Ethereal-users: Re: [Ethereal-users] full duplex clarification and performance consideration
Yes, capturing a 155MB ATM link will require two cards capturing 155Mbit/s
each, one for
each direction, for a total of 310Mbit/s. ATM is always full duplex, both
pure-ATM as well as ATM over SDH/SoNET.
This is only if you use pure-ATM though.
I dont know whether pure-ATM is very common today or if what you want to
capture today is really
just ATM ocer STM-1.
Though a normal STM-1 link is 155Mbit/s, a lot of bandwidth is lost to
regenerator, multiplexor and vc-4 layer which leaves only
126Mbit in each direction for ATM traffic.
It would still need two cards to capture the data in both directions
since both pure-ATM as well as ATM over SDH (or SoNET depending on your
location)
are both full duplex always.
It would only mean that the available throughput would be slightly less and
the line interfaces would be
alot more expensive.
----- Original Message -----
From: "Enoch Root"
Sent: Thursday, May 01, 2003 10:27 PM
Subject: [Ethereal-users] full duplex clarification and performance
consideration
> Hi there;
>
> While searching archives for performance advices I
> came accross a mail authored by Ronnie Sahlberg
> (http://marc.theaimsgroup.com/?l=ethereal-users&m=104681304109441&w=2)
> in which he points out that to capture traffic on a
> 100baseT full-duplex link one should use two cards for
> capturing each direction of the flow. Andreas Sikkema
> asked
> (http://marc.theaimsgroup.com/?l=ethereal-users&m=104685253408455&w=2)
> how does one configure an interface to capture traffic
> only in one direction but I couldn't find the answer
> in the archives. Could someone answer this question?
>
> I'm planning to build a sniffer for a 155Mbit/s ATM
> link, assuming a fully saturated link, does that mean
> 310Mbit/s full-duplex traffic, hence, roughly 40MB/s
> disk write?
>
> I'd be thankful if people with similar experiences
> could share their findings, the performance issue
> definitely deserves to be FAQ entry.
>
> Thanks.
>
>
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