X3S3.3/90-104 2 April, 1990 ACCREDITED STANDARDS COMMITTEE X3 - INFORMATION PROCESSING SYSTEMS Proposed Standards Development Project for EXTENSIONS TO THE INTERMEDIATE SYSTEM TO INTERMEDIATE SYSTEM ROUTING INFORMATION EXCHANGE PROTOCOL TO SUPPORT THE EXCHANGE OF ROUTING INFORMATION IN TCP/IP INTERNETS SECRETARIAT: Computer and Business Equipment Manufacturers Association (CBEMA) Page 2 1 IDENTIFICATION OF PROPOSED PROJECT 1.1 Title: EXTENSIONS TO THE INTERMEDIATE SYSTEM TO INTERMEDI- ATE SYSTEM ROUTING INFORMATION EXCHANGE PROTOCOL TO SUPPORT THE EXCHANGE OF ROUTING INFORMATION IN TCP/IP INTERNETS 1.2 Proposer: Task Group X3S3.3 (Network and Transport Layers) A. Lyman Chapin, Chairman Data General Corporation 4400 Computer Drive Westborough, MA 01580 (508) 870-6056 1.3 Date Submitted: 2 April, 1990 Page 3 2 JUSTIFICATION OF PROPOSED STANDARD 2.1 Needs The Basic Reference Model for Open Systems Interconnection (ISO 7498) specifies that the Network Layer is responsible for determin- ing and employing routes from one end system to another end system. This is generally referred to as "the routing function". Existing Network Layer protocols, such as ISO 8473, include routing func- tions that are performed by Network entities during the forwarding phase of the protocol to determine the address of the next Network entity to which a given Network protocol data unit should be sent. The functions defined by the protocols, however, assume that the information necessary to make routing decisions is accessible to the Network entity; they do not themselves define the way in which this information is collected or disseminated. This is entirely appropriate, since these Network Layer protocols are concerned with specific instances of communication between end system Network entities for the purpose of supporting the OSI Network Service; the collection and dissemination of routing information is a Network Layer management activity that is not directly related to any specific instance of communication between Network entities. Additional protocols are needed to support the exchange of routing information among Network entities. The work that has been done in ISO/IEC JTC 1/SC 6/WG2 on the requirements for Network Layer routing has led to agreement that the aspects of Network Layer routing that are concerned with communication between end systems and intermediate systems on the same subnetwork are separable from the aspects that are concerned with communication among the intermediate systems that connect multiple subnetworks. The existing X3 project 756 covers develop- ment of a protocol, called the "Intermediate System to Intermediate System Intra-Domain Routing Information Exchange Protocol", that is designed to allow intermediate systems to exchange routing informa- tion among themselves in support of global Network Layer routing. The IS-IS protocol that is the subject of project 756 provides for dissemination of the routing information that is needed by a specific internetwork protocol (ISO 8473). An intermediate system that implements ISO 8473 can use the project 756 IS-IS protocol to advertise and acquire the information about network routes that it needs to perform the ISO 8473 routing function. If the same intermediate system also implements another internetwork protocol, however, it is likely that the other protocol's routing function will require information that is not exchanged by the project 756 Page 4 IS-IS. The other protocol's requirements must therefore be satis- fied by either a completely separate protocol designed specifically for that purpose, or by extensions to the existing project 756 IS-IS protocol. The widespread market penetration and growing commercial importance of computer networks that are based on the "TCP/IP protocol suite" (the set of protocols that include the Transmission Control Protocol, or TCP, and the Internet Protocol, or IP) has made it very likely that real-world intermediate systems will often be required to perform routing functions for both the OSI Internetwork Protocol (ISO 8473) and the TCP/IP Internet Protocol. Extending the capabilities of an OSI intermediate system to include the ability to route TCP/IP Internet Protocol traffic as well as ISO 8473 traffic implies a corresponding extension to the capabilities of the IS-IS protocol that is responsible for the distribution of routing information. These extensions support the coexistence of OSI and TCP/IP protocols in a heterogeneous internet, without adding the overhead of an additional TCP/IP-specific routing protocol to the operation of an OSI intermediate system. 2.2 Recommended Scope of Standard The proposed project will specify extensions to the project 756 IS-IS protocol to accomodate the distribution of routing informa- tion that supports the operation of the TCP/IP Internet Protocol. The project 756 IS-IS protocol will support the ISO 8473 routing function with or without the extensions that are the subject of the proposed project; however, only with the extensions will the protocol be able to support the routing function of the TCP/IP Internet Protocol. The extended IS-IS is therefore intended for networks in which only ISO 8473 traffic, or a combination of ISO 8473 and TCP/IP traffic, is present. 2.3 Existing Practice in Area of Proposed Standard Several different protocols are currently used to support the intra-domain IS-IS routing function in networks that use only TCP/IP; none of these is applicable to an intermediate system that supports both OSI and TCP/IP traffic, for which there is no curren- tly accepted existing practice. Page 5 2.4 Expected Stability of Proposed Standard The stability of an extended IS-IS protocol is closely related to the persistence of network configurations in which both OSI and TCP/IP protocols are deployed. The extended protocol is expected to be very stable with respect to the architecture of such a multi-protocol network; it is not possible, however, to predict the stability of the multi-protocol network architecture. 3 DESCRIPTION OF PROPOSED PROJECT 3.1 Type of Document The proposed development project will produce an American National Standard for Extensions to the Intermediate System to Intermediate System Intra-Domain Routing Information Exchange Protocol. 3.2 Definitions of Concepts and Special Terms 3.3 Expected Relationship with Approved X3 Reference Models The proposed standard will extend the capabilities of a protocol that supports the routing functions associated with the Network layer of the Open Systems Interconnection Reference Model (ISO 7498) architecture. 3.4 Recommended Program of Work The program of work will consist of the preparation of a document that specifies the protocol extensions that are necessary to adapt the IS-IS standard to the support of TCP/IP-specific routing information. Page 6 3.5 Resources The resources of Task Group X3S3.3, Network and Transport Layers, are expected to be available to carry out the program of work. X3S3.3 has 26 voting members, representing a broad spectrum of users and suppliers of computer and communications equipment and services. The resources of the Internet Activities Board, which administers the internet standards that apply to the operation of the internet, and of the Internet Engineering Task Force, which is responsible for the technical specification of the TCP/IP protocols, are also expected to be available. 3.6 Recommended X3 Development Technical Committee It is recommended that the proposed project, if approved, be assigned to Task Group X3S3.3, Network and Transport Layers, of X3 Technical Committee X3S3, Data Communications. The proposed project is closely related, both technically and administratively, to projects 643 and 756, which have previously been assigned to X3S3.3. 3.7 Anticipated Frequency and Duration of Meetings If the proposed project is pursued by task group X3S3.3, as recom- mended above, it is anticipated that the equivalent of half a day during each of the task group's 6 five-day meetings each year will be devoted to work on the project. 3.8 Target Date for dpANS to X3 A draft proposal for an American National Standard for Extensions to the Intermediate System to Intermediate System Intra-Domain Routing Information Exchange Protocol could be conveyed to X3 by December 1, 1990. 3.9 Estimated Useful Life of Standard The useful life of the proposed standard coincides with the period of time during which protocols based on the set of internet stan- dards that comprise the "TCP/IP protocol suite" coexist, in multi-protocol networks, with protocols based on OSI standards. This lifetime is expected to be at least ten years. Page 7 4 IMPLEMENTATION IMPACTS 4.1 Impact on Existing User Practices and Investments 4.2 Impact on Supplier Products and Support 4.3 Techniques and Costs for Compliance Verification Verification of compliance with the proposed standard will take place in the context of verification of compliance with the IS-IS protocol being developed under X3 project 756. The additional cost associated with the extensions to IS-IS specified by this standard is expected to be a very small fraction of the total cost of IS-IS conformance testing. 4.4 Legal Considerations No special legal issues are raised by the proposed project, which covers material that is non-proprietary and freely distributed. 5 CLOSELY RELATED STANDARDS ACTIVITIES 5.1 Existing Standards No standards currently exist for the exchange of routing informa- tion that supports the operation of both ISO 8473 and the TCP/IP Internet Protocol. Several standards exist for the exchange of routing information that supports the operation of the TCP/IP Internet Protocol only. Page 8 5.2 X3 Standards Development Projects The proposed project is closely related to the work on the IS-IS protocol itself under X3 project 756, and to the work on the OSI Internetwork Protocol under X3 project 365. 5.3 X3/SPARC Study Groups The proposed project has no relationship to any existing X3/SPARC Study Group. 5.4 Other Related Domestic Standards Efforts The internet standards effort pursued by the Internet Engineering Task Force and its parent organization, the Internet Activities Board, is and will continue to be the source of technical input to the process of developing the American National Standard proposed here. 5.5 ISO Standards Development Projects There is no related ISO standards development project, and it is not anticipated that the proposed project will result in the initiation of any new work in ISO. 5.6 Other Related International Standards Development Projects As above. 5.7 Recommendations for Coordinating Liaison None. 5.8 Recommendations for Close Liaison Close liaison, in the form of joint development work and/or joint meetings, with the Internet Activities Board and the Internet Engineering Task Force (and/or its appropriate working groups) will Page 9 be essential.