Nortel BCM50 2.0 Installation Manual

Also see for BCM50 2.0: User guide System overview guide User guide Configuration guide User guide

Contents

Nortel BCM50 2.0 Installation Manual Manual pdf 46 page image

46 Chapter 6 IP telephone overviewNN40020-309NN40020-309IP networkIn the network shown in Figure 10, several LANs and a WAN are shown. When planning yournetwork, be sure to consider all requirements for a data network. Your network administratorshould be able to advise you about the network setup and how the BCM50 2.0 fits into thenetwork.WANA Wide Area Network (WAN) is a communications network that covers a wide geographic area,such as state or country. For BCM50 2.0, a WAN is any IP network connected to a WAN card onthe BCM50 2.0 system. This may also be a direct connection to another BCM50 2.0 system.If you want to deploy IP telephones that will be connected to a LAN outside of the LAN that theBCM50 2.0 is installed on, you must ensure the BCM50 2.0 is able to communicate across theWAN interface at that location.LANA Local Area Network (LAN) is a communications network that serves users within a confinedgeographical area. For BCM50 2.0, a LAN is any IP network connected to the integrated interface(a LAN card) on the BCM50 2.0 system. Often, the LAN can include a router that forms aconnection to the Internet. A BCM50 2.0 can have up to two LAN connections.Public Switched Telephone NetworkThe Public Switched Telephone Network (PSTN) can play an important role in IP telephonycommunications. In many installations, the PSTN forms a fallback route. If a call across a VoIPtrunk does not have adequate voice quality, the call can be routed across PSTN lines instead, eitheron public lines or on a dedicated ISDN connection between the two systems (private network).The BCM50 2.0 also serves as a gateway to the PSTN for all voice traffic on the system.Key IP telephony conceptsIn traditional telephony, the voice path between two telephones is circuit switched. This meansthat the analog or digital connection between the two telephones is dedicated to the call. The voicequality is usually excellent, since there is no other signal to interfere.In IP telephony, each IP telephone encodes the speech at the handset microphone into small datapackets called frames. The system sends the frames across the IP network to the other telephone,where the frames are decoded and played at the handset receiver. If some of the frames get lostwhile in transit, or are delayed too long, the receiving telephone experiences poor voice quality.On a properly-configured network, voice quality should be consistent for all IP calls.