RFC 1185 (rfc1185) - Page 1 of 21

TCP Extension for High-Speed Paths

Network Working Group                                        V. Jacobson
Request for Comments: 1185                                           LBL
                                                               R. Braden
                                                                     ISI
                                                                L. Zhang
                                                                    PARC
                                                            October 1990


                   TCP Extension for High-Speed Paths

Status of This Memo

   This memo describes an Experimental Protocol extension to TCP for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "IAB
   Official Protocol Standards" for the standardization state and status
   of this protocol.  Distribution of this memo is unlimited.

Summary

   This memo describes a small extension to TCP to support reliable
   operation over very high-speed paths, using sender timestamps
   transmitted using the TCP Echo option proposed in RFC-1072.

1. INTRODUCTION

   TCP uses positive acknowledgments and retransmissions to provide
   reliable end-to-end delivery over a full-duplex virtual circuit
   called a connection [Postel81].  A connection is defined by its two
   end points; each end point is a "socket", i.e., a (host,port) pair.
   To protect against data corruption, TCP uses an end-to-end checksum.
   Duplication and reordering are handled using a fine-grained sequence
   number space, with each octet receiving a distinct sequence number.

   The TCP protocol [Postel81] was designed to operate reliably over
   almost any transmission medium regardless of transmission rate,
   delay, corruption, duplication, or reordering of segments.  In
   practice, proper TCP implementations have demonstrated remarkable
   robustness in adapting to a wide range of network characteristics.
   For example, TCP implementations currently adapt to transfer rates in
   the range of 100 bps to 10**7 bps and round-trip delays in the range
   1 ms to 100 seconds.

   However, the introduction of fiber optics is resulting in ever-higher
   transmission speeds, and the fastest paths are moving out of the
   domain for which TCP was originally engineered.  This memo and RFC-
   1072 [Jacobson88] propose modest extensions to TCP to extend the



Jacobson, Braden & Zhang