With the development, application of increasingly wide range of broadband routers.Sharing a broadband router to the network provides the perfect solution, as an access router, broadband router, users first aim is to solve the network share.Broadband routers ensure that the premise of low price guarantees on the speed of the user requirements.Now the market flooded with a variety of routers, the performance how? How to choose? General performance of the router and grade level of the mark, mainly by the processor, memory and cache to decide.
Router processor
Router processing chip the same as the computer's CPU is the core router components, router performance will directly affect the level of key components, the processor often determines the quality of the broadband router's throughput, the most important parameters.Therefore, I analyze here, the router chip.
Processor speeds are less in the 100M or lower frequency, such a broadband router for home and SOHO users ordinary.100M-200M moderate frequency.A higher frequency of more than 200M for Internet cafes, small and medium users and large enterprise branch offices.
Usually in the low-end broadband router, the processor is responsible for exchanging routing information, routing table lookup and forwarding data packets, the processor's ability to directly affect the throughput of the router (routing table lookup time), and routing of computing power (of network routing convergence time.)In the high-end broadband routers, packet forwarding, and usually by the ASIC chip look-up table to complete, the processor only to realize the routing protocol, routing and distributed routing table calculation.Development of technology, broadband router, the processor cores used in many types.
Generally speaking, the router processor is an embedded processor.Mainly x86, ARM7, ARM9, RDC, and some MIPS architecture.ARM7 and the RDC framework is already in position to be eliminated by the poor performance of the two processor architectures, mainstream manufacturers are not used.Currently using ARM9 and MIPS core processor architecture is a broadband router mainstream configurations.Common Common type of 920T/922T/940T ARM9 and enhanced 926E/946E/966E, and MIPS sub 2K, 3K, 4K series, the different types of processor performance will be quite different.Intel Xscale core processor is a senior network processor for high-end products.General processors are single-processor, multi-processor, distributed processing is advanced processor, high-performance.
Of course, broadband router, broadband router, the processor is only a part, so special is that it is only the core of the device.Broadband router processor performance does not reflect the router performance.Router Performance by a router throughput, delay and routing computing power and other indicators reflected.
Broadband router processor used is poor, no better router performance, but a good processor, router performance is not necessarily good.Processor frequency is only one processor performance, processor performance to know, you must also understand the bus width (16-bit or 32-bit), Cache size and structure, the internal bus structure, a single-CPU or multi-CPU Distributed Processing, operation mode, etc., which could greatly affect the processor performance.
Router memory
Router might have a variety of memory, such as Flash (flash memory), DRAM (dynamic RAM) and so on.Memory for storage configuration, the router operating system, routing protocol software and so on.In the low-end routers, routing tables may be stored in memory.Generally, the bigger the better router memory (regardless of price).However, a similar capacity with the CPU, memory, the router also does not directly reflect the performance and capabilities.Because of efficient algorithms and good software can greatly save memory.
Generally speaking router memory is divided into four types:
First, read-only memory (ROM)
Function in the router's ROM similar to the computer, mainly used for system initialization and other functions.As the name implies, ROM is read-only memory, which stored the code can not be modified.To upgrade, will have to replace the ROM chip.ROM included in the main: the system POST code (POST), to detect the router hardware is intact; the system boot code (BootStrap), used to start the router and load the IOS operating system; backup IOS operating systemto the original IOS operating system is removed or destroyed to use.Typically, this IOS is running IOS version than the low, but sufficient to support the router startup and work.
Second, the flash memory (Flash)
Is readable and writable memory, restart or shutdown the system can still save the data after.Stored in the current use of Flash in the IOS. In fact, if large enough Flash capacity, or even store more than one operating system, which is useful during the IOS upgrade.When the new version of IOS do not know whether the stable, can be retained after the upgrade earlier versions of IOS, when problems arise can be quickly back to the older operating system, thus avoiding a long network failure
Third, non-volatile RAM (Nonvolatile RAM)
Is readable and writable memory, restart or shutdown the system can still save the data after.Only to save the NVRAM startup configuration file (Startup-Config), so the capacity is small, usually only configured on the router size 32KB ~ 128KB NVRAM. At the same time, NVRAM is faster, the cost is relatively high.
Fourth, random access memory (RAM)
RAM is readable and writable memory, but it is the content stored in the system reboot or shutdown will be cleared.The RAM and the computer as the router is running in RAM for temporary storage during the operating system and data memory, so the router can quickly access the information.RAM access speed than the aforementioned three kinds of memory access speed.
During operation, RAM items included in the routing table, ARP cache items, journal entries, and the queue waiting to send the packet.In addition, also includes the running configuration file (Running-config), is implementing the code, IOS operating system programs and temporary data.However, different types of routers, IOS code to read the way they are different.
The composition of the router
In general form the router has four elements: input port, output port, the switch and routing processors.Input port is the physical link and enter the entrance of the package.Usually by the line card port, a line card generally support 4,8 or 16 ports, one input port with many functions.The first feature is the data link layer encapsulation and decapsulation.The second function is to look at the forwarding destination address of incoming packets to determine the destination port (called route lookup), use the normal route lookup can be implemented in hardware, or each line by a microprocessor embedded in the card to complete.Third, in order to provide QoS (quality of service), port should receive the packet into several predefined service levels.Fourth, the port may need to run such as SLIP (Serial Line Internet Protocol) and PPP (Point to Point Protocol) such as data link level protocol or PPTP (Point to Point Tunneling Protocol) that network-level protocol.Once the route lookup to complete, the package must be sent to the switch output port.If the router is added the input queue, there are several share the same input of the switch.This input function is to attend the last public resources (such as the switch) the arbitration agreement.
Output port in the packet is sent to the output link to the package before storage, you can implement complex scheduling algorithms to support the priority requirements.As with the input port, output port also to be able to support data link layer encapsulation and decapsulation, and many of the more advanced protocols.Route processor computing forwarding routing protocol implementation, and operation of the router configuration and management software.It also does not deal with line card destination address in the packet forwarding.
Router features
A typical router has two major functions, namely, data path functions and control functions.Data path functions, including forwarding decision, forwarding the backplane and output link scheduling, usually done by a specific hardware; control functions typically implemented in software, including the exchange of information between adjacent routers, system configuration, system management, etc..
The role of the router is connected, a different network, and the other role is to select the information transmission lines.Choose smooth and fast shortcut, can greatly increase the communication speed and reduce network traffic load and save network resources, improve the flow rate of network systems, enabling network systems to play a greater benefit.