A1 VoIP RequirementsGetting Started 51Is the card located appropriately?Transmission delays can cause pauses and loss in VoIP communications. The more network devices(e.g., routers and switches) there are between the communicating cards, the larger the transmissiondelays, because a certain amount of delay is inevitable when packets go through each network device(hop).One preventative measure is to install the card so that the number of transmission hops is kept to aminimum. In the diagram below, the card is located as close to the IP network interface as possible.A1.3 Network DevicesYou must evaluate the network devices that are used in the existing network to see if a VoIP networkcan be implemented. Below are the points that should be taken into your evaluation.Can the firewall pass packets from the VoIP Gateway Card?If the VoIP network contains a firewall, the firewall must be configured appropriately to allow VoIPpackets, which are listed in the table below, to pass through the network without being blocked byfiltering.For more information, consult your network administrator.Protocol TCP/UDP Default Port No.HTTP *1 TCP 80RTP/RTCP *2 UDP 5004 to 5035H.225.0 Call Signalling *2 TCP 1720H.245*2 TCP 1712 to 1724H.225.0 RAS*2 UDP 1719QSIG Connectionless Tunnelling *1 TCP 1718*1 For the actual setting values, refer to "2.2.1 Network Parameters" in the VoIP Gateway CardProgramming Guide.RouterSwitchToo many hopsSwitchHubRouterSwitchBetter(PBX located nearest IP network access point)SwitchHub
