Reliable host-to-host protocols: Problems and techniques

ABSTRACT

Host-to-host protocols capable of supporting internetworking and reliable transmission have been under development for several years. This paper discusses problems and techniques related to one type of reliable protocol, which features end-to-end positive acknowledgement, retransmission, internetwork addressing capabilities, and ordered delivery. The issues of interest are protocol correctness and completeness, protocol efficiency, and complexity of implementation. These will be discussed in a framework of three problem areas, flow control, sequence number space management, and reliable transmission of controls. Flow control heuristics using windowing techniques are explored. Flow control information is augmented to allow fair apportionment of bandwidth, better bandwidth utilization through optimistic credits, flow control credits matched to the type of traffic, and increased performance for high precedence connections. Alternatives for selecting the startup sequence number for a connection are presented. Techniques and problems of several sequence number space management strategies are presented. These include delayed startup, incarnation numbers, and resynchronization. The transmission of controls are discussed, with emphasis on whether or not to share a logical transmission channel between controls and data. The effect of data flow control on the delivery of out-of-band signals is an important consideration. The findings are presented both to further the understanding of and to encourage intelligent implementations of reliable protocols.

REFERENCES

• 1: Cerf, V. and R. Kahn, "A Protocol for Packet Network Intercommunication," IEEE Transactions on Communication, Vol COM-20, No. 5, May 1974.
• 2: Cerf, V., Y. Dalal, C. Sunshine, "Specification of Internet Transmission Control Program," INWG General Note #72, December 1974 (Revised).
• 3: Sunshine, C., "Interprocess Communication Protocols for Computer Networks," Digital Systems Laboratory Technical Note #105, December 1975.
• 4: Tomlinson, R., "Selecting Sequence Numbers," INWG Protocol Note #2, September 1974.
• 5: Dalal, Y., "More on Selecting Sequence Numbers," INWG Protocol Note #4, October 1974.
• 6: Postel, J., L. Garlick, R. Rom, "Transmission Control Protocol Specification (AUTODIN II)," SRI-ARC Catalog 35938 & 35939, July 1976.
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INDEX TERMS

Primary Classification:
  C. Computer Systems Organization
  C.2 COMPUTER-COMMUNICATION NETWORKS
      C.2.6 Internetworking

Additional Classification:
  C. Computer Systems Organization
  C.2 COMPUTER-COMMUNICATION NETWORKS
      C.2.6 Internetworking
          Subjects: Standards (e.g., TCP/IP)
  C.4 PERFORMANCE OF SYSTEMS
      Subjects: Reliability, availability, and serviceability

General Terms:
Performance, Reliability, Standardization