02-28-2013 08:35 AM - edited 03-04-2019 07:09 PM
Hi,
I have 4 T1s going to a site, 2 of which are new (all 4 are with the same provider).
I initially noticed that throughput of the 4xT1 bundle seemed a bit off, so I did additional testing.
I found that whenever I have a certain T1 in the bundle (whether its 2xT1, 3xT1 or 4xT1), throughput is drastically decreased.
There are no errors on the circuit, so my provider is being difficult about "repairing" it since they also see no errors.
Is there anything I can specifically mention to them that might help the issue?
Here's now the T1s and Multilink are configured:
Serial n/0
no ip address
encapsulation ppp
ppp multilink
ppp multilink group 8577
Multilink 8577
ip unnumbered Loopback0
ppp multilink
ppp multilink group 8577
Pretty straightforward.
As an example, running a speedtest with the 3 "good" T1s I get ~4.5Mb each way as expected.
Adding the 4th T1 in, I get speeds of 3.8Mb.
Thanks.
02-28-2013 08:37 AM
MLPPP is not a good solution, obsolete, awkward and expensive, with poor performance. Get an Ethernet based service if you want to avoid all that.
04-13-2016 08:33 AM
I do not agree with the previous answer because you loose at least 14 percent to overhead by going with Ethernet encapsulation (more as the number of small packets goes up). Unless Ethernet is being delivered via fiber you also loose visibility to layer 2 errors on the T1 service modules being bonded to provide your service (which would now only be visible on the Carrier devices being used to convert bonded T1's to Ethernet when not delivered via fiber). Also, in many areas bonded T1 is still cheaper.
To address your problem apply a shaper based on percentage to your multilink interface like in this example:
class-map match-any EF
Description VOICE
match ip dscp ef
exit
Policy-map QOS-POLICY
class EF
!Note: Make sure carrier is provisioned to allow 700k of EF from the site!
priority 700
police 700000
class class-default
fair-queue 512
queue-limit 256
!-------Multilink interface config template
Policy-map Shaper_<INT>
Class class-default
shape average percent 100
service-policy QOS-POLICY
interface <MU_INTERFACE>
service-policy output Shaper_<INT>
As the number of T1's available in the bundle changes the shaper will dynamically adjust the bandwidth. For PPP this is done by multiplying the number of in service T1's by 1.536Mbit/sec.
Also, make sure that you use percentages everywhere BUT your EF rate. your EF rate will hopefully always be policed to to a specific rate by the carrier that is not based on total bandwidth as the total bandwidth changes based on the number of in service T1's.
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