The MPLS-OPS Archive

["J L T" <jlt@sbcglobal.net>]

Chris:

>From the sound of your message, it sounds like we must accept one other
the other and we simply can't have both.  In effect, I think your saying
that the hardware architectures are so different, and no simple
mechanism have been found that can effectively map the two environments.
Interestingly, in my review of the history of MPLS' development, Toshiba
introduced the concept of a Cell Switch Router.  Their proposal, if
taken to its natural conclusion, would have given label switch routers
the ability to offer hard QoS mechanisms in a packet network using IP
signaling mechanisms.  Yet, ultimately, it was determined that there was
not a clear market need nor problem that was being addressed with the
proposed architecture.   I'd be very interested in hearing whether this
is a solvable problem architecturally and whether there is indeed that
market need.  It seems that much of the "hard bounded" QoS needs revolve
around packet switched transit services and private networks in their
transition to packet switching.  Furthermore, private ATM and FR
networks appear to be one of the few decently profitable operations for
most providers.  IMHO, I would think that being able to offer both hard
guarantees for the vast majority of traffic, and allowing them to
transition to packet switching could be very appealing.  I it just not
architecturally possible at this point?

Jeff  

jlt@sbclobal.net


-----Original Message-----
From: Christopher Lewis [mailto:chrlewis@cisco.com] 
Sent: Monday, January 28, 2002 1:29 PM
To: Daniel Kharitonov
Cc: mpls-ops@mplsrc.com
Subject: Re: Guaranteed QoS using MPLS?


A long discourse on ATM vs MPLS is pointless. It just depends what
problem 
you are trying to solve. If your main aim is to transport IP traffic, IP

networks have more appropriate queuing mechanisms. Getting ATM networks
to 
differentiate between an IP application with high priority and an IP 
application with low priority is a real pain (as an aside, QoS is an end
to 
end issue, there is no ATM to the desk top, and the ethernet card is not

going to understand CBR or VBR). To map Ip to ATM QoS you either have to

perform something like a queue and drop on a per precedence basis in to
one 
VC, or have multiple VCs and map the IP traffic to the different VCs 
depending on how you want to map a given precedence level to a VC type.

If you want to have hard edge to edge QoS guarantees for all traffic,
ATM 
is probably what you want. So a provider that primarily wants to offer 
voice services on their private network, plus some data and no internet 
access may make a different choice than a provider that offers internet 
access, differentiated level of service for data and some voice.

Chris


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