NEC SL1100 Issue 6.0Networking Manual 9 - 43The following chart shows the supported CODECS for IP phones with differentpacket sizes over PPP and Ethernet.13.8 Some Network ConsiderationsWhen adding the SL1100 to a customers network there are many things to beaware of. Before implementation a detailed network diagram of the existingnetwork must be obtained from the customer. This diagram may provide youwith information about possible network conditions that can prevent or hinderthe VoIP equipment from functioning correctly.FirewallsAnother regular device in customer networks that can hinder VoIPperformance is a firewall. Most corporate LANs connect to the public Internetthrough a firewall. A firewall is filtering software built into a router or a standalone server unit. It is used to protect a LAN it from unauthorized access,providing the network with a level of security. Firewalls are used for manythings, but in its simplest form, a firewall can be thought of as a one way gate.It allows outgoing packets from the local LAN to the Internet but blockspackets from the Internet routing into the local LAN, unless they are aresponse to query.CODEC Packet Size PPP EthernetG.711 10 103.2 kbps 110.4 kbpsG.711 20 83.6 kbps 87.2 kbpsG.711 30 77.1 kbps 79.5 kbpsG.711 40 73.9 kbps 75.6 kbpsG.722 10 103.2 kbps 110.4 kbpsG.722 20 83.6 kbps 87.2 kbpsG.722 30 77.1 kbps 79.5 kbpsG.722 40 73.9 kbps 75.6 kbpsG.729 10 47.2 kbps 54.4 kbpsG.729 20 27.6 kbps 31.2 kbpsG.729 30 21.1 kbps 23.5 kbpsG.729 40 17.8 kbps 19.6 kbpsG.729 50 15.9 kbps 17.3 kbpsG.729 60 14.5 kbps 15.7 kbps
