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Re: Slashdot: Providers Ignoring DNS TTL?
> > First of all, let's ditch the term "PPLB." The usual alternative to per > > packet load balancing (what's been being talked about here) is per prefix > > load balancing, which would also be "PPLB." The abbreviation is therefore > > more confusing than anything else. > > Err. No, that would be worse. "Per prefix" load balancing is an artifact > of the Cisco route cache. The route engine (ie the route table) isn't > queried for every packet. Instead the route in the route cache is used. > One doesn't configure "per prefix" load balancing. One configures load > balancing, which adds multiple routes into the route table. Modern Cisco routers do not use a "route cache", they use a fully populated forwarding table. And load balancing is automatic if you have several equal cost routes. > The route > cache then causes only one of these routes to be used. On cisco, to > enable PPLB, you turn off the route cache. Many modern Cisco routers can perform per-packet load balancing without doing process switching (but this needs to be explicitly configured). > On Juniper, you configure it > to put multiple routes in the route table. Its actaully more likely to > happen on Junipers, because unless you configure additonal policies, you > get load balancing on divergent links as well as non-divergent links. On Modern Juniper routers cannot do per-packet load balancing *at all*. It is correct that the configuration statement says "per-packet", however it is really per-flow (and this is well documented). See for instance the description of Internet Processor II ASIC load balancing at http://www.juniper.net/techpubs/software/junos/junos70/swconfig70-policy/html/policy-actions-config11.html#1020787 I'm afraid your statements show a certain lack of knowledge about modern router architectures. Steinar Haug, Nethelp consulting, firstname.lastname@example.org