Test Tools, Protocol Analyzers, Call Monitors

In order to validate protocol implementations, various test tools are used today by the VoIP developers' community. As implementations mature, those tools are also used by service providers or technical marketing organizations during product interoperability testing or to verify protocol implementation compliance statements.

Protocol Capture Tool

A number of tools exist to perform real-time network packet capture. Some of the key features include real-time capture at wire speed, viewing and browsing the capture data in details, filtering of captured packets based on specific protocol or target network addresses, exporting of capture traces in various formats to be able to share the finding, printing capture in hex, text formats with frame number, etc.

Wireshark
Wireshark (formerly known as Ethereal) is a free network protocol analyzer for Unix and Windows. Wireshark is Open Source. It allows you to examine data from a live network or from a capture file on disk. You can interactively browse the capture data, viewing summary and detail information for each packet.
Support for numerous operating systems: WinNT, Win2000, Linux, Solaris, HP-UX, etc.
http://www.wireshark.org
Hints: make sure to disable Name Resolution when performing captures

Others
Network Associates' Sniffer™ products (since 1988), Acterna (WWG DominoNAS, Fireberd DNA), Spirent Communications (Netcom Systems), WildPackets' EtherPeek, NetXray™, snoop, Shomiti Surveyor, AIX's iptrace, Microsoft's Network Monitor, Novell's LANalyzer, RADCOM's WAN/LAN Analyzer, HP-UX nettl, etc.

Protocol Decoders for VoIP Packets

Some capture tools also offer protocol decoders which allows you to see the message details in a verbose format. The key is to find tools with decoders for protocols like H.323, SIP, MGCP, RTP, RTCP, etc.

Wireshark
As of version 0.8.16, the Wireshark distribution provides decoders for H.323 (H.225 RAS, H.225.0, H.245), SIP/SDP, MGCP, RTP, RTCP, etc. For the Wireshark binary with H.323 support, visit http://www.voice2sniff.org
Example of decodes: H.323 (H.225.0 & H.245 decodes included), SIP, MGCP, RTP/RTCP

LinkBit On-Line Protocol analyzer/decoder
This is an on-line protocol analyzer and decoder for a wide range of protocols, including H.323, SIP, ISDN, V5.2, MGCP, and H.248. Just copy and paste a hex dump and get something readable!

Others
Acterna software is known to have support for some VoIP protocols.
Artiza Networks, Inc. - VoIP Analyzer for H.323, MEGACO (H.248), MGCP, and SIP

VoIP Call Monitoring and Analysis Tools

Products in this category monitor VoIP calls in order to gather information related to quality of service (QoS) for the purposes of aiding engineers or service providers in product improvement and network planning.

• Empirix - Hammer Call Analyzer (H.323, H.248, MGCP, SIP, T.38, RTP, much more)
• Touchstone Technologies - WinEyeQ

Simulation Tools

Simulation tools are used to run a representation of the code in a controlled environment. The advantages of simulation are that tests are cheap and quick to assemble, controlled and reproducible. The cons are that simulation tests may differ from real implementations.

• Artiza Networks, Inc. - VoIP Simulator for H.323, MEGACO (H.248), MGCP, and SIP
• Catapult Communications Corporation - simulation products with support of multiple VoIP protocols.
• Touchstone Technologies Win323 and WinSIP - H.323 and SIP call generators for voice and video over IP
• iThinkTest, Inc. - FlowCoder MG/MGC Emulation Toolsets, simulate VoIP Call Flows (MGCP, SIP(-T), MEGACO)
• RADVISION - ProLab(tm) Test Management Suite