Comment Re:MPLS sucks (Score 5, Informative) 94
MPLS totally sucks. It's the X.25 of the new
millenia, just as ATM was the X.25 of the 90's.
Why? It's a CIRCUIT SWITCH methodology on top
of a PACKET SWITCHING network. Dumb! It's
another thing to manage and break from a network
engineering point of view. That, and most
vendors implementations don't work worth a damn
today.
[snip]
This would be enough for a person with an average education in MPLS to judge how much you (don't) know about MPLS. I am doing MPLS-oriented research for the last 1.5 years so let me try clearing some of the "bad air" around the issue:
1) MPLS is NOT circuit switching ON TOP of packet switching. If you would care to do some minimal reading before you flame a subject, you would find out that MPLS is not ISO layer >= 3 but it is a "layer 2.5" technology. In other words IP datagrams are carried on top of MPLS frames pretty much the way ATM worked.
2) The reasons behind MPLS are too complex to describe here (for the intrested reader, take a look at RFC3031). But basically it was acknowledged that despite ATM being "evil" circuit switched technology does offer some advantages. That's why you can (_very_ roughly) characterize MPLS as an "IP friendly ATM", minus some of ATM's design shortcomings (that were present there due to the technology limitations at that time and ATM's intended use).
But to rebute your misconception, MPLS is NOT about "routing IP datagrams fast", nor "replacing CIDR". Again, if you care to skim the mentioned RFC it is acknowledged that this _were_ some advantages few MPLS proponents claimed but this is simply not true, as you correctly state: Efficient algorithms for IP address lookup and routing are implemented in hardware by several vendors (incl. cisco, btw...) so MPLS doesn't have any edge there.
3) About "Traffic Engineering being a load of crap" I would say that few of the top 10 largest carriers in US might disagree a bit. Get a hold of an educated MCI network operations engineering (say MCI/UUNET) and ask how much improvement (and revenue) TE gives them. And yes, the reaction is "WOW".
And QoS... Same deal- load of crap.
4) Well, QoS is too broad a topic to disuss in any relevance here. But in saying that you automatically excluded _all_ mechanisms for traffic differentiation in a network. Enough said.
Also, to end this, MPLS is _not_ only about TE/QoS/IP fast switching. It is used for fast network restoration, it is extended for supporting WDM in a similar manner (see "Generalized"MPLS), etc. People w/ some network education might care to take a look here for a overall view on the MPLS-related topics.
All in all I would dare to say that your posting is the worst kind of mis-information:It contains a grain of truth and mixes completely different and unrelated subjects as "comparisons" (OPenGL w/ CIDR)
For the rest of the readers, the necessary grain of salt when reading the linked article: In IETF there is a lot of politics around MPLS (disguised in "technical debates") -- surprise,surprise. For example if someone cares to browse the MPLS mailing list archives Mr. Randy Bush long opposed BGP/MPLS VPNs (described initially in RFC2547.IIRC there is also draft updating it). Which happen to be a technology cisco pushes very hard and which Mr. Bush opposes violently.
What particular agenda Mr. Bellovin has escapes me. But I assume (again, this is _speculation_) since AT&T made a _huge_ investment in ATM in the past do not see MPLS (which is simply a better competening technology) so favorably.
All in all, remember that the most competent answer is "I don't know.It depends".
My $0.02
Florian-Daniel Otel
http://www.ce.chalmers.se/staff/otel
[snip]
This would be enough for a person with an average education in MPLS to judge how much you (don't) know about MPLS. I am doing MPLS-oriented research for the last 1.5 years so let me try clearing some of the "bad air" around the issue:
1) MPLS is NOT circuit switching ON TOP of packet switching. If you would care to do some minimal reading before you flame a subject, you would find out that MPLS is not ISO layer >= 3 but it is a "layer 2.5" technology. In other words IP datagrams are carried on top of MPLS frames pretty much the way ATM worked.
2) The reasons behind MPLS are too complex to describe here (for the intrested reader, take a look at RFC3031). But basically it was acknowledged that despite ATM being "evil" circuit switched technology does offer some advantages. That's why you can (_very_ roughly) characterize MPLS as an "IP friendly ATM", minus some of ATM's design shortcomings (that were present there due to the technology limitations at that time and ATM's intended use).
But to rebute your misconception, MPLS is NOT about "routing IP datagrams fast", nor "replacing CIDR". Again, if you care to skim the mentioned RFC it is acknowledged that this _were_ some advantages few MPLS proponents claimed but this is simply not true, as you correctly state: Efficient algorithms for IP address lookup and routing are implemented in hardware by several vendors (incl. cisco, btw...) so MPLS doesn't have any edge there.
3) About "Traffic Engineering being a load of crap" I would say that few of the top 10 largest carriers in US might disagree a bit. Get a hold of an educated MCI network operations engineering (say MCI/UUNET) and ask how much improvement (and revenue) TE gives them. And yes, the reaction is "WOW".
And QoS... Same deal- load of crap.
4) Well, QoS is too broad a topic to disuss in any relevance here. But in saying that you automatically excluded _all_ mechanisms for traffic differentiation in a network. Enough said.
Also, to end this, MPLS is _not_ only about TE/QoS/IP fast switching. It is used for fast network restoration, it is extended for supporting WDM in a similar manner (see "Generalized"MPLS), etc. People w/ some network education might care to take a look here for a overall view on the MPLS-related topics.
All in all I would dare to say that your posting is the worst kind of mis-information:It contains a grain of truth and mixes completely different and unrelated subjects as "comparisons" (OPenGL w/ CIDR)
For the rest of the readers, the necessary grain of salt when reading the linked article: In IETF there is a lot of politics around MPLS (disguised in "technical debates") -- surprise,surprise. For example if someone cares to browse the MPLS mailing list archives Mr. Randy Bush long opposed BGP/MPLS VPNs (described initially in RFC2547.IIRC there is also draft updating it). Which happen to be a technology cisco pushes very hard and which Mr. Bush opposes violently.
What particular agenda Mr. Bellovin has escapes me. But I assume (again, this is _speculation_) since AT&T made a _huge_ investment in ATM in the past do not see MPLS (which is simply a better competening technology) so favorably.
All in all, remember that the most competent answer is "I don't know.It depends".
My $0.02
Florian-Daniel Otel
http://www.ce.chalmers.se/staff/otel
