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tildeleb
Premium
join:2004-06-22
Sunnyvale, CA
|  [HELP] QOS: problems with RTP packets on very lightly loaded 362
Hi,
I've got a DSL line 3008/768 sync rate (interleaved). It used to be directly attached (via a DSL modem) to a D-Link DVG-1120M VOIP box. This worked pretty well and VOIP glitches were minimal.
Recently I decided to use a 3620 running IOS 12.3(9) and hook the DSL line up to a WIC-1ADSL (in a NM-2FE2W) and the DVG-1120M to an ethernet port on a NM-4E. The router has virtually no other traffic. This config doesn't work nearly as well and there are significantly more VOIP glitches to the point where the VOIP line is unusable.
Some data:
1. The ATM interface show a TX and RX load of about 18-19
2. The Ethernet interface show a TX and RX load of 1
3. CPU utilization for five seconds: 1%/1%; one minute: 5%; five minutes: 6%
4. The UDP/RTP packet size is 138 bytes with a payload of 80 bytes. That's 53,000 bits/sec before ATM overhead.
5. See below for show interface output for the two interface involved.
I'd be happy to add QOS although I really don't understand how, at this light load, it would help.
1. Any thoughts as to what might be going on here?
2. At some point there will be other traffic on this router and I will absolutely need QOS. I am still reading up on QOS, but since I only have 1 VOIP stream I was hoping to keep it simple and use PQ (Priority Queuing) but that doesn't seem to work with ATM interface used by the DSL line as there appears to be no place to use the "priority-group" command. Does PQ work with ATM.
3. Given that I have RT flows in both the in and out direction I assume i need to apply QOS twice, once for each flow, correct?
4. Any thoughs on simple QOS scheme for my 1 VOIP channel? I need something that would scale to 3 or 4 VOIP channels.
squeeze#show interface ATM 0/0
ATM0/0 is up, line protocol is up
Hardware is DSLSAR (with Alcatel ADSL Module)
MTU 4470 bytes, sub MTU 4470, BW 768 Kbit, DLY 2660 usec,
reliability 255/255, txload 18/255, rxload 19/255
Encapsulation ATM, loopback not set
Encapsulation(s): AAL5 AAL2, PVC mode
23 maximum active VCs, 256 VCs per VP, 1 current VCCs
VC Auto Creation Disabled.
VC idle disconnect time: 300 seconds
Last input 00:00:14, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: Per VC Queueing
5 minute input rate 59000 bits/sec, 50 packets/sec
5 minute output rate 57000 bits/sec, 50 packets/sec
150824 packets input, 46189106 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
128736 packets output, 18632738 bytes, 0 underruns
0 output errors, 0 collisions, 2 interface resets
0 output buffer failures, 0 output buffers swapped out
squeeze#
squeeze#show interfaces Ethernet 1/2
Ethernet1/2 is up, line protocol is up
Hardware is AmdP2, address is (removed)
Internet address is (removed)
MTU 1500 bytes, BW 10000 Kbit, DLY 1000 usec,
reliability 255/255, txload 1/255, rxload 1/255
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:03:43, output 00:00:00, output hang never
Last clearing of "show interface" counters never
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 0
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 52000 bits/sec, 48 packets/sec
5 minute output rate 53000 bits/sec, 50 packets/sec
124334 packets input, 16597959 bytes, 0 no buffer
Received 180 broadcasts, 0 runts, 0 giants, 0 throttles
201 input errors, 201 CRC, 178 frame, 0 overrun, 0 ignored
0 input packets with dribble condition detected
144959 packets output, 19231089 bytes, 0 underruns
0 output errors, 0 collisions, 2 interface resets
0 babbles, 0 late collision, 0 deferred
0 lost carrier, 0 no carrier
0 output buffer failures, 0 output buffers swapped out
squeeze#
--
~leb | |
snarohyans
join:2005-11-10
Indianapolis, IN
| Re: [HELP] QOS: problems with RTP packets on very lightly loaded
Well for one, you are paying for a 3mb/768k DSL line, and the last ADSL WIC I was investigating was only rated for 1.5mb/512k. That could have changed though...but it's something to investigate. Even @ 1.5 and 512, that is more than adequate bandwidth to run VoIP. | |
belushi
Premium,MVM
join:2000-11-08
Twinsburg, OH
| reply to tildeleb
For voice you'll want to implement Low Latency Queueing. Basically all it entails is an extension of the priority queue you've previously mentioned within a class-based weighted fair queueing structure. It is necessary for voice packets because it transmits them first during times of congestion thus reducing problems such as jitter and higher delay. I've been extremely general in my description so why don't you read up on it here:
»www.cisco.com/en/US/products/sw/···b13.html | |
tildeleb
Premium
join:2004-06-22
Sunnyvale, CA
| Thanks. But what is going on here? There is almost no other traffic on this router and it still has issues compare to going straight into the DSL modem.
1. There do not appear to be any packet drops. I assume that I can tell that by looking at the stats on the two interfaces or are there other places where packets might be getting dropped?
2. Is there something that might be causing packet delay or skew just by routing from one interface to the other?
--
~leb | |
aryoba
Premium,MVM
join:2002-08-22 | tildeleb,
Can you post the 3620's show running-config ? | |
rovernet
Premium
join:2004-02-11
Richardson, TX | reply to tildeleb
Also, if running pppoe, make sure the MTU is set at 1492 on the dialer interface. | |
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