nanog mailing list archives
Re: anyone running GPS clocks in Southeastern Georgia?
From: Anton Kapela <tkapela () gmail com>
Date: Sun, 23 Jan 2011 10:26:06 -0600
What about Modular DOCSIS 3.0 deployments with external timing sources between the QAM and CMTS
A CMTS DS payload is formatted as an MPEG TS (it even has PIDs; however, no PCR). This in turn establishes cadence for associated downstream devices (eg. they sync to whatever is within allowable tolerances). Any digital 'baseband' output from a so-called 'modular' CMTS (one with external QAM modulation) should likewise serve as a recoverable timing source for the modulator. Inter-DS cadence is allowably async; the only important coupling here are these associated US channels available for a given DS. Unless I've missed something horribly obvious, I can't see where strict timing is important, nor can I see where inter or intra-system synchronization would be critical either, save for corner-cases (i.e. US or DS dynamic channel change, DCC/UDC, etc). Even in these cases, the modem is more than able to rapidly resynchronize with a new/differing cadence in both frequency and phase domains. I guess, in short, don't worry (about this). -Tk
Current thread:
- Re: anyone running GPS clocks in Southeastern Georgia?, (continued)
- Re: anyone running GPS clocks in Southeastern Georgia? Brandon Ross (Jan 22)
- Re: anyone running GPS clocks in Southeastern Georgia? Michael Holstein (Jan 21)
- Re: anyone running GPS clocks in Southeastern Georgia? Gary Buhrmaster (Jan 21)
- Re: anyone running GPS clocks in Southeastern Georgia? Cutler James R (Jan 21)
- Re: anyone running GPS clocks in Southeastern Georgia? Robert E. Seastrom (Jan 21)
- Re: anyone running GPS clocks in Southeastern Georgia? Owen DeLong (Jan 21)
- Re: anyone running GPS clocks in Southeastern Georgia? Jay Ashworth (Jan 23)
- Re: anyone running GPS clocks in Southeastern Georgia? Cutler James R (Jan 21)
- Re: anyone running GPS clocks in Southeastern Georgia? Robert E. Seastrom (Jan 21)
- Re: anyone running GPS clocks in Southeastern Georgia? James Brown (Jan 21)
- Re: anyone running GPS clocks in Southeastern Georgia? Anton Kapela (Jan 23)
- Re: anyone running GPS clocks in Southeastern Georgia? Joel Jaeggli (Jan 21)
- Re: anyone running GPS clocks in Southeastern Georgia? Robert E. Seastrom (Jan 21)
- Re: anyone running GPS clocks in Southeastern Georgia? Peter Lothberg (Jan 22)
- Re: anyone running GPS clocks in Southeastern Georgia? Gary Buhrmaster (Jan 21)
- Re: anyone running GPS clocks in Southeastern Georgia? Lamar Owen (Jan 21)
- Re: anyone running GPS clocks in Southeastern Georgia? Pete Carah (Jan 21)
- Re: anyone running GPS clocks in Southeastern Georgia? Cameron Byrne (Jan 23)