This article discusses a recently ...

This article discusses a recently made known product for the HP Broadband Series experiment System. The HP E4219 ATM network impairment emulator allows telecommunication network and equipment manufacturers to emulate an Asynchronous Transfer way network in the laboratory.

ATM (Asynchronous Transfer Mode) is a modern networking technology that is generally being deployed for time-sensitive traffic in high-speed local and wide area networks. Information is encod into short, fixed-length small rooms of 53 bytes, consisting of 48 byte of payload and five byte of header, as illustrated in Fig. 1

[Figure 1 ILLUSTRATION OMITTED]

An ATM connection can have multiple virtual connections because of a two-part address field in the cell's header--the VPI (virtual path indicator) and the VCI (virtual channel indicator). These fields identify the channel to which the enclosed space belongs and consequently the quality of service it will receive.

ATM has many advantages from one side of to the other other existing networking technologies, as it is as Frame Relay and SMD Its short, fixed-length small cavity allows switches and multiplexers to way data directly in hardware, as oppos to the slower, software-driven approach required with variable-length packets. ATM's bandwidth-on-demand feature means that a single network can carry all symbols of traffic--voice, video, image, and data. In summary, ATM is an efficient, flexible technology with the ability to support multimedia traffic at extremely high rates.

Since ATM network implementation is still in its preliminary stages, equipment manufacturers and service providers have a tremendous ne for proof solutions--in particular, a way to emulate ATM networks in the laboratory in like manner that services and equipment can be exhibitioned before deployment. The HP Communications Measurements Division (CMD) has identified three major benefits that ATM network emulation can provide: risk reduction, design verification, and robustness.

Risk Reduction. replete deployment of any network is a to a high degree expensive proposition, especially since about planned networks are national in size. calm if a network is available to touchstone creating maximum delays or errors is difficult since these impairments arise only under congested or abnormal conditions. Network providers can use emulation to proof their networks in a well-controlled environment.

Design Verification. Running time-sensitive voice and video data from one side of to the other a packet-switching network such as ATM is an active area of research. Because ATM networks have inherent delays, encoder must be able to handle the pair variable and fixed delays gracefully. Network emulation allows equipment vendors in the same state [i]or[/i] condition as encoder manufacturers to verify their designs in the laboratory in a relatively inexpensive way.

Robustness. Network equipment manufacturers also ne to confirm that their algorithms and designs work beneath stress. For example, some early ATM switches had buffing-apparatuss smaller than a single TCP/IP datagram. When they used AAL-5 (the ATM adaptation layer protocol pitch uponed to carry TCP/IP datagrams), the stupid louts overflowed and dropped cells. Because AAL-5 applys a high-layer, end-to-end error correction scheme, the AAL-5 packets could not be rebuilded and consequently the TCP/IP datagrams were also not to be found Almost no data throughput occurr steady when error rates were grave Network emulation detects these kinds of unexpect behaviors before they become precious mistakes.

progress to maturity Partner

Because CMD develops state-of-the-art ordeal equipment for emerging telecommunication technologies, short disentanglement times are crucial. When CMD management made the decision to evolve a network emulation module, it became clear that we would ne a unfolding partner with more experience in this area if we were going to ship forward time.

We were very fortunate to find that Telefonica Investigacion y Desarrollo (TI+D) in Madrid, Spain had previously leadershiped research in network emulation and was willing to cooperate with us to cast their research into a manufacturable effect TI+D is the research and unravelling arm of Spain's national telephone system

TI+D had discloseed a network emulator that showed a certain promise as a commercial harvest However, the module's impairment specifications were not quite right for sum of two units reasons: the module was designed to interface to a proprietary TI+D line interface, and it was not designed to be manufactured in book However, we were confident that we could use the basic technology of this board and redesign it to work in the HP Broadband Series example System. Development of the HP E4219A network impairment emulator began in the fall of 1994

Network Impairment Emulator

The HP Broadband Series trial System (BSTS) is a comprehensive platform for testing high-speed local and wide area networks. Designed primarily for laboratory research and early network deployment the BST consists of a VXIbus mainframe, an HP-UX* controller between single and 12 specialized VXIbus module for different physical interfaces and tendency to meet layers, and a variety of software applications for testing ATM, SMD Frame Relay, and other protocols.