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gnuttisch
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VPLS/MPLS via ospf in wireless network

Tue May 12, 2015 7:37 pm

Hi,

I have a wireless network whit some ptp and ptmp links routed via ospf. On top of that I recently implemented mpls/vpls to the end customers.

The wireless network is based on 411AH, 433AH, 912UAG,SXT and Sextant links running NV2.

Everything works, the vpls tunnels are up and running but I cant achieve any bandwidth higher then 20-30mbit in each direction, but in a singel ptp link I can push about 60mbit tcp in bandwidth test whit the rb cpus so probably more, as each ptp link is in 300/300 connection and ptmp is in 150/150 connection whit good ccq.

So, Iam now wounder if I might have an mtu problem? How can i determine that?
Maybe I have an switch that dont support jumbo frames?

What mtu/l2mtu do I must have in every interface to get this to work?

For exampel the RB411AH has only 1500 mtu and 1526 l2mtu, is that enough?
The vpls tunnels are set to 1500 mtu, 1500 l2mtu and advertised l2mtu 1500.
MPLS Interface is set by default 1508 mtu *all interfaces.

Regards!
 
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Re: VPLS/MPLS via ospf in wireless network

Wed May 13, 2015 12:00 pm

Hi,

From what I can understand from this presentation I need 1522 l2mtu at least; RB411 and RB433 got 1526 l2mtu so it should be fine. the rest of the routerboard hw got more l2mtu.
http://mum.mikrotik.com/presentations/US13/kirnak.pdf

Eth header 14, MPLS 4, VPLS 4, IP header 20, data 1480 = 1522 bytes.

But how can I test my wireless network to work whit that size of mtu?

I have seen other post where they are talking about tagged and untagged vpls interfaces? My vpls interfaces looks like this;
 0 R   name="vpls1" mtu=1500 l2mtu=1500 mac-address=02:1C:D3:40:C4:CE arp=enabled 
       disable-running-check=no remote-peer=1.0.0.1 vpls-id=0:0 cisco-style=no cisco-style-id=0 
       advertised-l2mtu=1500 pw-type=raw-ethernet use-control-word=default
       
 
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Re: VPLS/MPLS via ospf in wireless network

Tue May 19, 2015 9:11 am

nobody ?
 
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Re: VPLS/MPLS via ospf in wireless network

Fri May 22, 2015 3:44 pm

Eth header 14, MPLS 4, VPLS ID 4, VPLS 4, IP header 20, data 1480 = 1526 bytes.

Is this correct for my setup? Can I then use my RB4xx board who has 1526 only 1526 l2 mtu?
 
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Re: VPLS/MPLS via ospf in wireless network

Fri May 22, 2015 7:07 pm

Yes, your calculations are correct, and it will work.
Just remember to set the L2MTU correctly on all interfaces on all devices.

As for how to test it:
Simply create a VPLS tunnel between 2 routers, and try to ping within that tunnel with 1472 packet size with do-not-fragment set.
(1472 because ICMP has a 8byte header as well)

So assign an IP address to both devices inside the VPLS tunnel, and do the ping using those IPs.
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Re: VPLS/MPLS via ospf in wireless network

Mon May 25, 2015 11:08 am

Hi,

Well, that works, but I have read somewhere that the vpls interface will fragment the package anyway, due that I can ping whit 1500 packetsize as well.

Eth header 14, MPLS 4, VPLS ID 4, VPLS 4, IP header 20 + data 1500 + ping header 8 = 1554
How does this work ? ? ?
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Re: VPLS/MPLS via ospf in wireless network

Mon May 25, 2015 11:50 am

Hi,

Well, that works, but I have read somewhere that the vpls interface will fragment the package anyway, due that I can ping whit 1500 packetsize as well.

Eth header 14, MPLS 4, VPLS ID 4, VPLS 4, IP header 20 + data 1500 + ping header 8 = 1554
How does this work ? ? ?
Yes, VPLS interface will fragment frames automatically.
BUT it fragments based on its L2MTU and MTU values. So if you have L2MTU and MTU set on the VPLS interface correctly, and full size frames pass through, it means the rest of your topology does not have MTU issues.
Usually MTU issues are L2MTU issues on actual ethernet (or wireless) interfaces that carry the traffic.

Regarding the ping, it indeed should NOT work (should return fragmentation needed error).

Please show us:
/int vpls exp
/mpls exp
/ip add exp

Also please show us the General tab of the ping window, to see what and how you are pinging.
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Re: VPLS/MPLS via ospf in wireless network

Mon May 25, 2015 12:03 pm

Well then I guess that it would work because the vpls interface are set to 1500 ? It should be set to 1480 to fit the l2mtu on the interfaces that are 1526,
Eth header 14, MPLS 4, VPLS ID 4, VPLS 4, IP header 20 + data 1480 = 1526?

/interface vpls
add disabled=no l2mtu=1500 mac-address=02:B8:9D:71:3F:FD name=\
    vpls-test remote-peer=10.10.20.1 vpls-id=0:14
/mpls ldp
set enabled=yes lsr-id=10.10.20.51 transport-address=10.10.20.51
/mpls ldp interface
add interface=Eth1_Radio
add address=1.0.0.1/30 interface=vpls-test network=1.0.0.0
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Re: VPLS/MPLS via ospf in wireless network

Mon May 25, 2015 12:23 pm

1500 is the correct L3 and L2 MTU on the VPLS interface in your test scenario.

Remember that MTU (L3 MTU) in MKT is with the data, L4 and L3 headers counted in.

Calculation of MTU from the point of view of the VPLS interface:
1472 data + 8 icmp header + 20 ip header = 1500 L3 MTU for the VPLS interface. (but that realistically is 1472 packet size for ping)

Why ping is working for you with 1500 size and do-not-fragment flag, I do not know.
It might be that the VPLS interface is not respecting the DF flag, which would of course be a bug.

Or it might be some other particularity in your setup, where the ICMP packet is getting routed somehow over the "naked" path, which supports such high L3 MTU.

Without seeing the whole setup, its hard to tell.
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Re: VPLS/MPLS via ospf in wireless network

Mon May 25, 2015 12:44 pm

Okey, thanks for sharing!

Now I dont know where to look to get some higher speed in my wireless network, as I described in my first post.


Internet connection from ISP is 100/000.

ptp links are in 300/300
ptmp are in 150/150

tcp speed for example downloading a torrent is about 20-30mbit via an vpls interface.
 
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Re: VPLS/MPLS via ospf in wireless network

Mon May 25, 2015 12:58 pm

Are you using nv2 for wireless?
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Re: VPLS/MPLS via ospf in wireless network

Mon May 25, 2015 1:05 pm

Yes,

In the weekend I am also going to replace an old central switch that I am unsure if its capable to handle jumbo packages.
If it only handles 1514 mtu, it will be an bottleneck.
 
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Re: VPLS/MPLS via ospf in wireless network

Sun May 31, 2015 3:09 pm

RouterOS calculates the packet size differently from a PC so it may well show 1500 byte packets unfragmented whereas a PC pinging on the same path would max out at 1472 due to the ICMP and IP headers.
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Re: VPLS/MPLS via ospf in wireless network

Mon Jun 01, 2015 5:49 pm

1522 is too small because VPLS requires two MPLS labels instead of one. One label is for the MPLS endpoint, and the other is for the VPLS tunnel identification. hence the 1526 minimum.

Standard MTUs for MPLS to hand off a 1500 bytes frame are:

minimum of:

1526 - if planning to use untagged frames with VPLS
1530 - with tagged VPLS frames

In reality, most MPLS networks are designed using jumbo frames whenever possible on the transport side. It simplifies adding more advanced services like QinQ at a later date.

Great reference on MTU:

http://wiki.mikrotik.com/wiki/Manual:Ma ... uterBoards
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gnuttisch
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Re: VPLS/MPLS via ospf in wireless network

Tue Jun 02, 2015 11:38 am

1522 is too small because VPLS requires two MPLS labels instead of one. One label is for the MPLS endpoint, and the other is for the VPLS tunnel identification. hence the 1526 minimum.

Standard MTUs for MPLS to hand off a 1500 bytes frame are:

minimum of:

1526 - if planning to use untagged frames with VPLS
1530 - with tagged VPLS frames

In reality, most MPLS networks are designed using jumbo frames whenever possible on the transport side. It simplifies adding more advanced services like QinQ at a later date.

Great reference on MTU:

http://wiki.mikrotik.com/wiki/Manual:Ma ... uterBoards
Hi,

May you please explain the different between tagged and untagged VPLS frames?

Regards
 
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Re: VPLS/MPLS via ospf in wireless network

Thu Jun 04, 2015 1:16 am

Tagged VPLS is when you hand off the Layer 2 segment to the customer or endpoint with an 802.1q VLAN tag. The extra 4 bytes for that tag is what causes the MTU requirement to change from 1526 to 1530.
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Re: VPLS/MPLS via ospf in wireless network

Thu Jun 04, 2015 8:30 am

Aha, so you are talking about vlan tag.

No, we dont use any vlans in the vpls tunnels, just plain vpls tunnel to the customer whit either static or dhcp addresses to the customers/our router.

So our l2mtu on 1526 should then be enough?
Eth header 14, MPLS 4, VPLS ID 4, VPLS 4, IP header 20 + data 1480 = 1526
 
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Re: VPLS/MPLS via ospf in wireless network

Thu Jun 04, 2015 7:04 pm

Correct,

1526 is the absolute minimum to hand off a 1500 byte frame to the customer. Your MTUs should look like this

L2 MTU - 1526 or higher (L2 MTUs should match on each side of a link and can be higher than 1526)
L3 MTU - 1500 bytes (This must match on every IP in that subnet to be RFC compliant)
MPLS MTU - 1526 or higher (This must be the same on every MPLS router to avoid issues and cannot exceed the max supported L2 MTU)

MTU mismatch is the single biggest issue we see on MPLS networks. Sometimes it takes a while to rear it's ugly head and often times, it is misdiagnosed as a RouterOS bug.

Here is a very easy test you can do to see if a segment will support over 1500 bytes

[Admin@MPLS-CORE-1] > /ping 100.64.0.2 size=1501 do-not-fragment
SEQ HOST SIZE TTL TIME STATUS
0 100.64.0.2 timeout
1 100.64.0.2 timeout
2 100.64.0.2 timeout
3 100.64.0.2 timeout
sent=4 received=0 packet-loss=100%
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Re: VPLS/MPLS via ospf in wireless network

Thu Jun 04, 2015 9:17 pm

Thanks for your reply!

The reason why Iam talking about l2 1526 mtu is that we have some older RB4xx boards where the interface is only 1526.

but then you are talking about;
MPLS MTU - 1526 or higher (This must be the same on every MPLS router to avoid issues and cannot exceed the max supported L2 MTU)
Do you mean this?
[admin@mikrotik] /mpls interface> pr
Flags: X - disabled, * - default 
 #    INTERFACE                                                          MPLS-MTU
 0  * all                                                                    1508
 
Where I should set 1526 on every router that is member of the mpls network?

Thank you again for looking into this =)
 
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Re: VPLS/MPLS via ospf in wireless network

Fri Jun 05, 2015 3:15 am

Yes the MPLS-MTU needs to change from 1508 to 1526 on every router. The MPLS MTU cannot be larger than the L2 MTU

So...it needs to be this
[admin@mikrotik] /mpls interface> pr
Flags: X - disabled, * - default 
 #    INTERFACE                                                          MPLS-MTU
 0  * all                                                                    1526
 
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Re: VPLS/MPLS via ospf in wireless network

Fri Jun 05, 2015 2:24 pm

Should it be set to according to the device who has the smallest mtu in the mpls network or should it be set individually?
For ex.
RB411AH - l2mtu 1526
RB912UAG - 1600
 
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Re: VPLS/MPLS via ospf in wireless network

Fri Jun 05, 2015 5:13 pm

That's it...the smallest L2MTU in your transport network is the largest MPLS MTU you can support.
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Re: VPLS/MPLS via ospf in wireless network

Mon Jun 08, 2015 12:12 pm

Hi, how about the advertised-l2mtu on the vpls interfaces, how should it be set? what should I consider before editing this value? it has l2mtu 1500 per default, but in this presentation he has set it to 1508 ?
http://mum.mikrotik.com/presentations/US13/kirnak.pdf
       name="vpls-1" mtu=1500 l2mtu=1500 
       mac-address=02:E0:F5:4D:72:26 arp=enabled disable-running-check=no 
       remote-peer=10.10.20.1 vpls-id=0:0 cisco-style=no cisco-style-id=0 
       advertised-l2mtu=1500 pw-type=raw-ethernet use-control-word=default
edit.
Could it be that he wants to deliver full frame pppoe to the customer, and pppoe header is 8byte?
But in my case where I only use the vpls tunnel, It will fit fine whit just 1500 l2mtu ?
 
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Re: VPLS/MPLS via ospf in wireless network

Mon Jun 08, 2015 5:33 pm

1508 is incorrect for a VPLS deployment if you need to hand off 1500 bytes without fragmentation, then 1526 is the absolute minimum...this is not a MikroTik requirement but rather a basic network engineering requirement. Cisco, Juniper, Adtran, etc all have the same 1526 minimum to hand off a 1500 byte VPLS frame.

Advertised MTU should be 1500 as this is the handoff segment and not the transport.
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Re: VPLS/MPLS via ospf in wireless network

Tue Jun 09, 2015 11:48 am

1508 is however correct if you need to deliver full frames (1500) in a pppoe session inside of the vpls tunnel.

Which is what the presentation was dealing with.
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Re: VPLS/MPLS via ospf in wireless network

Mon Nov 30, 2015 2:42 am

1508 is however correct if you need to deliver full frames (1500) in a pppoe session inside of the vpls tunnel.

Which is what the presentation was dealing with.
Please, can you tell me:

Whats the difference between "MPLS MTU" which is configure inside MPLS ? Will the ether's MTU interfere if I set a different MTU inside MPLS MTU ?

I'm not sure about difference between L2MTU and MTU and MPLS MTU ?

Thanks! Many thanks!
 
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Re: VPLS/MPLS via ospf in wireless network

Sat Dec 19, 2015 8:11 am

1508 is however correct if you need to deliver full frames (1500) in a pppoe session inside of the vpls tunnel.

Which is what the presentation was dealing with.
@tomaskir - Could you provide an example of your naming convention of the VPLS tunnels. Thanks.
 
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Re: VPLS/MPLS via ospf in wireless network

Thu May 19, 2016 1:40 pm

Just to add to this thread, How to calculate (if required!) VLAN L2MTU

433AH AP that has Max Ethernet L2MTU 1526 (eth1) to CPE that is set to “Station Bridge” which also has 1526 L2MTU

At present VLAN L2MTU is 1596
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Re: VPLS/MPLS via ospf in wireless network

Sat May 21, 2016 12:48 am

and do you change your MTU on your back hauls ? you need to adjust these as well.
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Re: VPLS/MPLS via ospf in wireless network

Mon May 23, 2016 7:27 pm

and do you change your MTU on your back hauls ? you need to adjust these as well.
From where VPLS is setup from all the way to the AP on this section has the same MPLS L2MTU 1526 ?
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Re: VPLS/MPLS via ospf in wireless network

Tue May 24, 2016 1:55 am

and do you change your MTU on your back hauls ? you need to adjust these as well.
From where VPLS is setup from all the way to the AP on this section has the same MPLS L2MTU 1526 ?
try with 1536
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Re: VPLS/MPLS via ospf in wireless network

Tue May 24, 2016 5:05 pm

and do you change your MTU on your back hauls ? you need to adjust these as well.
From where VPLS is setup from all the way to the AP on this section has the same MPLS L2MTU 1526 ?
try with 1536
433AH has a max L2MTU of 1526 on ether1, I cannot go above that ?
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