From: "Xiaoliang \(David\) Wei" <weixl@caltech.edu>
To: <netdev@oss.sgi.com>
Subject: A question on RTT estimation of SACKed packet.
Date: Thu, 29 Aug 2002 03:17:24 -0700 [thread overview]
Message-ID: <037601c24f45$4549fe10$f1fa010a@weixl> (raw)
In-Reply-To: 20020828074112.A13868@nero.doit.wisc.edu
Hi Everyone,
I am studying the Linux 2.4.19 TCP code. I have a question on the RTT
estimation.
In the function tcp_clean_rtx_queue (tcp_input.c), all the packet before
snd_una is checked:
1. When a packet was not SACKed before, we can calculate the seq_rtt
from its skb's timestamp (now - scb->when).
2. When a packet was SACKed but not retransmitted, the linux also
calculate the seq_rtt from it when there is no unSACKed packet in the queue.
I cannot understand the second situation: The packet was SACKed before,
that means it arrived the receiver and triggered a SACK sometime before. The
interval between when packet is sent and when the SACK is received should be
the RTT for experienced this packet. Even now the packet is ACKed, I don't
think this ACK is triggered by this packet. Why is it used to calculate the
RTT?
Thanks.
-David
Xiaoliang (David) Wei Graduate Student in CS@Caltech
http://www.cs.caltech.edu/~weixl
====================================================
next prev parent reply other threads:[~2002-08-29 10:17 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-06-24 11:39 IP stack question Bloch, Jack
2002-06-24 13:34 ` jamal
2002-06-24 17:48 ` Ben Greear
2002-06-24 18:59 ` jamal
2002-06-24 19:27 ` Ben Greear
2002-08-28 6:25 ` IP stack question (how to force pkts to not route locally, but go out interfaces regardless of destination) Ben Greear
2002-08-28 12:41 ` James R. Leu
2002-08-29 10:17 ` Xiaoliang (David) Wei [this message]
2002-08-29 19:01 ` A question on RTT estimation of SACKed packet kuznet
2002-08-29 22:19 ` Xiaoliang (David) Wei
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to='037601c24f45$4549fe10$f1fa010a@weixl' \
--to=weixl@caltech.edu \
--cc=netdev@oss.sgi.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.