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Ask HN: Why isn't VoIP better?

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Re: Ask HN: Why isn't VoIP better?

#61

Post by jlgaddis »

MandieD wrote: post #58
zrm wrote: post #51

Earlier quoted context omitted.

> QoS (Quality of Service) can help, but only if it is applied at every router the traffic for a call goes through. You really only need it on routers where a bottleneck is. If a router is forwarding 100% of packets immediately there is nothing for QoS to do. In practice what this means is that the most important place to have it is at the border where you go from high bandwidth LAN to lower bandwidth internet. In pa…

QoS depends on tagging (DSCP), and if one of the routers along the way doesn't support it or isn't configured for it, those tags are often dropped - or at least that's what I've seen in our company's network.

Like so many other things in tech, "it depends".

Network gear can be configured to treat frames/packets in various ways -- leave the ToS/DSCP bits alone, strip them out, or remark them. At the edge of a network, it's common to mark them. In the core of a network, you'll usually leave them alone (but honor them). On connections to third-parties (such as ISPs), it's not unusual for them to strip your QoS markings -- unless you're paying extra for them not to.

For a random packet that leaves your home network and hits the Internet (even VoIP traffic), I'd be surprised if it ends up at its destination with those same QoS bits set.

Like zrm said, though, if there's no congestion on links, prioritizing traffic typically isn't going to do you much good. It's only when there's contention that moving packets to the front of the line helps out.

Re: Ask HN: Why isn't VoIP better?

#62

Post by rrmm »

scandox wrote: post #39
MandieD wrote: post #27

Earlier quoted context omitted.

Are the 1 in 3 good calls pretty random, or do they tend to be with the same counterparts? Do you notice a difference between the quality of your calls into conferences (if on the same platform) and direct calls with colleagues? WiFi can be a source of the problem even within the corporate network if the access points weren't designed for VoIP.

It seems random to me, but of course when I'm in User-mode I'm probably quite a poor observer. I'm not a power user of VOIP, but these are my common scenarios: 1. At home, Skype and Google Hangouts. Hardware setup as above. 240 Mbps connection. Making calls to family abroad. This is the 1 in 3 scenario - we just keep trying till we get a connection that seems to work. Usually the call ends whenever the line finally "…

Scenario one stands out to me. There will be a lot of hardware between you and the other party in your call and trouble can happen at any of them. The connection quality you get will depend on the worst performing hardware in that chain.

Re: Ask HN: Why isn't VoIP better?

#63

Post by asymmetric »

mikekchar wrote: post #37

Lots of good answers, but there is another one that's important too: echo cancellation. Most telco equipment has very good echo cancellation hardware in it. It's not impossible to do a decent job in VOIP, but not all of the software does it well. This can be very important when you have high latencies or if you are doing conference calls. The other main overlooked problem is automatic gain control in software. This o…

Got any link to good echo cancellation hardware? Not that I'd every buy it, I'm just interested in tech (and businesses) that's not for average consumers.

Re: Ask HN: Why isn't VoIP better?

#64

Post by rrmm »

tomfanning wrote: post #10

I find I agree. - lossy vs lossless codecs (PSTN isn't analogue end-to-end any more, but is lossless as far as I'm aware. VoIP seems to have been about squeezing as much traffic down the pipe as possible, at the expense of quality.) - circuit vs packet switched networks (Congestion, contention, jitter on shared packet switched networks. While I'm sure PSTN doesn't have "physical" circuit switching any more, I do get…

The lossy part of PSTN occurs at the front-end where only a 3KHz band of audio is passed through the network.

Re: Ask HN: Why isn't VoIP better?

#65

Post by jlgaddis »

scandox wrote: post #4
iopuy wrote: post #2

Where do you live where you can get 2 gigabit speeds at home?

240 Mbps. So AFAIK 240 megabits per second. Is my original notation ambiguous?

Networking speeds are pretty much universally represented in bits (per second) -- "little b". Storage, on the other hand, uses bytes -- "big B".

So, yeah...

> I have 240MB/s at home ...

You're saying you have a 240 MBytes x 8 -- or 1920 Mbit/s -- connection.

Re: Ask HN: Why isn't VoIP better?

#66

Post by ra1n85 »

richbhanover wrote: post #52

I'm surprised that no one has mentioned bufferbloat yet. In most home routers, people can see seconds of delay when there's significant other traffic on the link. (And remember, "other traffic" can be ordinary web browsing, where pages average 2 mbytes these days...) The latency (and jitter) caused by bufferbloat has been a solved problem for almost five years: fq_codel, and the newer cake qdisc's are are in the Linu…

Bufferbloat is a side affect of congestion or microbursts, and not the primary cause of poor voice calls. Either packets get dropped (shallow buffer) or queued (enough buffer), and in both cases the quality of the call will suffer.

Mitigation: Don't congest. If you need to, mark VOIP traffic with a DSCP value that has queues that are serviced prior to all others (e.g., EF, DSCP46).

Re: Ask HN: Why isn't VoIP better?

#67

Post by NLips »

scandox wrote: post #39
MandieD wrote: post #27

Earlier quoted context omitted.

Are the 1 in 3 good calls pretty random, or do they tend to be with the same counterparts? Do you notice a difference between the quality of your calls into conferences (if on the same platform) and direct calls with colleagues? WiFi can be a source of the problem even within the corporate network if the access points weren't designed for VoIP.

It seems random to me, but of course when I'm in User-mode I'm probably quite a poor observer. I'm not a power user of VOIP, but these are my common scenarios: 1. At home, Skype and Google Hangouts. Hardware setup as above. 240 Mbps connection. Making calls to family abroad. This is the 1 in 3 scenario - we just keep trying till we get a connection that seems to work. Usually the call ends whenever the line finally "…

Sounds like your problem isn't with VOIP, it's with softphone VOIP clients and/or OTT carrier. The company phones are probably VOIP (do they just have ethernet connections?), but connected up to a telco which handles traffic nicely.

Most telcos are sending a huge amount of traffic round over IP. The difference is that they are controlling the bandwidth so stuff just-works, whereas when you use a purely OTT service, you're probably stuck with your packets getting the same treatment as any old web request. Most of the calls you think you can detect as POTS probably have VOIP legs in them somewhere if they're long distance.

Which of the services are the most expensive? My guess is the company phone. Are you paying for any of the others?

Re: Ask HN: Why isn't VoIP better?

#68

Post by snuxoll »

feld wrote: post #31

Both ends need to support wideband codecs, as does your phone (hard or soft phone). This includes the VOIP providers needing to be able to use wideband codecs between each other. If you achieve a wideband setup the call quality is amazing. I've used it for years. It really sucks when you have to call someone on a legacy POTS line or using a narrow band codec (bad voip, cell phones, etc) On that note it's unfortunate…

> On that note it's unfortunate that cell phones which can do wideband codecs within the same carrier (HD Voice!) won't work if your call leaves their network.

This is quite annoying, but it's because the PSTN overall is stuck on G.711 and G.729 - my SIP provider doesn't support anything else because they would be forced to re-encode the signal anyway and lose quality doing so.

Ultimately, we need to be putting pressure on the telco's to enable support for G.722 - until that happens we're going to be stuck with 4KHz audio for a long, long time.

Re: Ask HN: Why isn't VoIP better?

#69

Post by 2almalki »

asymmetric wrote: post #63
mikekchar wrote: post #37

Lots of good answers, but there is another one that's important too: echo cancellation. Most telco equipment has very good echo cancellation hardware in it. It's not impossible to do a decent job in VOIP, but not all of the software does it well. This can be very important when you have high latencies or if you are doing conference calls. The other main overlooked problem is automatic gain control in software. This o…

Got any link to good echo cancellation hardware? Not that I'd every buy it, I'm just interested in tech (and businesses) that's not for average consumers.

I work at a big telco in the voice group and we still have tons of DMS 100/200/250s. Anyways some interconnections we have require Ditech echo canceller (no idea what model but apparently when we need them, we use spare ones or have to buy them on the used market). We have been migrating traffic to newer equipment and the new gateways have echo cancel built into them (e.g. Genband G9s)

Re: Ask HN: Why isn't VoIP better?

#70

Post by AndyMcConachie »

I think your complaint is about VoIP over the internet. And that's simple, the internet is best effort. Packets get dropped and that's expected. Also, packets can take a long time to reach their destination and there are no guarantees for jitter. This absolutely sucks for voice quality and there's nothing anyone can do about it.
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