Frame-Relay Clocking

[nbhungalia]

Ok, we are having a huge debate at work about clocking and clock rate for Frame Relay circuit. Is clocking same as the port speed? Also, is clocking and clock rate are the same thing? Thanks in advance....

[jhalldn]

Hi,

As i was told this is a question about DCE and DTE.

Data Communication Equipment.

Data Termination Equipment.

DCE must provide clocking for the DTE.

If your running to routers back-to-back with an DTE and a DCE cable, one must be DCE and provide clocking. The configuration command is clock rate xx.

When running a link with modem and routers, the modem is the DCE and provide the clocking to the router (DTE). The modem and line are preconfigured with the rate of your order.

Hence, clocking and clock rate are the same and is the bandwidth provided over a link.

[rjackson]

Yes they are the same thing but they are pratically irrelevent to the "speed" of a frame relay circuit. The trick with frame relay is there are two local loops and a frame relay cloud in between. You can have a T1 at one end and multiple 56k loops at the other end/s. In the local loops the signal speed is the same the difference is the clock speed (and muxing on the t1) that crams more data bits into a time segment. The local loops get their clock from the csu/dsu's. The port on the frame switch that the local loops connect to is a separate device which you would think is the same speed as the local loop. But it only has to be as fast as the excess burst rate of the pvc. The frame cloud is usually much faster than either local loop. Carriers have high speed backbones (atm) that move the data as fast as possible to clear space in the network. Then the data comes back out on a 56k loop. Three different speeds. The design of the pvc is the real limiting factor on frame relay. You can have t1 speeds at both ends but if the pvc has a 16k cir you'll only get the burst limit over that.