3Com 3C888 User Guide - Page 23

Using the Modem Channels 23 If one or more Service Providers are configured as a Multilink-enabled connection, one high-speed call at a time is possible whenever one of these calls is in session, as shown in Figure 9. Eric's PC Anne's PC Suhlle's PC OfficeConnect¤ Dual 56K LAN Modem Message MODEM 1 MODEM 2 AA CD RD SD OH AA CD RD SD OH Alert Power LAN Status TX COLL 1 2 3 4 OfficeConnect Dual 56k LAN Modem Public telephone network Combining both analog lines with Multilink provides a single high-speed connection More connected 3 Com ANALOG 4 3 1 2 SLOT 1 D 12 BRI ISDN 3/4 UD 34 1/2SLOT 2 3Com SUPERRWemANote Access LTKX SyLsAteNm CROX 1500 SCTOANCSKONLEET SPtoawtRueesrsRSTeXTXtACK Private network Floyd's PC Figure 9 One High-Speed Connection to a Single Location Sharing an Already Established Connection In either of the above scenarios, once the dial-out connection is established, up to 25 users can share the already-open connection. The LAN Modem is designed to make use of already-established call connections in order to provide optimal line availability for all users sharing WAN access. Whenever the LAN Modem receives an information packet requesting WAN access, it looks for an already-established connection to the specified destination (such as an ISP for an Internet connection). If an open connection is available, the LAN Modem uses this for any authorized user. The LAN Modem uses the IP address translation system, Network Address Translation (NAT), to allow multiple users to transmit their individual information packets along this same open channel. If you choose, you can restrict line sharing so that only authorized users have access to an open connection to a specified destination. Note that speed may be affected when multiple users share a connection and attempt to download data simultaneously. For a further explanation of NAT and IP address translation in the LAN Modem, see "IP Address Translation Using NAT," at the end of this section, or refer to the Networking Primer in Appendix A. Callback Capability When you configure a Service Provider profile to a remote destination, you can choose to enable Callback in the LAN Modem. With Callback enabled, your outgoing call is immediately dropped by the receiving device and then returned, provided the call-receiving device is also set up with this feature. Callback can provide potential cost savings for the dial-out party, as well as security for the call-receiving device and its attached network.