T1 is the physical transport, delivered on 4 wires, 2 send and 2 receive, and capable of delivering 1.544 Mbps. T1 defines the voltage states.
DS1 is a service that is readily built on top of a T1 transport. The DS1 delivers 1.536 Mbps. With a framing and coding applied to a T1, you can interpret the voltage transitions as bits. You can also deliver a DS1 via DS3 service. O'Reilly's book "T1 Survival Guide" goes into this a good bit. >>> [email protected] +1-229-316-0013 http://ecg.co/lindsey On Mar 8, 2014, at 11:38 , Frank Bulk <[email protected]> wrote: > Mark, > > Can you expand what you mean by "... the DS1 ... is a layer above the T1 > where the clock ticks happen"? I'm not familiar with that concept. > > Frank > > -----Original Message----- > From: Mark Lindsey [mailto:[email protected]] > Sent: Saturday, March 08, 2014 10:34 AM > To: Alex Balashov > Cc: Frank Bulk; [email protected] > Subject: Re: [VoiceOps] Timing slips on subrate DS1s on CT3 > > Normally in the TDM world, you don't try to time a DS3 off anything on > a DS3, including a DS1. You time a DS3 off a T1 transmitting all 1s, > preferably one generated by a BITS clock. > > As I think you alluded, the DS1 -- what you're using to derive timing > -- is a layer above the T1 where the clock ticks happen. > > But whatever it takes to discipline the internal 1.544 MHz clock to > sync up with the transmitter will work. It's interesting that Cisco > has this option. > > Cisco TDM always seems a little out of step with traditional (and > often overpriced) 1970s-thought-process TDM gear. > >>>> [email protected] +12293160013 http://ecg.co/lindsey > >> On Mar 8, 2014, at 0:43, Alex Balashov <[email protected]> wrote: >> >> The T3's timing is logically independent of the subrate channels. The T3 > is configured to take clock from the line. But the timing on the subrate > DS1s should be identical, since they're all on the same DS3, right? >> >>> On 03/08/2014 12:37 AM, Frank Bulk wrote: >>> >>> No, I was just wondering if there is generally one that carries the > timing >>> on a T3. >>> >>> Frank >>> >>> -----Original Message----- >>> From: Alex Balashov [mailto:[email protected]] >>> Sent: Friday, March 07, 2014 11:33 PM >>> To: Frank Bulk; [email protected] >>> Subject: Re: [VoiceOps] Timing slips on subrate DS1s on CT3 >>> >>> No particular reason for choosing that one. Should I have chosen another? >>> >>>> On 03/08/2014 12:28 AM, Frank Bulk wrote: >>>> >>>> Thanks for sharing. Why did you choose that T1? >>>> >>>> Frank >>>> >>>> -----Original Message----- >>>> From: VoiceOps [mailto:[email protected]] On Behalf Of Alex >>>> Balashov >>>> Sent: Friday, March 07, 2014 1:33 PM >>>> To: [email protected] >>>> Subject: Re: [VoiceOps] Timing slips on subrate DS1s on CT3 >>>> >>>> Someone e-mailed me privately off-list with a link to: >>> > http://www.cisco.com/c/en/us/support/docs/routers/2600-series-multiservice-p >>>> latforms/48567-clocking.html >>>> >>>> Which clued me into the fact that I can take global TDM clocking off a >>>> particular T1: >>>> >>>> tdm clock priority 1 6/0:1 >>>> >>>> So far, that seems to have fixed the slips! I'll see if it holds. >>>> Thanks a lot for the pointer! >> >> >> -- >> Alex Balashov - Principal >> Evariste Systems LLC >> 235 E Ponce de Leon Ave >> Suite 106 >> Decatur, GA 30030 >> United States >> Tel: +1-678-954-0670 >> Web: http://www.evaristesys.com/, http://www.alexbalashov.com/ >> _______________________________________________ >> VoiceOps mailing list >> [email protected] >> https://puck.nether.net/mailman/listinfo/voiceops > > _______________________________________________ VoiceOps mailing list [email protected] https://puck.nether.net/mailman/listinfo/voiceops
