RE: WG Last Call: draft-ietf-ccamp-lmp-06

["Naidu, Venkata" <Venkata.Naidu@Marconi.com>]

LMP guys,

-> 1)  3.2.1 states that HelloInterval and HelloDeadInterval 
-> MUST be agreed upon by the local and remote nodes, but I
-> am still looking for a description of how they agree, if
-> it's there would appreciate a pointer to this (e.g., shortest
-> value wins?)

  I have something to say regarding this point.

  Synchronized Parameter settings are sometimes harmful.
  Most of the LMP Hello protocol fundamentals are derived
  from OSPF. But, inherently there are some issues with 
  the OSPF Hello protocol parameter exchange.

  Radia's 1991 paper reads (FYI):

  In OSPF, there are several parameters that must be 
  configured identically in routers, or else the router will 
  refuse to communicate with each other. This creates a 
  problem because it is virtually impossible to change the 
  parameter setting via network management. Once a router's 
  parameter setting is changed, it is cut off from the 
  rest of the network since no other routers will be able 
  to communicate with it. 
  . . .

   - HelloTime and DeadTime: 
     . . .
     ISIS reports only DeadTime in its Hello messages (not 
     HelloTime). As a result, the ratio between DeadTime and
     HelloTime is fixed in ISIS, but can be configured in
     different ways by OSPF. ISIS uses the information solely
     to determine how long to wait between receipt of Hellos
     from a particular neighbor before declaring the link
     to that neighbor down. There is no necessity for 
     neighboring nodes to have the same value.

     Being able to change these timers in a running network is
     important. As a LAN becomes larger it might be decided
     that the overhead from hellos is too great. It also
     might be important in some configurations to be able to
     run with different hello timers for different routers.
     There might be some routers for which quick deletion 
     of failure would be very desirable, whereas for other
     routers quick deletion of failure might not be as
     important. To lower overhead these routers might be 
     configured with a longer HelloTime. This cannot be done
     in OSPF since all routers must have identical timers.

  Moreover, please remember that LMP hellos are very very
  granular. The scalability requirements for LMP are little
  strict when compared to traditional protocols.

  So, please revisit the LMP hello protocol timer configurations.

  After all, my 2 cents... :)

--
Venkata.