nanog mailing list archives
Re: MPLS VPNs or not?
From: David Charlap <david.charlap () marconi com>
Date: Tue, 07 Aug 2001 17:15:21 -0400
Craig Partridge wrote:
the notion MPLS is faster to switch than IP reflects a poor knowledge of router innards, or a poor router design.
Or just outdated information. It wasn't too long ago that IP best- match lookup hardware couldn't do line-rate at the high speeds needed in the cores of large networks. At that time, ATM was able to do line- rate forwarding at those speeds. This is one of the reasons that ATM was adopted in those networks. One of the big reasons for ATM's speed is its use of fixed-length VPI/VCI header lookups instead of variable- length IP best-match lookups. MPLS, thanks to its use of a fixed- length label header lookup has the same advantage. Over time, however, this advantage disappeared. IP best-match lookup chips were developed that could do a proper IP lookup at full line rate for OC-48 and even OC-192. With line-rate IP lookup, it's no longer possible for something else to be faster. It is possible that the pendulum may swing back the other way in time, of coruse. It is possible that IP lookup chips that can handle the next generation of line rate may not become available in a timely manner, which would once again give the advantage to fixed-length header lookup chips. But not having a crystal ball at hand, I have no idea if this is actually going to happen or not. -- David
Current thread:
- RE: MPLS VPNs or not?, (continued)
- RE: MPLS VPNs or not? Daniel Golding (Aug 07)
- Re: MPLS VPNs or not? Christian Kuhtz (Aug 07)
- RE: MPLS VPNs or not? Irwin Lazar (Aug 07)
- RE: MPLS VPNs or not? Kavi, Prabhu (Aug 07)
- Re: MPLS VPNs or not? Fletcher E Kittredge (Aug 07)
- Re: MPLS VPNs or not? Dave Israel (Aug 07)
- Re: MPLS VPNs or not? Craig Partridge (Aug 07)
- RE: MPLS VPNs or not? Daniel Golding (Aug 07)
- Re: MPLS VPNs or not? Neil J. McRae (Aug 08)
- RE: MPLS VPNs or not? James Cumming (Aug 08)
- Re: MPLS VPNs or not? Fletcher E Kittredge (Aug 07)
- Re: MPLS VPNs or not? David Charlap (Aug 07)
- RE: MPLS VPNs or not? Daniel Golding (Aug 07)
- Re: MPLS VPNs or not? [ bust a gut laughing] Fletcher E Kittredge (Aug 08)
- Re: MPLS VPNs or not? Valdis . Kletnieks (Aug 08)
- Re: MPLS VPNs or not? Craig Partridge (Aug 07)
- Re: MPLS VPNs or not? Scott Brim (Aug 08)
- Re: MPLS VPNs or not? Craig Partridge (Aug 08)