Ethernet LAN MPLS vs VLAN and 802.1q tags for QOS

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MPLS vs VLAN and 802.1q tags for QOS NewToDataNetworks 08-28-06
Posted by NewToDataNetworks on August 28, 2006, 1:13 pm
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I am trying to understand why the current access networks are going
towards ethernet based systems. We already have MPLS on the core
network side. Now we have ethernet on the access side.

We use VLAN and 802.1q tags for QOS in the ethernet. Why cant we have
MPLS everywhere and dont have to worry anything else. MPLS already does
the QOS for us.

thanks.


Posted by Albert Manfredi on August 28, 2006, 3:38 pm
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>I am trying to understand why the current access networks are going
> towards ethernet based systems. We already have MPLS on the core
> network side. Now we have ethernet on the access side.
>
> We use VLAN and 802.1q tags for QOS in the ethernet. Why cant we have
> MPLS everywhere and dont have to worry anything else. MPLS already
> does
> the QOS for us.

Because MPLS establishes paths among layer 3 boxes, routers, and not
inside a layer 2 network.

You could use MPLS in small geographic areas, in principle, but that
would mean setting up a lot of small IP subnets first. Most nets are not
set up that way, but there's no reason to think they can't be. Make
every Ethernet switch a router, for example.

As to "current access networks," they have traditionally been Ethernet
for a good many years. I mean, leaving aside the other old standby,
which was modem over a POTS line.

Bert


Posted by Steinar Haug on August 31, 2006, 3:02 pm
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> > We use VLAN and 802.1q tags for QOS in the ethernet. Why cant we have
> > MPLS everywhere and dont have to worry anything else. MPLS already
> > does
> > the QOS for us.
>
> Because MPLS establishes paths among layer 3 boxes, routers, and not
> inside a layer 2 network.

For another take on this: I'm sure several vendors would be very happy
to sell you boxes that can do both L2 and MPLS for your whole network.
But you probably wouldn't be very happy with the price tag.

Steinar Haug, Nethelp consulting, sthaug@nethelp.no

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