Links between the schools and their district office will be T1. This is a decicated line with a data rate of 1.544 Mbps.
Links between the district offices will be 4 T1 lines each running at 1.544 Mbps.
The three district offices are linked together, this provides redundancy in the event of one of the links stops working.
The Washington School District Wide Area Network, as shown above, uses a Two-Layer design model.
The Serial Port at the router at the school would be connected to an NTU (Network Terminating Unit) supplied by the Telephone company (e.g. Telstra). The cable used would be a X21 cable, 60 pin Cisco connector at one end and 25 pin X21 connector at the other end.