Tony Li <tli@juniper.net> writes:
A SONET MPLS switch makes for a very interesting exchange.
Yes, for all the reasons you outlined, and because we've been talking about it for a couple years, this what I would deploy in the short run if I were interested in getting large-provider business. Having a circuit per peer has some advantages with respect to failure modes, but is expensive. Assuming that there is still a per bit per second per kilometre cost even for inhouse applications, if a reliable alternative existed, I expect that would be used, particularly as the growth curve of inter-provider traffic necessitates expansion of the private peering circuits. I would hope that people at Sprint, UUWHO (and ANS and MCI) and the various other places using private peering points are thinking about migrating from a "you buy one circuit i will buy one circuit" model to a more general "we will run an exchange point here, you bring circuits to us; you run an exchange point there, we will bring circuits to you, they will be running an exchange point there we will both bring circuits to that" one, although actually making a decision to do this would be dependent on costs and the reliability of new big fast routers and MPLS implementations and interoperability. One fat physical circuit that buys you N peers is probably going to be cheaper than N not-so-fat physical circuits at one peer each, in line costs, manageability and capital expenses (router ports etc.) Of course, the key downside to using a SONET MPLS switch/router is back to scaling. A question for you Tony. What does one do when one has an N port MPLS switch/router and has filled all N ports with traffic? Consider that each of the N ports will become fuller and that there will probably be a desire or requirement for N+1 ports with more to come. The lesson of the Gigaswitches and the ATM counterparts is that scaling beyond a single switch is hard. I don't have an answer, given what I know and can imagine about near-term technology (as opposed to stuff I want you and Crashco to build :) )
the forseeable future.
How long is that these days anyway? Anyway, other than the "what do you do other than give up on port density when you have more traffic or connections than one MPLS switch can handle" concern, I am in complete agreement with you, surprise surprise. Sean.
What does one do when one has an N port MPLS switch/router and has filled all N ports with traffic? Consider that each of the N ports will become fuller and that there will probably be a desire or requirement for N+1 ports with more to come.
The lesson of the Gigaswitches and the ATM counterparts is that scaling beyond a single switch is hard.
I don't have an answer, given what I know and can imagine about near-term technology
Two answers. Parallelism and bypasses. Vadim is working on the parallelism idea with his project at pluris.com so we will soon see whether or not this is a workable approach. Bypasses are good old-fashioned highway network technology. When the switch is overloaded (i.e. the cross-bar street network in the city core) divert traffic around the city (switch) with a bypass. Or in other words, when all N ports on your switch are getting full, look at the other end of the circuit going into each port and try to divert some traffic into a bypass that does not go through the switch. Remember that the switch's backplane is essentially a backbone network that has been collapsed into a single box. The scaling problem arises when too much traffic from other networks wants to go through this one box. Step back and look at the bigger picture and you will see that there are solutions that do not require chaining switches together. Of course a simple private interconnect circuit is the classic and the simplest form of bypass, but anything which causes traffic to flow through a different path meets the criteria. Exchange points cannot be designed or scaled as discrete objects; they exist in the context of the entire network mesh. ******************************************************** Michael Dillon voice: +1-650-482-2840 Senior Systems Architect fax: +1-650-482-2844 PRIORI NETWORKS, INC. http://www.priori.net "The People You Know. The People You Trust." ********************************************************
A question for you Tony. What does one do when one has an N port MPLS switch/router and has filled all N ports with traffic? Consider that each of the N ports will become fuller and that there will probably be a desire or requirement for N+1 ports with more to come. The lesson of the Gigaswitches and the ATM counterparts is that scaling beyond a single switch is hard. Yup. The obvious answer is build a bigger switch, and I believe (without demonstrable proof) that some fairly large switches can be built. The less obvious answer is to build a mesh, which I assume has been done for the ATM solutions. If you're familiar with the failure modes, I'd love to hear 'em. Yes, you do fall into the 'small switch penalty' in which you start using up significant bandwidth interconnecting your switches. I've got no magic around that one.
the forseeable future.
How long is that these days anyway? 2 weeks, 3 hours and 17 minutes. ;-) Tony
participants (3)
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Michael Dillon -
Sean M. Doran -
Tony Li