Measure the test taker's knowledge about the basic principles of Performance Comparison of routing technologies.

First, we need to know the basic principles of the Performance Comparison of the routing technology. Q: exchange network routing technology. A: exchange is the development direction of network technology. The routing technology is an important part of the exchange network. The correct choice of Routing Technology in the exchange network will directly affect the overall performance of the network. As a result, the routing technology is increasingly valued by manufacturers and network designers.

Performance Comparison of three routing technologies

Currently, there are three types of routing technologies in the exchange network, the first of which is the most conservative method, that is, the combination of the layer-3 router and the layer-2 switch. Layer 2 switches are strictly limited to the bridge structure and used for data exchange between different nodes in the same virtual network. The Layer 2 of the OSI reference model, that is, the data link layer, implements the virtual LAN function, the layer-3 function is left to the router for implementation. The router completes data transmission between the virtual network and establishes a connection between the LAN and the enterprise backbone network.

The second method adopts the distributed routing technology. It is characterized by the use of a multi-layer switch that combines the second-layer bridge with the Third-layer route. Some documents also refer to a multi-layer switch as the third-layer switch. Its routing function supports Virtual LAN and most nodes in the same virtual network or between different virtual networks, reducing the number of routers used between the Working Group and department. However, it still cannot completely get rid of traditional routers, because multi-layer switches can only provide a subset of the protocols, security, traffic management, and WAN connection functions provided by high-end routers.

For example, CISCO 7000 Series routers can process 12 protocols and support point-to-point, circuit exchange, and cell exchange Wan communication. Alantec's Powerhub multi-layer switch can only process three protocols: DECnet, IP, and IPX, and there is no WAN interface. Therefore, a vro must be used as the WAN gateway in a multi-layer switch network to compare the complex routing technology performance.

The third Routing Technology in the exchange network adopts a new structure: the Routing Server and the border switch are combined. We know that the traditional router completes packet forwarding and routing selection. The Routing Server-based network has two independent devices to complete the above two functions: the border switch forwards information packets, the routing information is determined by the expensive Routing Server.

The vswitch accesses the Routing Server only when the address of the target node cannot be found in its address table. In this case, the vro responds to the correct address and the vswitch caches the information for backup. It should be pointed out that the current communication protocols between the Routing Server and the switch are not uniform, and the products of different manufacturers are not compatible.

Performance Comparison of routing technology: connection with the ATM trunk

As there is no uniform standard for the interconnection between the exchange LAN and the ATM trunk composed of the routing server and the distributed routing mode, the connection methods provided by various companies are also different. A common method is to send traffic from all the virtual networks of the Ethernet or ring LAN switch to a router with an ATM interface card. However, the disadvantage of this method is that the router will become the bottleneck of the entire network, affects the overall performance of the network.

The better way is that the Ethernet switches have their own ATM interfaces, which allows the LAN switches to directly establish connections with the ATM switches without going through the routers. This is a significant improvement. However, the data transmission between different virtual networks still needs to pass through the router, and the bottleneck still exists.

Currently, there are two standards for traditional Traffic Transmission over ATM: one is LAN simulation developed by the ATM Forum, another standard is the traditional IP standard (IPOverATM) on the ATM set by IETF, an International Computer Interconnection Network Engineering Task Group ). LAN simulation runs on the MAC layer of media access control. The biggest benefit of LAN simulation is that, it can ensure that the traffic of the Ethernet and the traffic on the ATM network runs normally without any changes to the application and man-machine interface.

The IPOverATM standard has the same purpose as LAN simulation. Unlike LAN simulation, it only allows ATM traffic to run on an IP network. However, they do not completely solve the problem of traffic transmission between different virtual networks. They still need to have routers between different virtual networks: routers assemble cells into information packages to complete route selection, the information package is restored to the metadata before being sent, which is much less efficient.

To eliminate the bottleneck caused by routers, the ATM Forum has developed a multi-protocol transmission standard (MPOA) on the ATM to solve the transmission of multiple protocols on the ATM, this includes IP, IPX, SPX, and Appletalk. The routing traffic between different virtual networks of MPOA is based on network layer traffic information (such as IP subnet addresses) to avoid using external routers.

Performance Comparison of Routing Technology

According to the performance comparison of the routing technology, the three router technologies have their own characteristics and have their own advantages. You can choose one based on your actual needs. It should be emphasized that the routing technology is still a very important part of the switching network in the present and foreseeable future, the correctness of the routing technology directly affects the overall performance of the network.