Due to the continuous advancement of social informatization, people's demand for data communication is increasing. Since the launch of the TCP/IP protocol cluster in the mid-1970s, it has now developed into the de facto standard for network layer communication protocols, and the Internet based on TCP/IP has also become the largest and most important network. Routers, as the core equipment of IP networks, have been widely used unprecedentedly.
As the core equipment of IP networks, routers have become the key technology of the current information industry, and their equipment itself plays an increasingly important role in data communication. At the same time, due to the powerful functions and complex technology, various manufacturers have too many choices in implementing routers. As the core device of the public network, routers must make minimum requirements through device specifications. Therefore, it is important and necessary to regulate router equipment. The published standards for router equipment are as follows: YD/T1156-2001 "Router Test Specification - High-end Router"; YD/T1098-2001 "Router Test Specification - Low-end Router".
1. Router definition
The router is a packet forwarding device that works in the third layer of the OSI reference model - the network layer. Routers enable network interconnection by forwarding packets. Although routers can support multiple protocols (such as TCP/IP, IPX/SPX, AppleTalk and other protocols), most routers in my country run TCP/IP protocols. Routers usually connect to two or more logical ports identified by IP subnets or point-to-point protocols, with at least 1 physical port. The router determines the output port and the next hop address based on the network layer address in the received data packet and the routing table maintained by the router internally, and rewrites the link layer packet header to forward the packet. The router dynamically maintains the routing table to reflect the current network topology and maintains the routing table by exchanging routing and link information with other routers on the network.
2. Router classification
The current router classification methods are different, and the various classification methods have certain correlations, but they are not completely consistent.
From the structure, routers can be divided into modular structures and non-modular structures. Usually, mid- and high-end routers are modular structures, while low-end routers are non-modular structures. From the network location, the router can be divided into core routers and access routers. The core router is located in the center of the network and usually uses a high-end router, requiring fast packet switching capabilities and high-speed network interfaces, usually in a modular structure; the access router is located at the edge of the network and usually uses a mid- and low-end router, requiring relatively low-speed ports and strong access control capabilities. From a functional division, routers can be divided into general routers and dedicated routers. The routers generally referred to as general-purpose routers. Dedicated routers usually make special optimizations to router interfaces, hardware, etc. to implement a specific function. For example, the access router is used as an access dialer user to enhance PSTN interfaces and signaling capabilities; VPN routers enhance tunnel processing capabilities and hardware encryption; broadband access routers emphasize the number and types of broadband interfaces. In terms of performance, routers can be divided into linear speed routers and non-linear speed routers. Usually, line speed routers are high-end routers that can forward data packets at media rates; mid- and low-end routers are non-line speed routers, but some new broadband access routers also have line speed forwarding capabilities.
In the formulation of standards, routers can be divided into categories such as high-end routers and low-end routers in terms of capabilities. Routers with backplane switching capabilities greater than 20Gbit/s and packet switching capabilities greater than 20Mbit/s are called high-end routers; routers with packet switching capabilities less than 1Mbit/s are called low-end routers. Taking Cisco, which has the largest market share, as an example, the 12000 series is a high-end router, and the 7500 series of routers are low-end routers. Obviously, there is a gap in the above division: routers with packet switching capabilities above 1Mbit/s and below 20Mbit/s do not refer to the standards. According to the standard series, there should be a mid-range router specification. However, since mid-range routers are not special, they can refer to low-end routers or high-end routers, so there is no separate standard.
3. Standard setting basis
The router standard is mainly based on RFC documents. Due to the complex router technology, there are many related RFC documents, about hundreds.
In addition, there are a large number of documents such as routing protocols, network management protocols, and interface standards, which are also very important, so I will not list them one by one here. The most closely related RFC document to the router is RFC1812, that is, the IPv4 router technical requirements. The router equipment technical specifications can be added and deleted as long as they refer to RFC1812 and the public telecommunications network equipment standards.
Although the router standard is mainly based on RFC documents, it is by no means a simple translation. It mainly depends on the results of router testing in terms of performance indicators. Since routers involve a large number of technologies, the standards cannot contain the content of all relevant protocols. For the specific content of all protocols, please refer to the relevant protocol standards or RFC documents. However, it is inappropriate to simply translate or list the relevant RFC document number and protocol name. This is because:
(1) Some of the requirements of the protocol are more important, and some are optional; (2) Some requirements are very critical in router applications and are irrelevant to other applications or devices; (3) Some manufacturers will choose different features for specific reasons. In addition, in the formulation of standards, the protocol that specifies that the router must implement will not repeatedly apply the content of the protocol, but only stipulates the content that must be implemented, optional content, and unimplemented content in the protocol to make choices for similar protocols.
The router standard is mainly based on current Internet technology and current versions of protocols and RFC documents. With the update of these technical fields and the update of related protocols or RFC document versions, the router standard should be updated or supplemented accordingly.
IV. Standard scope
Routers can support multiple protocols (such as TCP/IP, IPX/SPX, AppleTalk and other protocols). Even TCP/IP protocols can be divided into version 4 and version 6. However, since TCP/IP has become the de facto standard and IPv4 has an absolute advantage in the network, the router standard focuses on regulating devices that support IPv4. Since IPv6 has its inherent advantages and may be widely used in the future, it is recommended that routers support IPv6, but are not specified.
In addition to the routers described in the standard, routers also have embedded routers and transparent routers. An embedded router refers to a computer system that provides operating system functions in addition to providing routing functions. Due to its inherent defects, it is recommended not to use it in the standard. Transparent routers, also known as shared address routers, are not standardized in the standard, but are not excluded from use.
Router standards are specifications that routers working in complex and diverse Internet must comply with. Although the current router cannot fully comply with the standards, gradually complying with the router standards is the direction of efforts. Due to the complexity of the Internet and the diversity of reality, current router standards should be used as recommended standards.
5. Main contents of router standards
There are certain differences in the contents of low-end router standards and high-end router standards. The differences are mainly reflected in the router interface type, performance requirements, reliability requirements, etc. Generally speaking, high-end routers have high performance requirements, high interface speed requirements and high reliability requirements. They are mainly used for high-speed forwarding; low-end routers require many functions. In addition to enterprise network applications, they are generally used for access in public networks. The above two types of routers have little difference in basic functions. Therefore, the following is a low-end router as an example to introduce the main contents of the router standard.
The first part of the standard specifies the scope of the application of the standard and specifies the technical requirements of the router, including functions, indicators, communication interfaces, communication protocols, environmental requirements, etc. The second part lists the standards and specifications cited by router standards. As mentioned above, there are nearly a hundred documents. The third part lists all definitions, terms and abbreviations used in the standard, mainly defining routers and low-end routers. The fourth part points out the functional division and implementation methods of routers, which are as follows.
(1) Interface function: used to connect the router to the network. It can be divided into LAN interface and WAN interface. The LAN interface mainly includes Ethernet, token ring, token bus, FDDI and other network interfaces. WAN mainly includes network interfaces such as E1/T1, E3/T3, DS3, general-purpose serial ports (converted to X.21DTE/DCE, V.35DTE/DCE, RS232DTE/DCE, RS449DTE/DCE, EIA530DTE) and other network interfaces. (2) Communication protocol function: This function is responsible for handling communication protocols, which can include TCP/IP, PPP, X.25, frame relay and other protocols. (3) Packet forwarding function: This function is mainly responsible for forwarding packets between ports (including logical ports) according to the contents of the routing table and rewrite the link layer packet header information. (4) Routing information maintenance function: This function is responsible for running the routing protocol and maintaining the routing table. The routing protocol can include RIP, OSPF, BGP and other protocols. (5) Management and control functions: The router management and control functions include five functions, which are the SNMP proxy function, Telnet server function, local management, remote monitoring and RMON function. The router is controlled and managed through five different ways and allows logging. (6) Security function: This function is used to complete data packet filtering, address conversion, access control, data encryption, firewall and address allocation. There are also basic functions that routers must implement as pointed out in Part IV.
The fifth part of the router standard specifies the physical layer specification of the router interface, including the E1 interface, ISDN interface, Ethernet interface, serial synchronization port, FDDI interface and other interfaces. The above interface specifications all reference ready-made standards and are not described in detail. The sixth part mainly specifies the link layer specifications of the router interface by citing other standard specifications, including serial line link layer protocol, frame relay port link layer protocol, X.25 link layer protocol, ISDN link layer protocol, etc. In addition, it also includes additional requirements for the link layer by the router: address resolution protocol-ARP, regarding coexistence between Ethernet and 802.3, maximum transmission unit-MTU, point-to-point protocol-PPP, and interface testing, etc. The seventh part stipulates the router's Internet layer protocol, including the IP protocol, the ICMP protocol and the IGMP protocol. The router's implementation of the above protocol is not a simple reference or translation, but a special provision made by router devices on the options of the above three protocols, and is one of the important contents of the router standard. The eighth part stipulates the basic functions and forwarding of the router. The packet forwarding process specifically stipulates that it complies with the Internet layer protocol (STD5 RFC791, STD5 RFC950, STD5 RFC792, RFC1016). This part of the content mainly refers to RFC1812, and combines the above RFC documents to make requirements for router forwarding, which is one of the important contents in the router standard. The ninth part stipulates the transport layer protocol, including the TCP protocol and the UDP protocol. The router works at the IP layer and there is no need to implement the transport layer protocol, but due to the operation and maintenance requirements (Telnet) and the routing protocol requirements, the router usually implements the above transport layer protocol. The TCP and UDP protocols describe mainly simple applications and only define a few options. Part 10 specifies the most complex protocol running in a router by referring to other protocols: the routing protocol. It contains two parts, internal routing and external routing. The internal gateway protocol is used to partially send routing information within the AS (i.e., AS internal routing). The external gateway protocol is used to exchange routing information between AS (i.e., inter-AS routing). Part 11 points out the provisions on router network management. The router is required to support the SNMP v2 specified in RFC1902 to RFC1906 and the corresponding standard MIB. Part 12 stipulates other application agreements. For all other application layer protocols implemented by the router, the router must comply with the relevant requirements in STD3 and RFC1123. Part 13 points out the regulations on router operation and maintenance. It mainly formulates the content of router operation and maintenance, specific regulations on router initialization, operation and maintenance, router security considerations, etc. Part 14 stipulates the main technical indicators of routers. It mainly includes the router's packet loss rate, router throughput, router delay, router authentication technical indicators, routing table capacity, back-to-back frame count, and its billing, synchronization, reliability indicators. Finally, it stipulates the router supporting AppleTalk and Novell protocols, and also stipulates the router environment requirements and power and grounding requirements.
As the core equipment of IP networks, routers have become the key technology of the current information industry, and their equipment itself plays an increasingly important role in data communication. At the same time, due to the powerful functions and complex technology, various manufacturers have too many choices in implementing routers. As the core device of the public network, routers must make minimum requirements through device specifications. Therefore, it is important and necessary to regulate router equipment. The published standards for router equipment are as follows: YD/T1156-2001 "Router Test Specification - High-end Router"; YD/T1098-2001 "Router Test Specification - Low-end Router".
1. Router definition
The router is a packet forwarding device that works in the third layer of the OSI reference model - the network layer. Routers enable network interconnection by forwarding packets. Although routers can support multiple protocols (such as TCP/IP, IPX/SPX, AppleTalk and other protocols), most routers in my country run TCP/IP protocols. Routers usually connect to two or more logical ports identified by IP subnets or point-to-point protocols, with at least 1 physical port. The router determines the output port and the next hop address based on the network layer address in the received data packet and the routing table maintained by the router internally, and rewrites the link layer packet header to forward the packet. The router dynamically maintains the routing table to reflect the current network topology and maintains the routing table by exchanging routing and link information with other routers on the network.
2. Router classification
The current router classification methods are different, and the various classification methods have certain correlations, but they are not completely consistent.
From the structure, routers can be divided into modular structures and non-modular structures. Usually, mid- and high-end routers are modular structures, while low-end routers are non-modular structures. From the network location, the router can be divided into core routers and access routers. The core router is located in the center of the network and usually uses a high-end router, requiring fast packet switching capabilities and high-speed network interfaces, usually in a modular structure; the access router is located at the edge of the network and usually uses a mid- and low-end router, requiring relatively low-speed ports and strong access control capabilities. From a functional division, routers can be divided into general routers and dedicated routers. The routers generally referred to as general-purpose routers. Dedicated routers usually make special optimizations to router interfaces, hardware, etc. to implement a specific function. For example, the access router is used as an access dialer user to enhance PSTN interfaces and signaling capabilities; VPN routers enhance tunnel processing capabilities and hardware encryption; broadband access routers emphasize the number and types of broadband interfaces. In terms of performance, routers can be divided into linear speed routers and non-linear speed routers. Usually, line speed routers are high-end routers that can forward data packets at media rates; mid- and low-end routers are non-line speed routers, but some new broadband access routers also have line speed forwarding capabilities.
In the formulation of standards, routers can be divided into categories such as high-end routers and low-end routers in terms of capabilities. Routers with backplane switching capabilities greater than 20Gbit/s and packet switching capabilities greater than 20Mbit/s are called high-end routers; routers with packet switching capabilities less than 1Mbit/s are called low-end routers. Taking Cisco, which has the largest market share, as an example, the 12000 series is a high-end router, and the 7500 series of routers are low-end routers. Obviously, there is a gap in the above division: routers with packet switching capabilities above 1Mbit/s and below 20Mbit/s do not refer to the standards. According to the standard series, there should be a mid-range router specification. However, since mid-range routers are not special, they can refer to low-end routers or high-end routers, so there is no separate standard.
3. Standard setting basis
The router standard is mainly based on RFC documents. Due to the complex router technology, there are many related RFC documents, about hundreds.
In addition, there are a large number of documents such as routing protocols, network management protocols, and interface standards, which are also very important, so I will not list them one by one here. The most closely related RFC document to the router is RFC1812, that is, the IPv4 router technical requirements. The router equipment technical specifications can be added and deleted as long as they refer to RFC1812 and the public telecommunications network equipment standards.
Although the router standard is mainly based on RFC documents, it is by no means a simple translation. It mainly depends on the results of router testing in terms of performance indicators. Since routers involve a large number of technologies, the standards cannot contain the content of all relevant protocols. For the specific content of all protocols, please refer to the relevant protocol standards or RFC documents. However, it is inappropriate to simply translate or list the relevant RFC document number and protocol name. This is because:
(1) Some of the requirements of the protocol are more important, and some are optional; (2) Some requirements are very critical in router applications and are irrelevant to other applications or devices; (3) Some manufacturers will choose different features for specific reasons. In addition, in the formulation of standards, the protocol that specifies that the router must implement will not repeatedly apply the content of the protocol, but only stipulates the content that must be implemented, optional content, and unimplemented content in the protocol to make choices for similar protocols.
The router standard is mainly based on current Internet technology and current versions of protocols and RFC documents. With the update of these technical fields and the update of related protocols or RFC document versions, the router standard should be updated or supplemented accordingly.
IV. Standard scope
Routers can support multiple protocols (such as TCP/IP, IPX/SPX, AppleTalk and other protocols). Even TCP/IP protocols can be divided into version 4 and version 6. However, since TCP/IP has become the de facto standard and IPv4 has an absolute advantage in the network, the router standard focuses on regulating devices that support IPv4. Since IPv6 has its inherent advantages and may be widely used in the future, it is recommended that routers support IPv6, but are not specified.
In addition to the routers described in the standard, routers also have embedded routers and transparent routers. An embedded router refers to a computer system that provides operating system functions in addition to providing routing functions. Due to its inherent defects, it is recommended not to use it in the standard. Transparent routers, also known as shared address routers, are not standardized in the standard, but are not excluded from use.
Router standards are specifications that routers working in complex and diverse Internet must comply with. Although the current router cannot fully comply with the standards, gradually complying with the router standards is the direction of efforts. Due to the complexity of the Internet and the diversity of reality, current router standards should be used as recommended standards.
5. Main contents of router standards
There are certain differences in the contents of low-end router standards and high-end router standards. The differences are mainly reflected in the router interface type, performance requirements, reliability requirements, etc. Generally speaking, high-end routers have high performance requirements, high interface speed requirements and high reliability requirements. They are mainly used for high-speed forwarding; low-end routers require many functions. In addition to enterprise network applications, they are generally used for access in public networks. The above two types of routers have little difference in basic functions. Therefore, the following is a low-end router as an example to introduce the main contents of the router standard.
The first part of the standard specifies the scope of the application of the standard and specifies the technical requirements of the router, including functions, indicators, communication interfaces, communication protocols, environmental requirements, etc. The second part lists the standards and specifications cited by router standards. As mentioned above, there are nearly a hundred documents. The third part lists all definitions, terms and abbreviations used in the standard, mainly defining routers and low-end routers. The fourth part points out the functional division and implementation methods of routers, which are as follows.
(1) Interface function: used to connect the router to the network. It can be divided into LAN interface and WAN interface. The LAN interface mainly includes Ethernet, token ring, token bus, FDDI and other network interfaces. WAN mainly includes network interfaces such as E1/T1, E3/T3, DS3, general-purpose serial ports (converted to X.21DTE/DCE, V.35DTE/DCE, RS232DTE/DCE, RS449DTE/DCE, EIA530DTE) and other network interfaces. (2) Communication protocol function: This function is responsible for handling communication protocols, which can include TCP/IP, PPP, X.25, frame relay and other protocols. (3) Packet forwarding function: This function is mainly responsible for forwarding packets between ports (including logical ports) according to the contents of the routing table and rewrite the link layer packet header information. (4) Routing information maintenance function: This function is responsible for running the routing protocol and maintaining the routing table. The routing protocol can include RIP, OSPF, BGP and other protocols. (5) Management and control functions: The router management and control functions include five functions, which are the SNMP proxy function, Telnet server function, local management, remote monitoring and RMON function. The router is controlled and managed through five different ways and allows logging. (6) Security function: This function is used to complete data packet filtering, address conversion, access control, data encryption, firewall and address allocation. There are also basic functions that routers must implement as pointed out in Part IV.
The fifth part of the router standard specifies the physical layer specification of the router interface, including the E1 interface, ISDN interface, Ethernet interface, serial synchronization port, FDDI interface and other interfaces. The above interface specifications all reference ready-made standards and are not described in detail. The sixth part mainly specifies the link layer specifications of the router interface by citing other standard specifications, including serial line link layer protocol, frame relay port link layer protocol, X.25 link layer protocol, ISDN link layer protocol, etc. In addition, it also includes additional requirements for the link layer by the router: address resolution protocol-ARP, regarding coexistence between Ethernet and 802.3, maximum transmission unit-MTU, point-to-point protocol-PPP, and interface testing, etc. The seventh part stipulates the router's Internet layer protocol, including the IP protocol, the ICMP protocol and the IGMP protocol. The router's implementation of the above protocol is not a simple reference or translation, but a special provision made by router devices on the options of the above three protocols, and is one of the important contents of the router standard. The eighth part stipulates the basic functions and forwarding of the router. The packet forwarding process specifically stipulates that it complies with the Internet layer protocol (STD5 RFC791, STD5 RFC950, STD5 RFC792, RFC1016). This part of the content mainly refers to RFC1812, and combines the above RFC documents to make requirements for router forwarding, which is one of the important contents in the router standard. The ninth part stipulates the transport layer protocol, including the TCP protocol and the UDP protocol. The router works at the IP layer and there is no need to implement the transport layer protocol, but due to the operation and maintenance requirements (Telnet) and the routing protocol requirements, the router usually implements the above transport layer protocol. The TCP and UDP protocols describe mainly simple applications and only define a few options. Part 10 specifies the most complex protocol running in a router by referring to other protocols: the routing protocol. It contains two parts, internal routing and external routing. The internal gateway protocol is used to partially send routing information within the AS (i.e., AS internal routing). The external gateway protocol is used to exchange routing information between AS (i.e., inter-AS routing). Part 11 points out the provisions on router network management. The router is required to support the SNMP v2 specified in RFC1902 to RFC1906 and the corresponding standard MIB. Part 12 stipulates other application agreements. For all other application layer protocols implemented by the router, the router must comply with the relevant requirements in STD3 and RFC1123. Part 13 points out the regulations on router operation and maintenance. It mainly formulates the content of router operation and maintenance, specific regulations on router initialization, operation and maintenance, router security considerations, etc. Part 14 stipulates the main technical indicators of routers. It mainly includes the router's packet loss rate, router throughput, router delay, router authentication technical indicators, routing table capacity, back-to-back frame count, and its billing, synchronization, reliability indicators. Finally, it stipulates the router supporting AppleTalk and Novell protocols, and also stipulates the router environment requirements and power and grounding requirements.
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Article entry: csh Editor in charge: csh