The MPLS-OPS Archive

[Dave Stewart <dave_stewart1576@yahoo.co.uk>]

Some nits I would like to clarify, thank you for the response:

"M. ELK" <elkou141061@hotmail.com> wrote:

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 .

Q. Is this attribute propogated using Opaque LSA?

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 .

 

Q. What is the method used to propogate the TE information? These are the 2 drafts I am aware of which come from the OSPF and ISIS WG. Does cisco support the same? Can someone please tell me the IOS version this is supported from? We need to get the same for our network here.I have been following new IOS releases closely to get the same.

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 b! est 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 .

What is the present method to be doing it? Is it the TE tool?

 

-Dave Stewart

 

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