3Com OfficeConnect 3C892A User Manual

Also see for OfficeConnect 3C892A: Getting started guide

Contents

3Com OfficeConnect 3C892A User Manual Manual pdf 29 page image

Understanding Dynamic Bandwidth Allocation 23and agrees to use BAP, then the Bandwidth Allocation Protocol (BAP) negotiatesthe addition and removal of the second B channel with the peer equipment basedon a user-defined threshold. A key advantage of BACP/BAP is that it provides ahigher probability of establishing a Multilink PPP call during high traffic conditionsby providing a specific telephone number for the second B channel to call.Multilink PPP Configuration OptionsWhen configuring Multilink PPP, you can choose one of the following optionsfrom the ISDN LAN Modem’s Service Provider Parameters window.n Use One B ChannelWhen this option is configured, only one B channel is used to connect to thisservice provider. Multilink PPP is thereby disabled and BACP/BAP is thereforenot used.n Use Two B ChannelsWhen this option is configured, both B channels are always used to connect tothis service provider, regardless of the amount of traffic over eachB channel. Note that when this option is selected, the DBA feature does notwork because both B channels are being used. To use both DBA and MultilinkPPP, select the option Add Second B Channel as Required.n Add Second B Channel As RequiredWhen this option is configured (referred to as bandwidth on demand) only oneB channel is used to connect to this service provider, and the secondB channel is automatically added only when the amount of traffic on the firstB channel reaches a threshold you define.In order for you to use Multilink PPP, the destination you are calling must alsosupport Multilink PPP. For example, if you are trying to dial in to the Internet, yourISP must also support Multilink PPP in order to successfully place a Multilink PPPcall. If you attempt to place a Multilink PPP call and the location you are callingdoes not support Multilink PPP, then a single B channel PPP connection isestablished.UnderstandingDynamic BandwidthAllocationDynamic Bandwidth Allocation is used in conjunction with Multilink PPP ondemand (to use DBA, you should choose Add Second B Channel As Requiredwhen you configure Bandwidth Allocation). The Dynamic Bandwidth Allocationfeature allows you to automatically and temporarily remove one of the B channelsand use it either to place or receive a call (voice or data) without disturbing theoriginal call. The only effect on the original call is that it is reduced from a MultilinkPPP call to the speed of one B channel.Once the interrupting call ends, that B channel is automatically returned to theMultilink PPP call. Although throughput is reduced while the interrupting call isactive, the reliability of the Multilink PPP call is maintained.Understanding VPNsand PPTPVirtual private networks (VPN) are private, secure networks created in publicnetworks such as the Internet. A VPN is essentially a secure, private tunnel withinthe Internet. Since VPN calls are placed through a local ISP, they eliminate longdistance charges that would occur from directly dialing to a remote privatenetwork.