Re: [Asterisk-Users] T1 Sync clarification
Stephen Davies wrote: On Wed, 14 Jan 2004, TC wrote: What are the practical effects with in-correct clock sync -like to you hear odd buzzing, or dropped voice or gaps of audio ?? Old-fart anecdote about this - in the early 80s we had some 1200bps modems that we used to connect to client sites. When our phone company went digital we suddenly started getting a } character at a regular interval of 10 or 15 seconds. This turned out to be clock slips in the new digital trunk between the two exchanges. So there is one effect of clock slips. Steve That must have been an FSK modem. Most advanced modems completely loose sync on the first sample slip. The sample slip causes a jump in phase, and phase is critical to the correct operation of most modems. Regards, Steve ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
Rich Adamson wrote: To complete this rather lengthy topic... what happens if you ignore all of this and just slap a bunch of systems together with no regard to a master sync source? The quality and stability of your network will likely not be as good as what it could be. If your clocks (in each device) happen to be running very very close to what is expected, your network might run just fine. But, if one of the clock's frequency drifts around, it could impact quality via frame slippage and other unwanted events, and if off by a large amount could even be the source of failures. (Your milage will vary directly with the stability of your clocks.) What are the practical effects with in-correct clock sync -like to you hear odd buzzing, or dropped voice or gaps of audio ?? As mentioned earlier, it depends entirely upon how far off one clock is from the clock at the other end of the T1. If they are off by a little bit, you would see frame slips but probably not hear any quality differences. As the slip rate increases (to some unknown value since I've not tried personally to qualify this), the audio would be infrequently interrupted from the lost frames. I would expect you to hear it as repetitive clicks of some sort that might be construed as noise. The exact noise would again depending upon how far off the clocks really were. Each audio channel consists of 8,000 voice samples per second (on a normal US T1), so if the slip occurred once/second on average and then recovered, one would probably not hear 1/8000 second of a hickup. If the slips were 100/sec average, it's likely the end nodes would have a hard time recovering from it (best guess), and I would expect noise to be apparent. Others that have more experience correlating slip rates to noise levels might have a better description of the noise vs slip rate. Rich You would only have a fast slip rate if something is faulty. Anything complying with the E1 or T1 specs should never have its clock 50ppm in error. Anything coming from the PSTN is essentially bang on, as it comes from an atomic clock. Some people have commented about potentially difference clock rates from different providers. In practice that doesn't happen. Providers have a rhubidium clock in each exchange. These are so accurate, frame slips would be a one a year event. However, phase locking between carriers usually ensures even that does not occur. The globe's phone systems are pretty much all locked together these days. The older higher order digital links - 8, 34, 140, and 565M in E1 land, and DS3 etc. in T1 land - have a bit stuffing scheme that allows individual E1s or T1s to be at slightly different rates. This is called PDH - plesiochronous (almost synchronous) digital heirarchy - and was very helpful in moving from a totally analogue network to a mixed analogue/digital one. Once the network backbones became 100% digital, this became a huge liability. SDH (synchronous digital heirarchy, or Sonet) was born to solve this. SDH assumes the entire network is perfectly synchronised. Drop and insert is *far* cheaper in a truely synchronous stream. SDH is the norm for anything new today. Regards, Steve ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
What are the practical effects with in-correct clock sync -like to you hear odd buzzing, or dropped voice or gaps of audio ?? You may get gaps where frames are discarded, this will be across all timeslots so an individual loss isnt a lot of data, you'll probably get away with the odd one but if you get too many and the T1 realigns it could restart and you could see the whole T1 go down and up.. Not sure how this works in the US with such diversity available but in the UK telcos generally derive sync from another one so most of them are on the same clock source.. It's the same in the US, however in the US there are far more independent telcos (example, Iowa had the distinction of the most independent telcos at 600+ of all states) and many of those do not have an engineering staff nor the expertise to address this. Their engineering is typically farmed out to either the central office switch vendor or to independent engineering firm(s) when needed. Those groups should have addressed it, but in at least some cases it was not. The US also has some carriers that got into the national and/or international long distance business with a low budget staff that ran hard but never documented anything. (I've done some consulting work for two of those and wouldn't bet a dollar on their attention to detail.) Rich ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
On Wed, 14 Jan 2004, Steve Underwood wrote: That must have been an FSK modem. Most advanced modems completely loose sync on the first sample slip. The sample slip causes a jump in phase, and phase is critical to the correct operation of most modems. It was V.22. No error correction or anything new-fangled like that. (Not auto dial either). Steve ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
Rich Adamson wrote: What are the practical effects with in-correct clock sync -like to you hear odd buzzing, or dropped voice or gaps of audio ?? You may get gaps where frames are discarded, this will be across all timeslots so an individual loss isnt a lot of data, you'll probably get away with the odd one but if you get too many and the T1 realigns it could restart and you could see the whole T1 go down and up.. Not sure how this works in the US with such diversity available but in the UK telcos generally derive sync from another one so most of them are on the same clock source.. It's the same in the US, however in the US there are far more independent telcos (example, Iowa had the distinction of the most independent telcos at 600+ of all states) and many of those do not have an engineering staff nor the expertise to address this. Their engineering is typically farmed out to either the central office switch vendor or to independent engineering firm(s) when needed. Those groups should have addressed it, but in at least some cases it was not. The US also has some carriers that got into the national and/or international long distance business with a low budget staff that ran hard but never documented anything. (I've done some consulting work for two of those and wouldn't bet a dollar on their attention to detail.) Rich If they have frame slips too often FAX will not work. It would be hard for even the most incompetant telco to ignore that. However, their core equipment is likely to use a rhubidium clock and keep everything OK, even if they done sync to their peers properly. Regards, Steve ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
At 9:17 PM +0800 1/14/04, Steve Underwood wrote: [snip] It's the same in the US, however in the US there are far more independent telcos (example, Iowa had the distinction of the most independent telcos at 600+ of all states) and many of those do not have an engineering staff nor the expertise to address this. Their engineering is typically farmed out to either the central office switch vendor or to independent engineering firm(s) when needed. Those groups should have addressed it, but in at least some cases it was not. The US also has some carriers that got into the national and/or international long distance business with a low budget staff that ran hard but never documented anything. (I've done some consulting work for two of those and wouldn't bet a dollar on their attention to detail.) Rich If they have frame slips too often FAX will not work. It would be hard for even the most incompetant telco to ignore that. However, their core equipment is likely to use a rhubidium clock and keep everything OK, even if they done sync to their peers properly. Regards, Steve This is getting pretty far off the topic of Asterisk, but I'll confirm that several of the small CLECS that I've worked for/consulted for do _not_ have their own timing sources in the form of a rubidium standard. These also are carriers that sell PRI's and T1 connections out of their switching equipment. They typically use clocking source from one of their interconnect providers, or they simply don't know the answer to the question of who provides clock in your network? If they're taking sync off one of their upstreams, this is not so bad. If they simply don't know where they're getting sync, this is much worse. If my experiences have been this poor in what I think are fairly dense population/financially wealthy areas, I can only imagine what it's like as one moves further away from high-budget telephony centers. A scrupulous tech will fix those problems... but there are a dwindling number of scrupulous techs, and an even shorter supply of money for rubidium standards or cesium beam timepieces. In other words: I suspect a great number of Asterisk users, being (sometimes) budget conscious, will run across these types of shady clocking situations since the lowest budget carriers often don't have the funding to implement the right solutions. JT ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
What are the practical effects with in-correct clock sync -like to you hear odd buzzing, or dropped voice or gaps of audio ?? snip As mentioned earlier, it depends entirely upon how far off one clock is from the clock at the other end of the T1. snip If they are off by a little bit, you would see frame slips but probably not hear any quality differences. snip You would only have a fast slip rate if something is faulty. Anything complying with the E1 or T1 specs should never have its clock 50ppm in error. Anything coming from the PSTN is essentially bang on, as it comes from an atomic clock. snip So, to summarize and address the original posters questions and stop the thread from deviating too far off topic... (add to the wiki?) 1. pstn providers worldwide have understood and addressed syncing of digital clocks (eg, T1/E1 clocks, not operating system clocks) for years. Its probably safe to assume the majority of pstn providers either sync to some common source (eg, atomic clock), or, have internal mechanisms to ensure interoperability with all other providers. (Some exceptions do exist but their numbers are believed to be very small.) 2. For asterisk purposes, current T1/E1 facilities (regardless of source) carry timing information embedded within the transmit leg (not an optional configuration parameter) that is used by the attached device for recover of clock sync. 3. Channel banks typically have only a single T1/E1 uplink, and therefore recover clock sync from the T1/E1 receive-side of that link. If a specific channel bank model supported two or more uplinks, then the manufacturer would provide a user configurable option to select which uplink to use for clock sync. 4. Likewise, since the Digium TE410P (as an example only) supports four T1/E1 inputs, a user configurable option is provided to select one port for primary clock sync, and alternates (secondaries) should the selected primary T1/E1 fail. Users should select the T1/E1 link that is closest to the pstn where possible. 5. Asterisk configurations that include multiple T1/E1 links that close a wide area loop, for example: ast#1 - T1 - ast#2 - T1 - ast#3 - T1 - ast#1 should not be of concern from a clock sync perspective as each system recovers the clock sync from its associated T1 receive leg if that receive leg is specified correctly in the TE410P configuration. EXCEPT... If this same config included a pstn T1 link into ast#2 (as an example) then the TE410P should be configured to obtain clock sync from the port on which the pstn T1 is connected. If that is not configured, then clock sync within the wide area loop is 100% dependent upon the accuracy of the TE410P clock (which is not a high-accuracy clock), and frame slipage will occur at the T1 interface to the pstn. 6. If frame slipage does occur, the impact is: a. for small slipage: users would not notice b. for medium slipage: repetitive clicks are likely to be heard across all voice channels in use, and fax machines are likely to be less then reliable. c. for large slipage: T1/E1 circuits are likely to fail then recover intermitently. General Rules of Thumb: 1. Devices with a single T1/E1 interface will automatically recover clock sync from the receive-side of the T1/E1, and users never need to be concerned with it. 2. Devices that have multiple T1/E1 interfaces (like the TE410P) need to select a clock sync source, and that source should be a T1/E1 port that is closest to the pstn (or derived from the pstn) if it exists. Anyone take exception to any of this before it goes into the wiki? Rich ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
If you've got spans from different providers...you're in for an adventure. You'll be able to do one of the following (which one is telco and luck dependant): So what you're saying is that the TE410P is not capable of *independently* clocking each of the T1s. Hell even the venerable old AS5248 can handle that. This is going to be fun... Is it possible to accept clock from the telco for one span and *generate* clock on the other three spans (i.e. for internal channel banks and whatnot) ? Will I run into problems there? I don't forsee it but I also didn't forsee the problem being discussed in this thread... Regards, Andrew ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
RE: [Asterisk-Users] T1 Sync clarification
On Tuesday, January 13, 2004 7:36 AM, Andrew Kohlsmith [SMTP:[EMAIL PROTECTED] wrote: If you've got spans from different providers...you're in for an adventure. You'll be able to do one of the following (which one is telco and luck dependant): If all providers are referenced back to a stratum 1 clock (which they should be) then all provider spans should have very very very close timing. Close enough that only a few frame slips a year may occur. So, in general spans from different providers should not be a problem. So what you're saying is that the TE410P is not capable of *independently* clocking each of the T1s. Hell even the venerable old AS5248 can handle that. This is going to be fun... That is correct. Is it possible to accept clock from the telco for one span and *generate* clock on the other three spans (i.e. for internal channel banks and whatnot) ? Will I run into problems there? I don't forsee it but I also didn't forsee the problem being discussed in this thread... Yes it is possible to receive clock from one span and provide it for the other three. That is how I am running. Regards, Andrew Don Pobanz ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
If you've got spans from different providers...you're in for an adventure. You'll be able to do one of the following (which one is telco and luck dependant): So what you're saying is that the TE410P is not capable of *independently* clocking each of the T1s. Hell even the venerable old AS5248 can handle that. This is going to be fun... Is it possible to accept clock from the telco for one span and *generate* clock on the other three spans (i.e. for internal channel banks and whatnot) ? Will I run into problems there? I don't forsee it but I also didn't forsee the problem being discussed in this thread... Think we're trying to make this more difficult then what it really is. Every T1 card has a clock, period. The card, regardless of whether it is in a channel bank or a PC, runs at some frequency determined by the engineer that designed the card. A specific card's clock might run at 15.44 mega-units/sec, however the exact frequency at any point in time might be 15.43999 or 15.44001, or some other variation. Letting the clock slide around over time is not a cool thing in high speed digital communications. Therefore, the person implementing the card usually has to choose a source from which to sync his card's clock. There isn't any need to attempt to sync the card's clock from multiple sources simultaneously. The telephone company engineers have had to make the exact same engineering decisions for each central switching office, however since many of these offices have digital facilities from several external companies, they simply coordinate with these other companies as to who is going to be the source (for clock syncing) verses who will simply listen. Those decisions are based on a rather well understood hierarchical arrangement that usually starts with a large carrier and an atomic clock. (The telco will also engineer for a primary and one or more failover secondaries, etc.) Since the digium card has a clock, you simply pick one source to sync from. If you just happen to have multiple T1's coming from different companies, you can only hope/expect those companies have participated in the effort to follow the hierarchical, historically well understood, syncing arrangements. If one of them happens to be a fly-by-night organization that hasn't understood the international sync requirements, your only option is to either encourage them to participate or find a different provider. Period. Once you've chosen a sync source, your card's clock should now be in sync with master atomic clock via layers of this well understood hierarchy. If you connect channel banks to this same card, the digital signals transmitted by your card to the channel bank is going to be derived from your card's in-sync clock. That says your channel banks should then be configured to sync from that card. If you don't do that, then you are breaking the hierarchical structure within your network. If you are large enough to have many asterisk boxes all interconnected via T1's in some sort of full mesh configuration, then as an engineer you have to design your systems in such a way as to pick a clock source to sync with (call it your Master), and design each component in your network to sync from that Master via your own hierarchy. Its not that hard, but it really needs to be done. Just like the telephone company engineers, you should think about what happens if your primary source of sync fails. If you enjoy T1's from multiple external sources, then pick a secondary (backup) for syncing. However you choose to do that is based on your exact network configuration, and not on how the digium card was designed, etc. If your asterisk box interconnects with a traditional pbx that has T1 connections to the pstn, then whoever engineered that pbx had to make the same sync decisions (even though they didn't tell you about it). In this case, your asterisk machine should sync from the traditional pbx. If you have a T1 from your pstn telco terminating on your asterisk, and another T1 going from asterisk to your traditional pbx, then configure asterisk to sync from the telco and the traditional pbx to sync from your asterisk. To complete this rather lengthy topic... what happens if you ignore all of this and just slap a bunch of systems together with no regard to a master sync source? The quality and stability of your network will likely not be as good as what it could be. If your clocks (in each device) happen to be running very very close to what is expected, your network might run just fine. But, if one of the clock's frequency drifts around, it could impact quality via frame slippage and other unwanted events, and if off by a large amount could even be the source of failures. (Your milage will vary directly with the stability of your clocks.) Hope that helps someone Rich ___ Asterisk-Users mailing list [EMAIL PROTECTED]
Re: [Asterisk-Users] T1 Sync clarification
If you've got spans from different providers...you're in for an adventure. You'll be able to do one of the following (which one is telco and luck dependant): So what you're saying is that the TE410P is not capable of *independently* clocking each of the T1s. Hell even the venerable old AS5248 can handle that. This is going to be fun... Dont think they do.. on the controllers you specify clock source primary/secondary and the box will sync to only one clock. This is true in all telco systems afaik.. taking lines from another telco which is on a different clock source isnt necessarily a big problem but you should expect to see the odd slips on the line where the clocking is slightly mismatched.. Steve ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
To complete this rather lengthy topic... what happens if you ignore all of this and just slap a bunch of systems together with no regard to a master sync source? The quality and stability of your network will likely not be as good as what it could be. If your clocks (in each device) happen to be running very very close to what is expected, your network might run just fine. But, if one of the clock's frequency drifts around, it could impact quality via frame slippage and other unwanted events, and if off by a large amount could even be the source of failures. (Your milage will vary directly with the stability of your clocks.) What are the practical effects with in-correct clock sync -like to you hear odd buzzing, or dropped voice or gaps of audio ?? ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
Think we're trying to make this more difficult then what it really is. [ lengthy and accurate text snipped ] I think you're oversimplifying. There is *no* need to have individual T1 spans synchronized to each other unless you're trying to aggregate the data on those individual spans. DS2/DS3 takes care of this with 'slop' bits in which the individual DS1 frames can float around in. We're not talking about aggregating the data though. We're talking about four individual T1/E1 framers -- Maybe my telco design has slipped a little over the years but I see no necessity for the requirement that the four T1s on a TE410P be in sync with each other. As soon as you come out the ass end of the framer you're running on internal card bus and more than likely on PCI time, which has nothing at all to do with the T1s you started with. So while you are absolutely correct in that for an overall network you need to have everyone agree on a single clock source, it's often not going to happen if you're running with different providers. And if you're doing this in anything other than a backup situation, you need to be able to sync to both of these sources. Whether that means you need two T100P cards since they can individually sync, or some form of T1 buffer which will sync to two clocks to satisfy this requirement... well that's up to the design spec. Which brings me back to my original question: Can I sync to the telco, and then have my channel banks synchronized to the TE410P, which I've synchronized to the telco? Regards, Andrew ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
If you've got spans from different providers...you're in for an adventure. You'll be able to do one of the following (which one is telco and luck dependant): So what you're saying is that the TE410P is not capable of *independently* clocking each of the T1s. Hell even the venerable old AS5248 can handle that. This is going to be fun... Dont think they do.. on the controllers you specify clock source primary/secondary and the box will sync to only one clock. This is true in all telco systems afaik.. taking lines from another telco which is on a different clock source isnt necessarily a big problem but you should expect to see the odd slips on the line where the clocking is slightly mismatched.. Right on. Keeping an eye on slips over time can also provide insight into larger issues to come. Telcos and others sometimes forget to address the clock sync on new additions of equipment, etc. ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
On Wed, 14 Jan 2004, TC wrote: What are the practical effects with in-correct clock sync -like to you hear odd buzzing, or dropped voice or gaps of audio ?? Old-fart anecdote about this - in the early 80s we had some 1200bps modems that we used to connect to client sites. When our phone company went digital we suddenly started getting a } character at a regular interval of 10 or 15 seconds. This turned out to be clock slips in the new digital trunk between the two exchanges. So there is one effect of clock slips. Steve ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
To complete this rather lengthy topic... what happens if you ignore all of this and just slap a bunch of systems together with no regard to a master sync source? The quality and stability of your network will likely not be as good as what it could be. If your clocks (in each device) happen to be running very very close to what is expected, your network might run just fine. But, if one of the clock's frequency drifts around, it could impact quality via frame slippage and other unwanted events, and if off by a large amount could even be the source of failures. (Your milage will vary directly with the stability of your clocks.) What are the practical effects with in-correct clock sync -like to you hear odd buzzing, or dropped voice or gaps of audio ?? As mentioned earlier, it depends entirely upon how far off one clock is from the clock at the other end of the T1. If they are off by a little bit, you would see frame slips but probably not hear any quality differences. As the slip rate increases (to some unknown value since I've not tried personally to qualify this), the audio would be infrequently interrupted from the lost frames. I would expect you to hear it as repetitive clicks of some sort that might be construed as noise. The exact noise would again depending upon how far off the clocks really were. Each audio channel consists of 8,000 voice samples per second (on a normal US T1), so if the slip occurred once/second on average and then recovered, one would probably not hear 1/8000 second of a hickup. If the slips were 100/sec average, it's likely the end nodes would have a hard time recovering from it (best guess), and I would expect noise to be apparent. Others that have more experience correlating slip rates to noise levels might have a better description of the noise vs slip rate. Rich ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
RE: [Asterisk-Users] T1 Sync clarification
On Wednesday, January 14, 2004 11:41 AM, TC [SMTP:[EMAIL PROTECTED] wrote: What are the practical effects with in-correct clock sync -like to you hear odd buzzing, or dropped voice or gaps of audio ?? It depends on how out of sync the clocks are and the type of signaling being used. For a T1 with robbed bit signaling you would just hear a click or pop on the line. If the clocks are close this may just occur a few times a day. If there is more difference in the clocks it could happen every few minutes or more. For PRI ISDN it may drop the calls or not allow a call to be set up. There have been some in the past who have had problems getting PRI ISDN to stay up and it was due to clocking. Don Pobanz ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
What are the practical effects with in-correct clock sync -like to you hear odd buzzing, or dropped voice or gaps of audio ?? You may get gaps where frames are discarded, this will be across all timeslots so an individual loss isnt a lot of data, you'll probably get away with the odd one but if you get too many and the T1 realigns it could restart and you could see the whole T1 go down and up.. Not sure how this works in the US with such diversity available but in the UK telcos generally derive sync from another one so most of them are on the same clock source.. Steve ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
Think we're trying to make this more difficult then what it really is. [ lengthy and accurate text snipped ] I think you're oversimplifying. There is *no* need to have individual T1 spans synchronized to each other unless you're trying to aggregate the data on those individual spans. DS2/DS3 takes care of this with 'slop' bits in which the individual DS1 frames can float around in. We're not talking about aggregating the data though. We're talking about four individual T1/E1 framers -- Maybe my telco design has slipped a little over the years but I see no necessity for the requirement that the four T1s on a TE410P be in sync with each other. I don't have a TE410P, but I'd bet a small amount there is only one clock on the board, and since that clock will be in sync with something (probably the telco), all four ports are in sync (by design, not by option). As soon as you come out the ass end of the framer you're running on internal card bus and more than likely on PCI time, which has nothing at all to do with the T1s you started with. So while you are absolutely correct in that for an overall network you need to have everyone agree on a single clock source, it's often not going to happen if you're running with different providers. And if you're doing this in anything other than a backup situation, you need to be able to sync to both of these sources. Whether that means you need two T100P cards since they can individually sync, or some form of T1 buffer which will sync to two clocks to satisfy this requirement... well that's up to the design spec. Which brings me back to my original question: Can I sync to the telco, and then have my channel banks synchronized to the TE410P, which I've synchronized to the telco? Yes, and I agree with everything that you've noted above. Rich ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
TC wrote: To complete this rather lengthy topic... what happens if you ignore all of this and just slap a bunch of systems together with no regard to a master sync source? The quality and stability of your network will likely not be as good as what it could be. If your clocks (in each device) happen to be running very very close to what is expected, your network might run just fine. But, if one of the clock's frequency drifts around, it could impact quality via frame slippage and other unwanted events, and if off by a large amount could even be the source of failures. (Your milage will vary directly with the stability of your clocks.) What are the practical effects with in-correct clock sync -like to you hear odd buzzing, or dropped voice or gaps of audio ?? It usually sounds like a click each time a frame slip occurs. Regards, Steve ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
On Sun, 11 Jan 2004, John Brown (CV) waxed: THank you. Thats what I thought it should be. Off to call the telco and tell them they are mucked up. I'm wondering if I should do the same for my T400, as I seem to be getting similar errors. Might not be just the telco. I set one span to 1, to sync off the telco, and the second to 0, since the clock is already set by the first span. The other 2 spans are channel banks with sync set to 0. Does anyone else have 2 t1's plugged into their T400 ? If so, how are they synced ? This was just happening at night, but I lost the second span a dozen times already today, all within less than an hour earlier this afternoon. Thanks, --Chris -- Chris Maj cmaj_hat_freedomcorpse_hot_info Pronunciation Guide: Maj == May Fingerprint: 43D6 799C F6CF F920 6623 DC85 C8A3 CFFE F0DE C146 ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
Quoting C. Maj [EMAIL PROTECTED]: On Sun, 11 Jan 2004, John Brown (CV) waxed: THank you. Thats what I thought it should be. Off to call the telco and tell them they are mucked up. I'm wondering if I should do the same for my T400, as I seem to be getting similar errors. Might not be just the telco. I set one span to 1, to sync off the telco, and the second to 0, since the clock is already set by the first span. The other 2 spans are channel banks with sync set to 0. Does anyone else have 2 t1's plugged into their T400 ? If so, how are they synced ? This was just happening at night, but I lost the second span a dozen times already today, all within less than an hour earlier this afternoon. I have 3 T1's plugged into my T400P, 1 to the telco and 2 to channel banks. Basically a T400 has one clock. This clock will free run (internal clock) if you have not told it to get timing from one of the incoming spans. Otherwise it will set the clock to the incoming T1 line which has a sync of '1'. Should this T1 be unavailable, the clock will be derived from the T1 with a sync of '2'. If both 1 and 2 are not available then it will derive the timing from 3. Again if the first 3 sync sorces are not available, it will look at 4. Note that at any one time only 1 of the 4 T1s can be used for a clock. Now, it is possible for you to have two telco T1's which do not have the same timing. This is not real likely but possible. Should this happen, there is no way to sync with both T1s at the same time. Only your telco could fix this. -- Don Pobanz Thanks, --Chris -- Chris Maj cmaj_hat_freedomcorpse_hot_info Pronunciation Guide: Maj == May Fingerprint: 43D6 799C F6CF F920 6623 DC85 C8A3 CFFE F0DE C146 - This mail sent through IMP: http://horde.org/imp/ ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
Re: [Asterisk-Users] T1 Sync clarification
THank you. Thats what I thought it should be. Off to call the telco and tell them they are mucked up. On Sun, Jan 11, 2004 at 06:54:11PM -0600, Don Pobanz wrote: On Sunday, January 11, 2004 5:41 PM, John Brown (CV) [SMTP:[EMAIL PROTECTED] wrote: Hi List, After reading a bunch of the docs, list post archives, it still seems that a clear definition of how to clock the T100P card is muddy. zttool says that the link is INTERNALLY CLOCKED, does this mean the T100P is providing clock, or does this mean the T100P is getting clock from the T1 line side (ergo getting clock from the Telco) ?? This was really confusing for me when I started. Let me explain it this way. If you want to run on the internal T100P clock then set sync to '0' To derive the timing from the incoming T1 line (loop timing) set sync to '1' If you have sync = 0 then zttool says internally clocked if sync 0 then zttool says Digium... and link goes into an error condition. I don't know what this would be. Thus the million dollar question is this: What should the SYNC value be if you want to clock from the TELCO ? sync should be set to 1 to time from telco. Maybe zttool is reporting things in error ?? thanks mucho -- Don Pobanz ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users ___ Asterisk-Users mailing list [EMAIL PROTECTED] http://lists.digium.com/mailman/listinfo/asterisk-users To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
