 1. Conventions Used In This Document . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. The ICMP Extension Structure . . . . . . . . . . . . . . . . . 4 4. ICMP Extension Objects . . . . . . . . . . . . . . . . . . . . 5 5. ICMP Extensibility . . . . . . . . . . . . . . . . . . . . . . 5 5.1. Destination Unreachable . . . . . . . . . . . . . . . . . 8 5.2. Source Quench . . . . . . . . . . . . . . . . . . . . . . 8 5.3. Time Exceeded . . . . . . . . . . . . . . . . . . . . . . 9 5.4. Parameter Problem . . . . . . . . . . . . . . . . . . . . 10 6. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 10 6.1. Classic Application Receives ICMP Message With Extensions . . . . . . . . . . . . . . . . . . . . . . . . 12 6.2. Partially Compliant Application Receives ICMP Message With No Extensions . . . . . . . . . . . . . . . . . . . . 12 6.3. Partially Compliant Application Receives ICMP Message With Fully Compliant Extensions . . . . . . . . . . . . . 12 6.4. Fully Compliant Application Receives ICMP Message With No Extensions . . . . . . . . . . . . . . . . . . . . . . 13 6.5. Fully Compliant Application Receives ICMP Message With Partially Compliant Extensions . . . . . . . . . . . . . . 13 7. Security Considerations . . . . . . . . . . . . . . . . . . . 14 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 9.1. Normative References . . . . . . . . . . . . . . . . . . . 14 9.2. Informative References . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Intellectual Property and Copyright Statements . . . . . . . . . . 16 Bonica, et al. Expires March 20, 2006 [Page 2] Internet-Draft Extending ICMP September 2005 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 defines a syntax that can be used to extend ICMPv4 [2]. In this document, the term ICMP refers exclusively to ICMPv4. Unless explicitly noted, ICMPv6 is NOT discussed in this memo. The syntax defined in this document MUST NOT be used to extend ICMPv6. This syntax was designed to be backwards compatible with currently deployed, MPLS-aware ICMPv4 implementations. Consequently, the syntax is not as clean as would be desirable. For ICMPv6, where there are no similarly deployed implementations, a better format should be created. However, other than this note, ICMPv6 is beyond the scope if this memo. The syntax defined herein is characterized by an extension structure that is appended to currently defined ICMP messages. The extension structure contains an extension header followed by one or more objects. Each object contains an object header and a payload. All object headers share a common format. This document also addresses a fundamental problem in ICMP extensibility. Many ICMP messages, as currently defined, end with a variable-length field that lacks a length attribute. Application software infers the length of this final field from the total length of the ICMP message. If an extension structure were appended to these messages, without adding a length attribute for the variable- length field, application software would not be able to parse the ICMP message. Specifically, application software would not be able to determine where the variable-length field ends and where the extension structure begins. 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. However, the current memo does not define any ICMP extension objects. It defines only the extension header and a common header that all Bonica, et al. Expires March 20, 2006 [Page 3] Internet-Draft Extending ICMP September 2005 objects will share. 3. 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 by Section 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 unknown 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 1 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 1: 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 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. Bonica, et al. Expires March 20, 2006 [Page 4] Internet-Draft Extending ICMP September 2005 If the checksum field contains a value other than described above, the ICMP message does not include the extensions described in this memo. However, due to backwards compatibility, this does not imply that the ICMP message is malformed. See for Section 6 details. 4. 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 2 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 2: 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. 5. ICMP Extensibility RFC 792 defines the following ICMP message types: Bonica, et al. Expires March 20, 2006 [Page 5] Internet-Draft Extending ICMP September 2005 - Destination Unreachable - Time Exceeded - Parameter Problem - Source Quench - Redirect - Echo Request/Reply - Timestamp/Timestamp Reply - Information Request/Information Reply Subsequent RFCs define the following messages: - Address Mask Request/Reply [4] - Router Solicitation/Advertisement [5] - Traceroute [6] - Domain Name Request/Reply [7] - Security Failure [8] Most 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 Bonica, et al. Expires March 20, 2006 [Page 6] Internet-Draft Extending ICMP September 2005 - Echo Reply - Domain Name Reply These ICMP messages contain a 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 leading eight payload octets of the original datagram. RFC 1812 [3] extends this field to contain as many payload octets as possible, without exceeding a limit of 576 octets for the entire ICMP message. Unfortunately, the above mentioned 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 ICMP message, without adding a length attribute for the variable-length field, application software would not be able to parse the ICMP message. Specifically, application software would not be able to determine where the variable-length 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. It SHOULD be specified when the ICMP Extension Structure is not appended to the above mentioned ICMP messages. The length attribute represents the size of the associated variable- length field, measured in octets. Space for this field is claimed from reserved octets, whose value was previously required to be zero. When this length attribute is specified, its value MUST be a multiple of four. In order the achieve backwards compatibility, when the ICMP Extension Structure is appended to the Time Exceeded or Destination Unreachable messages, the variable length field MUST contain at least 128 octets. If the orignal datagram that the variable length field represents did not contain 128 octets, the variable length field MUST be zero padded. (See Section 6 for rationale.) Bonica, et al. Expires March 20, 2006 [Page 7] Internet-Draft Extending ICMP September 2005 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 described in this memo cannot be used in conjunction with the above mentioned ICMP messages. The following sub-sections depict length attribute as it has been introduced to selected ICMP messages. 5.1. Destination Unreachable Figure 3 depicts the 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 | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Internet Header + leading octets of original datagram | | | | // | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: Destination Unreachable The syntax and semantics of all fields are unchanged from RFC 792, except for a length attribute which is added to the end of the second word. When the ICMP Extension Structure is appended to this message, the "original datagram" field MUST contain at least 128 octets. 5.2. Source Quench Figure 4 depicts the Source Quench Message. Bonica, et al. Expires March 20, 2006 [Page 8] Internet-Draft Extending ICMP September 2005 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Internet Header + leading octets of original datagram | | | | // | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Source Quench The syntax and semantics of all fields are unchanged from RFC 792, except for a length attribute which is added to the end of the second word. 5.3. Time Exceeded Figure 5 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Internet Header + leading octets of original datagram | | | | // | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: Source Time Exceeded The syntax and semantics of all fields are unchanged from RFC 792, except for a length attribute which is added to the end of the second word. When the ICMP Extension Structure is appended to this message, the "original datagram" field MUST contain at least 128 octets. Bonica, et al. Expires March 20, 2006 [Page 9] Internet-Draft Extending ICMP September 2005 5.4. Parameter Problem Figure 6 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 | unused | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Internet Header + leading octets of original datagram | | | | // | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: Parameter Problem The syntax and semantics of all fields are unchanged from RFC 792, except for a length attribute which is added to the end of the second word. 6. Backwards Compatibility ICMP messages can be categorized as follows: - Messages that do not include any ICMP extensions - Messages that include partially compliant ICMP extensions - Messages that includes fully compliant ICMP extensions Any ICMP implementation can send a message that does not include extensions. ICMP implementations produced prior to 1999 never send ICMP extensions. Some ICMP implementations, produced between 1999 and the present, may send a partially compliant version of ICMP extensions described in this memo. Specifically, these implementations may append the ICMP 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 do not specify a length attribute to be associated with the "original datagram" field. Bonica, et al. Expires March 20, 2006 [Page 10] Internet-Draft Extending ICMP September 2005 It is assumed that ICMP implementations produced in the future will send ICMP extensions that are fully compliant with this specification. Likewise, applications that consume ICMP messages can be categorized as follows: - Classic applications - Partially compliant applications - Fully compliant applications Classic applications do not parse extensions defined in this memo. Partially compliant implementations parse the extensions defined in this memo, but only in conjuntion 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 that field. Partially compliant applications were produced between 1999 and the present. Fully compliant applications comply fully with the specifications of this document. In order to demonstrate backwards compatibility, Table 1 describes how members of each application catagory would parse each category of ICMP message. +-------------------+-------------+------------------+----------------+ | | No | Partially | Fully | | | Extentions | Compliant | Compliant | | | | Extensions | Extensions | +-------------------+-------------+------------------+----------------+ | Classic | | Section 6.1 | Section 6.1 | | Application | | | | | . | | | | | Partially | Section 6.2 | | Section 6.3 | | Compliant | | | | | Application | | | | | . | | | | | Fully Compliant | Section 6.4 | Section 6.5 | | | Application | | | | +-------------------+-------------+------------------+----------------+ Table 1 In the table above, cells that are left blank represent the nominal case and require no explanation. In the following sections, we Bonica, et al. Expires March 20, 2006 [Page 11] Internet-Draft Extending ICMP September 2005 assume that the ICMP message type is "Time Expired". 6.1. 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 begining 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. 6.2. Partially Compliant Application Receives ICMP Message With No Extensions When a partially 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 164 octets, the application can correctly determine that the message does not contain any extensions. The 164 octet sum is derived from 20 octets for an IP header, 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 message contains 164 octets or more, the application must examine the 157th 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. Partially compliant applications assume that the ICMP Extension Structure begins on the 157th octet of the Time Exceeded message, after a 128 octet field representing the "original datagram" message. 6.3. Partially Compliant Application Receives ICMP Message With Fully Compliant Extensions When a partially compliant application receives a message that contains fully compliant ICMP extensions, it will parse those extensions correctly only if the "original datagram" field contains exactly 128 octets. This is because partially compliant applications are insensative to the length attribute that is associated with the Bonica, et al. Expires March 20, 2006 [Page 12] Internet-Draft Extending ICMP September 2005 "original datagram" field. (They assume its value to be 128.) Therefore, fully compliant ICMP implementations SHOULD restrict the "original datagram" field to its minimum length, 128 octets, for the forseeable future, until partially compliant applications have been removed from service. 6.4. Fully Compliant Application Receives ICMP Message With No Extensions When a fully compliant application receives a message that contains no extensions, it first examines the length attribute that is associated with the "original datagram" field. If that length attribute is not specified, the application examines the total length of the ICMP message. If the total ICMP message length is less than 164 octets, the application can correctly determine that the message does not contain any extensions. The 164 octet sum is derived from 20 octets for an IP header, 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 message contains 164 octets or more, the application must examine the 157th 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. 6.5. Fully Compliant Application Receives ICMP Message With Partially Compliant Extensions When a fully compliant application receives a message that contains partially compliant extensions, it first examines the length attribute that is associated with the "original datagram" field. Because length attribute is not specified, it examines the total length of the ICMP message. Because the ICMP message contains 164 octets or more, the application must examine the 157th 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. Bonica, et al. Expires March 20, 2006 [Page 13] Internet-Draft Extending ICMP September 2005 7. Security Considerations Upon receipt of an ICMP message, application software must check it for syntactic correctness. Improperly specified length attributes and other syntax problems may result in buffer overruns. 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. 8. IANA Considerations IANA should establish a registry of ICMP extention classes and class- sub-types. 9. References 9.1. 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] Baker, F., "Requirements for IP Version 4 Routers", RFC 1812, June 1995. 9.2. Informative References [4] Mogul, J. and J. Postel, "Internet Standard Subnetting Procedure", STD 5, RFC 950, August 1985. [5] Deering, S., "ICMP Router Discovery Messages", RFC 1256, September 1991. [6] Malkin, G., "Traceroute Using an IP Option", RFC 1393, January 1993. [7] Simpson, W., "ICMP Domain Name Messages", RFC 1788, April 1995. [8] Karn, P. and W. Simpson, "ICMP Security Failures Messages", RFC 2521, March 1999. Bonica, et al. Expires March 20, 2006 [Page 14] Internet-Draft Extending ICMP September 2005 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 Bonica, et al. Expires March 20, 2006 [Page 15] Internet-Draft Extending ICMP September 2005 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 (2005). 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 March 20, 2006 [Page 16]