Re: Re: [mpls-linux-general] reg LDP

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Hello,

On Thu, Mar 21, 2002 at 08:09:23AM +0800, Lauren H wrote:
> Hi,Jim
>   =20
>     If the operation mode is Downstream on Demand/Ordered/Conservative, w=
hat will change to the following mesg ordering you have provided?
>=20
> This is my opinion:
> (1) Once a TCP connection is established the active LDP speaker instead o=
f each LDP speaker sends an  Init message first.

The draft says that the active should send an Init mesg first for both case=
s,
(DoD and DU).  The main point that I was trying to get across with the
Init message is that both sides sent them independent of each other (ie
the passive should not adjust its Init message after hearing what the
active sends, it is not a negotiation, it is a comparison).

> (2) When a route changes, label releases and requests are issued first, t=
hen label withdraws and mappings are issued later.

In DU when the session is finally established each side sends label mappings
for every FEC in it routing table.  In DoD mode they will send label reques=
ts
instead.

>  Is it right? Anything else?
>=20
> In addition, I have other questions:
> (1) If a LDP session is established between lsrs that are not directly co=
nnected at the link level, should the lsrs be configured to be able to send=
 and/or receive Targeted Hello? So the network operators should know which =
lsr can send/receive Targeted Hello?

Yes.  It is not necessary, but all implementations I have worked with
are implemented this way.

> (2) When operating in Downstream on Demand mode, is it necessary to send =
the Address message?

Yes.  Otherwise how would a LSR know who to send a label requets to?

> Best Regards,
>=20
> Lauren H
>=20
>=20
> ----- Original Message -----=20
> From: James R. Leu <jl...@mi...>
> To: Anil H <ani...@ya...>
> Cc: <mpl...@li...>
> Sent: Wednesday, March 20, 2002 5:56 AM
> Subject: Re: [mpls-linux-general] reg LDP
>=20
>=20
> > I can give you a quick overview of mesg odering, but you will want to
> > look at RFC3036 for the details.
> >=20
> > I'm only going to explain the direct/DU/Independent/Conservitive mode
> > of operation (look to the RFC as to what those mean)
> >=20
> > -Each LDP speaker is configured to talk LDP on specific interfaces.
> > -Each LDP speaker sends udp hello's on their interface to the all route=
rs
> >  multicast address, port 646.
> > -When an LDP speaker recieves a hellos it creates a logical adj for it.
> > -For each adj the LDP speaker decides whether it will play the
> >  active role or the passive role in the adj. (only 2 LDP speakers per a=
dj,
> >  on a broadcast medium an LDP speaker will form multiple adj).  The
> >  process of deciding active vs passive is outlined in the RFC.
> > -The active LDP speaker in the adj will attempt to create a TCP connect=
ion
> >  to the passive LDP speaker on port 646.
> > -Once a TCP connection is established each LDP speaker sends an Init
> >  message.
> > -When an LDP speaker recieves a Init message it looks at the parameters
> >  in the Init message and compares them with it configured parameters.
> >  If the parameters are acceptable a keepalive message is sent back.
> >  If the parameters are un-acceptable a notification is sent back and the
> >  TCP connection is closed
> > -When an LDP speaker hears the first keepalive for an adj, it then send=
s out
> >  one or multiple address messages which advertise the IP address attach=
ed
> >  to the LDP speaker.
> > -After sending address messages, the LDP speaker sends label advertisem=
ents
> >  for each FEC in it routing table.
> > -When a route changes, label withdraws and mappings are issued.
> > -When an interface changes, address withdraw and address messages are i=
ssued.
> >=20
> > I hope this atleast gives you a starting point.  The RFC is really the
> > best place to get the details though. (ofcourse you can alwyas read the
> > source to ldp-portable as well :-)
> >=20
> > Jim
> >=20
> > On Tue, Mar 19, 2002 at 11:20:34AM -0800, Anil H wrote:
> > > hi,
> > >=20
> > > Could ne1 give me the basic flow for LDP (for eg the
> > > sequence of messages) r some pointers to were i can
> > > find the information apart from the RFC.
> > >=20
> > > Thanks in advance,
> > > Anil
> > >=20
> > > __________________________________________________
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> > >=20
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> >=20
> > --=20
> > James R. Leu
> >=20
> > _______________________________________________
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> > mpl...@li...
> > https://lists.sourceforge.net/lists/listinfo/mpls-linux-general
> =FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=FF=
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=8A=CBl=FE=CA.=AD=C7=9F=A2=B8=1E=FEw=AD=86=DBi=B3=FF=FF=96+-=B3=FB(=BA=B7=
=1E~=8A=E0{=F9=DE=B7=F9b=B2=DB?=96+-=8Aw=E8=FEje=B3=F9b=9E=EC=FF=81=E9=DE

--=20
James R. Leu