The MPLS-OPS Archive

["M. ELK" <elkou141061@hotmail.com>]

Dave

AFAIK ,

Qa. How do cisco routers learn the information on link utilisation?
Aa. IGP (any link state , IS-IS or OSPF both supported by cisco) flood the 
link utiilization
     as an attribute for link state .
     RSVP do the accounting , ie: start with certain B.W anmount per 
interface ( % of link speed)
     and decrease the amount of each LSP set up through this interface .
     Of course RSVP and IGP process at the router need to commuicate .
     U could set the frequency of IGP fllooding due to link utilization 
change (normally as % of
     change ) .

Qb. The 12.3 IOS set does not have anything on support for Katz-Yeung or 
Smit-Li drafts.
Ab. Ufamiliar with those draft .

Qc. Does this mean all LSP setups are independentof IGP? How does it tell 
RSVP how to setup LSP?
Ac. IGP populate a TE D.B ,RSVP could use the TE D.B to calculate the path 
of the LSP ie: CSPF ,
     in other word this is an EDUCATED-GUESS .
     RSVP could totally ignore the TE D.B and set LSP with strict or loose 
path , this is when U config
     static path . seting LSP this way is a blind trial which could succeed 
if their is avail B.W on the path
     specified .

Qd. Assuming it is not CSPF either, can RSVP-TE be simply used to set up 
label with constraints? How do routers get information on these constraints?
Ad. LSP should always have a constrain even if constrain is none ie:LSP B.W 
requirement  = 0 .
     CSPF help to calculate best path which statisfy the constraint before 
setting the LSP .
     The RSVP could take a completely blind trial simply setting the path as 
{loose Egress} ,now
     every node along the path find the best path to the egress , this 
appropriate if U set the
     LSP contarin as zero .
    U could set the full path still set the constarin as zero ,this is 
mainly if U calculate the TE by
    offline-tool and U need to totally disable the online CSPF of the 
HEAD-END node and any
    RSVP accounting on transit node .

Qe. Is RSVP used just like DoD mode of LDP? If so what is the Traffic 
Engineering in the same?
Ae- 2 Dimesnion : If U set constraint for ALL LSP as zero .
                         AND
                         If U set the path for all LSP as { Loose Egress}

                       so now U have almost RSVP LSP as LDP LSP and RSVP 
have no added value .
                       (LDP as unsolicited or on-Demand is not a 
differentiator here ) .

        If U start to change any dimension so TE start .


Brgds

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