If you can get 1496-byte packets all the way to the UE's IP through the EPC, 
then that shows (interestingly) that S1 traffic from EPC <-> eNB is somehow not 
beholden to the MTU as-reported on the S1 VLAN (or on the master interface for 
that matter), but that PDN traffic definitely is restricted by that 1496 MTU.  
I'm guessing that Telrad would need to release a software fix to increase the 
PDN VLAN MTU to 1500 or above to work around that problem.

That VPLS traffic seems to be constrained by the S1 VLAN MTU, even though L3 
traffic isn't, is also interesting.  It must have something to do with how VPLS 
is implemented on the EPC side...something is paying attention to that MTU 
value set on that VLAN in certain scenarios but not in others.  Again, sounds 
like a software fix may be in order?

What did Nick have to say when you talked to him on the phone?

-- Nathan

From: [email protected] [mailto:[email protected]] On Behalf Of 
Jeremy Austin
Sent: Friday, November 04, 2016 5:56 PM
To: [email protected]
Subject: Re: [Telrad] Telrad Digest, Vol 25, Issue 1


Quick report on L2 experiments.

I have VPLS working, with a few caveats, on both 7000s and 8000s.

I still can't get a tunneled packet larger than (S1 interface - 74 bytes). For 
now, this is 1496-74=1422.

UE management IP returns pings *up to 1496*, even with DNF.

Oddly, if the UE WAN MTU is set higher than ~(S1-28)<=1468, the UE management 
IP *stops* responding up to 1496, and cuts off at 1460.

I've successfully run PPOE from Mikrotik -> Mikrotik, with MRRU, inside the L2 
tunnel. Not a huge amount of extra overhead.

HOWEVER, I have completely failed to get a non-Mikrotik PPPoE client working 
over the tunnel. Packets leave the server (upstream) but don't actually reach 
the client downstream. Has anyone ever seen anything like this?

For an L2 PDN, though, what is the mechanism for setting/knowing the actual MTU 
size? In this instance, we would like to be able to pass a full L2 1500 byte 
packet, if the functionality is there.



--
Jeremy Austin

(907) 895-2311
(907) 803-5422
[email protected]<mailto:[email protected]>

Heritage NetWorks
Whitestone Power & Communications
Vertical Broadband, LLC

Schedule a meeting: http://doodle.com/jermudgeon
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