how do we connect to frame relay cloud

[sarahr202]

hi every body!

how remote office is connected to frame relay cloud?

my understanding is remote office router------dsu/csu------------ frame relay cloud

Do we connect to frame relay switch on service provider network by digital lines such as T1. ds3 etc?

thanks a lot!

[Giuseppe Larosa · Accepted solution]

Hello Sarah,

you can access a frame-relay cloud by using any kind of synchronous serial links from fractional T1 to DS3.

In some cases a dsu/csu is present as a separate box.

On the router side you configure the frame-relay encapsulation that overrides the default Cisco HDLC.

Actually the access link is a point-to-point connection to the FR switch port.

FR provides the capability to build the L2 logical circuits (PVC or sometimes SVC) that can reach multiple different locations via the FR cloud.

the router serial interface and the FR switch port exchanges LMI messages that inform about what DLCI are defined and the status of each PVC.

on the router you can use

sh frame-rel lmi

sh frame-rel pvc

to check lmi exchange and PVC status and counters.

Hope to help

Giuseppe

[sarahr202]

Thanks a lot Giuseppe!

I studied about frame relay for my ccna few years a go.

I just want to know how in real life, we connect the remote side for example to frame relay cloud.

I undestand that some time we dont need seperate dsu/csu unit as it is implemented on wan card in router. But when we do need csu/dsu , what do we configure on it besides clock rate?

i understand we have to implement ip to dlci mapping besides other frame relay related configurations. But in real life, what do we need to configure on csu/dsu?

thanks a lot!

[Giuseppe Larosa · Accepted solution]

Hello Sarah,

thanks for your kind remarks.

the CSU/DSU actually works at ISO layer1 converting V.35 signals and cabling to the outgoing standard that for E1 can be G.703 on a pair of thin coax cables.

The CSU/DSU will have two ports: one V.35 port towards the router interface with L1 DCE role and one port to the TELCO provider link where it plays a DTE role (I suppose).

The V.35 CD signal to the router can be conditioned to the state of the TELCO line.

This is important because depending oh this setting the router interface can be up/down or down/down for the same problem.

CSU/DSU for E1 are called DCE3 have usually an RS-232 console port and offer a modem like CLI with the famous AT commands.

Some of them have a GUI software you can use to configure them.

Here, the DCE3 is provided by the TELCO provider. I think it is so in most european countries.

In US the CSU/DSU could be on the customer side as happens for ISDN.

Hope to help

Giuseppe

[sarahr202]

Thanks a lot Giuseppe!

Here in usa, is csu/dsu provided by service provider to customer?

Who configures it customer or teleco engineer ?

thanks a lot!

[Giuseppe Larosa · Accepted solution]

Hello Sarah,

I think that the device is configured by telco if provided by them.

If the customer provides the CSU/DSU it has to configure it following telco specifications.

Hope to help

Giuseppe