ECG Blog 200 OK

SIP and Fragments: Together Forever?

IP Fragmentation of SIP Messages is an enduring source of trouble. Fragmentation of SIP traffic is a problem on the rise. It appears when everything has been working fine, and seemingly without cause,  some SIP messages are lost in the network. The result is a frustrating scenario where some SIP messages are delivered fine, but others are not. To explain SIP fragmentation, let's start at the be...


Interop I: SIP Number Formatting: Local, National, E.164, Oh My!

  When we teach classes on VoIP networks, we discuss the variety of SIP standards that can be used by working systems. For example, identifying the calling party varies between platforms: One system uses P-Asserted-Identity to indicate the caller, and another uses From. Then there's the codec used for audio: One system uses G.722 and another uses G.722.2. One system expects national telephone n...


Using SIP to Block Robocalling: On the Telephone, Nobody Knows You're a Robot

Robocalling, enabled by VoIP, causes real social harm Filtering based on Caller ID brings some temporary relief The telecom industry has real work ahead to protect Caller ID with STIR VoIP Drove down the cost of making phone calls. We love that about VoIP: free long distance! In the telecom industry now, the idea that calls within a country would cost a retail user more than local calls seems...


Mentoring IT Professionals: Start by Answering Questions.

Committing time to answer questions is the crucial first step This is Part 3 in my Series on Supporting/Managing Engineers Configuring bridging, building bridges Unlike software, systems, network, and voice engineering, regulated engineering disciplines require licensing. According to the National Society of Professional Engineers, a college engineering graduate candidate can "begi...


Work Flows Up: Effectively Distributing Work on a Team of Engineers

Sometimes junior technical staff are starved for interesting work while senior staff are overworked This is Part 2 in my Series on Supporting/Managing Engineers If a team has lots of technical work to do, and only a few brilliant engineers available, how do you get work to the right people? In this article, I discuss methods for managing work in IT and technology teams, such as those doing Netw...


Mentoring Junior Engineers is Worthwhile

Most experienced professionals value the opportunity to mentor others; not so for some elite technologists To enable more people in a technical team to do work, more people have to know how to do it. But for many engineers, training doesn't come natural. This is Part 1 in my Series on Managing Engineers Is one-on-one training a rational activity, or just a feel-good strategy from the HR departm...


BroadWorks CDR Decoder

If you use BroadWorks with CSV CDRs, you're probably accustomed to reading these: 00255943365CF3FC1CF15820160404194616.3061-040000,ECG,Normal,+12296543428,+19125293400,Originating,+12296543428,Public,+12296543409,20160404194616.306,1-040000,Yes,20160404194624.106,20160404194650.684,016,VoIP,,3409,private,,,,local,Group,,PCMU/8000,216.128.52.5,fd390cb4-eb6d3d15-f8fb7fd2@10.23.6.217,,,,Herme...


Polycom and Adtran AOS Geo-Redundancy Support

Background The Polycom SoundPoint IP SIP Phones and Adtran IADs are used for Hosted IP PBX Access Devices, managed by the BroadWorks platform. In a non-geographically-redundancy network, the devices use SIP to register to a single SIP SBC IP address. To support geographic redundancy of SBCs, the devices must support registration to multiple IP addresses. It must select the proper IP address in...


See only a Sampling of RTP frames in a Wireshark Packet Capture

Question: How do you make a display filter that filters out most RTP frames, but leaves a representative sample? Sometimes it's convenient to see a sampling of RTP frames in Wireshark, without having to see 50 per second. Answer: Rather then see 50 frames per second for every RTP flow, how about one frame every 5 seconds? Wireshark display filter: rtp[3:1]==0 or rtp.marker==1 Shows an RTP pa...


RTP Troubleshooting Tip: See a Sample of RTP frames in a Packet Capture

Question: How do you make a display filter that filters out most RTP frames, but leaves a representative sample? Sometimes it's convenient to see a sampling of RTP frames in Wireshark, without having to see 50 per second. Answer: Rather then see 50 frames per second for every RTP flow, how about one frame every 5 seconds? Wireshark display filter: rtp[3:1]==0 or rtp.marker==1...


SIP Trunking: Public, Private, VPN, and Why

When you're connecting to the rest of the world to make and receive phone calls, you have several design options available. Or, more precisely, your Voice Service Providers have many options available. VoIP via Layer-3 VPN In this case, a Layer-3 VPN, such as MPLS over the Voice Provider’s own equipment, is used to connect a Voice customer to the Voice service provider. Shared infrastructure i...


BroadSoft BroadWorks Database Server (DBS) - Cheat Sheet

The BroadSoft BroadWorks DBS is a different animal than other BroadWorks servers, and it requires a special set of commands to keep it alive and well. The level of care and feeding required for the database reminds of BroadWorks App Server release R12 and R13; those were not happy days. Check status of the FRA Disk Group dbsctl diskinfo /etc/init.d/oracleasm listdisks On a healthy, normal sys...


Net Neutrality: Nobody Wants an ISP To Mangle Their Data

"Network Neutrality" advocates teach us that banning certain Active Queue Management (AQM) algorithms will result in greater freedom on the Internet. For example: Barack Obama wants to ban "Paid Prioritization," which Cisco calls "Low Latency Queueing". Even folks interested in computers, but who don't build or run networks, seem to have some downright strange opinions. For example, when Net...


Cisco Crowdsources Critical Announcements: SSL Certificate Changes on SPA-500 phones

The Cisco Small Business SPA-500 series phones (such as the SPA-502G, SPA-508G) include a Cisco-signed SSL certificate. Until very recently, all of the Cisco SPA-500-series phones shipped were signed by a Sipura certificate. Sipura was the Korean company that was bought by Linksys before Linksys was bought by Cisco. Sometime after August 2013, Cisco Small Business started shipping phones sig...


152 Test Criteria for SIP Phones, ATAs, and other Telephony Endpoints

When it comes to telephones, everybody has certain expectations. Nobody wants a phone that fails occasionally. And most service providers have a model of phone that they trust; nobody wants to try out a new SIP phone and learn that it fails in an obscure, but important feature. For example: Have you seen the new Yealinks? Or what about the improved Grandstreams?   How do you ensure the phone is...