To allow you and your customer to lock down site firewalls, here we document the active ports and their services used by Connect it.  For firewall configurations that allow any outbound traffic, and its returning inbound traffic, you should not need to specify any particular rules in order to use Connect it's platform.

However, please take note of the Application Layer Gateway and UDP Flooding sections below, if you experience any of the following:

• Unable to REGISTER
• Unable to Transfer calls
• Unable to Conference calls
• Unable to perform a Call Pickup
• No, or one-way, audio (in either direction) on PSTN or local calls (ie within your LAN)
• Audio stopping after a given period of time (eg 5 minutes) but the call stays 'up'

Application Layer Gateway

Application Layer Gateway's (ALG's), or sometimes called 'SIP Helpers', are software services which are installed and enabled by default on most SOHO grade Routers.  It is designed to aid VoIP to traverse NAT Gateways (ie a Router performing Public IP to Private IP translation) to allow IP Phones sitting behind the gateway to receive calls without opening specific firewall holes.

However, we are able to perform this service (and in a more efficient manner) with our carrier-class Session Border Controller (SBC), which supports all types of NAT Traversal.  Even when one user calls another user behind the same NAT gateway, our SBC will instruct the two endpoints to send RTP to each other over the local LAN, thus avoiding "tromboning" the media up the WAN link to us, and then back down the WAN link.

It is therefore vital to disable any ALG services running on your Router, as they conflict with our SBC (which cannot be bypassed) as they both try to do the same job.

Disabling an ALG

Please see the article Defeating ALG's for information on how to identify and disable ALG's.  It also includes some techniques which can sometimes work around a persistent ALG.

UDP Flooding

RTP audio streams send 40 UDP packets per second, in each direction.  On some Routers, this traffic can be interpreted as a UDP Flood whereby the Firewall application on the Router believes it is under attack, and automatically blocks the traffic from entering the network.  Typically, this occurs after a period of time (eg 5 minutes in the conversation) rather than from the start.  So if your audio appears to stop, particularly inbound to your network, after a predicable period of time, it is most likely due to the Firewall's UDP Flood controls.

Disabling UDP Flood controls

To resolve this issue, consult your device's technical manual and look for "UDP flood". We recommend one of the following actions:

• Adjust the Flood Control to be greater than (number of simultaneous calls * 41), or
• Disable UDP Flood controls