TCP and Explicit Congestion Notification

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TCP and Explicit Congestion Notification (1994)

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by Sally Floyd

Venue:	In: ACM Computer Communication Review, V. 24 N
Citations:	631 - 13 self

BibTeX

@ARTICLE{Floyd94tcpand,
    author = {Sally Floyd},
    title = {TCP and Explicit Congestion Notification},
    journal = {In: ACM Computer Communication Review, V. 24 N},
    year = {1994},
    pages = {10--23}
}

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Abstract

This paper discusses the use of Explicit Congestion Notification (ECN) mechanisms in the TCP/IP protocol. The first part proposes new guidelines for TCP’s response to ECN mechanisms (e.g., Source Quench packets, ECN fields in packet headers). Next, using simulations, we explore the benefits and drawbacks of ECN in TCP/IP networks. Our simulations use RED gateways modified to set an ECN bit in the IP packet header as an indication of congestion, with Reno-style TCP modified to respond to ECN as well as to packet drops as indications of congestion. The simulations show that one advantage of ECN mechanisms is in avoiding unnecessary packet drops, and therefore avoiding unnecessary delay for packets from low-bandwidth delay-sensitive TCP connections. A second advantage of ECN mechanisms is in networks (generally LANs) where the effectiveness of TCP retransmit timers is limited by the coarse granularity of the TCP clock. The paper also discusses some implementation issues concerning specific ECN mechanisms in TCP/IP networks.

Keyphrases

explicit congestion notification ecn mechanism tcp ip network first part reno-style tcp tcp response red gateway tcp retransmit timer tcp clock ip packet header implementation issue unnecessary delay specific ecn mechanism new guideline low-bandwidth delay-sensitive tcp connection tcp ip protocol ecn bit packet header second advantage coarse granularity unnecessary packet drop ecn field source quench packet

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