DLCI

hi,

I'm struggling to understand the role of a dlci in regards to frame relay. It is said that the dlci is of local significance only, with that how is data forwarded to through the cloud to the reciever. If frame relay virtual circuits use dlci as the addresses, how is it possible to forward data across the cloud bearing in mind that other access lines can use exactly the same dlci. I guess what am trying to ask is how dlci replaces the send and recieve addresses and an idiots guide on how the process works. Thanks

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Comments

EdTheLad

It's very simple

DLCI is used to identify a stream of data on a port, you can multiplex multiple streams on a port using differenbt DLCIs.

rta

FRsw

rtb

FRsw has 2 ports, 1 and 2. The mappping in FRsw is 1.500 to 2.600 , that means when a frame arrives on FWsw port 1 with a dlci 500 it will be sent out port 200 with a dlci 600.
RTA must have dlci 500 locally configured so it knows to send a frame tagged with dlci 500 towards FRsw, RTB must have dlci 600 locally configured so it can recognise a frame arriving from FRsw with dlci 600.

Paul Boz

The DLCI is locally significant, and is only identified by the ingress frame relay switch. Inverse ARP is used to map IP addresses to DLCI's so that the frame relay can traverse the internet cloud while remaining locally significant.

terminal

EdTheLad wrote:

It's very simple

DLCI is used to identify a stream of data on a port, you can multiplex multiple streams on a port using differenbt DLCIs.

rta
FRsw
rtb

FRsw has 2 ports, 1 and 2. The mappping in FRsw is 1.500 to 2.600 , that means when a frame arrives on FWsw port 1 with a dlci 500 it will be sent out port 200 with a dlci 600.
RTA must have dlci 500 locally configured so it knows to send a frame tagged with dlci 500 towards FRsw, RTB must have dlci 600 locally configured so it can recognise a frame arriving from FRsw with dlci 600.

Thanks for the response. It it be right to say that for frame relay to work Mapping has always got to be configured.If that is right, what would be the case if you also had another router, rtc in which you also wanted to communicate with.

Paul Boz

no different. Hub/Spoke is exactly what you're describing.

To clarify, you would have a different frame relay DLCI for each point to point connection. Usually you set up sub interfaces on routers that carry multiple frame relay connections.

ATLANTA-DLCI 102----------------------DLCI 201-HOUSTON
|
DLCI 103
|
|
|
|
DLCI 301
|
MIAMI

As you can see in my crappy diagram, the Atlanta router has a DLCI mapped for each frame relay connection. You could fully mesh them by assigning another frame relay connection from Miami to Houston, which would also be configured using sub interfaces.

terminal

Paul Boz wrote:
no different. Hub/Spoke is exactly what you're describing.

To clarify, you would have a different frame relay DLCI for each point to point connection. Usually you set up sub interfaces on routers that carry multiple frame relay connections.
ATLANTA-DLCI 102----------------------DLCI 201-HOUSTON
|
DLCI 103
|
|
|
|
DLCI 301
|
MIAMI
As you can see in my crappy diagram, the Atlanta router has a DLCI mapped for each frame relay connection. You could fully mesh them by assigning another frame relay connection from Miami to Houston, which would also be configured using sub interfaces.

Brilliantly explained, unable to get that kind of clarity at the academy for the last couple of weeks.......thanks to the tutor. Big Thanks n good luck

Paul Boz

terminal wrote:

Brilliantly explained, unable to get that kind of clarity at the academy for the last couple of weeks.......thanks to the tutor. Big Thanks n good luck

No problem, best of luck