Abstract
This document describes TCP performance problems that arise because
of asymmetric effects. These problems arise in several access
networks, including bandwidth-asymmetric networks and packet radio
subnetworks, for different underlying reasons. However, the end
result on TCP performance is the same in both cases: performance
often degrades significantly because of imperfection and variability
in the ACK feedback from the receiver to the sender.
The document details several mitigations to these effects, which have
either been proposed or evaluated in the literature, or are currently
deployed in networks. These solutions use a combination of local
link-layer techniques, subnetwork, and end-to-end mechanisms,
consisting of: (i) techniques to manage the channel used for the
upstream bottleneck link carrying the ACKs, typically using header
compression or reducing the frequency of TCP ACKs, (ii) techniques to
handle this reduced ACK frequency to retain the TCP sender's
acknowledgment-triggered self-clocking and (iii) techniques to
schedule the data and ACK packets in the reverse direction to improve
performance in the presence of two-way traffic. Each technique is
described, together with known issues, and recommendations for use.
A summary of the recommendations is provided at the end of the
document.
of asymmetric effects. These problems arise in several access
networks, including bandwidth-asymmetric networks and packet radio
subnetworks, for different underlying reasons. However, the end
result on TCP performance is the same in both cases: performance
often degrades significantly because of imperfection and variability
in the ACK feedback from the receiver to the sender.
The document details several mitigations to these effects, which have
either been proposed or evaluated in the literature, or are currently
deployed in networks. These solutions use a combination of local
link-layer techniques, subnetwork, and end-to-end mechanisms,
consisting of: (i) techniques to manage the channel used for the
upstream bottleneck link carrying the ACKs, typically using header
compression or reducing the frequency of TCP ACKs, (ii) techniques to
handle this reduced ACK frequency to retain the TCP sender's
acknowledgment-triggered self-clocking and (iii) techniques to
schedule the data and ACK packets in the reverse direction to improve
performance in the presence of two-way traffic. Each technique is
described, together with known issues, and recommendations for use.
A summary of the recommendations is provided at the end of the
document.
Original language | English |
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Volume | RFC 3449 (BCP 69) |
Specialist publication | Internet Society |
Publication status | Published - Dec 2002 |