In order to accommodate the increasing amount of data traveling over networks, communication speed improvements for network communication devices are constantly sought. Speed improvements mandate new transmission protocols. The new transmission protocols may be evolutionary or revolutionary. In both cases, however, comprehensive testing is mandatory.
An example of a data or network communication device that requires testing and is used to transmit data over networks, such as the internet, is a router. Routers select the best path to send a message, based on the destination and source addresses. Routers perform a number of tasks. High level routing tasks are partitioned into smaller subtasks, forming layering and service models. The idea behind layering is that each layer is responsible for providing some service to the layer above and does this by using the services of the layer below. There are certain interfaces required to communicate between layers, and there are protocols for communicating between the same level layers located on different routers. Router and other network device manufacturers must test communication links and protocols between each layer combination exhaustively as part of device and network validation.
Besides layer communication protocols, there are intra- and inter-domain routing protocols. Examples of intra-domain routing protocols are RIP, IS-IS, OSPF, and integrated routing. Some examples of inter-domain routing protocols are static routing, EGP, BGP, IDRP. These protocols are also continually evolving, and the network communications devices implementing the protocols must be tested before new features are released to market.
Like routing protocols, switching modes in routers are also evolving. Some examples of switching modes are CEF (Cisco Express Forwarding, which is a non-cache-based switching mode for IP packets), IP switching (which is cache-based), and Tag Switching (where "tags" are added to each IP packet). Improvements and extensions are being made continually to these and other switching modes. Consequently, extensive testing of new features is critical.
Hardware interfaces are also increasing in variation, sophistication, and bandwidth (among other features). Example interfaces include Ethernet, Fast Ethernet, Token Ring, FDDI (fiber distributed data interface), and HSSI (high speed serial interface). Some routers support multiple interfaces of the same type or different types. Like the routing protocols and the switching modes, hardware interfaces are also evolving. And, like routing protocols and switching modes, hardware interfaces also require comprehensive testing on a network topology level.
Still further, in order to communicate between a source and a destination, data packets may have to travel over networks using different routing protocols, different switching modes, and hardware interfaces as they travel from link to link on their data paths. To do this, the data packets are typically encapsulated, in Ethernet frames for example. These encapsulation modes are also modified periodically in order to keep up with the changing interfaces, switching modes, and routing protocols.
Developments in new routing protocols, switching modes, encapsulation modes, and hardware interfaces require new sets of tests; but, backward compatibility is usually a requirement in order to maintain an existing client base so that new computers and new data communication devices can be added to their existing networks with minimal cost and impact to an existing, running network. This means that each time a small improvement is made, new testing must be performed on the data communication devices, as well as testing to ensure backward compatibility.
In general, most testing code is the same for performing standard network testing tasks, such as establishing network communication and network configuration, and collecting data, while specific functionality tests are often unique, being written to test a single functionality of a specific network communication device in a specific test environment.