VoIP woes: Troubleshooting?

[Piyono]

I have a TalkBroadband VoIP line from Primus Canada.
It was working quite acceptably until a few months ago when I started getting serious dropouts every few seconds. It's really quite intolerable.

There are three (sometimes four) other computers on the network at home. All are malware/virus-free to the best of my knowledge and nobody really engages in heavy torrenting, except at night and never without consulting me first.

I know I could troubleshoot this by systematically removing computers from the network while monitoring VoIP call quality, but I'm wondering if there isn't a way to monitor network traffic without buying a managed switch. Is there a software application that can do this?

Piyono

 

[P5-133XL]

Is your router QOS savy? VOIP requires real-time access to the data stream. If there is other traffic and there is no QOS, then it is first-come first serve and that will cause problems with your telephone service. VOIP needs to be able to cut infront of the line ...

For most networks, the BW choke-point is the router! Thats where you should start ...

 

[Piyono]

BW?

My current router doesn't have QoS but I'll pick up a WRT54G and flash it with the latest, greatest 3rd party firmware and see what happens to my network traffic.

Piyono

 

[ddrueding]

I know Vonage sells a router that includes the VoIP gateway, I'd assume that it has QoS built-in.

 

[Piyono]

I'd use my Primus/D-Link DVG-1120 as the house router but
a) it is woefully short on router features and
b) I want my VoIP router to live next to my desk so that I detect errors at a glance and restart it when it crashes without needing to run downstairs. Practicality dictates it being positioned behind the house router.

]-[

 

[ddrueding]

I don't think mine has ever crashed...

 

[P5-133XL]

BW?

My current router doesn't have QoS but I'll pick up a WRT54G and flash it with the latest, greatest 3rd party firmware and see what happens to my network traffic.

Piyono

BW stands for Bandwidth. The router is a choke-point for several reasons. first is that it accumulates data from several sources. Next, is that most home network traffic is traveling through 1000/100/10 Ethernet but most cable systems operate at even a slower speed (1-10 Megabit). The result is the creation of an outbound queue. Without QOS, the VIOP data has to wait its turn but that produces problems for it. With QOS, the router can identify and prioritize the data and allow data that is more sensitive to delays (VOIP, gaming) ahead of data that is relatively time insensitive (FPT, Torrent).

The flaw is that there will need to be some router configuring so that the router will know what is a higher priority and what is lower priority. Typically a VIOP router is already configured to prioritize VIOP traffic. However, you are using a standard household router, so you will have some work to do.

 

[P5-133XL]

Using two routers is not recommended, if you are doing any file-sharing within your home network. Most routers try very seriously to prevent file-sharing data from being transfered across the WAN port (in either direction) for security reasons. Even if you totally turn off the firewall and use a DMZ it will stil prevent file sharing via the network IP address change change between the WAN and the Lan networks in your VOIP router.

 

[Fushigi]

If your VOIP is provided via a gizmo and not through your PC, you can put the gizmo between the cable modem & the router. Like this.

In theory this would give your gizmo control over the bandwidth. With the SunRocket gizmo I linked to, it works fairly well but heavy downloading can still cause the phone line to be a little choppy.

 

[Sol]

You could try re-prioritising your voip codecs so that a lower bandwidth codec comes higher up the list (for G7xx codecs the higher the xx the lower the bandwidth and more expensive in terms of processing, except G729a which is cheaper than G729 with the same bandwidth) I'm not sure about what other codecs you'll have available or relative bandwidth use, you'll lose a little bit of quality but use less bandwidth which should help avoid drop outs. (alternatively reducing the computation required could help, but this is doubtful since the problem is new).

You could also try using a softphone to rule out problems with your endpoint (I have had very little luck getting voip phones to work reliably together).

Is your voip device an ATA (analogue telephone adaptor, device with an ethernet port and a pots port) or a voip phone? (just a phone with an ethernet port)

It's possible but unlikely that forwarding ports for RTP (most commonly UDP 5004 & 5005 but can be anything) to your end point might help as some proxys do strange things to get around NAT traversal problems.

Another way around this would be to set your end point to use the same port for SIP and RTP (Typically UDP 5060) and then set your endpoint to register at some fairly short interval (I think anything less than 2 minutes will work).

Both options are a bit involved and kind of a long shot though.

 

[Fushigi]

A coworker was just telling me today he hacked his cable modem using utilities & advice he found in a forum somewhere. Basically DOCSIS devices are pretty open from a config standpoint. He has a 6Mb connection and told the cable modem it was 20Mb. Ran tests and streamed upwards of 22Mbps.

So maybe your solution is to hack your cable modem for a faster connection.


But then you didn't hear that from me.

 

[Mercutio]

I've heard of Comcast pressing criminal charges on people doing that to rented modems, too.

 

[time]

In theory this would give your gizmo control over the bandwidth. With the SunRocket gizmo I linked to, it works fairly well but heavy downloading can still cause the phone line to be a little choppy.

Just to clarify, QOS on a router affects upload traffic, not download (think about it). AFAIK, you need QOS further upstream (i.e. the ISP) to successfully prioritise download traffic.

 

[ddrueding]

I thought that a QoS-capable router would drop incoming frames, forcing the download stream to slow down?

 

[time]

Here's something I found that explains it pretty well:

http://vonage.nmhoy.net/qos.html

Although, I thought that routers weren't usually designed to deliberately lose packets ...

 

[Sol]

I thought that a QoS-capable router would drop incoming frames, forcing the download stream to slow down?

My understanding is that "trying to convince" would be more accurate than "forcing".

 

[MaxBurn]

Been looking into this and haven't found a real clear idea of what the problem is. Our group has a similar problem when a PC grabs the bandwidth and the person on the other end can't hear you.

Does the ISP have to support QoS as well? I though I read that somewhere that it did?

At any rate the router/PIX unit they gave us does not support QoS so we know it won't work until that gets changed, typical.

 

[P5-133XL]

Been looking into this and haven't found a real clear idea of what the problem is. Our group has a similar problem when a PC grabs the bandwidth and the person on the other end can't hear you.

Does the ISP have to support QoS as well? I though I read that somewhere that it did?

At any rate the router/PIX unit they gave us does not support QoS so we know it won't work until that gets changed, typical.

It would be nice, but extremely unrealistic for your ISP to prioritize its traffic according to your needs. So your first goal is to to eliminate the lag issues within your own network. As more internet carriers sell VOIP solutions, there will be of an effort on their part to ensure that they are not the cause of VOIP problems within their own customer base. Untill then, choose your ISP carefully ...

 

[time]

Actually, my ISP provides QOS that prioritizes VOIP over other traffic - only their own VOIP, mind you. But this is unusual.

Quality of Service is a feature of Internet routers which allows them to prioritise traffic according to the 'quality' it needs or requires.

Without Quality of Service control, voice traffic, such as NodePhone calls, may be disrupted if you use your Internet connection whilst on a phone call. Quality of Service controls ensure that your Internet traffic does not cause the quality of your NodePhone calls to degrade.

QoS is a feature which is effective in the 'transmitting' direction for IP packets. It needs to be properly configured at both ends of a connection which may potentially be placed under high load, such as an ADSL end-user connection.

Internode does its part, by configuring QoS into the devices that we use at our side of the connection to our ADSL broadband customers. This means that NodePhone packets are automatically given preferential treatment when other information is being sent to your line - basically so the NodePhone packets always 'go first'.

The direction in which your own equipment configuration becomes critical is for packets being sent from your analogue telephone adapter back to NodePhone. Those packets pass through your ADSL router, and your ADSL router needs to provide 'QoS' for those packets, so that they, too, travel 'first' on their way back into the ADSL network and on to the NodePhone voice switching devices.

 

[Sol]

If you have QOS then the ISP isn't as important since the tightest bottleneck will likely be between you and your ISP.

Unless your ISP is overselling bandwidth to a spectacular degree. In this case your screwed and need to find a better ISP.

 

[Mercutio]

Don't all ISPs oversell bandwidth to a spectacular degree?

 

[Sol]

Well yes, but I mean to an unusually spectacular degree. A good example would be neighbourhood cable in Ballarat where the bandwidth was so badly over sold that they dropped up to 20% of all UDP packets at some times and where getting up to 1/3rd of your peak bandwidth between midnight and 7am was a feat only possible for a few talented (the trick was lots and lots of concurrent sessions), and was beyond any ones abilities the rest of the time.

In those sort of situations voip just ain't going to work (in fact no time critical applications at all could be said to work and things like browsing leave you in doubt for long periods).

 

[time]

Firstly, a 1/3rd of your peak bandwidth on cable can be 3 - 6Mbps. Most people would be extremely happy with this. In Oz, it's far more than enough to hit the overseas bandwidth limitations that the ISP imposes. That is, you'll only ever see those speeds to international sites when they're being cached by the ISP's proxy.

If you have QOS then the ISP isn't as important since the tightest bottleneck will likely be between you and your ISP.

Huh? Isn't that why ISP-EndUser prioritization is important? Can you elaborate?

 

[Piyono]

I've attached a simplified diagram of my network. I re-purposed an old diagram I made for someone else and was too lazy to delete the text at the bottom, which has nothing to do with the pictures on top.

I'm looking into getting a WRT54G and some third-party firmware that supports QoS. More effort than I want to expend right now, really, but it may come together.

Piyono

 

[Fushigi]

If you can't put the VOIP router between the Cable Modem & the LAN Router/Switch then how about hanging it directly off the LAN Router/Switch? That'd take two switches and their accompanying latencies out of the configuration.

 

[Fushigi]

*Sigh* Possible new VOIP woe: SunRocket looks to be dying. I'll wait it out as I like the service & the price, but if they do shut down, I'll need to transfer my home line to another provider. Skype doesn't appear to have a gadget that would allow me to connect my DVR & home phone for outbound calling so the main alternative looks like Vonage. Any other suggestions? Anything related to AT&T will not be considered.

 

[ddrueding]

I like my Vonage connection. It just works.

 

[P5-133XL]

I would be wary of going with Vonage. Vonage lost a patent dispute with Verizon over VOIP. Verizon successfully got a cease and desist order which has been stayed untill an appeal has been ruled upon. Judge: no new customers for Vonage. It is my understanding that Vonage does not have a work-around to the offending patents.

 

[Santilli]

David:
I'm looking at Vonage. What router are you using? How do you have yours setup?

Thanks

GS

 

[ddrueding]

I have a Linksys 350N that is flashed with the DD-WRT firmware. I have the MAC of the Vonage box set as high priority in the QoS.

 

[Mercutio]

I thought that a QoS-capable router would drop incoming frames, forcing the download stream to slow down?

Actually, after reading some posts about VoIP installations on Slashdot and some comments from knowledgeable parties, it turns out that pretty much nobody implements QoS on incoming connections; certainly not $50 home routers, even the ones that have dd-WRT or Tomato on them.

Comments on Slashdot suggest that the "right" way to get incoming QoS is to deal with an ISP that is small enough to be willing to implement it on their outbound connection.

I've never investigated what people with $$$ Cisco installs are doing about QoS, but I do know that the level of service that's build into Windows doesn't communicate with anything not local to the PC. It's reasonable to assume that applications needing QoS would somehow communicate that fact to network partners, but that does not appear to be the case. I guess this is a case where the protocols for doing so just aren't mature?

 

[ddrueding]

Actually, after reading some posts about VoIP installations on Slashdot and some comments from knowledgeable parties, it turns out that pretty much nobody implements QoS on incoming connections; certainly not $50 home routers, even the ones that have dd-WRT or Tomato on them.

Comments on Slashdot suggest that the "right" way to get incoming QoS is to deal with an ISP that is small enough to be willing to implement it on their outbound connection.

That is the impression those sources left me with as well. That the unregulated incoming connection and the large number of open connections (common with BT users - correctable in some firmwares) can mess things up regardless.

 

[Santilli]

HMMM.

If I went with the 6mb/sec connection over the 1.5 mb/sec, would that be enough to not have to worry about interrupts with Vonnage?

Thanks

Greg

 

[Mercutio]

It doesn't work that way. There's more to network transfers than bandwidth.

 

[mubs]

I've used (and continue to do so) Vonage over 2mbit connections and have had zero issues. No QoS settings in the router; just plain vanilla connections. In fact, the internet line is connected to a wi-fi router, and the Vonage adapter is on the client end of the wi-fi. Quality is land-line like.

Sad thing is the the Linksys PAP2 Vonage adpater just died; ~ 16 months old. Need to get another.

 

[Mercutio]

You don't really need QoS unless you do more with your internet connection than light E-mail and web browsing. I've done Skype over a 100kbit upstream connection, and it worked as well as Skype ever does.

It's the people who like to play games, use P2P software or run some kind of server off their connection who really need QoS.

 

[Fushigi]

This is from memory, so I could be off a bit, but a T-1 (1.54Mb) line can carry 24 uncompressed voice channels. So an uncompressed channel only needs 64Kbps. Now compress that.

You're really only talking about a 12Kbps or so bandwidth requirement per voice channel. In theory a dial-up modem can handle that with ease, although I'd suspect latency issues may be troublesome.

 

[MaxBurn]

It's funny but our business just continues to deal with the crappy connection saying that's just the way it is. QOS won't help us at all as the phone is on the other side of a Cisco PIX 501 hardware VPN so the ISP can't see the QOS information anyway.

 

[blakerwry]

actually, IPv4 itself supports QoS... and I'm sure you're all using IP packets if you're using the internet.

However, I think the original suggestion of using Tomato to prioritize traffic is the best solution, and the only one that a single entity can implement.

Using IP's TOS (Type of service) flag allows an IP device (host or router) to prioritize the traffic it receives based on this flag. However, how to handle each service ID is up to the ISP to decide and implement. Very few make use of this, and even fewer would want to trust their customer's use of this.

There's also COS (cost of service) that's implemented on switches and modems. I've seen SBC/ATT use these in their 2wire modems. However, playing with it never improved my connection noticeably. It's certainly possible that COS is not implemented fully in their network or they were ignoring the settings I configured in my modem.


The kind of QoS in soho routers is typically a traffic shaping setup local to the router and does not modify or pass the QoS information through the network. It simply allows certain types of traffic to cut to the front of the line when there's a queue. Traffic shaping usually works well when you have an aggregation point where one side of the router is much faster than the other side of the router... for example a home network setup (>100Mbps LAN, <10Mbps WAN). Again, it only effects traffic when there's a queue, so if you can't get reliable VoIP when the VoIP phone is the only thing on the connection then it will not help, you're problems are likely upstream.