Wireshark-dev: Re: [Wireshark-dev] DS1 Decode?
From: "Luis EG Ontanon" <[email protected]>
Date: Wed, 22 Aug 2007 15:38:06 +0200
On 8/22/07, maillistnoll <[email protected]> wrote:
> I've taken a quick look through the supported protocols and what's in CVS,
> but I can't seem to find any decode for DS1 (T1) signals.
>
> Before I go writing one, has anyone tackled this decode before?

DS1 is usually handled by hardware, the line-code is electric impulses
(HDB3, AMI) so it's hardware that deals with it, finding DS1 frames
out from a bitstream could be done by software, but if you have an
interface that handles HDB3 or AMI it probably does handle sync and
multi-frame alignment as well. And it probably handles also "higher
levels" of framing as well (like FR, HDLC, MTP2, ATM, etc) so libpcap
(that's what wireshark uses for capture) gets fed with frames already
extracted from the bitstream by the hardware and its driver.

Considering that Wireshark handles frames (not electric signals or
bitstreams) and most hardware that can allow to connect a computer to
an E1 will do the framing by itself. There's little use for such an
implementation,

There are a lot of interesting bit oriented protocols out there whose
implementation makes little useful sense in Wireshark even if in some
cases they can actually be found encapsulated in packets of other
protocols (e.g. bitstreams of V.110 or PCM encoded V.32->V.90 might be
found in NbUP frames). The DS1 case is more extreme the only cases of
frames that can contain DS1 bitstreams I can think of are SDH and DS3
for which the same issues regarding hardware apply.

Luis


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