March 1999

IADs On the Network's Cutting Edge

BY RON KEENAN

Competitive Local Exchange Carriers (CLECs) are looking for network edge equipment that integrates multiple functions and services in a single unit. The idea is to simplify installation and significantly reduce operating costs. Ultimately, carriers want to integrate access to all network switching and transport services into a single network edge device. How business network users reach the new carrier networks is the task of a new type of "network edge" product known as an Integrated Access Device (IAD).

IADs, as defined by Dataquest Corp., are "point-to-point Customer Premises Equipment (CPE) and Central Office (CO) devices that terminate customers' data, voice, and video traffic and trunk it upstream to backbone switches via T1 lines." They also allow carriers to offer bundled services that customers can utilize via a single network access device. These devices incorporate various Digital Subscriber Loop (DSL) modems and Channel Service Unit/Data Service Units (CSU/DSUs). IADs provide a single unified services platform operating under an integrated management system, rather than multiple single-application devices with separate management requirements.

However, IADs are located on the customer premises (i.e., at the edge of the carrier network) and are provisioned and managed by network service providers. These IADs consolidate voice from PBXs or key telephone systems, and data traffic from multiprotocol routers and IP gateways. IADs support the following network service types: frame relay over DDS, T1/Fractional-T, ISDN, ATM over T1 or DSL, voice over channelized T1 (DS-0s), and Voice-over-IP (VoIP) gateways.

TYPES OF IADs
These CPE network-edge IADs fall into three basic product categories: Sophisticated CSU/DSUs, First Generation Unified Services Platforms, and Second Generation Unified Services Platforms.

Sophisticated CSU/DSUs
A sophisticated CSU/DSU is a carrier network edge device that terminates the end user's data, voice, and video traffic and trunks it upstream to the carrier switch/access concentrator via T1 or DSL links. This type of IAD provides consolidation of all user traffic types for transport over a common uplink to the carrier's network access equipment. It can be viewed as a black box with a common uplink toward the carrier network and multiple types of user interfaces (e.g., analog POTS ports and Ethernet LAN ports) broken out for the CPE side. As such, the device provides separate network terminations for existing data, voice, and video CPE equipment.

The "sophisticated CSU/DSU" type of IAD incorporates the functions of a traditional CSU/DSU and channel bank and, typically, an IP gateway, frame relay assembler/disassembler (FRAD) and IP firewall. As the deployment of ATM services to the premise becomes more popular, ATM Segmentation and Reassembly (SAR) units and inverse multiplexing will be incorporated into this type of IAD. This category of IAD must also include simple network management protocol (SNMP) in order for it to be managed remotely by the carrier. In addition, providing remote access for system configuration and maintenance via an embedded Web server is very desirable.

First Generation Unified Services Platforms
First generation unified services platforms are IADs that incorporate the network access functions of the "sophisticated CSU/DSUs" described above, but also include additional local user interfaces and feature functionality. The "sophisticated CSU/DSU" type of IAD typically has a single Ethernet port providing access to its internal IP gateway/access router for the existing Ethernet LAN on the customer's premises. By contrast, the first generation unified services platform typically provides an internal Ethernet LAN hub (multiport shared Ethernet segment device) enabling multiple Ethernet enabled devices to be connected directly to the IAD. In this case, the IAD takes the place of, or can be used in conjunction with, the Ethernet LAN equipment on the customer premises.

The first generation unified services platform also provides some PBX-like call processing features and/or CENTREX feature emulation. These features have been designed to be accessed from the traditional industry standard analog telephone (2500 set) because a majority of these products provide separate voice and data wiring infrastructures and only analog tip and ring interfaces for voice terminals. However, there are a limited number of products in this category that provide "LAN telephones," which use either standards-based or proprietary methods to transport voice over the data wiring infrastructure to the desktop.

The most predominant functions/features promoted by the manufacturers of this type of IAD are some form of unified management software and PC-to-telephone logical (not physical) software association and coordination.

Second Generation Unified Services Platforms
Second generation unified services platforms are IADs that incorporate the network access functions of the "sophisticated CSU/DSUs" and also truly integrate all network switching and transport services over a single high-bandwidth link to the desktop. The first generation unified services platform typically provides an internal Ethernet LAN hub enabling multiple Ethernet devices to be connected directly to the IAD. However, the second generation unified services platform provides an integral 10/100 Mbps Ethernet LAN switch with VLAN support for servicing multitenant installations. The second generation device also includes an IP router capable of servicing multiple IP subnets.

Advanced data networking functions, including traffic shaping and bandwidth management, are supported by this type of IAD. In addition to providing data, voice, and video transport services from the edge of the carrier network to the desktop over a single high-bandwidth link, the second generation unified services platform provides a guaranteed Quality of Service (QoS) for the transport of delay sensitive information. The "LAN telephones" used on first generation unified services platforms require that a QoS mechanism be implemented by the legacy data networking equipment, and/or by the deployment of additional networking equipment.

The second generation unified services platform also provides PBX-like call processing features and CENTREX feature emulation that can be accessed from the traditional industry standard analog telephone (2500 set). However, the highly integrated call processing software of the second generation unified services platform also provides full feature support for multiline digital key telephones and an API for interfacing sophisticated CTI applications.

Ron Keenan is chief technology officer of Merlot Communications. Merlot Communications is a Local Area Network (LAN) product company with a breakthrough technology that allows cost-effective, real-time multimedia (voice/video/data) over Ethernet with guaranteed quality of service. Merlot is embodying its "Deterministic Ethernet" switching technology in an Application Specific Integrated Circuit (ASIC) and building a unified services platform that brings converged, cost-efficient, high-speed multimedia communications solutions to small to mid-sized businesses.