[cisco-bba] ATM : VP & VCI

[Bryan Campbell]

Let's make this a bit more simple.

VPI/VCI is kinda like a phone number.

Imagine the phone number 22-333-444-5555.

A call to that number can be switched at country code (22), area code 
(333), exchange (444), or end customer digits (5555).  The only 
difference is that ATM is not native voice traffic.  It is ATM cell 
traffic.  And, the traffic can have switching treatment by VPI, VCI, or 
both, that is applied at layer 2 or layer 3 by the ATM network.

The most comparable data technology is Q-in-Q vlan tagging.

And, if you don't understand VPI-VCI now, you should read "Essentials of 
ATM Networks and Services" by Oliver C. Ibe.

Enjoy!





raghuram chary wrote:
> Doug Thanks for the reply.But I couldnt understant what you are saying.
> 
> 
> On Sat, Jan 3, 2009 at 1:23 AM, Doug McIntyre <merlyn at geeks.org 
> <mailto:merlyn at geeks.org>> wrote:
> 
>     On Fri, Jan 02, 2009 at 08:05:35PM +0530, raghuram chary wrote:
>      > Hi all,I'm unable to understand/imagine the VP and VC concept in ATM
>      > technology.Can anyone explain the concept in detail?Any website
>     pointers or
>      > animated videos will also be appreciated.
> 
>     Its much like a DLCI in frame relay or a VLAN tag in ethernet networks..
> 
>     An identifier to mark this cell/packet/frame/whatever is identified
>     with this number and we differentiate that from other cells that could
>     be for other things.
> 
>     As to the reason for splitting the identifier into two seperate ones,
>     ATM allows you to do path switching as well as VPI switching. You can
>     take everything within the same VPI and push it out a different port
>     than another.
> 
>     You could have all of customers X traffic on VPI 10, and all of
>     customer Y's traffic on VPI 11. Now, no matter how many VPI's customer
>     X lights up, your switching setup continues to work without additional
>     setup on your switching gear.
> 
>     There's reserved VCI's so that also comes into play (ie. why the first
>     PVC may be on 0/32 instead of 0/0 like you'd expect).
> 
> 
> 
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