The MPLS-OPS Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] Re: IGP tuning for TE versus MPLS-TE
You have to look at two cases (at least): 1. Steady state: If you keep your trunks and routers lightly loaded (as Sprintlink does), then IGP metrics should work fine in the steady state. The key is that you don't go beyond about 30% loading in the steady state. Both queuing theory and experience show that it is impossible to completely avoid congestion (and packet loss) in the steady state if you go much past that due to IP routing's hyperaggregation, even with carefully designed metrics. Sprintlink has chosen to lightly load their network. MPLS TE works very well if you want to make more efficient use of network resources. 2. Outages: You have to ask, both with IGP metrics and with MPLS TE, what happens when outages occur. It is pretty straightforward to do MPLS TE network designs that include restoration paths without having to reserve a lot of headroom for outage restoration (of course, you do have to reserve SOME headroom - nothing comes for free). The situation is much worse for IGPs, because it is just about impossible to predict in advance what will happen if a particular switch or link fails - how long it will take the IGP to reconverge, and how it will reconverge (where will the traffic go?). And the network will continue to use incorrect metrics until either the outage is repaired, or the metrics are updated to reflect the outage topology. Cheers, Andy --------- At 10/30/2002 09:31 AM +0000, M. ELK wrote: Their is some hot debate previously on this list about an article on MPLS which stated that no need for MPLS ,anyhow the conclusion from this debate was that the writer of such article is clueless .
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