Cell Relay Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] Oldies question: switch VP or VC?
Hi all, I study a migration from ATM to MPLS and encounter a problem in MPLS which leads me to ask a basic question in ATM. So I'll first ask the question in ATM and explain the MPLS context which creates this doubt in my mind. Question: switching VPs instead of VCs is preferable in ATM because of less overhead and is usualy done by big providers who don't want to manage VC levels in their backbone. But in this case how an ATM switch knows it must switch only on VPI instead of the couple (VPI.VCI)? In other words, how to tell an ATM switch that it is a VP switch, not a VC switch? MPLS context: the label stacking in MPLS is similar to VCI/VPI switching in ATM i.e. VPI is the outer label and VCI is the inner label. A LSR (label switch router) switch only on outer label. But the push/pop operation on labels is done always by an edge router (LER) who knows it is an edge router (by configuration?). What is the similitudes/differences between ATM and MPLS approches? Many thanks, Anouch Sent via Deja.com http://www.deja.com/ |
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