3Com NETBuilder SI, SuperStack II manual Telco Services

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-uplines, 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-switchedservices, 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

		Serial Device (Required
Telco Line	Protocol	on Flex-WAN Serial Ports)	Data Transfer Rate
Dial-Up Lines:
Plain Old Telephone	PPP	Modem	Up to 56 Kbps
Service (POTS)
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