Protocol Action: TCP Performance Implications of Network Asymmetry to BCP

[The IESG <[e-mail]>]

The IESG has approved the Internet-Draft 'TCP Performance Implications
of Network Asymmetry' <draft-ietf-pilc-asym-08.txt> as a BCP.  This
document is the product of the Performance Implications of Link
Characteristics Working Group. The IESG contact persons are Allison
Mankin and Scott Bradner.


Technical Summary

  This document describes TCP performance problems that may arise if 
  network paths have asymmetric characteristics. 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.
 
  This document details several mitigations of 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 when they should be used, and 
  recommendations of techniques that should not be used.

Working Group Summary
 
  The working group supported the advancement of the document.

 
Protocol Quality
 
  This document was reviewed for the IESG by Allison Mankin.