200 OK

The ECG staff technical blog.


What is "Enterprise Quality Video"?

Psytechnics has a troubleshooting product that sounds neat. Expensive, but pretty neat. Their marketing folks have sent me this email, announcing they'd teach me how to ensure "Enterprise-Quality" Video and Voice. What is "Enterprise Quality"? To be honest, most "enterprises" I know do a lot of business over cell phones. Is cell phone quality what we're aiming for? And even if we accept that "...


Writing Detailed MOPs, and the Distinction between Planning and Doing

Service Providers often want a detailed Method of Procedure (MOP) for any change in their network. Some service providers, like Level(3), have Engineering people plan the procedure, while Operations people actually do the procedure. This does encourage careful planning. But sometimes things go wrong; most MOPs have a back-out procedure, so that any changes can be reversed. But wouldn't it be ...


On Organizing People and Work at a VoIP Service Provider

VoIP service providers these days face the technical challenges of huge flexibility, and no single integrated solution with interop-tested partner devices. You can't just buy a "switch", plug in some TDM/SONET transport and turn up "smart remotes" made by the switch manufacturer. Even integrated VoIP systems like MetaSwitch leave a lot of design space: -- What signaling protocols? -- Which of t...


The "Just Do It" approach to network design

The natural way networks are designed is "just do it". We just do whatever seems obvious; very little thought is given to design. Instead, neophytes think it's "just" a matter of configuration. This approach leads to incomprehensibly complex designs. Cables going in every which way, poorly-planned fault tolerance, VLAN inconsistencies (e.g., VLAN 200 is one broadcast domain on this switch,...


Sales folks and work avoidance

Sales folks are a funny breed. It's a salesman's job to work to convince you to buy his product. But he's only willing to do so much work! The amount of work he's willing to do is vaguely correlated to the amount of money he might make from you. For example, when I was at BellSouth, if I called Empirix to get information on their product, they wanted to get on a plane and come explain it t...


Wireshark Memory Bloat on VoIP capture files

Wireshark is a really neat tool for analyzing phone calls. But when you load a 100 MB capture file of VoIP calls, you need much more than 100 MB of RAM. But how much more? Here's a data point from which you can make a line: a 326.15 MB PCAP file contained lots of SIP, and a little RTP. This wasn't a raw capture file; I had thrown away a lot of the RTP and RTCP. The file compressed to 121.1...


BroadSoft Connections 2008: the obvious ideas are all here

From the flight from Phoenix, AZ to Raleigh, NC: The BroadSoft Connections 2008 conference completed today. This is my third time at Connections. The stated goal of the show is networking and dealmaking. The former is difficult to measure, but I suppose I did some of that. I know the latter occurred, and the work will occupy me for a while. BroadSoft spent some time advertising the "xtend" pla...


How important is a lab system?

How important is it to have a lab replicating your production (VoIP) environment? Conventional wisdom says that everybody has a lab: some people just host their production users on it. Having a lab incurs a lot of additional cost and work: -- You have to buy the lab equipment, and the software. -- You have to install and integrate the lab system. -- You have to keep it up to date and secure. ...


This CDR has been brought to you from the letters B, F, and the symbol #

TWICE in the past month, I've bumped into CDRs from SS7 equipment in Atlanta that include alphabetic characters and pound signs in the calling party number (ANI) field of the CDR. One of the calls was from 5176#0B600. (That's a phone number.) What's going on here?


Voicemail peak-hour oversubscription ratio (48:1)

If I'm a phone company and I have 100 subscribers, and every one of them has voicemail, how many people will be calling into the voicemail system at any one time? Back in the old days, they'd provision trunks into the voicemail system between the Class-5 switch and the voicemail system. They'd have to know how many trunks to provision to let all the subscribers both receive voicemails, and call...


The cat in Aastra 2.2 SIP Software

The Aastra 57i 2.2 software has this ASCII art embedded: | ("`-''-/").___..--''"`-._ | Line (`6_ 6 ) `-. ( ).`-.__.`) | Manager (_Y_.)' ._ ) `._ `. ``-..-' | _..`--'_..-_/ /--'_.' ,' | (il),-'' (li),' ((!.-' Is it a Cat? Or is it a Pig?


On Having an Opinion: Goodness/Badness vs. Pros/Cons

There are two ways of giving recommendations on technical issues:  (a) To say that something is "good" or that something is "bad".  (b) To list Pros and Cons, or else Advantages and Limitations. The most popular, and natural way is just to say what's good, or often, what's best. In my opinion Linux servers are better than Windows servers; I'm ascribing goodness to Linux servers. But I've no...


Interop Lab Testing for VoIP Devices (2008 edition)

In an Interoperation (Interop) Lab, devices are made to work together. When they seem to, the vendors of the devices claim that they "interop with" each other. This is necessary, but not sufficient, to know things will work together. Background Suppose you make telephone soft-switch or application server, such as BroadSoft BroadWorks, Sylantro, MetaSwitch, or the Alcatel-Lucent Network Gateway ...


Why won't anybody build far-end echo cancellation into their VoIP phones and ATAs?

Nobody VoIP Phone or ATA on the market offers talker far-end echo cancellation. They should. Background Some background: echo is when you hear yourself talking. It's usually the caused by the device on the other end of the call, but it's exacerbated in VoIP networks because they have long delays. Suppose you have a phone call that includes a VoIP device (such as a PolyCom SoundPoint 65...


Call Transfer Scenarios in VoIP, SIP, IMS

UPDATED: 2014 October 1: A "Semi-consultative" call transfer cases are now included. The IETF Call Control - Transfer draft seems to have the best and latest info on call transfer scenarios. But I haven't find a good summary of the cases involving transfer-like scenarios. -- Blind transfer, original recipient is facilitator: Alice calls Bob, Bob answers, Alice and Bob talk, Bob transfers to C...