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Telco Services 25
Serial Ports The serial ports are multifunction Flex-WAN ports that provide connection
to industry-standard V.35, RS-232, RS-449, RS-530, or X.21 Data
Communications Equipment (DCE) or Data Terminal Equipment (DTE)
serial devices. You can buy Flex-WAN cables separately from 3Com. See
Appendix D for more information about Flex-WAN cables.
If you are using two SuperStack II NETBuilder SI bridge/routers connected
directly to each other by the serial ports (back-to-back), the
bridge/routers do not meet radiated emissions specifications.
For boundary routers, only one serial or WAN port can be active. The
remaining ports are used for back-up only.
Telco Services To create a WAN, you must buy lines and services from a
telecommunications company (Telco). Services include dial-up lines,
leased lines, and packet-switched services.
Dial-up lines, like ISDN, allow you to dial your destination when necessary
and hang up when you no longer need the connection. A leased line is
always available between two locations. Dial-up and leased lines both use
the Point-to-Point Protocol (PPP).
Packet-switched services, like Frame Relay, use a combination of leased or
dial-up lines with Telco-owned switching, which frees you from the cost
of owning the line the entire length.
Table 4 describes dial-up and leased line services available for the WAN
and serial ports. Table 5 describes packet-switched services.
Table 4 Dial-Up and Leased Line Services
Telco Line Protocol
Serial Device (Required
on Flex-WAN Serial Ports)
Data Transfer Rate
Dial-Up Lines:
Plain Old Telephone
Service (POTS)
PPP Modem Up to 56 Kbps
ISDN BRI PPP TA 2 channels up to 64 Kbps each
*
Switched 56 PPP CSU/DSU 56 Kbps
Leased Lines:
E1 PPP CSU/DSU 2.048 Mbps
T1 PPP CSU/DSU 1.544 Mbps