DISCLAIMER: Much of the following rant assumes ideal (typical) internet conditions.
On 1/4/09, Trixter aka Bret McDanel <[email protected]> wrote: > > > which is why I suggested looking at the media gateways, which are the > rtp endpoint addresses. Sure, but how many providers are actually capable of doing this: - Billing paranoia (I have to be in the media stream) - Supporting non-Tier 1 compatible codecs (popular with the Asterisk community) such as GSM, Speex, iLBC, etc. - Supporting IAX. No Tier 1 (more like the equipment they use) will take IAX. If your "provider" is using IAX, your media is most likely ultimately being proxied to SIP/RTP somewhere. Best of luck to you. - Asterisk based platforms. Asterisk doesn't (yet) properly support direct RTP setup. Re-INVITEs are not appropriate for carrier trunks. If your provider is using Asterisk, it is probably in the media path for at least a little while (assuming the Re-INVITE goes well). This is not an indictment of Asterisk, IAX, or any of those codecs. It's just the reality in this environment. > But the problem with that is that recqual no matter how good it is can > only check based on where its run, it cannot check for any other network > that its not on. And it can only detect issues at the time the test was > run, issues come and go, look at broadvoice, they either work well or > not at all and it floats from which gateway the call is going through at > any given time. Further the particular route that is used at that > particular time the call is made can influence results. Due to ratio > concerns some providers will dump traffic onto a link they would not > normally to balance it and keep that trunks routes costs lower, so the > sum of calls for that billing cycle can influence call quality. Thank you, I appreciate that. Recqual was designed to test carriers. The carrier is the variable, and the underlying machine, network, etc are the controls. If I'm testing multiple carriers from my recqual machine (which I often do) I can tell you, conclusively, which carriers provide for better actual call quality. That's not definitively saying that one is *better* for everyone, but from that machine, one IS better than the other. No question. One could even argue that with sufficiently good connectivity from that machine carriers could be directly compared to one another, with an inference that one could possibly be better than all the others for everyone (or at least most people). If one carrier proxies their media in Dallas and another in NYC, the actual difference in call quality should not matter that much (short of some major, often temporary internet hiccup), even if the recqual machine is in Tampa (or wherever). I know, I know. This makes no sense, and I don't know what I am talking about. The reality is once you get past the last couple of hops on each side it really doesn't matter that much. I have run recqual tests against multiple geographically diverse SBCs and multiple Tier-1 carriers. If the carrier is crap, they are crap. Geography doesn't matter all that much. If they are good and my setup is good, recqual will (and does) report fairly consistent results irrespective of geography (assuming everything else is consistent). Every Tier-1 backbone provider's public internet SLA should provide sufficient quality for VoIP. You just need to get there and your VoIP reseller does too. Oh yeah, that SLA has to mean something too. What will matter, and what recqual will detect, is if their connectivity is oversubscribed, their components overworked, or their configuration idiotic. Especially when testing over time. This would (and does) provide for somewhat relevant comparisons of one carrier to the next, regardless of media proxying, etc. If they are cheap they are cheap and this will show. Carriers (you mention Broadvoice) throwing calls to random IP addresses... Shame on them. Every Tier-1 I have dealt with lately will give you an SBC for signaling and media. That's it. Some don't even allow for "public internet" connectivity or will only configure trunk groups so small it's basically worthless and rely on MPLS or other QoS enabled connectivity, in which case you are *definitely* proxying media to your public internet customers. It's up to the reselling carrier to properly leverage this. If they don't they are doing their customers a disservice and this will show both in recqual tests and complaints from end users. If you are "lucky" (I hate to use that term because those of us that deal with these carriers should never be considered "lucky") you will be given multiple, redundant, geographically diverse SBCs to originate and terminate calls; complete with consistent, verifiable RTP endpoint addresses. Luckily that provider will also be very well peered (most are) and you will be in a situation where you can provide for consistently good call quality as long as you know what you are doing. If you look at recqual it was designed to watch for the actual RTP endpoint address in the SDP. This was not an accident. <sales pitch> Star2Star, for example... I don't have the exact numbers of the last report but at least %90 of our customer's endpoints are within 50ms or less average RTT from the nearest Tier 1 media gateway/SBC (you can probably guess who this is). Most are far better than that. We provision the endpoint, it handles media, and it's always on the edge of the customer's network. We can (and do) constantly monitor this situation to adjust our provider agreements, outbound/inbound routing decisions, and upstream IP trunk group configurations accordingly. </sales pitch> > As such using tools like that can be highly misleading as to quality, > why I just suggested looking at how well connected the network is where > the proxies and media gateways are located and suggested not doing a > quality ranking based on the service since its the sum of all the parts > at the time that the test was performed and unless you do this from many > origination points over an extended duration, and is kept current the > results can be misleading at best. Proxy the media once, as "carriers" often do (see reasons above) and all of a sudden this doesn't matter. They could have the best public facing connectivity in the world, proxy their media and hand it off to the next carrier over an oversubscribed Cogent link. You just don't know. Actual, experienced audio quality is the *only* thing that tells the full story. Not to mention, let's take an architecture like Level(3) Vector. How many resellers properly leverage that with the proper components? I might be pessimistic again, but I doubt very many do. > that is a start but the tests have to be ongoing, it may work well > initially, then a surge of customers start using the provider, and their > quality degrades until they increase capacity. Silent back end route > changes can have a similar effect, and you have to have different > destination numbers all over as they would also be influenced by the > routes that provider uses. What reasonable provider does not LCR at the > very least? Agreed. Those of us that have been around long enough (certainly you and I, along with many of the others in this discussion) have seen the ups and downs of various resellers. It is very, very difficult to LCR *properly* while still having an ideal network architecture (direct RTP setup, for example) while providing somewhat consistent call quality. One provider uses Sonus, another Lucent, another Cisco. How do your customers all deal with even the various intricacies in RTP implementations alone? Each of the vendors I just listed has a myriad of known RTP issues, whether it be timestamps, sequence numbers, or RFC2833 issues. I know you know what I'm talking about here ;). Last I checked the various major SBC manufacturers were sitting pretty. Business is booming. > I am just saying that quality measurements have to be done many times in > an ongoing effort per provider, with multiple origination and > destination points, and all that and even then it can be misleading for > some customers since they may not be as well connected as any of the > test boxes for a given provider but are better connected for others. In a perfect world, yes but I still maintain some *base* numbers can be obtained fairly easily from one point of measurement. While this rant may read contradictory it's probably from lack of clear definition: - Carrier (Qwest? Broadvoice?) - Tier-1 (IP? VoIP?) I (somewhat foolishly) interchanged these terms when describing various entities. For the sake of clarity and argument I could go back and remedy this but I've already spent enough time on this at the moment. -- Kristian Kielhofner http://blog.krisk.org http://www.submityoursip.com http://www.astlinux.org http://www.star2star.com _______________________________________________ --Bandwidth and Colocation Provided by http://www.api-digital.com-- asterisk-biz mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-biz
