有效操作管理的数据通信网络解决方案

Tackling Challenges in Operations Management

Today's service providers face a series of mounting challenges.

They must contain costs, increase profitability, and differentiate themselves from competitors, even as they deploy new network technologies and services. One of the

keys to meeting these challenges is to streamline the operations support network (OSN), also known as data communications network (DCN).

A DCN is an out-of-band network used to connect central office equipment to a network operations center for centralized service provisioning, alarm monitoring, testing,

billing, and software upgrades and backups. DCNs transport network management traffic between network elements and their respective operational support systems, making them the vital link between the service network and the network operations center.

Many network managers think of a DCN as the central nervous system of the business—a vital component of the infrastructure that controls and manages a highly complex

body of networking equipment.

Historical Precedents

Until recently, incumbent telcos experienced even-paced growth of their networks. Franchise carriers were the norm, and competitive pressures were limited to the new generation of competitive access providers. Network management technologies evolved, without major incident, from dedicated or dialup access to X.25 packet-based access.

These operations networks endured without drastic change for long periods, and many of these DCNs still operate today. Often, separate operations networks were employed

to manage the older technologies, such as dedicated lines for discrete alarms and Lucent's Datakit or other suppliers'X.25 PADs and switches for both asynchronous and X.25 networks. But IP services were limited to the noncommercial Internet and a few commercial enterprise users.

Everything changed with the passage of the Telecommunications Act of 1996 and the subsequent wide-scale adoption of IP technologies for services. More competitive carriers appeared, giving customers more service alternatives. The Internet took off at a dizzying rate. Internet Protocol (IP)-based routers and switches grew more commonplace and fiber-optic transmission systems exploded to meet the unrelenting

demand for high-speed Internet access services and greater bandwidth. The net result was a dramatic increase in the number of network elements in central offices——an equipment ramp-up that shows no signs of slowing.

Today's service providers are deploying new equipment to accommodate users with the latest high-speed services,along with new IP-based technologies to meet exploding

Internet usage. At the same time, incumbent service providers still have to manage their embedded network infrastructures consisting of voice switches, time-division multiplexing (TDM) transmission equipment, and data transport equipment for ATM and Frame Relay technologies.

In many cases, these networks remain the primary revenue generators.

Changing Face of Operations

Operations support networks are also evolving quickly. In the past, they were built with private lines connecting pointto-point and point-to-multipoint networks. In the 1980s to mid-1990s, X.25 networks replaced private lines for cost, reliability, and manageability reasons. Today, most operations support networks are evolving toward the IP and the Open Systems Interconnect—Connectionless Services (OSI CLNS) protocols.

The use of IP and OSI CLNS in DCNs is driven by the deployment of next-generation network elements, IP packetbased technologies, and fiber-optic Sychronous Optical Network/Synchronous Digital Hierarchy (SONET/SDH) and Dense Wavelength Division Multiplexing (DWDM) systems. The OSI CLNS protocol is used with SONET/SDH and DWDM network elements, and IP is used with other newer generation network technologies, as well as IP packet-based network elements.

As network technologies evolve and service networks grow,DCNs must be able to migrate from embedded legacy technologies ased on asynchronous and X.25 protocols to new network

interfaces and protocols such as Ethernet, IP, and OSI CLNS.

DCNs are needed to provide efficient connectivity for remote provisioning of network elements, as well as for common maintenance and billing functions. Common channel signaling (CCS) applications such as local number portability (LNP) have created distributed databases (CCS Service Control Point servers), each of which must be managed

and updated.

To complicate matters further, the number of network elements generating billing data is increasing. Historically,most billing data was collected from voice switching systems.

As packet-switched data networks were introduced, X.25 usage billing data began to be collected. Now, with IP services becoming prevalent, usage data on IP flows from

routers and other IP devices must be collected as well.

Testing equipment, provisioning, and maintenance ports on voice and data switching equipment, transmission equipment,and digital cross connect switches—all are transitioning to TCP/IP connectivity.X

Rising to the Challenge

The limitation of the DCN technologies prior to multiprotocol networking was that no single network was capable of supporting asynchronous, X.25, TCP/IP, and OSI/CLNS

protocols and serial, Ether et, and Fast Ethernet switching interfaces. Multiple networking devices were required, frequently from multiple vendors. Further complications were added with the need to accommodate different WAN technologies.

Whether a service provider is delivering voice services with next-generation network elements, or IP services over packetbased networks with SONET/SDH or DWDM transport,

the DCN must be able to support Ethernet and the OSI CLNS and IP protocols. Additionally, service providers need to be able to promptly deploy new features and services, to

monitor network performance and status, and to collect billing data.

DCNs play a crucial role in fulfilling these requirements.

Service providers can leverage their existing operations knowledge and reuse traditional transport facilities for their future DCNs. When used with versatile routing, Ethernet switching technology, and DCN-specific software, dedicated

lines such as T1/E1, and data transport networking based on ATM and Frame Relay can be easily reapplied to form a robust operations support network.

Migration of these legacy network elements to IP-based DCNs is a logical strategy. Service providers can begin building new DCNs to accommodate network elements

with Ethernet interfaces, then later migrate older X.25 elements onto the network. Alternatively, some service providers will choose to implement their X.25 network elements first and plan for adding new Ethernet network elements as their networks evolve.

For example, using Cisco DCN technology, X.25 network elements can be connected over IP-based DCNs. This protocol feature is commonly used when the network element and OSS

have X.25 interfaces. As the OSS migrates to Ethernet and TCP/IP, an X.25-to-IP protocol translation feature can facilitate connectivity from an X.25 network element to its IP OSS.

Figure B: Before DCN operations handled by two dozen Cisco 2500 Series Routers

Figure C: After DCN operations are consolidated into one Cisco 3662-DC-CO Router with ISL/802.1Q VLAN Trunking

Transitioning to IP

Astute service providers realize that the continued support of legacy X.25 and asynchronous network elements using separate operation