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Michelot

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Jun 28, 2009, 5:08:25 PM6/28/09
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Hello,

I read that MPLS uses the IP control plan. What would it mean?

Thanks,
Michelot

Thrill5

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Jun 29, 2009, 8:30:52 PM6/29/09
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That statement doesn't make sense without a lot more explaination behind it
because without a context, it could mean just about anything.

"Michelot" <mhost...@voila.fr> wrote in message
news:b26f6e16-4315-47b9...@y17g2000yqn.googlegroups.com...

bod43

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Jun 30, 2009, 1:34:40 AM6/30/09
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On 30 June, 01:30, "Thrill5" <nos...@somewhere.com> wrote:
> That statement doesn't make sense without a lot more explaination behind it
> because without a context, it could mean just about anything.
>
> "Michelot" <mhostett...@voila.fr> wrote in message

>
> news:b26f6e16-4315-47b9...@y17g2000yqn.googlegroups.com...
>
> > Hello,
>
> > I read that MPLS uses the IP control plan. What would it mean?
>

I read it as control plane.

Sadly I can't think how to explain right now. And I may
be wrong, again.

Michelot

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Jun 30, 2009, 3:27:27 PM6/30/09
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Hi Thrill5 and bod43,

Let's consider an IP/MPLS network. If MPLS uses IP routing protocols,
we can't say that MPLS is connectionless, like it is for IP.

(1) What's the main difference between OSPF and OSPF-TE ?

(2) MPLS can setup its own path setup once it has the IP routing map.
Do you know why?

Best regards,
Michelot

Michelot

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Jul 1, 2009, 6:25:27 AM7/1/09
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Hi Michelot,

> (2) MPLS can setup its own path setup once it has the IP routing map.
> Do you know why?

It's probably for a PE which has an LSR function together with an IP
router function. For a pure LSR which doesn't terminates the IP path,
the LSP path set up doesn't need to run firstly an IP routing
protocol.

It seems there are ambiguous statements about that.

Best regards,
Michelot

Steinar Haug

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Jul 1, 2009, 11:07:41 AM7/1/09
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> > (2) MPLS can setup its own path setup once it has the IP routing map.
> > Do you know why?
>
> It's probably for a PE which has an LSR function together with an IP
> router function. For a pure LSR which doesn't terminates the IP path,
> the LSP path set up doesn't need to run firstly an IP routing
> protocol.

In a normal MPLS network today the LSP path setup is done either by
LDP or by RSVP. These both run on top of IP.

It would be perfectly possible to setup LSP paths in a different way.
For instance: Some types of MPLS equipment let you configure static
MPLS paths - which are then somewhat similar to static IP routes.

But the standard way of doing it is via signaling protocols (LDP and
RSVP) that run on top of IP.

Steinar Haug, Nethelp consulting, sth...@nethelp.no

Michelot

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Jul 2, 2009, 9:47:04 AM7/2/09
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Hi, Steinar

Happy to read you

> In a normal MPLS network today the LSP path setup is done either by
> LDP or by RSVP. These both run on top of IP.

Thanks for reminding me that. Yes, we don't have to forget that LDP or
RSVP run on the top of IP, through UDP or TCP.

So, before to setup an LSP path, each LSR equipment has to build its
IP routing table, using an IP routing protocol, probably BGP or OSPF.

> It would be perfectly possible to setup LSP paths in a different way.
> For instance: Some types of MPLS equipment let you configure static
> MPLS paths - which are then somewhat similar to static IP routes.

Thanks for this remark


With your comments, we certainly have to be more precise to
distinguish an LSR router when it plays a role of PE or P equipment.

- As PE equipment, the LSR considers all the IP datagrams, it
terminates the IP traffic paths and the IP signaling paths,
- As P equipment, the LSR doesn’t consider all the IP datagrams. The
IP traffic paths are not terminated, but the IP signaling paths are
terminated when the destination IP address is those of its own
signaling interface.

Now, I’m wondering how we can distinguish MPLS packets carrying IP
traffic packets from MPLS packets carrying IP signaling packets.
Perhaps with the number of the label (perhaps #14).

Best regards,
Michelot

Steinar Haug

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Jul 2, 2009, 4:08:18 PM7/2/09
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> Now, I�m wondering how we can distinguish MPLS packets carrying IP
> traffic packets from MPLS packets carrying IP signaling packets.
> Perhaps with the number of the label (perhaps #14).

Packets for the various IP signaling protocols (IS-IS, OSPF, BGP) and
MPLS signaling protocols (LDP, RSVP) are normally sent unlabelled -
i.e. they are *not* sent as MPLS packets. IP packets and MPLS packets
can normally be distinguished by at the link layer by checking the link
layer type (i.e. for Ethernet: IP = 0x0800, MPLS = 0x8847). And IS-IS,
of course, does not run on top of IP at all.

Michelot

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Jul 6, 2009, 4:48:22 AM7/6/09
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Hi Steiner,

> Packets for the various IP signaling protocols (IS-IS, OSPF, BGP) and
> MPLS signaling protocols (LDP, RSVP) are normally sent unlabelled -
> i.e. they are *not* sent as MPLS packets. IP packets and MPLS packets
> can normally be distinguished by at the link layer by checking the link
> layer type (i.e. for Ethernet: IP = 0x0800, MPLS = 0x8847). And IS-IS,
> of course, does not run on top of IP at all.

Thanks for these words.

Perhaps, we can have another behaviour, because MPLS packets are
"stackable".

Through Ethernet e.g. the equipment discovers MPLS with the Ethertype.
If S=0 in the MPLS header the packet is switched to the next hop. If
S=1, the client packet is analyzed. For an IP datagram, the
destination address is then analyzed.

If the IP destination address is those from the equipment, the payload
is locally treated. It can carried LDP, RSVP, OSPF, BGP information.

If the IP destination address is not those from the equipment the IP
datagram is routed to the next hop.

Finally, it is your description, but by adding MPLS levels. Do you
agree?

Best regards,
Michelot

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