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Access Technologies Primer By Albert Ankhoa Traditionally, access technologies are defined as enabled technologies that allow communications between the end-users and the local tel. co.'s network to take place, hence they are often referred to as the local loop or edge technologies. If the communication path extends beyond the service provider's Central Office or the ISP's head-end office and connect to the Internet, this service is also known as having both the local loop and Internet Access service components. This is how service providers typically offer and charge for most Internet access services such as dial-up modem services and DSL services (the local loop access and the Internet port charges). The equipment involved in providing this type of services are known as Access equipment. For Internet dial-up modem services, the typical access equipment are V.90 56K or lower speed analog modems at the customers' end; and modem banks, multiplexers, T1 channel banks, CSU/DSU, Router and associated servers and cabling at the service provider's end (aka C.O.). For DSL always-on services, the typical access equipment at the customer's end consists of a DSL modem, a DSL router or a 10/100 Ethernet switch (used when the customer have more than one PC and they want to network them), and a Network Interface Card (NIC) mounted inside their PC. At the tel. co.'s end, the DSL access equipment comprises of a bank of voice-and-data splitters mounted on the tel. co.'s Main Distribution Frame (MDF), which provides a data connection to a DSL modem bank and DSL access multiplexer (DSLAM). The DSLAM is in turn connected to an ATM transport switch that interfaces directly to the Internet for data transmission. The other end of the second cable from the splitter connects to the service provider's Voice Switch (such as Lucent Technologies No. 5ESS, ACG's GTD-5, or Northern Telecom's DMS100) which in turn directly interfaces with the World's Public Telephone Switching Network (PSTN) to provide ubiquitous Voice communication services. For businesses, the availability of different access technologies is many folds than that of the consumer market due to different grades of service requirements. For example, the mission critical nature of business communications involved in financial transactions, payroll, proprietary product, customer and employee information often demands much more stringent Service Level Guarantees (SLG), Quality of Service (QoS), and Reliability requirements from the Service Provider. Such stringent requirements presently can not be met by the lower-cost access technologies such as DSL and Cable Modem. This is due to the simple reason - they are simply not designed and provisioned to address the same business concerns. Frame Relay, fractional T1 and dedicated point-to-point T1 and T3 are some of the popular communication access technologies designed for businesses. In recent years, the proliferation of non-licensed in-building wireless technologies such as IEEE 802.11.b (aka WiFi operated at 2.4 GHz), 802.11a (operates at 5GHz and offers up to 54Mbps) and 802.11g (operates at the same 2.4GHz frequency band as with 802.11.b, and offers the same speed as 802.11a and backward compatible with 802.11.b), have created a boom in wireless LAN at both the business and the home networks. However, due to security reasons, many businesses and research labs such as the National Livermore Labs have dismantled its own wireless LAN and banned the use of wireless LAN within its own campus. Does this mean the death of Wireless LAN? Not really, as with many questions involving overlapping access technologies, "the answer is not a matter of which product or technology is better than the other", but more of "which product or technology is better suited for which applications that we have in mind." During the course of our technology consulting, we have witnessed many popular IT decisions to replace robust access technologies such as Frame Relay and T1 services with lower-grade and lower-cost access technologies such as DSL. The fact is DSL and similar access technologies such as Cable Modem and Wireless T1 are over subscribed with as many as 96 subscribed lines to one T1 access port at the carrier Central Office or head end. The key message here is - try not to employ the same low-cost access services that are designed primarily for the residential market at the Enterprise business places. They just aren't the same. DSL, Cable Modem, and licensed and unlicensed Wireless access technologies will continue to thrive in the consumer market place and small business environments. For business-graded applications, IP over Optical access and core technologies such as Resilience Packet Ring (RPR), Rapid Ring Spanning Tree (RRST), Spatial Reuse Protocol (SRP), PON (Passive Optical Network), ATM, MPLS, and Gigabit Ethernet are being deployed at the edge and the core of Metropolitan Area Network. They will continue to be in demanded and evolved to offer better interoperability at lower deployment costs. This should translate into lower service costs to the most business customers and the residential market thanks to the lower-cost windfall of the core and the edge access equipment. ============================================================== Mr. Albert Ankhoa is the CEO and founder of Infomatek and a 23-year veteran of GTE/Verizon. He held key Network Engineering Operations for GTE Western Region and Internet Sales and Marketing positions at GTE and Verizon during a career span from 1977 to 2001. He received his MBA in Marketing from University of Phoenix, Southern California Campus in 1995 and BSEE from California State Polytechnic Pomona in 1979. ============================================================== To comment or request more information about this article, please write to:
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