Cisco Cisco Multichannel Port Adapter White Paper
White Paper
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Dedicated Access Solutions for Internet Service Providers
INTRODUCTION
Revenue from business connections to the Internet represents, on average, almost 60 percent of the total revenue to
Internet service providers (ISPs). As business use of the Internet grows with new Web-enabled applications, voice over
IP (VoIP), and dropping tariffs on leased lines, the demand for high-bandwidth, dedicated connectivity from corporate
sites to the ISP point of presence (POP) has swelled. ISPs face significant challenges keeping up with the bandwidth
requirements, management and provisioning complexities, and POP space constraints in the face of increased customer
demand. This white paper focuses on solutions for dedicated customer connections that address these challenges,
including platform and interface selection criteria.
INTERNET SERVICE PROVIDER ACCESS
Large-scale ISP networks have been challenged by the large number of customer connections coming into a single location (POP) for some
time. Today a typical POP terminates thousands of DS-0, hundreds of DS-1, and dozens of DS-3 customer connections. This level of scale has
been possible only with the advent of channelized and multichannel router interface technologies. However, before discussing these
technologies, let’s consider the state of a typical Internet POP one or two years ago.
ISP POPs (Figure 1) contain a diverse set of equipment to provide connectivity between POPs (backbone), connectivity within the POP
(interconnect), and connections to customer sites (access). Service providers can handle many types of access, including dialup, XDSL, cable,
and dedicated or leased lines. Figure 2 shows a typical dedicated access router. Multiple leased-line and Frame Relay customers connect
through point-to-point links to a large router. In the past these individual connections were terminated through standard V.35, X21, or RS-232
interfaces on the router, requiring that every connection have a separate physical interface. Additionally, for each interface, a channel service
unit/digital service unit (CSU/DSU) or similar device was needed for each connection to convert between the serial interface to the transmission
signaling (DS-0, DS-1, DS-3, etc.) on the telecommunication carrier side.
Figure 1. POP Model