ok. well my own personal idea of a tunnel is a thing that ecapsulates
traffic to make it transparent to the underlying network, or vice-versa...
the VL does not meet my own definition, but it is an alternate path that the
traffic can take.
In reality, the traffic is ROUTED along the path that you need to take to
get to the opposite endpoint.
I am putting one of these dumb things together to see how it really
functions.
...am i correct?
----- Original Message -----
From: "Chuck Larrieu"
To: "Peter I. Slow" ;
Sent: Tuesday, May 29, 2001 1:54 AM
Subject: RE: Question on the meaning of "tunneling" [7:6136]
> My quote was from the RFC, which I believe is the authoritative source.
>
> All that happens is that a particular bit in the router LSA is set, and
> when the two end points agree, based on the V-bit setting and the
respective
> RID's, the virtual link is established.
>
> Jeff Doyle puts his pants on the same way you and I do. I'm sure he's made
a
> mistake or two in his life. There are a few pages of errata to be found
for
> his book. :->
>
> Chuck
>
> -----Original Message-----
> From: Peter I. Slow [mailto:[EMAIL PROTECTED]]
> Sent: Monday, May 28, 2001 10:52 PM
> To: Chuck Larrieu; [EMAIL PROTECTED]
> Subject: Re: Question on the meaning of "tunneling" [7:6136]
>
> " Virtual links are part of the backbone, and behave as if they were
> unnumbered point-to-point networks between the two routers. "
> its a virtual link. its an unnumbered network. a network/segmrnt
> nonetheless, and that description sounds like a tunnel.
>
> it's possible im reading it out of context and misunderstanding....
>
> / me goes to grab his Doyle book
>
> ..Page 464, P1,
> "the VL is a tunnel through which packets may be routed on the optimal
> pathfrom one endpoint to the other."
>
> ...It would be unwise to tell god he is wrong.
> Doyle is the man who wrote the book, literally...
>
> ----- Original Message -----
> From: "Chuck Larrieu"
> To:
> Sent: Tuesday, May 29, 2001 1:18 AM
> Subject: RE: Question on the meaning of "tunneling" [7:6136]
>
>
> > Did some more research. In the context of the question, I went to the
RFC
> to
> > see what the source says. It occurred to me that the behaviour of
virtual
> > links must be defined in there somewhere.
> >
> > Sure enough, in the router LSA there is something called the V bit,
which
> > when set determines that the originator of the LSA is one endpoint of a
> > virtual link. when two routers agree that they are the endpoints of the
> same
> > virtual link, as determined by their RIDs as defined when the VL is
> > configured, then the virtual link is established.
> >
> > "bit V When set, the router is an endpoint of one or more fully adjacent
> > virtual links having the described area as Transit area (V is for
virtual
> > link endpoint)."
> >
> > In another place:
> >
> > " Virtual links are part of the backbone, and behave as if they were
> > unnumbered point-to-point networks between the two routers. "
> >
> > I believe this lays to rest the question as to whether of not an OSPF
> > virtual link is a tunnel. It is not.
> >
> > Chuck
> >
> >
> >
> > -----Original Message-----
> > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]] On Behalf Of
> > Marty Adkins
> > Sent: Monday, May 28, 2001 7:24 PM
> > To: [EMAIL PROTECTED]
> > Subject: Re: Question on the meaning of "tunneling" [7:6136]
> >
> > "Howard C. Berkowitz" wrote:
> > >
> > > In the most general sense, a tunnel is a means of taking a protocol
> > > data unit payload of OSI layer N of protocol family P1: (N,P1)-PDU,
> > > and transmitting it with a delivery header at layer M of protocol
> > > family P2. What is actually transmitted is, minimally, a (N,P1)-PDU
> > > encapsulated in a (M,P2)-PDU. There may be a "shim" between the end
> > > of the delivery header and the beginning of the payload header;
> > > there's no good OSIRM term for the shim.
> >
> > In a slightly less mathematical explanation:
> > Think about the encapsulation steps while traveling down the stack.
> > Are one or more layers repeated? If so, then tunneling is involved.
> > Yeah, that's simplistic.
> >
> > - Marty
> > FAQ, list archives, and subscription info:
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> > Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
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> http://www.groupstudy.com/list/cisco.html
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