Are there any consumer DSL modems that offer QoS (eg. separate tx queues)?
My outgoing DSL traffic will sometimes have short bursts that saturate the link for a second or two. That of course kills quite a few voice packets and makes the VOIP sound quite bad for the other guy.
After playing with tcpdump and tweaking everything I now have all my VOIP data (sip/udp and rtp/udp) marked with the elevated IP precedence of 0xb8. Now all I have to do is find a DSL modem that has at least two internal QoS queues. Are there any such things? A quick google didn't turn up anything in consumer price range.
I'm trying to avoid buying a Sangoma PCI DSL card and doing it all in software.
Ok I got up off my *** and looked and the WRT54G has a page (under games and applications!) for QoS adjustments with a good range of adjustments. I'll take a look at the office and see what the WRT54G is up to.
Thanks! I should fire up my WRT54G and see what it can do. Is this with the Linksys firmware or the Sveasoft one?
The part I'm uncomfortable about is the fact that the DSL modem will not be doing QoS too. If the modem has only one queue, it will end up having all sorts of non-voip packets at the end of the queue. If the tx queue is stuffed full (which is almost certainly going to be the case when the uplink is fully used) then the next voip packet that needs transmitting can and will be dropped by the modem.
Well if it's *that* critical, you should get a second connection. You should be able to gain some efficiency with the router QoS. Especially if your speeds are around 2-4megs the rest won't matter.
Draytek Vigor 2600V or 2600VG, excellent piece of kit, not cheap, but very reliable. Zoom X5V also has a VoIP port, but I am not sure about QoS. Regards, Martin
you have to remember that in a DSL network with contention - it may be someone elses traffic that "kills" your voip packets.
So unless your service provider supports QoS so that your Voip packets get priority at the DSLAM, it may not matter how you mark the packets - all that affects is which packet you send down the DSL link 1st, nnot how they get treated further into the network.
The dropping I'm seeing now is definitely caused at my modem-to-dsl interface. I can demonstrate it by just uploading a big file during the conversation.
On the asterisk mailing list someone recommended the Sangoma S518 PCI DSL card very highly. It effectively lets one control the queue right at the outgoing DSL junction. He said that with that card and TOS queuing in the kernel, his problems of dropped voice packets have been cured.
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I was hoping to avoid having to get an internal card, but it seems like the pickings for a low coast DSL modem with QoS are pretty slim.
I just took a look around the net ("adsl router qos"). Found some modems, none super low cost, but maybe worth checking:
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(QoS "in new firmware") ($62)
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(scroll down to the "NB5") ($95)
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($112)
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($172)
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($194)
Barely know anything about them. Three Australian companies, one in California, and a British one.
Question arises: the QoS support seems to often be based on the port numbers. Are the outgoing port numbers for companies like Vonage fixed, or are they variable?
Hope this helps. Not sure what I'm going to do. My Vonage modem will =not= tolerate any upbound traffic. But I have other problems with Vonage too -- the Vonage voice time delay when the call is forwarded to a landline is being a killer.
Initially I was excluding anything that wasn't a pure modem (eg. with one telco port and one 100base-tx port.) I was afraid of buying more stuff that came with a NAT I couldn't turn off. (Like my Linksys WIFI router.) All I really wanted was a pure bridge that rearranged packets according to the packet's TOS field.
I can't answer about vonage or their ATA, but I can tell you that all three of my viop units (Budgetone-101, Sipura-3000, Sipura-841) can be configured to have the voip packets marked with a higher than normal TOS. A QOS-aware router or bridge wouldn't have to resort to hacks like looking at the port numbers to elevate the voip packet's position in the queue. It could just do it from the TOS field directly.
If you are in a position to look at the voip packets with tcpdump (or similar) you should see something like this if the TOS is elevated from the default (0x0):
Hmm. Don't have the means to check the packets. But I have discovered that there must be =some= level of ToS going on on my system. My test:
disabled all my ftp/web/mail/etc servers, set up a Vonage call to another phone in the house, gave the other phone a loud radio hum to listen to, and then initiated an ftp transfer on my desktop, through the Vonage
And I get exactly one phone burble for each ftp transfer, at exactly the same place at the start of the ftp each time. Once the ftp is up and running, the phone connection is just fine.
Which leads to me to believe that *somebody* in my chain (DSL -> Vonage VT1005V -> servers) is doing ToS and smoothing things out. But whichever it is, it's just not taking effect quickly enough.
(When I re-enable servers, everything goes to h--- again. Today, because I seem to have had an infestation of web bots on my web server. Be nice if I could just let the web crawlers in, you know, like at 3AM one night a month.)
I agree. I'm seeing a lot of recent pages on the subject, and the beginnings of product lines designed to solve the problem.
But none of the DSL/VOIP products I named last time were directly available in the U.S. Hmm.
It's reported on the Vonage pages that using an "integrated" VOIP/router like the Linksys WRT54GS cures the problem. But that doesn't make any particular sense, because the simple VT1005V I'm using is already an integrated VOIP/router, albeit with only one downstream ethernet port.
So... I think I'll just wait... I just ordered Packet8. They have fewer of the features I need than Vonage, but maybe they'll have better voice-lag time. And maybe their box will handle the QoS problem better.
(Wish I could have gone with AT&T Callvantage -- they had the =best= voice quality when I tested them alongside Vonage and Lingo. But they unfortunately design-botched a couple of the features of their service.) (Lingo was a distant third.)
Well, got the Packet8. A "BPA 410" telephone box, with essentially zero documentation. Not a router, not a NAT, no DHCP, no nothin'. Does have one extra LAN port, which appears to be a straight pass-through (i.e., the box acts as a 1-port ethernet hub).
Given the lack of routing, it can only be put at the head of the food chain if it and the next thing down can -each- be given their own real Internet IP numbers. I don't have that ability, so no way to test head-of-food-chain QoS handling.
(The only recommended installation is =after= a router, as a leaf node. Yes, according to Packet8 you must have a router to be able to set up the device.)
That said,
The thing doesn't seem to =care= that it's not at the head food chain! I ran multiple ftp's simultaneously with a phone call, and I found it impossible to get a phone burble.
Unfortunately.... the Packet8 service, as implemented through this box, does suffer from a nasty voice-lag time. That may be how they avoid the burbles: they don't even try to keep the conversation real-time.
(The Vonage, plugged into the identical DSL port, has a really small voice-lag.)
So I'll be packing the Packet8 up now and cancelling the account.
Sigh.
After a lot of research and experimentation, I've about had it with VoiP. Maybe I should wait and try the technology again in a few years.
Or I would be if they were answering the phone. Right there's no answering machine, no nothin', when I call the Packet8 customer service line. Just rings.
I noticed that too. I wonder what the deal is. Maybe they don't have their FCC approval yet?
If you average less than 1000 minute per month, you might also want to look into one of the 2cent per minute folks. Both of the ones I use (gafachi and teliax) allow ulaw encoding which is standard phone encoding with no compression.
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