On Saturday, September 10, 2011 01:52:12 PM Dobbins, Roland wrote:
All this problematic state should be broken up into smaller instantiations and distributed as close to the access edge (RAN, wireline, etc.) as possible in order to a) reduce the amount of state concentrated in a single device and b) to minimize the impact footprint when aberrant traffic inevitably fills up the state tables and said devices choke.
Certainly a consideration when an ISP considers scaling avenues for LSN's. The issue is that there are simply too many variables, not least of which is what business the ISP is in. The mobile types are a lot more problematic because they tend to centralize IP intelligence, and keep the RAN's pretty simple (although the RAN's are now becoming more intelligent thanks to your garden-variety IP vendors getting into the game). What we've seen also, with some mobile carriers, is that if you ask them to consider distributed IP architectures, they/you quickly realize that IP routing isn't really their core business or skill. For your typical ISP, size notwithstanding, it will invariably come down to how much money and effort they're willing to spend or save with either centralized or distributed architectures. Mind you, they're also battling with other problems re: centralized or distributed solutions, e.g., broadband aggregation, the ratio of access:aggregation intelligence, access topology lay-outs, e.t.c. And somehow, in all this mix, LSN's must work, be they small units thrown around the network, or one or two large monsters sitting somewhere in the core. We've certainly considered both options very thoroughly. Mark.