Are DLCI's locally or globally significant???

[deeze6]

Hello all!
I was doing some reading on DLCI's and came across the following statement (I've seen it elsewhere also):
DLCI...In the basic Frame Relay specification, DLCIs are 'locally significant' (connected devices might use different values to specify the same connection). In the LMI extended specification, DLCIs are 'globally significant' (DLCIs specify individual end devices). The FR Switch maps the DLCIs between each pair of routers to create a PVC. DLCI values are typically assigned by the Frame Relay service provider (for example, the telephone company).

So does that mean that with LMI the same DLCI number is used at each end of a Frame Relay connection? Don't all frame-relay implementations use LMI?

Thanks,
Nick

 

[StarTAC]

yes, all FR implementations use LMI, to keep the link alive..

DLCI's can be both globally or locally significant.. the telco's config shd let u know what to choose, but in a typical, simple setup, you have to points sharing a single DLCI, so they can map to each other easily..

FR will take care of the direction the packets take, even though the DLCIs are the same... this would be globally significant..

in locally significant, the DLCI's can differ, and the telco's FR switch will know how to route the packets across the network.. i haven't tried this one before, so i can't say how it really works.. all i have abt it is theory..

good luck..

 

[lve]

LMI is the protocol used on the link between the customer's equipment and the provider's FR switch (the "local loop&quot. All local loop links use some flavor of LMI.

The significance of the DLCI is local only (just look at the packet header - there's only one DLCI field). Once the packet gets to the FR cloud chances are its DLCI is changed multiple times by different FR switches before it reaches its destination. However, to make planning easier, you can assign unique DLCIs for each end point.

 

[deeze6]

So how does LMI make it globally significant?

Thanks,
Nick

 

[Lucas2]

DLCI and LMI are both Local significant. If your provider is talking about globally signicant DLCI he is telling you that they are going to provide de same DLCi# in both ends to make your planning and troubleshooting easy. But technically global significance has no mean.

 

[Jynxx]

What they COULD mean by it is something ont he order of what we have.

We have a head-end "hub" router that has a seperate virtual interface for each PVC...and each PVC having a seperate DLCI. However, on the remote ends, all of the DLCI's are the same, for connecting back to our head-end router. They do not HAVE to be though. As long as your carrier maps it properly through their network, then any DLCI's will work. You just can't have the SAME DLCI's specified on a single router...such as DLCI 30 for 3 virtual circuits on one router.