Re: [OSL | CCIE_Voice] Network side vs User side clocking !
Since no one responded, I guess I'll be the geek for now. The difference between using network-side clocking and user-side clocking is similar to the DCE / DTE difference. PRI and E1 are implementations of the ISDN protocol over T1 à a point-to-point, synchronous circuit. Synchronous circuits require timing, so one end should operate as the master of the clock and the other end should recover the clock/timing/synchronization from the master. One of the amazing things about T1 design is that one doesn’t necessarily have to setup clocking correctly to get the circuit to work. However, you must configure it correctly to get the circuit to work well. When I started out, clocking was rudely referred to as master/slave, but fortunately many vendors like Cisco adopted more politically-correct terminology. Network = Master (usually telco side). User side is the other end. In Cisco's case the clock master is defined under the controller T1 x/x/x as 'clock source internal.' Usually a PRI handoff from the PSTN in the real world would be set as so for you on whatever equipment they use to provide you your T1 span. I'd expect your controllers on the PSTN router in the lab to be set ‘clock source internal.’ Don't know for sure if Cisco does it that way in the lab; I assume they would if they wanted it to bear any resemblance to the real world. Therefore, the site A,B C controllers would normally be set opposite to network side, which would be to say, ‘clock source line.’ Since this is the default, the command becomes invisible in the config. A good way someone told me to remember this is, You set the controller to ‘clock source line’ if you want it to look up the line for the clock. The part in your question about layer 1 and layer 2 doesn't exactly pertain to clocking. The 4-wire T1 is layer 1, pins 1-2/4-5. Q.921 is layer 2. Q.931 is layer 3. Without going into much detail, what you can do with the network-clock-participate and network-clock-select command is to inform the router about your preferences as to what to do with the clock timing(s) it recovers on its various T1 controllers. For example in the real world, it is possible to have a PRI from carrier X and another span from carrier Y. In this case you might want to use network-clock-select to control the relative priority of the two clock sources. It is a best practice to set network-clock-select explicitly even if you have only one PRI/E1, as doing so avoids slips. Network-clock-participate informs the router that it may be possible to gather a clock source on a particular wic, and the network-clock-select informs the router as to which one of those to use to sync the backplane of the router. Your PVDM2s that provide the DSPs for the PRIs are probably installed on the backplane, so it would probably be nice if they had benefit to the same clock synchronication. This has nothing to do with NTP. Different kind of clock. Use the following command to check your T1 clocking. 2951R2#show network-clocks Network Clock Configuration --- Priority Clock SourceClock State Clock Type 1 T1 0/0/0GOODT1 2 T1 0/1/0GOODT1 10 Backplane GOODPLL Current Primary Clock Source --- Priority Clock SourceClock State Clock Type 1 T1 0/0/0GOODT1 https://supportforums.cisco.com/thread/189145 Thanks On Sat, Mar 23, 2013 at 6:07 PM, CCIEing aboaz...@gmail.com wrote: Hi geeks :) What is the difference between using Network side clocking and User Side clocking. Regarding the exam, do they ask us to use any one of the both in particular ? I saw practice question informing that the PRI circuit layer 2 should be user side where as it will be a network side clocking for layer 1 as for the last sentence (network site), I would assume that we will use *network-clock- participate wic X* * * *Waiting your valuable input * ___ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com ___ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com
Re: [OSL | CCIE_Voice] Network side vs User side clocking !
Really good explanation from Tony. As an addendum to him, you can use show controllers command to verify that the controller is set to clock source line, which, as Tony already mentioned, is hidden being default. On Tue, Mar 26, 2013 at 8:26 AM, Tony Zunt tony.z...@gmail.com wrote: Since no one responded, I guess I'll be the geek for now. The difference between using network-side clocking and user-side clocking is similar to the DCE / DTE difference. PRI and E1 are implementations of the ISDN protocol over T1 à a point-to-point, synchronous circuit. Synchronous circuits require timing, so one end should operate as the master of the clock and the other end should recover the clock/timing/synchronization from the master. One of the amazing things about T1 design is that one doesn’t necessarily have to setup clocking correctly to get the circuit to work. However, you must configure it correctly to get the circuit to work well. When I started out, clocking was rudely referred to as master/slave, but fortunately many vendors like Cisco adopted more politically-correct terminology. Network = Master (usually telco side). User side is the other end. In Cisco's case the clock master is defined under the controller T1 x/x/x as 'clock source internal.' Usually a PRI handoff from the PSTN in the real world would be set as so for you on whatever equipment they use to provide you your T1 span. I'd expect your controllers on the PSTN router in the lab to be set ‘clock source internal.’ Don't know for sure if Cisco does it that way in the lab; I assume they would if they wanted it to bear any resemblance to the real world. Therefore, the site A,B C controllers would normally be set opposite to network side, which would be to say, ‘clock source line.’ Since this is the default, the command becomes invisible in the config. A good way someone told me to remember this is, You set the controller to ‘clock source line’ if you want it to look up the line for the clock. The part in your question about layer 1 and layer 2 doesn't exactly pertain to clocking. The 4-wire T1 is layer 1, pins 1-2/4-5. Q.921 is layer 2. Q.931 is layer 3. Without going into much detail, what you can do with the network-clock-participate and network-clock-select command is to inform the router about your preferences as to what to do with the clock timing(s) it recovers on its various T1 controllers. For example in the real world, it is possible to have a PRI from carrier X and another span from carrier Y. In this case you might want to use network-clock-select to control the relative priority of the two clock sources. It is a best practice to set network-clock-select explicitly even if you have only one PRI/E1, as doing so avoids slips. Network-clock-participate informs the router that it may be possible to gather a clock source on a particular wic, and the network-clock-select informs the router as to which one of those to use to sync the backplane of the router. Your PVDM2s that provide the DSPs for the PRIs are probably installed on the backplane, so it would probably be nice if they had benefit to the same clock synchronication. This has nothing to do with NTP. Different kind of clock. Use the following command to check your T1 clocking. 2951R2#show network-clocks Network Clock Configuration --- Priority Clock SourceClock State Clock Type 1 T1 0/0/0GOODT1 2 T1 0/1/0GOODT1 10 Backplane GOODPLL Current Primary Clock Source --- Priority Clock SourceClock State Clock Type 1 T1 0/0/0GOODT1 https://supportforums.cisco.com/thread/189145 Thanks On Sat, Mar 23, 2013 at 6:07 PM, CCIEing aboaz...@gmail.com wrote: Hi geeks :) What is the difference between using Network side clocking and User Side clocking. Regarding the exam, do they ask us to use any one of the both in particular ? I saw practice question informing that the PRI circuit layer 2 should be user side where as it will be a network side clocking for layer 1 as for the last sentence (network site), I would assume that we will use *network-clock- participate wic X* * * *Waiting your valuable input * ___ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com ___ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com -- Suresh Bhandari
[OSL | CCIE_Voice] Network side vs User side clocking !
Hi geeks :) What is the difference between using Network side clocking and User Side clocking. Regarding the exam, do they ask us to use any one of the both in particular ? I saw practice question informing that the PRI circuit layer 2 should be user side where as it will be a network side clocking for layer 1 as for the last sentence (network site), I would assume that we will use *network-clock- participate wic X* * * *Waiting your valuable input * ___ For more information regarding industry leading CCIE Lab training, please visit www.ipexpert.com Are you a CCNP or CCIE and looking for a job? Check out www.PlatinumPlacement.com
