Vishwas, Your draft seems to be referring to the end-to-end delay of a packet forwarded entirely by data-plane. So those results would be applicable to the OSPF fast-notification. It would not be applicable to end-to-end delay of OSPF LSA flooding since the LSAs are processed at each hop by the control-plane.
Curtis, The control-plane delays you haven't listed include sending LSUpdate from data-plane to control-plane and its processing such as authenticating, comparing against LSDB, sending LSAck (with potential re-transmission), queueing for further flooding (including re-transmit if timer expires), re-adding interface specific auth params etc. All of these need to be done at each intermediate hop as the LSA gets flooded and hence the delay is cumulative. These delays may not seem like much but it does add to the overall delay in convergence. The SPF by itself does not take that much time in modern CPUs but the download of routes certainly increases with number of downloads. However, modern forwarding architectures are such that in many failure conditions many downloads are not needed. A single download can change the nexthop of a large number of routes. In such conditions the hop-by-hop control-plane flooding does not remain an insignificant component of convergence. There will of course be networks where geographic delay itself may be large enough to dwarf all other numbers, but there are a lot of networks where that is not true. We will be updating the draft to support the assertions. Thanks On Mon, Apr 4, 2011 at 1:36 PM, Vishwas Manral <[email protected]> wrote: > On Mon, Apr 4, 2011 at 1:33 PM, Curtis Villamizar <[email protected]> wrote: > Hi Curtis, > >> Has anyone measured the per hop flooding delay that is incurred in >> modern routers? > > From the few we have worked, it works from 10's of nanoseconds to > microseconds. > > You may see some work on > http://tools.ietf.org/html/draft-manral-ospf-te-delay-00. We need to > actually add per device delay to make the solution generic, which is > what we are trying to work on. > > Thanks, > Vishwas > _______________________________________________ > OSPF mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/ospf > -- - Sri _______________________________________________ OSPF mailing list [email protected] https://www.ietf.org/mailman/listinfo/ospf
