Know your network's backbone technology before deciding which access router to buy

Know your network's backbone technology before deciding which access router to buy

By J.B. Miles

Special to GCN

Your choice of access router depends largely on the technology behind the WAN used by your organization. Here are a few key elements of WAN technology to keep in mind, courtesy of Intel Corp. and Engage Communication Inc.:

Dedicated digital service. Dedicated digital lines usually are leased from phone companies and typically run at speeds of up to 64 Kbps. They are highly configurable'to as low as 2.4 Kbps'and much more reliable than standard analog phone services.

Switched 56 Kbps. Switched service is similar to 56-Kbps DDS but is designed for on-demand services in which users are allowed to select when and with whom to connect.

Dial-up analog telephone service. A standard telephone connection provides speeds of up to 56 Kbps per line and generally is cost-effective when communications between sites is limited to four hours per day. Basic telephone lines can be multiplexed together via routers or dual modems for faster speeds.

Integrated Services Digital Network. Basic'rate interface ISDN provides a full-duplex 128-Kbps data path over two B channels and a 16-Kbps signaling channel. Like analog phone service, ISDN BRI is a dial-up service and is cost-effective for small numbers of users seeking high-speed access to the Internet.

T1, E1 and fractional T1. T1 is an all-digital service offering throughput rates of 1.536 Mbps, with 8 bits left over for framing. E1 is the European equivalent of T1 and transmits at 2.048 Mbps. T1 signals are typically transmitted in groups of 64-Kbps bands. Fractional T1 uses some, but not all, of T1's available bandwidth.

Frame relay. Frame relay is a popular WAN topology for fractional T1 lines. It is based on the sharing of WAN backbones between multiple users but provides virtual connections between locations. X.25 is similar to the mesh network technology used by frame relay but is older and slower.

Internet virtual private network. Internet VPNs allow users to take advantage of the Internet for enormous cost savings, especially when long distances are involved. According to a Cisco Systems Inc. white paper, VPNs offer security, traffic prioritization, management and reliability as good as that of private networks, while reducing recurring WAN costs by 30 percent to 80 percent.

Point-to-Point Protocol. PPP is a set of encapsulation definitions for transporting different network-layer protocols, including but not limited to IP. It works over any asynchronous or synchronous dedicated or dial-up circuit.


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