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RE: MPLS in metro access networks

  • From: Daniel Golding
  • Date: Fri Nov 16 12:32:04 2001

The only problem with this approach is the idea that you can divource a
standards based approach like MPLS with the vendor specific implimentation
of switching methodologies. On the Cisco platform, for example, MPLS is
deeply tied into CEF, for somewhat logical reasons - Cisco saw no need to
reinvent the wheel, and didn't want to go down the path of a new forwarding
technology.

The platforms are STILL using proprietary switching methods - they always
will, as it is a distiguisher.

You seem to imply that if you use MPLS, you won't be using other methods of
distributed or fast switching on your routers. This simply is not the case.
On Cisco's you will still use CEF, and on Junipers you will use ASIC-based
FPC switching.

MPLS is not useful in and of itself as a switching mechanism. However, it is
useful for TE, VPNs, etc. If you enable MPLS on your network to get "better
performance", "faster speeds", or a "more reliable core", you will be
disappointed in the end, as the performance is the same, speed is the same,
and reliability is lower due to immature code.

- Daniel Golding

-----Original Message-----
From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu]On Behalf Of
Quibell, Marc
Sent: Thursday, November 15, 2001 1:04 PM
To: 'mcohen@thrupoint.net'; nanog@merit.edu
Subject: RE: MPLS in metro access networks



I guess you answered your own question: "And I'm not sure what faster
switching/routing has to do with MPLS:)"

As far as CEF and such goes, I couldn't disagree with that (as I was not
comparing MPLS to other optimized forwarding techniques), however, MPLS is
not a vendor-proprietary forwarding mechanism, which means that I can deploy
it worldwide, or state-wide, whatever the case may be, in my network and
have the benefit of using only ONE protocol with MPLS-enabled/aware
routers/switches. A definate plus over the other proprietary fast switching
techniques you mentioned.

Your last statement indicates "added services" have nothing to do with the
the fast switching processing of MPLS, when in fact these services depend
upon the faster delivery of the non-proprietary fast switching of MPLS. As
quoted from the rfc:

"This memo presents an approach for building core Virtual Private
   Network (VPN) services in a service provider's MPLS backbone.  This
   approach uses Multiprotocol Label Switching (MPLS) running in the
   backbone to provide premium services in addition to best effort
   services."

Marc


-----Original Message-----
From: Michael Cohen [mailto:mcohen@thrupoint.net]
Sent: Thursday, November 15, 2001 11:20 AM
To: nanog@merit.edu
Subject: RE: MPLS in metro access networks



I still have to disagree that MPLS results in faster switching/routing in
modern service provider networks.  Modern vendor caching mechanisms are just
as fast if not faster than MPLS processing.  With the small overhead of MPLS
labels and LDP I highly doubt that you're getting any performance increase
over Cisco's CEF or Juniper's FPC architecture.  I also doubt that speed is
a benefit that service providers consider when deciding whether or not they
want to implement MPLS.  Added services that run on top of MPLS like VPNs,
traffic engineering, and fast rerouting capabilities (all mentioned in the
original post) are more likely the benefits considered.  Perhaps when label
switching was first being marketed (Ipsilon and Cisco in 1996) there were
some speed benefits but now I think it's the services that use MPLS that are
the major benefit.

-Michael Cohen

-----Original Message-----
From: Quibell, Marc [mailto:mquibell@icn.state.ia.us]
Sent: Thursday, November 15, 2001 10:59 AM
To: 'mcohen@thrupoint.net'; 'nanog@merit.edu'
Subject: RE: MPLS in metro access networks


soooo...Label switching assigns labels to packet headers which results in
less time and processing looking up routes, and instead relies upon a label
index for forwarding decisions? Hence my statement "faster switching/routing
and less processing":)

Marc



-----Original Message-----
From: Michael Cohen [mailto:mcohen@thrupoint.net]
Sent: Thursday, November 15, 2001 10:56 AM
To: Quibell, Marc
Subject: RE: MPLS in metro access networks


I hope so:)

-----Original Message-----
From: Quibell, Marc [mailto:mquibell@icn.state.ia.us]
Sent: Thursday, November 15, 2001 10:46 AM
To: 'mcohen@thrupoint.net'; nanog@merit.edu
Subject: RE: MPLS in metro access networks


Are we talking about Multiprotocol Label Switching?

Marc


-----Original Message-----
From: Michael Cohen [mailto:mcohen@thrupoint.net]
Sent: Thursday, November 15, 2001 10:45 AM
To: nanog@merit.edu
Subject: RE: MPLS in metro access networks



And I'm not sure what faster switching/routing has to do with MPLS:)  I
believe one of the ideas behind MPLS benefiting metro access networks is
using MPLS to deliver layer 2 VPNs across an MPLS enabled core thus
simulating leased lines for access clients...but I'm sure somebody will
correct me if I'm wrong.  There seems to be some hype for Martini draft VPNs
and large enterprise customers in metro areas.

Cheers,

-Michael Cohen

-----Original Message-----
From: owner-nanog@merit.edu [mailto:owner-nanog@merit.edu]On Behalf Of
Quibell, Marc
Sent: Thursday, November 15, 2001 10:20 AM
To: 'srihari varada'; nanog@merit.edu
Subject: RE: MPLS in metro access networks



I would think faster switching/routing and less processing would be wanted
in any mid-to-large sized network...I'm not sure what load balancing and
fault restoration has to do with MPLS....

Marc



-----Original Message-----
From: srihari varada [mailto:varada@txc.com]
Sent: Thursday, November 15, 2001 10:12 AM
To: nanog@merit.edu
Subject: MPLS in metro access networks


Hello:

I have heard some stressing the role of MPLS in metro access networks.
It is difficult for me to visualize the need for it in them while it
is not so difficult to understand the utility (load balancing and fault
restoration etc.) of it in the metro backbone networks.

To characterize metro access networks in the context, the following is
provided:
-- aggregates traffic from residential (arriving via broadband access
   links such as xDSL, Cable) and business consumers (arriving via
broadband access links such as
   xDSL and high speed links such as Ethernet or SONET)
-- funnels aggregated traffic to metro backbone networks for destination

    hosts in the local metro region or remote regions across the
internet regional
   and backbone networks. Majority of such access networks are SONET/ATM
based (I didn't come
   across any case of Gig Ethernet. However, I do not preculde it).

Thus, there are two questions:
-- Are there known RBOCs/ILECs and CLECs entrenching MPLS in the said
   network scope? (I do not see many major ILECs in the un-official MPLS
service
   providers list being circulated but it may mean little)
-- If so, what motivates them to do so? Any analysis of the driving
forces is appreciated.

Regards,

Srihari Varada





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