man, 17,.10.2005 kl. 07.17 +0200, skrev Mikael Abrahamsson:
Both MPLS and any tunneled VPN over IP means the core won't have to know about all those prefixes (think aggregation of addresses regionally in the IP case and outer label in the MPLS case).
Hope you don't imply NAT and private addresses like it is usually associated with VPN in the IPv4 world ;)
So if you're building a 100G capable platform that'll do IPv6 and MPLS, how much difference would it be if you only had to support 16000 labels and 16000 IPv6 prefixes, rather than 2 million?
Then of course I guess the argument can be made to put everything on MPLS to avoid the core knowing about anything but outer labels.
<flame>MPLS on its own won't solve anything. Although MPLS has its uses, it smells too much like another desperate attempt from the telco-heads in the ITU crowd to make a packet-switched network look and behave like a circuit-switched network.</flame> What this discussion boils down to is that a long term solution has to remove the size of the routing-table as a limiting factor in internet routing. Something must eliminate the need for every node in the default-free transit-network to know how to reach every allocated address-block at all times. Allocation policies, operational agreements on filtering, BCPs etc can only slow the growth of the routing-table. Growth can't be eliminated. In the future network you'll have routers that may know a lot about their "local region" of the network but have to rely on nodes that are several hops (even AS-hops) away to pass the packets to more remote destinations. These trust-relationships have to be built and maintained automatically (may involve packet tagging / tunnelling etc), similar to current route-cache mechanisms, but will require a whole new set of routing protocols. Despite lots of research there's no such solution today or anytime soon. Just think of the added complexity. How do you build trust with remote nodes given the problems you see in trusting your direct peers in the BGP world today? How can routing loops be prevented in such a network? All we know is that if there is no such solution, at some point in time the network will fragment due to its size and complexity. In the meantime we have to manage with what we've got, and treat v6 just like we've done with v4 - multihoming and all. We know we'll run out of v4 addresses at some point, and that v6 is the only realistic alternative. Without improved routing protocols, all we can do is to pray that the development of routing hardware in terms of memory and processing capability outpaces the growth of the routing table. Initiatives like shim6 that changes the behaviour of leaf-nodes are only a supplement and won't replace the need for true multi-homing for end-sites. Here we have to adapt to business needs, and businesses have made it pretty clear that it is unacceptable to them to be tied to any single provider. Besides, shim6 doesn't eliminate the need for a mechanism to locate any globally unique address. What if there's suddenly 10M LIR's, or otherwise a trend towards a market with very small providers each handling only a small number of customers? Who gets to decide who may peer with whom, or decide which providers will be denied the ability to build redundant connectivity with multiple upstreams? //Per