2. Layer 3: Its main equipment is the router. Because the router works in the third layer, it has unique advantages in network connection ability, path selection, network management and control. With the development of network, especially IP network, routers have been widely used, but the poor data forwarding ability (unpacking/packaging, software working mode) and complexity of routers have always been the bottleneck of network development.
This has caused the problem that the router must be used, but the network transmission bandwidth cannot be improved.
Solution: Network Router A router on an ATM network-L3/L4 switching technology (switching router). Exchange as much as possible and route if necessary.
3. Layer 3 switching (L3 switching): L3 switching technology is developed on the basis of L2, that is, the routing function of network layer is added to the low-end L2 switch (which can not only improve bandwidth but also have routing technology); Or by adding a switching function to the original router structure. L3 switch, also known as switching router, has certain network control and routing functions.
4. Question: Is L3 switch a router?
Two. Classification of Layer 3 switching technology solutions
1. Based on the core model: Netflow, (network data flow)
2. Edge-based multi-layer hybrid switching model: 3Com FastIP.
3. Two L3 switching strategies: upgrading and transforming all equipment and systems; Design a brand-new L3 switching device to replace the traditional router.
Three. Typical L3 switching technology used in. local area network
Typical L3 switching technology in 1. The LAN system include FastIP of 3Com company and NetFlow of Cisco company. They are edge-based multi-layer mixed model and core model respectively.
2.3Com's FastIP technology: A typical scheme based on edge multi-layer hybrid model, which adopts the switching technology of "routing first and then switching". The main technical foundation is NHRP. Is a software solution provided by network interface card driver software. Do not replace the router.
3.NHRP protocol: NHRP protocol is an address resolution protocol for IP logical subnets of non-broadcast multiple access (NBMA) networks. IP addresses can be resolved and translated between multiple logical subnets. For example, working on an ATM network.
Working process: NHRP first sends an NHRP request (IP packet) from the source system to the destination system through routing, and the destination system returns a response packet according to the source address of the packet. If the destination and the source are in the same network, use NHRP protocol to resolve the address and establish a data exchange path from the source to the destination for data transmission. If the destination and the source are not in the same network, a data exchange path from the source to the border router and then to the destination is established for data transmission. (routing once, then switching).
FastIP implements the host-to-host NHRP protocol and reduces intermediate routing links, thus improving network performance. This is an efficient L3 technology. (three layers at a time, then two layers).
For application, please refer to the book P 103.
Features of FastIP: Try to avoid the third layer router in the process of data exchange, that is, the routing function based on IP address routing table is transformed into the forwarding function based on port-MAC address table. So as to realize complete end-to-end high-speed exchange communication and improve network performance.
4. Features of FAST IP technology: FAST IP technology avoids the third layer router as much as possible in the data exchange process, and transforms the routing function based on IP address routing table into the forwarding function based on port-MAC address table, thus realizing complete end-to-end high-speed exchange communication. It does not replace the router, but supplements the routing. Support: ATM 622Mbps and Gigabit Ethernet.
4.。 Cisco's network flow switching.
1.Netflow technology is a software upgrade technology based on the original router (the router must support the upgrade), which improves the performance of the router in forwarding data.
2. Working principle: After the first packet passes through the router, its address and routing information are stored in NetFlow Cache. After the subsequent packets arrive at the router, they first search the cache for address matching. If it is found, it directly uses the routing information cached in the cache for exchange and forwarding, otherwise it is forwarded according to the usual route. In this way, the subsequent data can save tasks such as finding the route again.
3. The significance of "netflow" switching: it is not a direct switching mode every two layers, but an improved stage technology using cache for traditional routing and forwarding. In addition, Netflow does not establish the second-layer switching path between the source system and the destination system, but completes it on the router, which is not the usual "switching".
Four. L3 switching technology in WAN
L3 switching technology in WAN mainly includes cascaded IP Navigator, CISCO Tag switching and MPLS.
Verb (abbreviation of verb) New Structure and High Performance L3 Exchange Technology
1. Structure-oriented Layer 3 switching device: switching router or routing switch.
2.3Com's high-performance switching based on FIRE (Flexible Intelligent Routing Engine). Using ASIC chip to provide high performance switching speed based on hardware. FIRE ASIC not only improves the performance of Layer 2, but also provides more capabilities of Layer 3 routing, traffic optimization, bandwidth reservation and QoS guarantee, as well as the performance of wire-speed forwarding.
3. A real layer 3 switching network structure is constructed, which realizes the performance of the layer 3 with the efficiency of the layer 2 and ensures the control ability of the layer 3 to the network. It also supports multiple network protocols (IP, IPX, Appletalk) and interfaces.
Type (FDDI, Ethernet, ATM). The performance of data pipeline speed exchange is realized.
4. The main structures are FIRE ASIC, RISC frame processor and RISC application processor. Reduced Instruction Set Computer
Beide IP routing switch
1. Using ASIC to realize the IP message forwarding function which has the greatest influence on the router performance, and improve the router performance.
2. The structure consists of two hardware modules: the core module and the I/O module. The core module carries out routing and the I/O module carries out message forwarding.
3. Application: In the network composed of traditional routers with L2 switch as the backbone switch, routers all undertake the packet forwarding between subnets, resulting in heavy routing tasks. In the network using L3 routing switch, packet forwarding is completed by the routing switch, which reduces the burden on the router and thus improves the efficiency of network data forwarding.
The networking application of intransitive verb L3 switch in LAN
1. In the local area network, it can be considered that the backbone switching equipment uses the third layer switch (switching router or routing switch), that is, L3 switch replaces the traditional L2 switch as the backbone switching equipment, which can greatly improve the bandwidth and connectivity of the whole network.
2. Used for interconnection between VLAN to replace routers.
Quality of service (QoS) refers to the agreement on information transmission and enjoyment between users who communicate with each other on the network, such as allowable time of transmission delay, minimum distortion of transmission picture, audio-visual synchronization, etc. Is part of a policy-based service.