Authors Mark Lindsey SMTS at ECG

The War over DNS and VoIP

Many people don't like using DNS to route VoIP traffic. I suspect other distributed applications have similar questions. They've had too many problems with DNS being reliable, or too slow for real-time call processing. In addition, many VoIP carriers use private IP addresses for their servers! This breaks Internet Engineering principles, and severely complicates name-to-address lookup services....


Black-Box Testing Fring for SIP and SkypeOut

"Fring" is a Instant Messaging and VoIP client for the iPod and iPhone Touch. It's a free download, and I decided to try it. Fring Setup When you start Fring, you have to register for a Fring User ID -- before you even enter your IM, SIP, or Skype contact info. That suggested to me that it was doing this stuff through a central server. I setup my MSN, AOL, and Yahoo IM contacts and se...


Selling more than you have for sale

Occasionally I get to observe a client who has made a mistake; sometimes they come to us to help clean things up. One such mistake is selling something that you don't have to sell. There are two forms of this mistake: the "Maximum Scale Error", and the "Unknown Cost Error". Maximum Scale Error. Suppose you have a service, like Shared Call Appearance (SCA), also called Shared Line Appearance...


Care and Feeding of Pet Ideas

Thorbjoern Mann's book, "Time Management for Architects and Designers" has a lot of good advice that applies to people doing network, system, or software design! No, I don't design physical structures or objects, but it's still design. There's always more than one way to satisfy a goal. And making Design Decisions that harmonize to create a good system or network overall is important. http://rc...


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?