3Com 3C888 - OfficeConnect Dual 56K LAN Modem Router, User Manual, Page: 23 / 168

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.
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.
OfficeConnect ¤
Dual 56K LAN Modem
Combining both
analog lines with Multilink
provides a single high-speed
connection
Eric’s PC
Private
network
Anne’s PC
Suhlle’s PC
Floyd’s PC
Mo re co nne cte d 3 Com
Sta tus Re set TX D D
1 2 1
2
4 3
1/2 3/4 3 4 RX
TX LK RX LA N Re mo te Ac ces s S yst em 15
00
WA N CO
Po we r BR I IS DN U
ANA LO G
SL
OT 1 SL
OT 2
ST AC KN ET CO NS OL E
SU PE R
STA CK
3 Com
Alert Power
Message
RD AA CD SD OH RD AA CD SD OH
OfficeConnect Dual 56k LAN Modem
1 TX COLL 2 3 4
LAN Status MODEM 2 MODEM 1
Public telephone
network