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RE: DLCI 1 more time [7:75984] posted 09/23/2003
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Steven Aiello wrote:
> 
> OK 1 more time  -  So i read this
> 
> Frame Relay virtual circuits are identified by data-link
> connection
> identifiers (DLCIs). DLCI values typically are assigned by the
> Frame
> Relay service provider (for example, the telephone company).
> 
> Frame Relay DLCIs have local significance, which means that
> their values
> are unique in the LAN, but not necessarily in the Frame Relay
> WAN.
> 
> Figure 10-2 illustrates how two different DTE devices can be
> assigned
> the same DLCI value within one Frame Relay WAN.
> 
> 
> DLCIThe 10-bit DLCI is the essence of the Frame Relay header.
> This
> value represents the virtual connection between the DTE device
> and the
> switch. Each virtual connection that is multiplexed onto the
> physical
> channel will be represented by a unique DLCI. The DLCI values
> have local
> significance only, which means that they are unique only to the
> physical
> channel on which they reside. Therefore, devices at opposite
> ends of a
> connection can use different DLCI values to refer to the same
> virtual
> connection.
> 
> on this link
> 
> http://www.cisco.com/univercd/cc/td/doc/cisintwk/ito_doc/frame.htm
> 
> So in a real life situation, there may be 25 users that share
> bandwidth
> on lets say a T3 line at a local ISP.  Each of these 25 people
> could go
> back to the same CO, and then their lines would all be on a
> telco trunk?
>   the major telco switches back to Joe's local ISP or where
> ever to a
> port on a router, or FRAD?  As long as there are not the same
> DLCI
> numbers on this 1 port things are ok?  And the DLCI's are used
> to
> identify that subcribers traffic becuase it is multiplex and
> put on the
> same line with other peoples traffic?
> 
> Is there some sort of mapping on the telco frame switch that
> points one
> DLCI's traffic to an end point?  Basicly what happens at the
> telco end
> with the DLCI?

The telco's Frame Relay "cloud" consists of a bunch of switches with
pre-configured tables that say, "if it comes in on this circuit with this
DLCI, send it out on this circuit with this DLCI." There's a table like this
at every hop in the cloud.

Priscilla


> 
> Thanks,
> Steve
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