NAMS Applications - Frame Relay

Frame Relay is an interface protocol for connecting diverse end user equipment over Wide Area Networks (WANs) which are offered by public data network service providers. The Frame Relay protocol allows data to efficiently travel from one user node to another across the WAN without the overhead imposed by older error handling schemes. Frame Relay is specifically designed to efficiently utilize the reliable facilities such as fiber which are now common in provider networks. This page first overviews the Frame Relay technology and then describes how Digilog’s Network Access and Monitoring System (NAMS) is used to provide centralized fault management capabilities in a Frame Relay environment.

Figure 1 illustrates a typical Frame Relay network, highlighting two end user nodes in Philadelphia and Pittsburgh.

Figure 1

Inside the Frame Relay network, the nodes are interconnected with high speed circuits. The physical connections between the Frame Relay network nodes and the subscribers can be through a variety of technologies: RS232, V.35, and T1 in the United States; X.21, V.35, or E1 in Europe. The protocol used between the subscriber and the network is the Frame Relay standard.

Frame Relay can transport a wide variety of protocols over the WAN. In fact, the most common use of Frame Relay today is to interconnect LANs across the WAN. Carrying LAN data inside WAN frames is known as encapsulation. While many encapsulation techniques have been developed, in general, they are all very similar. A packet of data called a Protocol Data Unit (PDU) is taken from the LAN. It is prefixed by a header that defines the encapsulated LAN protocol, and then converted into one or more Frame Relay packets. Frame Relay transports X.25, SNA, and LAN traffic with equal ease.

Managing Frame Relay network quality requires tools that insure physical level integrity and support the ability to analyze encapsulated protocol problems when they occur. The Digilog Network Access and Monitoring System (NAMS) can be combined with the Hewlett-Packard J2300 WAN protocol analyzer to bring cost effective trouble shooting capability to complex Frame Relay networks. The NAMS solution provides centralized remote control of the selection, access, and test, as well as real time monitoring of Frame Relay subscriber circuits. Figure 2 illustrates the NAMS solution.

Figure 2

As shown in Figure 2, the Digilog Network Supervisory System II (NSS II) hardware overlays subscriber lines emanating from the network. The NSS II provides proactive monitoring of the physical characteristics of all the various circuit types used in Frame Relay. Proactive monitoring provides an early detection scheme for physical faults in the network. Additionally, the NSS II provides built-in test capability for performing the Bit Error Rate Tests (BERTs) and loopbacks necessary to isolate the link component which is inducing errors.

Figure 2 also shows a HP J2300 WAN protocol analyzer at each site. The NSS II can place the J2300 on any Frame Relay subscriber circuit. The J2300 monitors the circuit and calculates link utilization and virtual circuit performance statistics. The J2300 can also capture and decode Frame Relay protocol from all the diverse circuit types used in this networking technology. The J2300 decodes not only Frame Relay protocol, but also the most popular LAN protocols, and the various encapsulation techniques. NAMS remotely controls the J2300 to bring the statistics and protocol decodes back to the central site for analysis.

Figure 3 shows the detail of how NSS II provides test access to a Frame Relay circuit.

Figure 3

The combination of the NSS II digital shelf and the NSS II matrix shelf provide the basic test access capability. In Figure 3, each circuit emanating from the Frame Relay node is run through an access card in the NSS II digital shelf. The access card provides the ability to bridge a node or network side access bus onto the circuit. The access card can also break the circuit for interruptive testing such as BERTs and loopbacks.

Each digital shelf access bus is connected to an NSS II matrix card. All test equipment, such as the J2300 shown in the diagram, is connected to a matrix card. NSS II matrix cards provide the cross connect between the access buses, and the attached test equipment. This NSS II configuration allows the test equipment to be shared across a large number of circuits.

Figure 4 shows how NAMS remotely controls the NSS II nodes and remote test equipment.

Figure 4

The NAMS software at the central site provides the following:

• Configuration database holding circuit connectivity detail

• Path Graphics which schematically illustrate the circuit under test

• NAMS specific user Ids and passwords for logon security

• User capability classes which limit the functions each operator can perform

• Database regionalization to limit the network elements an operator can access

• Remote control of the NSS II to perform a monitor or test access of one or more remote circuits

• Launch of HP J2300 remote control windows to bring data back to the central site

• Support of multiple simultaneous users, and multiple NSS II nodes

A typical Frame Relay debug session involves using NAMS to select the circuit that needs to be accessed, performing the access via the NSS II, and then launching the remote control window for the J2300 to capture information.

The Digilog NAMS software, the NSS II test access hardware, and the HP J2300 protocol analyzer are effectively integrated, allowing a small group of central site technicians to test and perform remote protocol analysis throughout the Frame Relay network. Problem detection and resolution take less time and fewer resources. Network maintenance costs are decreased. The more rapid problem resolution time increases network user satisfaction.