Router Review: Internet router is the main node device. Router, forwarding data through the routing decision. Forwarding strategy is called routing (routing), which is the origin of the name of the router (router, forwarding those).
Routers are often used for a large number of nodes in the network environment, it is in the ISO / OSI model network layer. Compared with the switches and bridges, in the realization of the internet backbone, the routers, especially high-end router has a clear advantage. Highly intelligent routers, the various routing protocols, network protocols and network interface of broad support, as well as its unique security and access control functions and features of bridges and switches, and other connected devices are not available. Low-end router product can be used to connect devices and small-scale backbone network endpoint access, high-end products can be used for the interconnection between the backbone network and the backbone network and Internet connection. Especially for the backbone of the Internet and the backbone network and the Internet, interoperability, not only technically complex, involving communication protocols, routing protocols and a number of interfaces, information transmission speed is high, and the requirements of network security is much higher than on other occasions . Therefore, using high-end router as Internet devices, has incomparable advantage of other Internet devices.
The role of the router
One role of the router is connected different networks, and the other role is to select the information transmission lines. Select smooth and efficient shortcut, can greatly increase the communication speed, to reduce network traffic load, saving network resources and enhance the network flow rate, so that networks play a more effective system to.
Filtering network traffic from the point of view, the role of routers and switches and bridges are very similar. But with the work of the network physical layer, from the physical demarcation of different segments of the switches, routers use specialized software protocol logically divide the entire network. For example, a router to support IP protocol can be divided into multiple subnets network segment, only point to specific IP addresses of network traffic can pass the router. For each received packet, the router will re-calculate the checksum value, and write the new physical address. Therefore, use the router to forward and filter data rate than is often only see the physical address of the packet switch slowly. However, for those complex networks, using the router can increase the overall efficiency of the network. Another significant advantage of the router that can automatically filter the network broadcast. Generally speaking, adding a router in the network throughout the installation process much more complex than plug and play switch.
Types and Characteristics of the router
Internet networks at various levels can be seen everywhere router. Access network to allow families and small businesses can connect to an Internet service provider; enterprise network router to connect a campus or thousands of computers within the enterprise; backbone network of the router end systems are usually not directly accessible, they long-distance backbone network to connect the ISP and enterprise networks. The rapid development of both the Internet backbone network, enterprise network or access network have brought a different challenge. Backbone router to a small number of links required for high-speed route forward. Enterprise-class router requires not only the number of multi-port, low cost, easy to configure and requires, and provide QoS.
1. Access Router
ISP access router within the home or small business customers. Access router has begun not only to provide SLIP or PPP connection, also supports such as PPTP and IPSec virtual private network protocols. These agreements to be able to run on each port. Technologies such as ADSL will soon enhance the family's available bandwidth, which will further increase the burden of access routers. Because of these trends, access routers in the future will support a number of heterogeneous and high-speed ports, and each port can run multiple protocols, but also to avoid the telephone exchange network.
2. Enterprise Router
Enterprise or campus-level router to connect many end systems, its main goal is the cheapest way possible to achieve as much as possible endpoint interconnection, and further requests to support different quality of service. Many existing corporate networks are connected by the Hub or Ethernet bridge section. While these devices are cheap, easy to install, no configuration, but they do not support the service level. In contrast, the participation of network routers can be machine into multiple collision domains, and thus can control the size of a network. In addition, the router also supports a certain service level, at least to allow into multiple priority levels. But the cost per port router more expensive, and can be used prior to a lot of configuration work. Therefore, the success of the enterprise is whether the router offers a large number of ports and each port low cost, ease of configuration, whether to support QoS. Also required to effectively support enterprise-class router, broadcast and multicast. Enterprise network had to deal with a variety of historical LAN technology supports multiple protocols, including IP, IPX and Vine. They also support the firewall, packet filtering, and a large number of management and security policies and VLAN.
3. Backbone routers
Backbone routers, enterprise-class network connectivity. Its speed and reliability requirements, while the cost of the seat. Hardware reliability can be used by telephone switching network technologies, such as hot backup, dual power, dual data paths, etc. to get. These technologies in terms of almost all backbone routers are standard. IP backbone routers, the main performance bottleneck is in the forwarding table to find a route by the consumption of time. When you receive a package, enter the port in forwarding the packet to find the destination address to determine its destination port, when the package should be as short or when the package when sent to a number of destination port, bound to increase the cost of routing lookup. Therefore, some of the frequently visited destination port into the cache can improve the efficiency of routing lookup. Regardless of the input buffer or output buffer router, all routes to find the bottlenecks exist. In addition to performance bottlenecks, the stability of the router is also an often overlooked problem.
4. Terabit router
The core of the Internet in the next three main technologies used in optical fiber and DWDM are already very mature and is ready. If there is no existing fiber-optic technologies and DWDM technology to provide the raw bandwidth of the corresponding router, the new network infrastructure will not be fundamentally improved the performance, so development of high-performance backbone switch / routers (terabit router) has become an urgent requirement. Terabit router technology development is still mainly in the experimental stage.
Router Technology
Router Architecture
From an architectural point of view, the router can be divided into the first generation of single-bus single-CPU structure of the router, the second generation single-bus structure of the main router from the CPU, the third generation of a single symmetric multi-CPU bus router; fourth generation routers, multi-bus multi-CPU , the fifth generation routers shared memory structure, the sixth generation crossbar switch architecture, cluster-based router and the router and other types.
The composition of the router
Router has four elements: input ports, output ports, switching and routing switch processor.
Input port is the physical link and enter the package's entrance. Line card port is usually provided general support for a line card port 4,8 or 16, an input port has many features. The first feature is the data link layer of packing and unpacking. The second function is to find the input packet forwarding destination address to determine the destination port (called routing lookup), route lookup can be used to achieve the general hardware, or through the line in each block of a microprocessor embedded in the card to complete . Third, in order to provide QoS (quality of service), the port should receive the package into several predefined level of service. Fourth, the port may need to run such as SLIP (Serial Line Internet Protocol) and PPP (Point to Point Protocol) link-level data such agreement or as PPTP (Point to Point Tunneling Protocol) network-level protocol such. Once the routing lookup to complete, the package must be sent to the switch output port. If the router is to increase the input queue, there are several inputs share the same exchange switch. This input function is to attend the last public resources (such as the exchange switch) the arbitration agreement.
Exchange switch can use a variety of different technologies. So far the most used technology is the bus exchange switches, cross switches and shared memory. The simplest use of a bus switch to connect all input and output ports, the bus switch drawback is its exchange capacity is limited by the capacity of the bus and brought to a shared bus arbitration overhead. Crossbar switch through the switch to provide multiple data paths, one with N × N crosspoint switch cross-section can be considered to have 2N bus. If a cross is closed, the data input bus is available in the output bus, or not available. Intersection of closed and open to control by the scheduler, thus, the scheduler limits the switching speed of the exchange. In the shared memory router, incoming packets are stored in shared memory in the exchange package is only a pointer, which increased the exchange capacity, however, switching speed is limited by memory access speed . Although the memory capacity to double every 18 months, but the memory access time of only 5% reduction each year, this is a shared memory limitations inherent in the switch.
Output port in the packet is sent to the output link on the package before storage, you can implement complex scheduling algorithm to support the priority requirements. As with the input port, output port also to be able to support the data link layer packing and unpacking, and many more advanced protocols.
Routing processor computing forwarding of routing protocols, and run on the router configuration and management software. It also does not deal with the line card destination address of the packet forwarding.
VPN
VPN (Virtual Private Network-VPN) solution is a router with one of the important functions. The solution is as follows:
1. Access Control
Generally divided into PAP (Password Authentication Protocol) and CHAP (Password Authentication Protocol senior) two kinds of agreements. Login required to target persons PAP router user name and password, instead of access list (Access List) information in the match allowed the log. Although it provides some security, but the user login information on the Internet without encryption pass, easily one steal. CHAP will come into being, it is to a random initial value and the original user login information (username and password) translated by the Hash algorithm to form a new login information. This online delivery of user login information is opaque to the hackers, and because different random initial values each time the user login information for each of the final will be different, even if a first user login information is stolen, hackers can not repeat use. Note that, due to the vendors with their own different Hash algorithm, so no Internet * for CHAP to speak of. To create a VPN need to be placed at both ends of the same brand router VPN.
2. Data Encryption
Encrypted in the encryption process median is a very important parameter, which is directly related to the difficulty of decryption, which Intel 9000 series routers, the most outstanding performance for more than 100 encryption.
3.NAT (Network Address Translation-Network Address Translation protocol)
The same as the user login information, IP and MAC addresses on the Internet without encryption communications were not safe. NAT can be the legitimate IP address and MAC address translation into the illegal IP address and MAC address of the Internet transmission, reach the target after the anti-translated into legitimate router IP and MAC address, a process somewhat like CHAP, translation algorithm manufacturers have different standards, can not to achieve mutual * for.
QoS
QoS (Quality of Service-service quality) would be ATM (Asynchronous Transmit Mode) in the jargon, the IP of the original is not talking about QoS, but the use of IP VOD and other multimedia information transfer more and more applications, IP as a package of agreements usually not a very: long delay and not as a fixed value, packet loss and distortion caused by signal discontinuities great. To solve these problems, a number of vendors solutions: The first scenario is based on the priority of different objects, some of the equipment (mostly multimedia) to send the packet can pass after the first. The second scheme is based on the priority of the agreement, the user can define the high priority which the agreement may be after the first pass, Intel and Cisco support. The third option is to do link integration MLPPP (Multi Link Point to Point Protocol), Cisco supports two points connected by lines to do more than the bandwidth aggregation, thereby enhancing the bandwidth. The fourth option is to do resource reservation RSVP (Resource Reservation Protocol), it will be part of the bandwidth of fixed points for multimedia signals, and other agreements in any case crowded, and shall not occupy this part of the bandwidth. These types of solutions can effectively improve the transmission quality.
RIP, OSPF and BGP protocols
Internet routing protocols are running a large number of RIP (Routing Information Protocol-Routing Information Protocol), OSPF (Open Shortest Path First - Open Shortest Path First) and BGP (Border Gateway Protocol-Border Gateway Protocol). RIP, OSPF is an internal gateway protocol, applicable to the unity of a single ISP to run routing protocols, operating from an ISP's network is called an autonomous system. BGP is the inter-autonomous system routing protocol, is an external gateway protocol.
RIP is the introduction of the longest routing protocol, is the simplest routing protocol. It is the main transfer routing information (routing table) to broadcast routing. Every 30 seconds, broadcasting a routing table, to maintain the relationship between adjacent routers, while calculated according to the routing table received their own routing table. RIP to run a simple, suitable for small networks, the Internet is still some use of the RIP.
OSPF protocol is "open shortest path first" abbreviation. "Open" is the fact that some manufacturers for "private" in terms of routing protocols, and it is open because the agreement only allows OSPF has a strong vitality and broad use. It does this by passing link state (connection information) to get network information, maintenance of a network with the topology graph, minimum spanning tree algorithm used by the routing table. OSPF is a relatively complex routing protocols.
In general, OSPF, RIP is the routing protocol within the autonomous system, suitable for a single ISP (autonomous systems) to use. In general, the Internet is not suitable for running a single routing protocol, as each ISP has its own interests, unwilling to provide details of their network routing information. In order to ensure the interests of the ISP, ISP Organization for Standardization has developed between the routing protocol BGP.
BGP route between the ISP deal with the transfer. It features a rich routing policies, it is RIP, OSPF and other protocols can not do, because the information they need to calculate the global routing table. BGP border router by ISP with a certain strategy, select the filter route, the RIP, OSPF, BGP routing, etc. to send to each other. Global scope, the range of the Internet is BGP routing with multiple instances of inter-ISP. BGP emergence of the Internet caused a major change, it is to connect multiple ISP organic, truly global network. A side effect of the Internet routing explosion, and now the Internet is about 60,000 route, this is through the "convergence" after the number. Configuring BGP requires the user needs, network status and BGP protocol is well aware, also need to be very careful, BGP is running at a relatively central position, once the error, their loss may be great!
IPv6 Technology
Rapid development of the Internet will no longer be simply a network connected computer, it will develop to the same phone network, cable network similar information and communication infrastructure. So, is using the IP (Internet Protocol) has failed to accomplish, people eager to the emergence of next generation IP or IPv6.
IPv6 is a version of IP, the Internet protocol TCP / IP, the OSI model is a layer 3 (network layer) protocol. It is widely used with the present, made in 1974 will be compared to IPv4, the address by the 32-bit expanded to 128. In theory, the address from the original number has swelled 4.3 × 109 4.3 × 1038 个. The reason to switch from the current IPv4 IPv6, mainly for two reasons.
1. As the rapid development of Internet, the address number was not enough, which makes network management effort and cost spent too much. Address depletion is to promote the 128-bit address space to have a primary cause of the transition.
2. With the increase in the number of hosts to determine the routing of the routing table data is constantly increasing. Processing performance of the router can not keep up this rapid growth. Over time, the Internet connection will be difficult to provide stable services. Via IPv6, routing can reduce the number of an order of magnitude.
To make Internet access a lot of things become simple, and easy to use, must use IPv6. IPv6 they are able to do this, because it uses four types of technology: the expansion of address space, routing table can decrease the address structure, automatically set to address and improve security confidentiality.
IPv6 in IPv4 routing technology inherited the favorable side, represent the future direction of the routing technology, many router vendors already invested heavily in efforts to produce a router to support IPv6. Of course, there are some noteworthy IPv6 and inefficient local, IPv4/NAT and IPv6 will coexist for a long period of time.