WIC 1DSU-T1 vs VWIC2-1MFT-T1/E1

[anestis.iliadis]

Hi all,

I'm looking at a production router with a VWIC2-1MFT-T1/E1 module and neither side of the serial p2p connection has any clock rate configurations. Now I know with the VWIC2-1MFT-T1/E1 that everything is configured under the controller interface. However I'm seeing no clock rate command like with the WIC 1DSU. How does this work? Does that mean that there is a DSU/CSU at that location? I'm just used to seeing the WIC 1DSU-T1 more and haven't worked with the multiflex modules before.

thank you,

[Jose Bogantes]

Hello,

WIC-1DSU-T1, WIC-1DSU-T1-V2, HWIC-1DSU-T1 and any  VWICX-XMFT-T1/E1 (First, second and third generation) offer an  integrated CSU/DS. Thus, you do not need the clock rate configuration  under the interface. WIC-1DSU-T1, WIC-1DSU-T1-V2 and HWIC-1DSU-T1 work always as T1s while VWICX-XMFT-T1/E1s can work as T1 or E1. The cards that need an external DSU/CSU are WIC-XTs and HWIC-XTs (X changes depending on the number of the ports). The 

Synchronous Maximum Speed (Per Port) is up to 8 Mbps and the external DSU/CSU is the one limiting the speed depending on the circuit specifications. You can find more informartion in  the next link:

http://www.cisco.com/en/US/prod/collateral/modules/ps5949/datasheet_c78-491363.html

[anestis.iliadis]

Jose, thank you for the excellent answer!

So just to make everything clear in my head, what happens when one side uses a VWICX-XMFT-T1/E1 or WIC-1DSU-T1 and the other side uses a WIC-XT with a DSU/CSU? Since the ones that don't use a clock rate command use the maximum of 8mbps how can they talk to to the other side that uses a DSU/CSU that needs a clock rate to be specified? Also another scenario is not clear to me is what happens if both sides use flexi cards or WIC-1DSU? Where do you specify that the capacity of the line is less than 8mbps... ie. 1.544mpbs ?

thank you,

[paolo bevilacqua]

If you check carefully, you will see there is no clock rate option for any variety of WIC/HWIC/VWIC T1, with or without CSU. The reason is that T1 circuits are of fixed speed.

[Jose Bogantes]

Hello,

When we have a VWICX-XMFT-T1/E1 or WIC-1DSU-T1 connected to a WIC-XT with a DSU/CSU, the external DSU/CSU will limit the speed for we are converting the circuit to a T1. External DSU/CSUs have a data port adapter where an RJ-45 can be connected. Thus, you can easily now connect it to a VWICX-XMFT-T1/E1 or WIC-1DSU-T1 for the interface connector is RJ-45. Clock rate is not needed in this case for the external DSU/CSU provides clocking.

When you have VWICX-XMFT-T1/E1s or WIC-1DSU-T1s on both sides, you do not need any clock rate for they have an integraded DSU/CSU. Thus, they will talk to each other as long as the framing, linecoding, clocking, encapsulation and timeslots pattern parameters are properly configured on both sides.

The clock rate command is used when you have a back-to-back connection so that one side is the DTE while the other is the DCE. The clock rate should be configured under the interface that appears as the DCE; otherwise the protocol will never come up.

Regards.

[anestis.iliadis]

Paulo thank you for the answer, I do see that now. I just wanted to understand why.

Jose, excellent aswer! Thank you for the thorough explanation. Everything is much much clearer now.

However, I'm still a bit confused about this... you did say that they will talk to each other as long as both sides have the correct framing, linecoding, encapsulation, timeslots AND clocking. So then what provides the clocking?

The modules with the integrated DSU/CSU will auto detect the line from the isp at the demarc point? So say if I have an agreement with my ISP for a 1.544mbps the wic will detect that?

For example here's a simple point to point link that I'm looking at using a VWICX-XMFT-T1/E1

controller T1 0/0/0
 framing esf
 linecode b8zs
 channel-group 0 timeslots 1-24

framing - set

linecoding - set

timeslots - set

no encapsulation so default to hdcl - set

so then where's the clocking? How does it know not what to use?

And also in the scenario that I just mentioned that the other side has a WIC-1DSU-T1 instead, where would I set the matching parameters (framing, liecoding) since there's no controller interface?

maybe like this?..

service-module t1 framing esf

service-module t1 linecode b8zs

service-module t1 timeslots 1-12 speed 64

service-module t1 data-coding normal

service-module t1 cablelength short 440ft

service-module t1 remote-loopback full

I'm sorry for all these little questions, you answered my original much more clearly that I was ever expecting to, it's just that the better I understand the details, the more clear everything becomes in my head

thank you and I really appreciate your time in answering me,

[Jose Bogantes · Accepted solution]

Hello,

If you have a WIC-1DSU-T1, WIC-1DSU-T1-V2 or HWIC-1DSU-T1, you need to go under interface configuration and type service-module t1 clock source:

3845_2(config)#int serial 0/1/0

3845_2(config-if)#service-module t1 clock source ?

  internal  Use adapter internal clock

  line      Recover clock from line

You have 2 options here as you can see. Internal provides clocking and line receives clocking. In a back-to-back circuit, it is recommended to configure one end as "internal" while the other remains "line". If your provider is in the middle providing clocking for both ends, the "line" configuration is recommended but this depends on the circuit specifications. You can use the "show service-module" (do not forget clearing the counters to see the fresh statistics) command to know if there are clocking issues. Basically, you need to focus on the " Slip Secs" value. If it is increasing, it is recommended to check if clocking is properly configured. Sometimes you will need to get the provider involved to confirm the proper clocking configuration you should have.

On the other hand, if you have a VWICX-XMFT-T1/E1 you need to enter controller configuration and choose the proper clocking configuration. It basically works the same as in a WIC-1DSU-T1 and similar hardware.

3845_1(config)#controller t1 0/0/0

3845_1(config-controller)#clock source ?

  free-running  Free Running Clock

  internal      Internal Clock

  line          Recovered Clock

"The free-running keyword  specifies a free-running clock derived from the oscillator on the  motherboard, which is used only for testing and back-to-back  connections".

http://www.cisco.com/en/US/docs/ios/12_2/12_2z/12_2zj/feature/guide/gthwecan.html

To look for statistics use the "show controllers t1 X/X/X" command and avoid using any "loopback" command for it would affect the connection since it is used just for testing purposes. I hope this information helps and do not forget rating the useful posts.

Regards.

[anestis.iliadis]

Jose Bogantes,

thank you for your excellent answers! Your replies have been very helpful and thorough!

I really appreciate it!