Multilink PPP Queueing: is it WFQ or FIFO ?

john_fuechsel · ‎03-23-2010

Cisco IOS QOS Solutions Configuration Guide, Release 12.4 says WFQ is enabled by default on interfaces configured for Multilink PPP.

But when I "show interface" on the multilink interface I see:

Queueing strategy: fifo

Oddly, the two T1 serial interfaces that are members of the multilink bundle show:

Queueing strategy: weighted fair [suspended, using FIFO]

"show queueing" doesn't indicate anything for the multilink interface:

FNYRC01#show queueing
Current fair queue configuration:

Interface           Discard    Dynamic Reserved Link    Priority
                      threshold queues   queues    queues queues
Serial0/0:1         64         256      0         8       1
Serial0/1:1         64         256      0         8       1

Is the "Queueing strategy: fifo" shown for the multilink interface just wrong? Is WFQ being done only on the physical members of the MLP bundle after MLP has already picked one of the links for that flow?

(At the time of these "show" commands, the link was not congested.)

Thanks in advance for any insight on this issue !

Lei Tian · ‎03-27-2010

Hi John,

Can you configure "fair-queue" under MLPPP interface? As far as i know, after you configure mlppp, the member interface will be put in FIFO queue. What you seen on the output of member ports "suspended, using FIFO" is expected.

HTH,

Lei Tian

john_fuechsel · ‎04-14-2010

Thanks, Lei Tian !

I finally got into the lab to try this out and found that coding "fair-queue" on the MLPPP interface gives me what I'm looking for.

I guess the documentation is just incorrect about the default queueing on that kind of interface.

Now I have:

CW-Test-Router#show int mu1
Multilink1 is up, line protocol is up
Hardware is multilink group interface
Description: Multi-T1 bundle
Internet address is 172.16.171.113/30
MTU 1500 bytes, BW 3072 Kbit, DLY 100000 usec,
     reliability 255/255, txload 1/255, rxload 1/255
Encapsulation PPP, LCP Open, multilink Open
Open: IPCP, loopback not set
Keepalive set (10 sec)
DTR is pulsed for 2 seconds on reset
Last input 00:00:14, output never, output hang never
Last clearing of "show interface" counters 00:13:30
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: weighted fair
Output queue: 0/1000/64/0 (size/max total/threshold/drops)
     Conversations 0/1/256 (active/max active/max total)
     Reserved Conversations 0/0 (allocated/max allocated)
     Available Bandwidth 2304 kilobits/sec
30 second input rate 0 bits/sec, 0 packets/sec
30 second output rate 0 bits/sec, 0 packets/sec
     4 packets input, 56 bytes, 0 no buffer
     Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
     0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
     4 packets output, 80 bytes, 0 underruns
     0 output errors, 0 collisions, 3 interface resets
     0 output buffer failures, 0 output buffers swapped out
     0 carrier transitions

and:

CW-Test-Router#show queueing
Current fair queue configuration:

Interface           Discard    Dynamic Reserved Link    Priority
                      threshold queues   queues    queues queues
Serial0/0:1         64         256      0         8       1
Serial0/1:1         64         256      0         8       1
Multilink1          64         256      0         8       1
Many thanks for your reply!

Yasir Ashfaque · ‎04-15-2010

seems to be something missing, even decreasing bandwidth from E1, it is still fifo, on both MLP and Virtual-template... Cisco might need to rectify their document.