Gotcha.

You can't do this on the 8K, and it wouldn't solve all of your problems, but 
with the 7K, you could set up a MikroTik L2TP BCP concentrator and have your 7K 
establish BCP tunnels to that.  Then your overheads would be 1496 - L2TP 
headers (which I think is normally 40 bytes when using IPCP, but I don't know 
what it looks like with BCP) instead of 74 bytes for S1 overhead.  Not full 
1500, but you can emulate that to the end-user with MRRU and having L2TP 
fragment the packets for you.

Oh, grr, scratch that, I just realized after typing that out that there is no 
MRRU option on the 7K interface.  Darn.

It might still be educational to try this, just to see if your PPPoE frames 
happen to make it through that tunnel.

I really haven't experimented much with this stuff because we decided in the 
end not to do bridging.  This was back when my understanding was that 
EPC-defined AMBRs meant that the EPC was working in concert with the eNB TDMA 
scheduler for the most efficient means of controlling bandwidth, but it is now 
unclear to me whether that is true.  But even if setting the AMBR on the EPC is 
no more efficient than using queues on a MikroTik upstream from the EPC, it 
just seemed weird to contemplate requiring two levels of authentication (SIM 
card, then PPP user/pass on top of that).

I'd still love to know how you end up making out on this.  Please keep us 
updated.

-- Nathan

From: [email protected] [mailto:[email protected]] On Behalf Of 
Jeremy Austin
Sent: Friday, November 04, 2016 7:10 PM
To: [email protected]
Subject: Re: [Telrad] Telrad Digest, Vol 25, Issue 1


On Fri, Nov 4, 2016 at 6:08 PM, Nathan Anderson 
<[email protected]<mailto:[email protected]>> wrote:
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?


My observations as well.

Nick is evidently working on the same issues. Didn't hear from him today.


--
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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