The MPLS-OPS Archive

[Vishal M <vishal_study@yahoo.com>]

Hi Carlos,

I agree that LDP applications could bundle multiple
LDP mappings into a single big-TCP buffer to save on
BW.

The issue I was trying to state was of
routing/topology change affecting multiple LDP
sessions. For the duration this (routing change
resulting in lots of LDP messages) is happening, the
default Hello/KA holdtimers value may be a bit low. 

Has anyone seen this kind of behavior? 

Regards,
Vishal.

--- Carlos Patriawan <carlos@xebeo.com> wrote:
> Vishal M wrote:
> 
> > Hi,
> >
> > According to RFC 3036, LDP Hello interval is 5
> sec, KA
> > is 15 sec, Hello Holdtime is 15 sec and KA
> Holdtime is
> > 40 sec.
> >
> > If a LSR is acting in DU mode and has to deal with
> > large number of FECs (say 100k), the holdTimes of
> 15
> > (hello) and 40 (KA) is quite small and may result
> in
> > timeouts when LDP (and/or IP) modules of the LSR
> are
> > busy transmitting/receiving these large number of
> TCP
> > messages (i.e. FEC mappings).
> >
> > Hence the operator may have to tune these
> holdtimers
> > to a higher number.
> >
> > Has anyone seen this kind of issue and would like
> to
> > share the experiences.
> >
> > What is a *realistic* (or practical) value for
> > Hello/KA holdtimers (say given a gigabitEthernet
> kind
> > of interface) in ISP world ?
> >
> > Could someone please comment on this.
> >
> > Thanks for your time,
> >
> > Regards,
> > Vishal.
> >
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> 
> I'm not sure if that would be an issue. First of all
> you can bundles
> some or all FEC
> in one packet so it doesn't consume lot of BW.
> Second, those messages
> usually
> only occured once unless you've lot of
> topology/routing changes.
> 
> 
> Carlos
> 
> 
> 
> 


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