Acceptable DSL Speeds (ms based)
Joe Maimon
jmaimon at ttec.com
Wed May 4 17:44:59 UTC 2005
Joel Jaeggli wrote:
>
> On Wed, 4 May 2005, Luke Parrish wrote:
>
>>
>> Andrew, traceroute is an effective tool is measuring roundtrip in ms
>> format.
>
>
> packets sent to a router are typically processed differently and with
> different priority then packets forwarded through it. This makes
> traceroute fairly unreliable.
>
Since it is probably a fair assumption that routers will never procces
forwarding packets slower than ICMP replies, the following applies.
The router receiving the traceroute response from its upstream would
process that in its forwarding path. So if you see a 30ms hit on hop A
and a 60 ms hit on hop B you can pretty much determine that hop A is
30ms away but you cant be quite sure about hop B until you see hop C's
replies.
To make this more interesting, its always possible that hop B or C's
path to you is different than your path to hop B or C.
Also, traceroute is effective at showing that the path rtt is good. Its
just when you are trying to find where the latency is that things can
get dicey.
More information about the NANOG
mailing list