Author’s Note: Since this article was originally published, WinPcap project has ceased development and WinPcap and WinDump are no longer maintained. They recommend using Npcap instead. See https://www.winpcap.org/install/. Config modifications recommended in this article are specific to WinPcap Version 4.1.2.
Voice Elements Platform SIP Stack (HMP Elements) in default mode can be constrained by Winsock. On modern servers, we have found that for all intents and purposes, HMP Elements gets limited to about 500 concurrent ports when using Winsock.
In order to accommodate higher density VoIP deployments, Voice Elements Platform can run in a special PCAP mode that allows it to achieve higher port densities of up to 750 and potentially 1000 concurrent ports.
When to Use WinPcapMode
If you are running 500 ports or less, you will want to continue using Winsock mode. By default HMP Elements uses Winsock. If you would like to run more than 500 ports on the same system, you should use WinPcap mode.
How to Use WinPcap Mode
- Make sure you have the latest version of HMP Elements installed
- Download and install WinPcap 4.1.2
- Modify your HmpElementsServer.exe.config configuration file to use one of the winpcap modes below.
- Restart HMP Elements
Modify your Configuration File for WinPcap
HMP Elements has 4 different settings for it’s packet capture mode.
<setting name="PacketCaptureMode" serializeAs="String"> <value>Legacy</value> </setting> <setting name="PacketCaptureMode" serializeAs="String"> <value>WinSock</value> </setting> <setting name="PacketCaptureMode" serializeAs="String"> <value>WinPcap</value> </setting> <setting name="PacketCaptureMode" serializeAs="String"> <value>WinPcapReceiveOnly</value> </setting>
Legacy and Winsock Mode
Both Legacy and Winsock Mode will both use Winsock for it’s underlying connections. This mode should be used when you would like to use 500 ports or less.
This mode will use WinPcap for both send and receive. Some network cards may have difficulty keeping up with WinPcap for both send and receive operations, so a separate mode allows WinPcap to be used for Receive only.
This mode uses WinPcap to receive packets only. This mode is useful for when network cards can’t handle all the traffic generated by using WinPcap mode for both send and receive operations.