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Bronze

Clock rate on back-to-back serial

Hello,

I have a back-to-back T1 circuit for LAB testing of Multicast along with QoS.

Anyone know with 100% certainty what the speed should be for a full T1 link?

I made the assumption 1600000 but not sure if this is correct.

Tks

Frank

These are my options:

WAN3(config-if)#clock rate ?

         Speed (bits per second)

   1200

   2400

   4800

   9600

   14400

   19200

   28800

   32000

   38400

   56000

   57600

   64000

   72000

   115200

   125000

   128000

   148000

   192000

   250000

   256000

   384000

   500000

   512000

   768000

   800000

   1000000

   1300000

   1600000

   2000000

   2600000

   3200000

   4000000

   5300000

   8000000

   <300-8000000>    Choose clockrate from list above

6 REPLIES
Super Bronze

Re: Clock rate on back-to-back serial

Disclaimer

The Author of this posting offers the information contained within this posting without consideration and with the reader's understanding that there's no implied or expressed suitability or fitness for any purpose. Information provided is for informational purposes only and should not be construed as rendering professional advice of any kind. Usage of this posting's information is solely at reader's own risk.

Liability Disclaimer

In no event shall Author be liable for any damages whatsoever (including, without limitation, damages for loss of use, data or profit) arising out of the use or inability to use the posting's information even if Author has been advised of the possibility of such damage.

Posting

1600000 is as close as you're going to get to a full T1 on your device's clock rate options.

New Member

Clock rate on back-to-back serial

I personally would go down one more rate. You will never get the full speed of a T1 or any connection for that matter. IMO.

Silver

Clock rate on back-to-back serial

fsebera wrote:

Hello,

I have a back-to-back T1 circuit for LAB testing of Multicast along with QoS.

Anyone know with 100% certainty what the speed should be for a full T1 link?

I made the assumption 1600000 but not sure if this is correct.

Tks

Frank

A T1 runs at 1.544 megabits per second (2048 megabits per second if you're in an enlightened country like me and run the proper "E" system. :-)) - or 1544000 bits per second - so the closest you're going to get is 1600000.

That would adequately simulate a "real" T1.

Cheers.

Bronze

Clock rate on back-to-back serial

Thanks for the help!!

After doing more research it looks like the Cisco IOS/Serial hardware will dynamically clock to the highest level the hardware supports if you select a clock rate higher than the actual hardware interface rate.

:

Setting the clock rate to the highest clock rate available, 8000000 (8 Million) will only provide the serial rate of a T1 (in this example) - according to some older Cisco documentation I found on a Google search.

:

In the other direction

You can slow the data rate passing through the serial link by setting the clock rate to a lower clock rate; this will definitely SLOW the throughput speed slower than the actual hardware rate. Sending the full T1 data rate from an upstream device will overflow the input buffers on the "lower clock rate" serial interface. You can also slow down the serial interface by setting the controllers channel-group to use fewer timeslots.

:

Thanks again for the help

Frank

Super Bronze

Re: Clock rate on back-to-back serial

Disclaimer

The  Author of this posting offers the information contained within this  posting without consideration and with the reader's understanding that  there's no implied or expressed suitability or fitness for any purpose.  Information provided is for informational purposes only and should not  be construed as rendering professional advice of any kind. Usage of this  posting's information is solely at reader's own risk.

Liability Disclaimer

In  no event shall Author be liable for any damages whatsoever (including,  without limitation, damages for loss of use, data or profit) arising out  of the use or inability to use the posting's information even if Author  has been advised of the possibility of such damage.

Posting

I believe you'll find the typical serial interface can go faster than T1; would expect them to at least support E1 (2 Mbps) too.  I believe I've been able to get 8 Mbps on a pair of 2811s configured back-to-back serials.

When you set the clock-rate you are adjusting the hardware rate of a serial interface.

As to sending at full T1 rate on one side of a serial interface and receiving on the other side with clock rate set slower, unsure you can do this with back-to-back serial connection.  One side is configured as DTE the other as DTC.  I.e. one side generates clock used by both sides.

As to using timeslots, believe that might be specific to using an intergrated DSU/CSU.  Back-to-back serial usually is back-to-back serial ports, but if you're going to use DSU/CSU, internal or external, available bandwidth will be different from serial port to serial port back-to-back.

Bronze

Clock rate on back-to-back serial

Ahhh, good point, yes if you are using the older serial modules without the built-in csu/dsu, then yea you are sort of limited as to what you can modify -with reference to the serial interface.

:

Tks

Frank

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