Folks,

Question #1:

Is it possible for me to put an MPLS router on both ends of a circuit leased from a transport service provider which does not support QinQ (i.e.

Only input I can give is on EOIP tunnels and MTU. Scenario is we had 1 remote router running, Tunneled back to our network using EOIP so that the remote network could use our ip space. Don't remember how I figured it out, But I was using the MTU of 1458 (On the EOIP interface). Everything was great, But weird things started happening. Certain sites wouldn't load, MSN.com....etc it was strange. Jacking it back up to 1500 flat fixed it. Nick Olsen Network Operations (877) 804-3001 x106 ---------------------------------------- From: "Francois Menard" <francois@menards.ca> Sent: Sunday, September 12, 2010 10:13 PM To: "Francois Menard" <francois@menards.ca> Subject: Re: Transporting QinQ across a Layer 2 link locked at 1518 octets AND across a Layer 3 link Oops two typos - sunday evening casualties. On 2010-09-12, at 10:06 PM, Francois Menard wrote: packets of 1526 bytes), and which requires us to tag traffic onto a well specified set of VLANs (i.e. if we want two VLANs, the service provider tells us which two VLANs to use).

I was thinking of lowering the MTU size on my MPLS router such that I

could do QinQ over VPLS, over MPLS, over Ethernet transport locked at @ 1514 octets.

I would imagine that my effective IPv4 payload would be reduced to

something like (not taking into account CRC removed in the Ethernet driver)

1514 minus 8 bytes for MPLS label minus 4 bytes for VPLS control word

1514 -8 -4 -4 -4 -4 = 1490 octets

So if I set my MTU on my MPLS router at 1490 octets and send QinQ over VPLS over , wouldn't that allow for all of the above mentioned overhead to

minus 4 bytes for VLAN tag #1 minus 4 bytes for VLAN tag #2 = pile-up without exceeding the 1514 octets size allowed by my transport provider ?

Question #2:

I have another link, which is restricted by the transport service

So if I set my MTU on my MPLS router at 1490 octets and send QinQ over VPLS over MPLS over Ethernet, wouldn't that allow for all of the above mentioned overhead to pile-up without exceeding the 1514 octets size allowed by my transport provider ? provider, which is an MPLS-VPN service, and which does not support QinQ, nor supports layer 2 bridging.

An option available to me is to use an EoIP tunnel on a Mikrotik RouterOS

router, which maps Ethernet over GRE over IP, causing some 28 octets of overhead. This is proprietary to Mikrotik.

So in this case, assuming that I want to do something as dangerous as:

QinQ over VPLS over MPLS over Ethernet over EoIP (over GRE, over IP)

And accordingly set my MTU to:

1480 (from above) minus 28 octets (Ethernet over GRE over IP) = 1452

octets

1490 (from above) minus 28 octets (Ethernet over GRE over IP) = 1462 octets

So if I set my MTU on my MPLS router at 1452 octets, wouldn't that allow for all of the above mentioned overhead to be successfully transported across an IP layer 3 circuit, effectively ending up with

1462 octets

QinQ over MPLS over Ethernet over IP ?

What are the consequences of setting the MTU as low as 1452 octets? What applications end-up breaking ?

1462 octets

-=Francois=-