Coderman wrote...
Of course, they could do it via SONET overhead bytes, thus avoiding the flakiness and vunerability that routers and switches still seem to have.
covert channels for backhaul? nah, that would still be too visible. especially if/when a customer puts link testing equipment on the line and sees something funny. SONET doesn't give you a lot of play room.
There are plenty of unused bytes in the SONET overhead, particularly at OC-48 and OC-192 (in fact, most of the line and section overhead is empty because the overhead bytes are only defined for the first STS-1! Not a lot of people know that). The problem, however, is that Line and Section layer overhead will be terminated pretty much every time they pass through a SONET box. There's the possibility of using the POH for control and management traffic, because that -should- stay with the payload. In terms of visibility they could of course encrypt those packets, possibly even using off-the-shelf VPN of they run a short stack management channel (though 7-layer/OSI is not impossible, given the old fondness for it in standards groups for so long). On the other hand they could possibly just go in-band and send the management info with their backhauled traffic, but I'm still a little doubtful about that. -TD