hi,

incase of a "hello" per se, i dont see how one evens run into MTU
issues..the hello packet is not that big (only router specific info)

i think may come about in DD and LSUpdates etc...which pass the LSA info....

the issues may come like this:

if i have a MPLS- PPVPN from A to B

the "label stacking" causes the frame size to grow
so we reach an MTU of above 1500 (whatever the value)
now if the routing nodes in the core (the LSRs) dont accomodate this ...the
edge has no way of knowing that the core has a drop in MTU....right?
and Labels in MPLS dont have DF bits :o) so you "cant fragment" there on the
"core".....

now what?

you have to make sure the MTU accomodates these "labelstacks" in the core
...but even now fragmentation using DF bits in IP header is ruled out
..right?

-rgds
Alok
----- Original Message -----
From: Shankar Agarwal <shankar_agarwalNET.COM>
To: <OSPFDISCUSS.MICROSOFT.COM>
Sent: Wednesday, February 12, 2003 11:41 PM
Subject: Re: Num of Nbrs and MTU size in hello pkts : OSPFv2

> I am not sure how the different implementations will behave in this
> case. But as far as RFC is concerned. It says in section 4.3 that each
> protocol packet can be broken into small protocol packet. But i am not
> sure in case of Hello. But then we can use Ip Fragmentation for Hello
> Packet and no one stops us from sending an IP packet greater than tõÿn
> MTU.
>
> alok wrote:
> >
> > ideally, you would have to build flow control on top of OSPF?
> >
> > ----- Original Message -----
> > From: Erblichs <erblichsEARTHLINK.NET>
> > To: <OSPFDISCUSS.MICROSOFT.COM>
> > Sent: Wednesday, February 12, 2003 11:02 PM
> > Subject: Num of Nbrs and MTU size in hello pkts : OSPFv2
> >
> > > Group,
> > >
> > > I guess you could say that I have a dumb question.
> > >
> > > If a DR wanted to support say 400+ adjs with a standard
> > > Ethernet 1.5 MTU, is it acceptable to send out more
> > > than 1 hello describing all of its nbrs?
> > >
> > > Note: each nbr id would consume 4 bytes and thus
> > > the length of the 1 pkt would be greater than MTU size.
> > >
> > > I am assuming that 2 pkts per hello interval would
> > > be transmitted.
> > >
> > > It is that I just don't remember any RFC describing
> > > this condition.
> > >
> > > Pointers please...
> > >
> > > Thanks,
> > >
> > > Mitchell Erblich
> > > Sr. Software Engineer
> > > ` ======================
> > >
>

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