Skip to Main Content
Internet Core Protocols: The Definitive Guide
book

Internet Core Protocols: The Definitive Guide

by Eric Hall
February 2000
Intermediate to advanced content levelIntermediate to advanced
464 pages
15h 57m
English
O'Reilly Media, Inc.
Content preview from Internet Core Protocols: The Definitive Guide

Excessive or Slow Retransmissions

One of the most important aspects of TCP’s reliability service is the use of acknowledgment timers (also called retransmission timers), which ensure that lost segments get recognized as such in a timely manner, resulting in the quick retransmission of that data. However, as was pointed out earlier in Section 7.1.7.4, accurately determining the correct timer values to use on any given virtual circuit is a complex process. If the value is set too low, then the timer will expire too frequently, resulting in unnecessary retransmissions. Conversely, if the value is set too high, then loss may not be detected quickly, resulting in unnecessary delays.

On some systems, you may notice that there are a high number of excessive retransmissions on new circuits (indicating that the default timer is set too low for those virtual circuits), or you may see very long gaps in between retransmissions (indicating that the default acknowledgment timer is set too high). Although these values are typically changed on a per-circuit basis as the smoothed round-trip time is calculated, the default settings can be problematic on new connections, where the smoothing has yet to begin in earnest.

For example, if the default acknowledgment timer is set to 3000 milliseconds, then the system may not detect a lost segment until three full seconds after the segment was sent. This would obviously cause problems with applications that only send one or two segments at a time (such as ...

Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Start your free trial

You might also like

Packet Guide to Core Network Protocols

Packet Guide to Core Network Protocols

Bruce Hartpence
Ethernet: The Definitive Guide, 2nd Edition

Ethernet: The Definitive Guide, 2nd Edition

Charles E. Spurgeon, Joann Zimmerman

Publisher Resources

ISBN: 1565925726Supplemental ContentErrata Page