Draft Report on the WORKSHOP ON CO/CL INTERWORKING Corporation for National Research Initiatives July 24-26, 1990 Reported by Workshop Co-chairs Phillip Gross (CNRI) and Les Clyne (JNT) 1. Introduction On July 24-26, 1990, an invited panel met at the Corporation for National Research Initiatives in Reston Virginia to consider the issues involved with interworking between protocol stacks based on Connection-mode Network Service (CONS, or CO) and Connectionless-mode Network Service (CLNS, or CL). The main example of a CO stack is OSI TP0 over X.25. Examples of CL protocol stacks include OSI TP4 over CLNP and TCP over IP. The workshop was convened at the direction of RARE and the U.S. Federal Networking Council (FNC). The meeting was organized and co-chaired by Les Clyne (UK Joint Network Team) and Phillip Gross (Corporation for National Research Initiatives). An electronic mailing list was established for use by both attendees and a wider audience of experts. This report gives an overview and synopsis of the deliberations at the meeting, and it describes the outcome. The major result of the workshop is given next in section 2, followed by a brief synopsis of the workshop deliberations in section 3. Finally, the milestones for concluding the papers and reporting the results are given in section 4. Attachment 1 provides the Terms of Reference for the meeting, agreed to beforehand by RARE and the FNC. Attachment 2 gives the working agenda, which provided the framework of the workshop. Attachment 3 lists the attendees. Attachment 4 gives an annotated list of documents distributed to attendees prior to the workshop. 2. Workshop Conclusions The workshop attendees decided to address the issues of CO/CL interworking in a series of 4 documents, the first of which would serve as an introduction and tutorial. The following description of the approach and the 4 document set is taken from the first document ``An Approach to CO/CL Interworking -- Part I: Introduction'', M.T. Rose (editor): ``Towards a Solution In the best solution, there is a single mode of OSI network service which is truly ubiquitous. In this case, a single community exists and interworking is achieved through the use of network-layer relays. In preparation for this long-term scenario, technology must be identified and perhaps incrementally advanced to promote a homogeneous network service. In the meantime, a large TCP/IP-based community exists and a TP0/CONS community is growing. Some interworking requirements exist today and these requirements are expected to increase. This suggests a short-term solution to address immediate requirements, an intermediate-term solution applicable as the TP0/CONS community grows large, and a long- term solution applicable once two large OSI communities, one CO-mode and the other CL-mode, exist and have interworking requirements. Thus, an approach towards the solution consists of three parts, and three companion memos have been been written, each corresponding to the short-term, intermediate-term, and long- term: In the short-term, one must rely on TS-bridges to provide connectivity between non-internetworking communities. The first companion memo, (see [a] below) describes the operation of TS-bridges in such an environment. The fundamental component of the long-term is the use of network-layer relays, supporting either the CO- or CL-mode OSI network service. Use of network-layer relays is well- understood. The second companion memo, (see [b] below), describes how steps can be taken to provide full CONS-interworking. However, even in the long-term, situations will arise in which both network services are required. In this case, TS-bridges are still necessary. The third companion memo, (see [c] below), describes the operation of TS-bridges in such an environment.'' [a] M.T. Rose (editor). An Approach to CO/CL Interworking -- Part II: The Short-Term -- Conventions for Transport- Service Bridges in the absence of Internetworking, CO/CL Interworking Workshop, (July, 1990). [b] C. Huitema (editor). An Approach to CO/CL Interworking -- Part III: The Intermediate-Term -- Provision of the CONS over TCP and X.25 subnetworks, CO/CL Interworking Workshop, (to be published). [c] C. Huitema (editor). An Approach to CO/CL Interworking: -- Part IV: The Long-Term -- Conventions for Network- Layer Relays and Transport-Service Bridges in the presence of Internetworking, CO/CL Interworking Workshop, (to be published). 3. Synopsis of Workshop Deliberations This synopsis follows the final agenda (given in Attachment 2). 3.1 TUESDAY, JULY 24, 1990 INTRODUCTIONS --- Bill Bostwick (Executive Director of the FNC) opened the meeting with greetings to the attendees,and a discussion of the spirit of cooperation between U.S. and European networking interests. Following the opening round of introductions, the attendees examined and agreed on the Terms of Reference and agenda with only minor adjustments. PRESENTATIONS --- Note: Hardcopy of all slides and handouts were provided to attendees, and can be provided by Phill Gross (CNRI) upon request. --- Kevin Mills (NIST) Kevin Mills described the two main OSI protocol stacks (i.e., CO and CL). He also described the current UK and US OSI profiles (ie, GOSIPs) for utilizing OSI in each respective government; His proposal involves dual stack machines on wide-area networks; He suggests that his proposal may look more attractive after we've gone through all the issues involved in transport service bridging; He also showed the DoD approach to interworking (pure stacks with application layer bridging). --- Les Clyne (JNT) Les Clyne described RARE, Eureka, and COSINE. Briefly, RARE is the association of European research networking organizations and their users, with over 20 member countries in Europe; Eureka formed COSINE (Cooperation for OSI networking in Europe); RARE developed the COSINE specifications). He showed slides of COSINE implementation funding and timetable for pilot projects and services. He also showed IXI service access topology and status. (IXI provides 1984 X.25 services.) --- Marshall Rose (PSI) Marshall Rose described the transport layer and the CO/CL problem. He defined the Transport-Service Bridge as a solution, which uses transport service primitives to ``copy'' from TS-stack to TS-stack. He gave a good synopsis of problems with TS-bridging (see his slides), and concluded by explaining terminolgy of ISO DTR "Active transport layer relay" vs "Passive transport layer relay"). --- Mitchell Tasman (University of Wisconsin) Mitchell Tasman's presentation was based on the distibuted Wisconsin paper (see Attachment 4) which described the Wisconsin implementation of a transport-service bridge. --- Christian Huitema (INRIA) Christian Huitema was concerned with the problem of ``locating''the TS-bridge. In current implementations, the originating host is required to know which destination addresses need to be reached via a TS-bridge, and the originating host also needs to know the address of the TS-bridge. He proposed treating transport-service bridge as network level gateway, and let IS/IS help solve the problem of locating the bridge. This removes the knowledge and functionality from the end system allows reliance on the networking and routing infrastructure to solve for you. This would not be a ``near-term'' solution, but it was viewed favorably by many attendees as a "longer-term" approach for alleviating the necessity of the originating host to know the TS-bridge address. He described various methods to cope with multiple parallel bridges/relays, including NSAP gateway subscription and modification of TP4. He also described enhancements to RFC 1006 based on the X.25 Subnetwork Convergence Protocol to make TCP look like a special case of ISO CONS. The associated routing involved using ISO 10030 (CONS ES Routeing Exchange Protocol). DEVELOP LIST OF ISSUES --- Les Clyne led a discussion of issues that needed to be solved. This included both implementation and deployment issues, and short- and long- term issues. The issues included: - Determination of TS-stack associated with a network address - Ordering of addresses - TS-bridge addressing - Accounting - Access control - Load balancing - Concatenation of IFUs - Availability of address extension facilities (X.25(84)) - Routeing to the gateway - Directory service and location independence - Address administration at the gateway - Modifications to the transport protocol/use of TP user data - Extensions to RFC 1006 to support OSI NS - Coordination of 8473 PDU Data Unit identifiers and Transport Reference number allocation - Alignment with DTR 10172 - Impact on end system implementations The requirement to be able to map between the RFC 1006 environment and TP0/CONS, where addresses on the CONS side are carried in the X.25(84) address extension fields, if available, was raised. 3.2 WEDNESDAY, JULY 25, 1990 Rose distributed a proposal for separating the TS-bridging problem into a short and long term approach. This proposal was modified in discussion to encompass a 3 step plan. In the short term approach, we would specify a method for encoding TS-bridge addressing in the NSAP. In the long-term, we would focus on Huitema's aproach of relying on the network layer to locate TS-bridges. Huitema's other proposal for enhancements to RFC 1006 would also be included as part of the transitional framework to the long-term solution. Other issues, such as security and end-to-end integrity were deemed beyond the scope of the workshop. The group decided to use Rose's draft ``Implementation Agreements for Transport Service Bridges'' (see Attachment 4), as the basis for an introduction to the workshop conclusions. In effect, Rose's paper was reworked into 2 documents. one document would contain a transport service bridge tutorial (which would also be applicable for reference in the long-term approach) and an explanation of the overall plan. The specific addressing methodology for the short-term approach would be placed into a second 2-4 page paper. Including two other papers to describe 1) the long-term approach, and 2) the proposed transitional modifications to RFC 1006, the group proposed a four document set: Doc #1 - I) TS-Bridge Tutorial and relation to ISO II) Explanation of Strategies for CO/CL Interworking - short-term solution (TS-Bridge Addressing) - Transitional modifications to RFC 1006 - long-term Doc #2 - Short-term specification Doc #3 - Transitional Modifications to RFC 1006 Doc #4 - Long-term Specification a. Subnet Gateway b. Internet Gateway Rose reworked his draft into documents #1 and #2 for review the following morning. Huitema volunteered to draft document #3 at the meeting for review on the following morning. The group agreed on a framework for document #4, and Rose produced an outline for the following morning. 3.3 THURSDAY, JULY 26, 1990 On the concluding morning, the group reviewed Documents #1 and #2 by Rose, and document #3 by Huitema. Huitema agreed to produced document #4 after returning to France. After review and editing by the attendees, Rose produced preliminary drafts of document #1 and #2, and distributed these documents to the Workshop mailing list for review. Finally, we developed the plan for reporting the workshop results to CCIRN, RARE, FNC, and IAB/IETF. These proposed milestones are given in the next section. 4. Workshop Milestones Documents and workshop report July 1990 Produce drafts of Documents 1 and 2; mail to COCL electronic mailing list for wider review (DONE) Aug 1990 Produce preliminary workshop report for RARE and FNC, Distribute initially to workshop attendees (DONE) Aug 1990 Produce drafts of Documents 3 and 4 and distibute for review (DONE) RARE/FNC Review Sept 1990 Present workshop report to RARE CoA and FNC Sept 1990 Present workshop results (report and other appropriate documents) for review at RARE WG4 Oct 1990 Present workshop results (report and other appropriate documents) for review at CCIRN Dec 1990 Present workshop results for approval at RARE CoA and FNC IETF/IAB Review Sept 1990 Present workshop results (report and other appropriate documents) to IETF OSI Integration working group for review Sept 1990 Distribute Documents 1-4 as IETF Internet-Drafts Dec 1990 Documents 1-4 reviewed in IETF, recommendation forwarded to IAB Jan 1991 IAB considers Documents 1-4 to be published as Internet RFCs Attachment 1 -- Workshop Terms of Reference Terms of Reference for Workshop on CO/CL Interworking July 24-26, 1990 The use of different OSI lower layer architectures will act as an impediment to the development of global OSI connectivity if it is not possible to interwork between them. This problem is particularly significant for interworking between the US and European research communities. Several solutions have been proposed to provide interworking and there is a need to agree a specification which meets the service requirements of the international research community. The CO/CL Workshop has been set up to recommend a specification that can be used to provide suitable interworking units. The workshop a) is asked to develop a technical specification for a general purpose TP0/CONS-TP4/CLNS interworking unit, taking into account existing or proposed solutions. The requirement to interconnect large national or international service networks is particularly important. b) should take into account the ISO work in this area and the recommended specification should align with the emerging ISO technical report wherever possible. c) is also requested to advise on the technical specification of a convertor which supports TP0/X.25-TP0/TCP interworking as there is an immediate requirement in this area to support OSI applications. The participants in the workshop will be invited experts from the US and Europe. It is expected that the workshop will hold one meeting complemented by the use of electronic mail to support its activities. The workshop is requested to report to RARE and FNC in autumn 1990. Attachment 2 -- Workshop Agenda Agenda and Issues for Workshop on CO/CL Interworking July 24-26, 1990 o Introductions and Administration - Introduction by Bill Bostwick (CCIRN Co-Chair, FNC Executive Director) - Agreement on chairing and secretarial duties - Review Terms of Reference - Agreement on agenda and objectives. o Presentations: - Kevin Mills (NIST) -- US OSI activity - Les Clyne (JANET) -- RARE/COSINE OSI activity. - Marshall Rose (PSI) -- Transport service bridging. - Mitch Tasman (U. of Wiscosin) -- ISO TP4 - TP0 gateway. - Christian Huitema (INRIA) -- NSAPs and transparent OSI transport bridges. - Others Issues or Approaches? o Determine what protocol stacks need to interwork and what priority the workshop should place on developing solutions for each scenario. - Issues -- Is it mainly connection between large CO and CL WAN communities with one or a small number of interworking units in the same geographic location, or do we deal with WAN-WAN connections in different countries, LAN-WAN-WAN-LAN connections with multiple serial interworking units and alternative routes etc. The complexity has an impact on problems of routeing and address management. On what timescales are the various interworking units needed ? o Develop detailed description of candidate solutions (e.g., Transport bridging, ISO Active Transport Level Relay, etc) for each combination of protocol stacks that need to interwork. Issues to consider include: - Impact on end systems of proposed solutions. - Address management. - Routeing considerations. - Agreement on further work, assignment of responsibilities, timescales, etc. o Reporting to RARE/FNC. Attachment 3 -- Workshop Attendees Workshop on CO/CL Interworking at Corporation for National Research Initiatives July 24-26, 1990 Name Organization Email William Bostwick Federal Net. Council bostwick@darpa.mil Les Clyne Joint Network Team L.Clyne@RUTHERFORD.AC.UK Walid Dabbous INRIA walid.dabbous@MIRSA.INRIA.FR Steve Goldstein Nat. Science Foundation goldstein@note.nsf.gov Phill Gross Corp. Nat'l Res. Init. pgross@nri.reston.va.us Christian Huitema INRIA Christian.Huitema@MIRSA.INRIA.FR Steve Kille Univ. College London S.Kille@CS.UCL.AC.UK Kevin Mills NIST mills@osi.ncsl.nist.gov Julian Onions Nottingham University J.Onions@cs.nott.ac.uk Marshall Rose Perf. Sys. International mrose@psi.com Rachid Sijelmassi NIST sijel@osi.ncsl.nist.gov Mitchell Tasman Univ. of WI - Madison tasman@cs.wisc.edu Full postal mailing addresses and phone numbers of each attendee are available on request from CNRI: Corporation For National Research Initiative 1895 Preston White Drive, Suite 100 Reston Virginia 22132 Attn: Phill Gross Phone: 703-620-8990 FAX: 703-620-5490 Attachment 4 -- Distributed Documents There were several documents and position papers distributed to attendees that provided a beginning point of view for the workshop. Many of these documents were authored by workshop attendees. An annotation of each distributed paper is provided below (based on the description given in ``An Approach to CO/CL Interworking -- Part I: Introduction''. These documents can be provided on request by either of the workshop co-chairs. - In "Implementation Agreements for Transport Service Bridges", Rose outlined the basic model of transport-layer relaying and proposed the basis for an approach in the short-term. This formed the basis for the first document of the workshop ``An Approach to CO/CL Interworking -- Part 1: Introduction''. - In "A Survey of Solutions to the Connectionless/Connection- mode and the OSI/DoD Interworking Problems", West and Sijelmassi outlined the various approaches and assigned comparative metrics. - The ISO/IEC Draft Technical Report 10172 (SC 6 N 5906) outlined a framework for transport-layer relaying. - In "An ISO TP4-TP0 Gateway", Landweber and Tasman described an implementation of a TS-bridge. - In "An NSAP approach to build transport OSI transport bridges, Huitema and Dabbous described how ES-transparency can be achieved, and in "Extension of OSI TP4 to support transport bridging", they described modifications to the TP4 protocol to aid in achieving the ES-transparency effect. - In "CO-CL and TCP/IP Interworking and Coexistence", Mills suggested that the problem can be solved by using a single mode of network service (CLNS), and further that interoperability with TCP/IP-based environments would occur through the use of application gateways. Copies of these documents are available upon request from CNRI: Corporation For National Research Initiative 1895 Preston White Drive, Suite 100 Reston Virginia 22132 Attn: Phill Gross Phone: 703-620-8990 FAX: 703-620-5490