SWG Networking & Engineering
ISDN
A
new site will be brought into the network. This site is small and will only
require connectivity from time to time. The decision has been made to connect it
into the WAN core network using ISDN technology. Also, you may want to consider
a DDR connection to each of the 33 sites in the district, for backup and traffic
load purposes.
Implementation
& Benefits
For ISDN to be inserted into the WAN implementation, either at the one remote site or at all of the sites, three things must be done: ISDN capabilities (router, router configuration, ISDN TA and NT devices) must be in place at the school site; ISDN connectivity must be provided by the telephone company or other provider; and the District WAN core must have ISDN capability (WICs, blades) in its access servers, switches, and routers (though not necessarily directly into the core routers). Data will be sent on a "call" basis. Benefits for a small site include reliability, relatively low cost if it is used intermittently, and fairly universal service compared to other WAN technologies.
Communication
& Bandwidth
Data communications will take place on a "call" basis. Dial-on-Demand Routing will be used; when WAN connectivity is required, the DDR configured router and ISDN devices will place an ISDN "call" and be connected, via the telephone companies' ISDN equipment, to the school district WAN. Costs will include installation, monthly access, and a duration-of-call charge. Bandwidth, for an ISDN BRI line, will be 128 kbps of data over two B channels, and 16 kbps of signaling data over 1 D channel, with much flexibility in how these channels are used.
Equipment
This equipment will depend upon your design. For example, if you use a Cisco 2621 router, you can order WIC modules that have the ISDN NT1 device built in, and you can connect the router directly to the ISDN line. On the District WAN end, the same situation occurs – it depends on your design. Note that on the District end that if you use DDR to all 33 sites then you will have to handle, via various means, all of that incoming ISDN traffic with a combination of access servers and appropriate routers and/or router modules.