[c-nsp] MPLS Label stack depth and MTU

[Gert Doering]

Hi,

On Tue, Apr 29, 2008 at 09:01:05AM -0700, Christopher Hunt wrote:
>     My understanding is there is one 4 byte label for the MPLS VPN 
> (MP-BGP label) plus one for MPLS transport (which is switched out by 
> each P, then popped by PE2. If I want to deliver an edge MTU (at points 
> a and e) of 1500 i expect to need a core MTU (at points b,c,e) of 1526 
> bytes (edge MTU 1500 + transport header (18 bytes for 802.1Q Vlan 
> tagging) + 8 bytes for the 2 MPLS labels.  

I don't see why you would need 18 bytes 802.1Q Ethernet framing here.

If this is a *L3* VPN, there are no Ethernet frames.

(If you do EoMPLS, then there is 18 bytes Ethernet, of course, plus
two labels - but that's L2 VPN)

gert
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
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