Classification, definition and standards of routers

Because of the continuous advancement of social informatization, people's demand for data communication is increasing. Since the launch of TCP/IP protocol cluster in the 70 's, it has developed into the fact standard of Network layer communication protocol, and the Internet based on TCP/IP has become the largest and most important network. As the core equipment of IP network, routers have been widely used.

As the core equipment of IP network, the technology of router has become the key technology of the information industry, and its equipment is playing more and more important role in data communication. At the same time because of the powerful router equipment, and technical complexity, the implementation of the router has too many choices. As the core equipment of the public network, the router must make the minimum requirements through the equipment specification. So it is important and necessary to make the specification of router equipment. The criteria for the release of router devices are as follows: yd/t1156-2001 "router test specification-High-end router"; yd/t1098-2001 "router test specification-low-end router".

First, router definition

Routers are packet forwarding devices that work in the third layer of the OSI Reference Model-the network layer. Routers implement network interconnection by forwarding packets. Although routers can support a variety of protocols (such as TCP/IP, ipx/spx, AppleTalk, etc.), most routers in China run TCP/IP protocol. Routers typically connect two or more logical ports identified by an IP subnet or Point-to-Point protocol, with at least one physical port. The router determines the output port and the next hop address based on the network layer address in the packet and the routing table maintained within the router, and overrides the link layer packet header to implement forwarding packets. Routers reflect the current network topology by dynamically maintaining the routing table, and maintain the routing table by exchanging routing and link information with other routers on the network.

second, router classification

At present, the classification methods of routers are different, and the classification methods are related to each other, but they are not identical.

From the structural point of view, routers can be divided into modular structure and non modular structure, usually high-end routers are modular structure, low-end routers are not modular structure. From the network location division, routers can be divided into core routers and access routers. Core routers are located in the network center, usually using high-end routers, requiring fast packet switching capabilities and high-speed network interface, usually modular structure, access to the router is located at the edge of the network, usually using the low-end routers, requiring relatively slow port and strong access control capabilities. From the functional division, routers can be divided into general routers and dedicated routers. Generally speaking, the router is a generic router. Dedicated routers typically optimize router interfaces, hardware, etc. for a particular function, such as access routers for dial-up users, enhancements to PSTN interfaces and signaling capabilities, and VPN routers to enhance tunneling and hardware encryption, and broadband access routers to emphasize the number and type of broadband interfaces. From the performance points, routers can be divided into wire-speed routers and non-wire-speed routers. Typically, a wire-speed router is a high-end router that forwards packets at a media rate; The low-end router is not a wire-speed router, but some new broadband access routers also have a wired speed forwarding capability.
In the establishment of standards, routers can be divided into: high-end routers and low-end routers and other categories, backplane switching capacity is greater than 20gbit/s, packet switching capacity is greater than 20mbit/s routers called high-end routers, packet switching capabilities less than 1mbit/s routers are called low-end routers. Cisco, the largest market share, for example, the 12000 series for high-end routers, 7500 of the following series routers for low-end routers. There is obviously a gap in the above division: packet switching capability 1mbit/s above 20MBIT/S routers have no reference standard. In accordance with the standard series, there should be a mid-range router specification. However, because the mid-range router is not specific, you can refer to low-end routers or high-end routers, so no longer separate standards.

iii. basis of standard setting

Router standards are based primarily on RFC documents. Because of the complexity of the routers, the relevant RFC documents are more than hundreds.

In addition to a large number of routing protocols, network management protocols and interface standards and other documents are also very important, here is no longer one by one list. The most closely related RFC document is the RFC1812, that is, IPv4 router technical requirements, router equipment specifications as long as the reference to the RFC1812, while referring to the public telecommunications network equipment standards can be deleted.

Although router standards are primarily based on RFC documents, they are by no means simple translations, and the performance metrics are based primarily on the results of router testing. Because routers involve a lot of technology, the standard cannot contain the content of all the relevant protocols, and the specifics of all the protocols refer to the relevant protocol standards or RFC documentation. However, it is not appropriate to simply translate or list the relevant RFC document numbers and protocol names. This is because:

(1) There are some more important in the requirements of the agreement, some of which are optional;

(2) Some requirements in the application of the router is very critical, for other applications or equipment or lack of importance;

(3) Some manufacturers will choose different characteristics for specific reasons. In addition, in the standard-setting, the protocol that the specified router must implement does not duplicate the content of the protocol, but only the content that must be implemented in the protocol, the optional content, the content that does not need to be implemented to select the same protocol.