Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

Ask HN: Why isn't VoIP better?

news.ycombinator.com

Post reply on HN
Print view View original

51–60 of 141 posts

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

#51

Post by zrm »

MandieD wrote: post #15

Jitter is one of the words you're looking for. 20 milliseconds does not sound like much, but when it's a delay in some (but not all) packets in a call getting to you, you can sure hear it! Jitter is why you could have a 1 GB/s connection at home, and still have the same occurrence of poor call quality. QoS (Quality of Service) can help, but only if it is applied at every router the traffic for a call goes through. Qo…

> 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 particular if you control a router there, make sure it knows to limit traffic to what the next hop link speed actually is. In will often see the link as gigabit ethernet even if it's slower than that and then forward all traffic when you really want it to be the device that chooses which traffic gets dropped.

Unfortunately if your ISP supports burst bandwidth it's not always easy to get it right without breaking that.

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

#52

Post by richbhanover »

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 Linux kernel, and people's home routers now could install LEDE/OpenWrt (https://lede-project.org). Two links:

What can I do about bufferbloat? https://www.bufferbloat.net/projects/bloat/wiki/What_to_do_a...

Test your network for bufferbloat: http://dslreports.com/speedtest

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

#53

Post by AnthonyMouse »

MandieD wrote: post #30
scandox wrote: post #23

Earlier quoted context omitted.

At home I use Ethernet, a Blue Yeti USB microphone and a solid pair of Philips USB headphones. Of course I don't know what my counterparts on the other end are using. I guess my problem seems to be that we swapped a system that had a consistent call quality for one that is inconsistent, for a whole bunch of reasons. It seems to me, as if the general quality of telephony took a huge step backwards. And I don't underst…

The only thing that could make VoIP voice quality as consistent as PSTN is a consistent application of QoS. And that is why I have very mixed feelings about Net Neutrality. Sure, I don't think that Verizon should be allowed to penalize NetFlix or $randomVideoStartup by favoring its video traffic over theirs, but there is no technical way for voice to be consistently good without a consistent handling of its data traf…

Network neutrality doesn't really have anything to do with QoS. Network neutrality says you can't prioritize packets from Comcast over packets from Netflix. It doesn't say you can't prioritize packets a customer has marked as more important over packets the same customer has marked as less important.

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

#54

Post by jeffdubin »

This is almost always a latency issue, and because nobody has figured out a way to milk extra cash for providing inter-network packet prioritization. In other words, this isn't an engineering problem, it's a money problem.

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

#55

Post by kalleboo »

AnthonyMouse wrote: post #53
MandieD wrote: post #30

Earlier quoted context omitted.

The only thing that could make VoIP voice quality as consistent as PSTN is a consistent application of QoS. And that is why I have very mixed feelings about Net Neutrality. Sure, I don't think that Verizon should be allowed to penalize NetFlix or $randomVideoStartup by favoring its video traffic over theirs, but there is no technical way for voice to be consistently good without a consistent handling of its data traf…

Network neutrality doesn't really have anything to do with QoS. Network neutrality says you can't prioritize packets from Comcast over packets from Netflix. It doesn't say you can't prioritize packets a customer has marked as more important over packets the same customer has marked as less important.

How much of the VoIP contention is on the user end vs the ISP end though?

I have a 1 Gbps connection at home and can still have a VoIP call across the world mess up since I might not have the best route to whoever I'm calling.

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

#56

Post by telebone_man »

I've been in the VoIP industry for over a decade now, and in almost all cases of 'bad VoIP' I can trace the blame to a bad implementation of it. Let me give you an extreme examples...

- It's fairly common practice in countries with poorly enforced telco law for people to resell access to the PSTN. They will connect to the PSTN (either via a GSM gateway or a server with an E1 card) and resell that access to a 'wholesale VoIP business'. - That 'wholesale VoIP business' will have an infrastructure, cobbled together with open source technologies with no ability to scale, in the operational or technical sense. - The same 'wholesale VoIP business' will undercut the cost to access the countries PSTN (compared to accessing it directly via a tier 1 carrier) and sell the access to other tier 1 carriers. - The other tier 1 carriers lap up this cheap access, an embrace it because international calls fulfil a small portion of their multi-million revenues. - Therefore, when someone in another country tries to call that country with poorly enforced telco law, it will route via the resold route until it's shut down by the law or it breaks because it's poor infrastructure. - This is currently happening on a big scale in lots of African countries, some central american countries and in the middle east.

I'll leave the context of 'office to office' comms to the other answers as it's been covered in detail elsewhere. But I will say VoIP, all it's forms, is an old technologies, and problems relating to poor bandwidth.. voice quality.. backwards compatibility have been solved for many years.

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

#57

Post by TYPE_FASTER »

It depends. I've noticed that sometimes my AT&T cell calls are of a higher quality, depending on who I'm talking to. I think this has something to do with their HD Voice product.

I like it, the quality reminds me of what I've experienced in the past with the Cisco UC platform on a well-provisioned network and UC platform.

The goal of Skype, Viber, etc. are to always give you some level of audio across all networks, so the codecs they are using have a different goal than Cisco UC.

All these codecs have low bandwidth requirements, much lower than what you have. If you have a residential ISP, QoS might be an issue with some of the higher sampling rate codecs, but you probably won't notice them with Skype.

Try running an open source VoIP MCU at home on your LAN to see how good it could be.

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

#58

Post by MandieD »

zrm wrote: post #51
MandieD wrote: post #15

Jitter is one of the words you're looking for. 20 milliseconds does not sound like much, but when it's a delay in some (but not all) packets in a call getting to you, you can sure hear it! Jitter is why you could have a 1 GB/s connection at home, and still have the same occurrence of poor call quality. QoS (Quality of Service) can help, but only if it is applied at every router the traffic for a call goes through. Qo…

> 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.

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

#59

Post by 102381281 »

bsaunder wrote: post #22
zamalek wrote: post #8

It's probably because most people have horrible quality microphones.

Sorry to down vote, but that's completely the wrong vector. Its a network issue (of some sort - bandwidth, latency, throttling).

Is it? Why do people with headsets sound 10x better over Google Hangout than people using the integrated laptop microphone?

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

#60

Post by feld »

feld wrote: post #33
scandox wrote: post #17

Earlier quoted context omitted.

So what you're saying is: VOIP will never match PSTN? Because that's the mood music I get from the sysadmins at work too.

VOIP is considerably better than PSTN if configured correctly. There's no comparison. Your sysadmins don't understand VOIP.

just want to point out: vast knowledge of telephony/VOIP is not something every sysadmin should be expected to know. If you don't have telephony expertise on staff I hesitate to suggest someone build out a VOIP infrastructure on their own. It can be extremely time consuming to learn and it is definitely painful to troubleshoot.
Post reply on HN