nanog mailing list archives
RE: ? how cisco router handle the out-of-order ICMP echo-reply packets
From: Mikael Abrahamsson <swmike () swm pp se>
Date: Tue, 6 Jan 2009 14:26:44 +0100 (CET)
On Tue, 6 Jan 2009, Scott Morris wrote:
There aren't sequence numbers with ICMP. And the timeout value is watched/triggered before the next ICMP is sent, so there shouldn't really be any ordering problem/interpretation anyway.
Linux ping command does sequencing (so that part of your statement isn't accurate), and you can get out of order packets. It'll say a sequence number and ping time, and there really isn't any "timeout", an ICMP packet can come back 60 seconds later and it'll be counted, even though there were 59 other packets send and returned in the meantime.
$ ping localhost PING localhost (127.0.0.1) 56(84) bytes of data. 64 bytes from localhost (127.0.0.1): icmp_seq=1 ttl=64 time=0.023 ms 64 bytes from localhost (127.0.0.1): icmp_seq=2 ttl=64 time=0.020 msIn IOS, my interpretation anyway, is that the timeout value (2 seconds) mean that it really considers this packet as dropped, so no, in IOS you cannot get out of order packets, at least not that the CLI will show. If the ICMP response packet comes back after timeout value has triggered, it's considered lost.
-- Mikael Abrahamsson email: swmike () swm pp se
Current thread:
- ? how cisco router handle the out-of-order ICMP echo-reply packets Zhao Ping (Jan 06)
- Re: ? how cisco router handle the out-of-order ICMP echo-reply packets Tom Storey (Jan 06)
- RE: ? how cisco router handle the out-of-order ICMP echo-reply packets Scott Morris (Jan 06)
- RE: ? how cisco router handle the out-of-order ICMP echo-reply packets Mikael Abrahamsson (Jan 06)
- Re: ? how cisco router handle the out-of-order ICMP echo-reply packets Steve Bertrand (Jan 06)
- Re: ? how cisco router handle the out-of-order ICMP echo-reply packets Steve Bertrand (Jan 06)
- RE: ? how cisco router handle the out-of-order ICMP echo-reply packets Scott Morris (Jan 06)