>>>>> On Mon, 22 Apr 2002 18:08:47 -0400, "Hassan, Shehzad" <shehzad.hassan@bell.ca> said:
> I agree with you that the box shud retain its TOS/DSCP value but I
> dont think Cisco 6509 retains the TOS value with QoS turned Off, I
> chatted with a couple of freinds and thye have experienced same, but
> need some documented proof.
A couple of weeks ago I have modified traceroute such that it prints
the TOS byte of the probe packets when it is changed along the path, e.g.
$ traceroute -t 64 www.surfnet.nl
traceroute to info2.surfnet.nl (192.87.5.150), 30 hops max, 40 byte packets
1 swiCS4-G3-13.switch.ch (195.176.255.53) 0 ms 0 ms 0 ms
2 swiCS3-G3-1.switch.ch (130.59.36.13) 0 ms 0 ms 0 ms
3 swiEZ2-G3-3.switch.ch (130.59.36.18) 0 ms 0 ms 0 ms
4 swiCE2-G2-2.switch.ch (130.59.36.41) 5 ms 5 ms 5 ms
5 switch.ch1.ch.geant.net (62.40.103.17) 5 ms 5 ms 5 ms
6 ch.fr1.fr.geant.net (62.40.96.30) 14 ms (TOS=0!) 14 ms 14 ms
7 fr.be1.be.geant.net (62.40.96.17) 25 ms 25 ms 25 ms
8 [...]
The (TOS=0!) indicates that the TOS byte has been rewritten from 64
(DSCP=16 or PREC=2) to 0 by the router switch.ch1.ch.geant.net - this
shows up at the next hop because the rewriting happens on egress.
My modification is included in the latest "NANOG traceroute" (6.1.4):
ftp://ftp.login.com/pub/software/traceroute/beta/traceroute.c
Hope this helps,
-- Simon Leinen simon@babar.switch.ch SWITCH http://www.switch.ch/misc/leinen/Computers hate being anthropomorphized.
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