Here's a few more details - We provision T1.

Salesdroid asks "You wanna give us $$$ for clear channel?"

Us: "..... ?"

Salesdroid: "It's so you can get 64kbit rather than the normal 56k"

Us: "We thought all DS-0s were 64kbit?"

Me: "I know! I'll ask NANOG!"

When you're ordering a full DS-1, it almost never makes a difference, because telco just passes everything, including the framing, without even looking at the individual channels. When you're asking Telco's to do DACSing on the circuti, it matters. The relevant difference is what happens with a DS0 is cross-connected by the Telco from one DS-1 to another. There are two options: (1) Just move the bits: Pull 8 bits at a time from timeslot X the incoming DS-1, slap them out on timeslot Y in the outgoing DS-1. This is what you want if you are doing data. This is not what you want if you are doing voice with channel-associated signalling. (2) Just move the bits, *except* that it also receives the signalling bits from the incoming DS-1 and regenerates them on the outgoing DS-1. This will run data (unless you're doing Nx56), because it will rearrange the LSB. But it is necessary for voice using channel-assocaited signalling. The above explanation doesn't help unless you know what channel associated signalling is. I'll briefly describe it since it's probably somewhat off charter: The bits in a T1 are sent as frames, consisting of one framing bit followed by 8 bits from DS0#1, followed by 8 bits from DS0#2, and so on. The frames are then organized into groups of 12 frames (Super Frame) or 24 frames Extended Super Frame). The LSB of each byte is used for signalling purposes in Frames 6 and 12 (or 6/12/18/24). Thus, if you're cross-connecting individual DS0's, it's possible that when you're clocking in Frame #12 on the incoming DS-1, you'll be clocking out frame, say, #3 on the outgoing DS1. In that case, you would lose the signalling, because the signalling bit on Frame 12 would go out on Frame 3 (where it's no longer a signalling bit); similarly, the essentially random LSB that comes in on Frame 3 would go out on Frame 6, so you'd effectively have a random signalling bit. So if you want the signalling to be kept right, you don't order clear channel, and then the DACS (Cross-connect system) regenerated the signalling on the outgoing DS-1, based on what it is receiving. If you aren't using signalling (for example, if you're doingg data), then you order clear channel. If you're ordering a Full T1, it raraly matters, because when they corss-connect everything at the T1 level, they generally just copy the framing bits through with everything else, so Frame 1 is going out when Frame 1 is coming in. (Note: replace DS-1 with T1 in the above if it helps you read it better.) (e-Mail privately if you want more details.) -- Brett

Here's a document that further obfuscates the matter for me - http://www.comtest.com/tutorials/t1.html

Anybody care to comment on its relevance in this situation? If I read it correctly, Clear Channel = Less Capacity. Doesn't sound right.

I know that most of NANOG has explained in detail about clear channel T1s, but I thought this webpage would be a lot of help if you never wanted to learn everything about T1s, but asked anyway! 8-) www.t1.org - Standards Committee T1 Telecommunications. This webpage helped quite a bit when I was researching about T1/T3 test patterns (which is document tr_25.pdf,"A Technical Report on Test Patterns for DS1 Circuits"). A more specific weblink is http://www.t1.org/html/trs.htm I'm now going to unsubscribe to nanog-post before I do something brain dead, e.g., continue a flamewar about DNS. FYI, Rachel -- C++ - Where only your friends can access your private parts.