Wireshark-bugs: [Wireshark-bugs] [Bug 9427] Dissector for T1-channels-over-raw-Ethernet protocol
Comment # 35
on bug 9427
from Mike Petersen
> So the question that raises is "what does it mean to "concatenate" the channels"? Does it mean taking 8 bits from channel 1, appending 8 bits from channel 2, then 8 bits from channel 3, ... 8 bits from channel 24, the next 8 bits > from channel 1, the next 8 bits from channel 2, ...?
>
> I'm assuming that
>
> 1. Only T1 payload or content is transferred to the Ethernet Frame (no T1 Framing or Overhead)
> 2. The Packets always start with DS0 Channel-1 (unless the T1 slips due to incorrect clocking)
> 3. and continues through to DS0 channel-24
>
Traditionally in TDM services(DDS, T1, ISDN or DS3) channelized means each
channel carries one specific stream of customer data, Unchannelized means that
the channels are concatenated (precisely as you describe) to form one large
stream of data. As an example, in Fractional-T1 modes multiple channels (they
need not be consecutive) are combined to form one larger nx64 (or nx56) bit
stream. the 192 bits represent the concatenated 24 channels.
Yes, if no slips and T1 is Framed up and in sync when Bridging is enabled, the
1st 8 bits are (what would be called) DS0 channel-1 (if Channelized) and the
last 8-bits are channel-24. The Next Frame begins anew with DS0 Channel-1.
RE an earlier query; the 193rd bit of the T1 (not payload and thusly not
transferred) consists of T1 Overhead (Framing Bit and misc link maintenance).
The 192 bits represents the actual customer data (channelized or
unchannelized).
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