【 Weak current College 】 router testing technology introduction and test types and methods

The router forwards the packets by for network interconnect devices can support more than one Protocol (e.g. TCP/IP, IPX/SPX, AppleTalk), multiple levels of forwarding packets (such as data-link layer, network layer and application layer).

1. purpose and content of the test

The router forwards the packets by for network interconnect devices can support more than one Protocol (e.g. TCP/IP, IPX/SPX, AppleTalk), multiple levels of forwarding packets (such as data-link layer, network layer and application layer).

Router you need to connect two or more logical port, at least one physical ports. Router based on the received packet network layer address of the router routing table maintained internally determines the output ports as well as the next router address or host address, and rewrite the link-layer header. Routing tables must be dynamic maintenance to reflect the current network topology. Routers usually by and other routers exchanging routing information to complete the dynamic maintenance of the routing table.

(A) the router category

The current router classification methods vary. Various classifications to be associated, but not entirely consistent. Usually you can follow the router capability classification, structure, classification, network location, classification, function classification and performance categories. In router standard classification according to capacity in the main, the capacity is divided into high-end router and low-end routers. Backplane switching capacity greater than 20Gbit/s, the throughput is greater than 20Mbit/s router called the high-end router. Exchange capacity in these data the following routers become low-end routers. And this corresponds to router test code into high-end test specification for low-end router test code and.

(Ii) for testing purposes and content

By testing the router, you can learn what routers are able to provide the best performance, the router in different load behavior, model-based design of the network using a router, the router can handle parameters of unexpected traffic, router performance limitations, routers can provide a different quality of service, the router different architecture for functionality and performance impacts, router features and performance indicators, the effects of using a router is a network security, router protocol implementation conformance, and router reliability and router products strengths and weaknesses.

Low-end router device test mainly include: the General test, i.e. electrical safety testing; environmental testing, including high and low temperature, humidity and high temperature storage test; physical interface testing, test low-end routers might have the electrical and physical interface Testability; Protocol conformance test, the test protocol implementation conformance; performance testing, test the performance of the router; manage tests, test a router-to-no major network management function.

High-end router tests include: interface test, high-end router may have interface test; ATM protocol testing, test the ATM protocol requirements PP protocol testing, test the consistency of the PPP protocols; IP protocol testing, test IP protocol conformance; routing protocol test, the test route conformance; network management function test, verify that the test gateway functionality; performance and QoS router performance testing, test and validate QoS capabilities; network synchronization testing, test device synchronization timing capabilities; reliability tests to verify the device reliability; power supply test, the test machine power consumption, and other content; environmental testing, including high and low temperature, humidity and high temperature storage test.

These two test code as drafting unit, as well as the drafting of the time, the organization is different. In addition to the above tests, it is recommended that you test in considering the test items listed below. (1) functional testing: mainly to verify product availability of the design of every feature. (2) the stability and reliability of the test: take a heavier load on the general approach to the assessment and analysis equipment for a long time, high load capacity of the run. (3) interoperability test: different network between products must be able to interoperate. Interoperability testing on a network product be in a variety of different manufacturers of network products interconnected network environment to work in, for example, verify that the routers and Cisco product interoperability, switches and Cisco, Lucent, 3Com, Intel, interoperability, etc.

2. test method

Router test method is typically divided into local test method, the distribution of the test method, remote test method and the collaborative test method. Because of space limitations, this article does not describe the characteristics of other test method and the scope of application, list only the most commonly used in testing the router to the remote test method.

Among them, the control of the observation point (PCO): usually consists of two first-in first-out (FIFO) queue, its function is similar to a pair of input and output ports, and send a command to the end of the queue, from the other end of the same queue receive answer signal; the measured entity (IUT): ItemUnderTest; next Tester (LT): located in the tested entity underlying PCO and the test layer interaction test system known as the lower test system.

III. testing category

Integrated in the test above, router tests generally can be divided into the following categories: functional testing, performance testing, stability and reliability testing, conformance testing, interoperability testing, and network testing.

(A) functional testing

Router functions can often be divided into the following areas.

(1) interface function: this function used as a router to connect to the network. Can be divided into the LAN interface and wide area network interface. LAN interfaces including Ethernet, token ring, FDDI, token ring, bus, and other network interfaces. WAN interfaces including E1/T1, T3, E3/DS3, generic serial interface (convertible into X.21DTE/DCE, V.35DTE/DCE, RS232DTE/DCE, RS449DTE/DCE, EIA530DTE) network interface. (2) communication protocol function: the function responsible for handling communication protocols, including TCP/IP, PPP, X.25, frame relay, etc. (3) packet forwarding: this feature is mainly responsible for the content according to the routing table in the port (including logical port) to forward packets between and overwrites a link-layer header information. (4) routing information maintenance function: this function is responsible for running the routing protocols to maintain the routing table. RIP routing agreement may include, OSPF, BGP, and other protocols. (5) management control functions: router management control features include five functional, SNMP agent feature, Telnet Server features, local management, remote monitoring and RMON function. There are several different ways to control the management of the router, and allow the record to the log. (6) security features: for complete packet filtering, address translation, access control, data encryption, firewalls, address assignment, and other functions.

The router is not necessary for the above functionality is fully realized. But because the router exists as a network device, the minimum set of features, the feature set to the minimum required functionality, the router must support. Because the vast majority of functional tests can be interface testing, performance testing, Protocol conformance test and network management tests cover, so the router function testing in General can only on other test cannot cover features for confirmatory testing. Router functionality testing generally use remote test method.

(Ii) performance testing

The router is the IP network core equipment, which have a direct impact on the performance of IP networks network size, network stability and network scalability. Because the IETF does not have the router performance testing for special provisions, in General can only follow RFC2544 (BenchmarkingMethodologyforNetworkInterconnectDevices) for testing. But the router is distinguished from ordinary simple network interconnect devices, performance testing should also be coupled with the router's unique performance testing. For example routing table size, routing protocols, such as the convergence time.

Router performance tests shall include the following indicators.

(1) throughput: testing the router packet forwarding. Usually a router without packet loss conditions forwarded packets per second, the limit is generally can find the ultimate point of dichotomy. (2) the delay: testing the router in throughput range from the receipt of the package to forward a package of time intervals. Delay test should be repeated 20 times and then take the average. (3) the packet loss rate: testing the router discards the packet under different load account receives a proportion of the package. From different load usually refers to the wire-speed throughput test (line transmission package highest rate), the step size generally use wire-speed 10%. (4) back-to-back frames: testing the router receives the minimum package interval transit packet loss condition can handle the maximum number of packages. The actual test router caching, if the router is equipped with wire-speed capabilities (throughput = interface media wire-speed), this test does not make sense. (5) system recovery time: testing the router in resuming normal work after overload. Test methods can be used to send a router port throughput of 110% and linear speed of the smaller value, 60 seconds after the rate drops to 50% of the moment to the last packet intervals. If the router is equipped with wire-speed, the test does not make sense. (6) the system reset: testing the router from software reset or off electrical reset to normal working time interval. Normally refers to forward data throughput.

In the test above RFC2544 in indicators should take into account the following factors.

Frame format: it is recommended that you follow the RFC2544 frame format test; frames long: from the smallest frame length to MTU sequentially incremented, such as Ethernet with 64, 128, 256, 512, 1024, 1280, 1518 bytes; certification receives frames: exclude received non-test frame, such as control of frame, frame, etc. routing updates; broadcast frames: Verify broadcast frames on the performance of the router, the above tests in the test frame in 1% of the broadcast frames and then testing; management frame: authentication management frame to router performance, the above tests in the test frame inclusion in a management frames per second and then testing; routing update: routing updates that next jump port change effect on performance; filter: filter condition on the performance of the router, it is recommended that you set 25 filter condition test; protocol address: testing the router to receive random is 256 network address performance impact; the bi-directional flow: testing the router port bidirectional transceiver data performance impact; multiport test: considering the flow distribution across the connection or non-whole connection distribution performance impact; multi-protocol testing: consider the router at the same time to handle multiple protocols, performance impact; mixed bag long: in addition to testing the proposed incremental package long, check for mixed packet length on the performance of the router, RFC2544 requires contains all the test package has no longer on the hybrid packet length in the proportion of the package for long. The author recommends in accordance with the actual network in each package long distribution test, for example, in the absence of special application requirements for Ethernet interface can adopt 60 byte packet of 50%, 128-byte packet 10%, 15% of the 256 byte packet, 512-byte packet 10%, 15% 1500 byte packet. In addition to the above recommendation of test entry RFC2544 also recommends test follows.

① Routing shocks: routing shocks on router forwarding capacity. The extent to which the route shocks per second update routing number based on network conditions. Routing update protocol can use BGP. ② routing table size: the size of the test routing table. Backbone routers typically run BGP routing table contains routes worldwide. Generally require more than 10 million records routing, it is recommended that you enter by using BGP to test the export route count. ③ clock synchronization: contains the corresponding ports such as POS-routerWithin the clock accuracy on test and synchronization capabilities. ④ Protocol convergence time: test routing change notification to the time of the whole network. The index while the stand-alone performance for the router, but generally can only test on the network, and will vary by configuration changes. You can configure in network is completed by examining the indicators to measure the overall network performance. Test time should be according to the specific project and the test target. Generally considered that the test time should be between 60 to 300 seconds. In addition to General can according to user requirements and test target for setting options. Router performance tests generally take remote test method.

(Iii) the conformance test

Router conformance testing usually uses the "black box" method, tested device IUT is called "black box". Test the system by controlling the observation point of the PCO and the tested device interface.

Different test events through different PCO to control and observation, and follow the answer whether compliance with norms, namely timing relationships and data matching, test results can be passed, failed, no results 3. A router is a complex network interconnect devices, various communication layers on a variety of protocols. For example, the interface of the physical layer and link layer protocols, IP/ICMP, and other Internet layer protocol, TCP/UDP transport layer protocol, such as Telnet/application layer protocols such as SNMP and RIP/OSPF/BGP and other routing protocols.

Protocol conformance testing should include all of the implementation of the router. As a result of the test content variety testing complex, in tests can select important agreements and are concerned about content testing. As the backbone of the Internet road there may affect global routing, so router tests should pay special attention to the routing protocol conformance test such as OSPF and BGP protocol. As a result of conformance testing can only choose a limited test cases to test, generally does not cover all the contents of the agreement. So even if the test is also no guarantee that the device fully achieved agreement all content, so the best way is in a real-world environment. Router conformance testing generally use distributed test method or remote test method.

(Iv) interoperability test

As communication protocol, routing protocols, is complex and has many options to achieve the same protocol router does not guarantee interoperability Interop. And because conformance testing capabilities are limited, even through Protocol conformance test may not be able to guarantee the full implementation of the agreement. Therefore it is necessary for interoperability testing equipment.

Interop test is actually testing the consistency in the instrument needs to be replaced by the exchange of interoperable equipment, select some important and typical interconnection configuration, observation of two devices can works as expected.

(V) the stability and reliability testing

Since most routers need 24 hours a day, 7 days a week, as the backbone of the Internet's core router device stability and reliability are particularly important. So users need to understand the dew from the stability and reliability.

The router's stability and reliability are hard to test. Generally two ways: (1) manufacturers through key parts of the degree of reliability and backup system reliability; (2) the user or by a large number of identical products manufacturers in the use of failure rate statistics product stability and reliability. Of course, may also be accessed at one time, the results of running the test require to guarantee the reliability and stability of the router.

(Vi) network management tests

Network Management test generic test network management software on the network, and network device management capability. Because the router is the IP network core equipment, so you must test the routers on the network management support. If a router with network management software, you can use the attached network management software to check for network management software implementation of configuration management, security management, performance management, billing management, fault management, topology management and view management functions. If the router does not come with network management software, you should test the router on the consistency of the SNMP protocol implementation and realization of the MIB. Because the router needs to implement many of the MIB, each MIB contains large amounts of content, it is difficult to completely test the MIB. Generally available through sampling important to check the router MIB entry on an implementation of the MIB.

【 Weak current College 】 server use mistakes and how to properly use

Server core is vital to ensure that the device to the network server to high-performance, stable and sustained work has always been a top concern for users. However, in the this issue, we found a lot of users do not have properly configured your server so that the server does not work in the best State. Typically the server configuration of common errors in performance in the following ways.

The server uses the common misconception
Error: server with redundant features without

A lot of high-performance server provides array function, but because users do not understand it, purchase only one hard drive, no data redundancy, lost for storage, security and performance optimization

Myth two: high-end servers using low configuration scenarios

Users purchase high-end server itself can meet very high performance requirements, but to configure a low-speed, smaller capacity hard disk and a small amount of memory that causes the server's overall performance significantly lower

Myth three: do not know the server performance bottlenecks resulting waste of resources

User for the server's understanding excessively one-sided, unilateral recognition of the importance of certain components, give your all to turn inputs, while ignoring the other components of the optimization work that resulted in the performance of these components is not play. From the above analysis can be seen, whether as a result of the user for the server capabilities are not fully understood or in the use and configuration problems, many of the operational status of the server is not optimal. According to the statistics show that the industry in 80 per cent of the server is not optimized design, 90% of servers are not scheduled for system performance monitoring, 95 per cent of the server does not have complete data redundancy, security measures, almost half of the server is not a data backup solution. The server is in a State of health, through the: power supplies, fans, hard drives, controllers, cables, network adapter, CPU, and other critical parts not used hardware redundancy and system security; use of low-speed, compatibility of equipment components, unreasonably configuration memory, CPU, hard drive controllers, and so causing the performance decrease; do not use any network server management software and hardware, system downtime in the event of a failure, management has serious flaws.

How to properly use the server

In order to improve the health of the server, Transocean waves is the company specializes in some disadvantages and feasibility of the proposal was presented:

As part of the hard disk storage to increase redundancy hard disks and array control cards, provide data redundancy, and substantially increase system IO performance.

Increased redundancy for the server, use of CPU SMP (symmetric multiprocessor) technology to improve system performance, and increased the Centre deal with redundancy.

Increase the redundant network card, improving network IO performance, to a certain block network connection fails, the server will not be disconnected from the network.

For the server to increase redundancy power module, server power supply capability, when a power supply module when problems occur, the system will not be because of power outages and downtime.

Increasing the RAM for the server to meet the operating system and increasing optimization and application requirements, and improve server performance.

In addition, the need for the server's overall performance balance, avoid performance bottlenecks and security implications. From the CPU processing power, memory size, data redundancy and data storage capacity and network IO IO performance, power supply, fan cooling capacity, system fault alarm capability, charged failover capability to do sections are devoted to the optimization work, e.g. by increasing the hard drive, array cards, increase the cache array card, optional hot-swappable hard drive bracket, use array card more than one channel, select the most suitable array level to meet various read and write performance to optimize storage subsystem.

Depending on your operating system, the number of users, applications, the number of CPUs used to determine the minimum memory capacity, increased remote control card online diagnosis memory running process failures.

According to the system the necessary processing power, system CPU redundancy requirements, number of users, the scope of application to determine the number of CPUs, use operating system performance monitoring software and network management software to detect CPU occupancy will be increased or decreased depending on the situation.

Use the AFT (NIC redundancy), ALB (network load balancing), FEC (Fast Ethernet) and other NIC redundant technology to increase server network IO performance.

Increase the redundant power supply module valid security server power supply to prevent damage due to a single power supply module causes system downtime, increase or decrease redundant fans ensure server system cooling effect, prevents the server from overheating and failure.

In short, carefully check the existing bottlenecks and deficiencies, tailored to optimize each part, eliminate barriers of the bondage performance, fully protected input-output ratio, these can give you the right fit with your server resources, avoid mistakes in entering the server use.

【 Weak current College 】 ADSL subscriber line maintenance fault analysis

ADSL access technology dramatically improves the user's Internet access speed, solve the past presence of network bottlenecks. But as the rapid increase in ADSL user, user fault complaint also has significantly increased, in these user fails the complaint line fault accounted for a considerable proportion. This phenomenon is due mainly to the direct use of the existing ADSL PSTN users access network business broadband access, the original lines were not suitable for high frequency signal transmission problems causing the ADSL subscriber line failures occur frequently, haunt the majority of Internet users and track maintenance personnel.


Causes the line ADSL user failure reasons mainly can be divided into two broad categories: the first is attenuation class line failure; the second category is interference class line fault. Attenuation class line fault main findings are: subscriber line is too long, the line material transmission performance difference, circuit breaker, short circuit and oxidation, bad connector, bridged taps, lines exist with Induction coil, etc. Disturbance class line fault main findings are: Central Office or client device background noise is high, radio interference, cables in different lines on the signal crosstalk, household appliances, electromagnetic interference, motor or electric locomotive caused by electromagnetic interference, weather causes interference (such as lightning), etc. While the user failures are often some of the above factors together. The following routine maintenance for some ADSL failsafe for further analysis.

Failsafe: bad, connector oxidation

S a weather phenomenon ADSL users call normal, but no Internet access, Modem activation indicator has been in Flash, users will call on the off-hook State to make the Modem activates lights correctly.

«Test section of the measuring Chamber in Central Office will subscriber line mixed line (that is, user A, B cable shorted), in the user-side measurement lines loop resistance Ω for 4653, in user floor outside junction Office measurement lines loop resistance Ω for 673.

«Analysis section of the call from user can properly concluded that the user does not exist outside line, short circuit breaker. At the junction of ring resistance test results to normal, but in the user-end test to ring resistivity index not working properly after the inspection found that the user is determined by three under huxian paragraph lines threaded together, joint replacement, the oxidation of serious users after fault disappears under huxian, phone and Internet users are normal, and no drop off.

«Summary section of the user drag test is maintaining Central ADSL lines, an important test, suitable for the opening of the line ADSL business ring resistivity index should be less than 900 Ω, depending on the test to the subscriber line loop resistance derived from the line length (with loop resistance per unit length divided by the number of lines on the DC resistance) and the user's actual line length deviation of the larger the circuit on a bad, connectors, such as oxidation. faults It should be noted that the use of 112 measurement automatic test users outside loop resistance, since its test online imposed DC current will breakdown some of the not very serious oxidation film of oxide film to get good results, this is also why the user will in this case placed off-hook State telephone Modem can activate reason (PSTN users pick up after the current line).

Failsafe 2: user inlet attenuation is too large

S a weather phenomenon ADSL user application Mbit/s downlink bandwidth, but unlike other 2Mbit/s bandwidth of a user compare slower.

«Test section of used instrument in the user-end test, the test results display the user maximum downlink direction can be opened at 1.3Mbit/s, loop resistance number 820 Ω; in user outdoor luminaires, test the user port downlink direction maximum opening speed 2.9Mbit/s, loop resistance 795 Ω, under users, no long 100m huxian.

«Eclipse from test results analysis, user opened rate lower mainly due to the user's next huxian signal attenuation is too large, will be replaced by the following huxian copper twisted pairs of the user-side measurement to downlink maximum opening speed 2.6Mbit/s, users go online rate gains.

«Summary section of the current user inlet (commonly known as "the next huxian") most of the parallel single-ply yarn, material for the ferro-alloy material, its transmission performance of high-frequency signal and anti-interference performance well below the twisted-pair copper material, it can cause line attenuation is too large to open rates low by user or activate the difficulties. Recommend copper material twisted pair, and the length should not exceed 100m.

Failsafe III: huxian wiring unreasonable cause signal interference serious

S a weather phenomenon ADSL users reflect the Internet slow download speed only 7kbit/s, and frequently dropped.

«Test section of used instrument to test the user side, the downlink direction maximum opening speed 232kbit/s, the actual opening rate only 96kbit/s. The user's next huxian length 150m, is parallel to, and to fixed-line, outdoor wire rod, indoor heating pipe, and many other places. Replace a user with a twisted pair huxian and to minimize the length to 100m, while not in other parts of the winding, user fault disappears down maximum opening rate reached 2.6Mbit/s, the actual opening of downlink speed for 512kbit/s download speed also increases, to 60kbit/s.

«Analysis section of the appropriate opening of ADSL business subscriber line ADSL band (10kHz-1.1MHz) background noise power spectral density should be less than-94dBm/Hz. In the user-end test to the background noise is too high, but in the sense of the next junction at huxian post test results to determine the normal user failure is largely due to excessively long and cabling under huxian, introduces too much interference signal,Causing the user to open rates low and often dropped.

«Summary section of the excessively long and under huxian excessive winding will lead to the introduction of its like antenna that external electromagnetic interference signal and the parallel lines of anti-interference ability, further exacerbated the problem.

Failure case study 4: device port high background noise

] [A type respondent access phenomenon ADSL Central Office equipment users generally open rate is low, line ring resistance of more than 500 Ω users is very difficult to activate.

«Test section from the failure of performance, you can determine the problem may be with the Central Office equipment, in the measurement units to disconnect a user outside line directly test the DSLAM ports found in this location on the direction to the downward direction on the maximum rate at which can be opened only 3.4Mbit/s, further testing background noise power spectral density and ADSL broadband noise band.

Analysis of the probabilities in measuring s test to user port downlink maximum opening rate only reached 3.4Mbit/s, and test point unit port is very near distance, line attenuation can be ignored, so the cause of this failure phenomenon is mainly due to signal interference. Select the measurement units to disconnect a user outside line for testing can be queued outside interference, which is used to verify the DSLAM port noise leakage. Suitable for the opening of the subscriber line ADSL business ADSL broadband noise band index reference values are: uplink direction is less than-50.23dBm; downlink direction is less than-40.23dBm. In this case the background noise of port power spectral density while there is no more than the given point of reference values-94dBm/Hz, but the entire ADSL band especially downward direction of noise power is high, resulting in a downward direction of broadband noise indicators are not eligible.

«Summary section of the work of taken G.DMT ADSL subscriber line in the measurement units to disconnect a user outside line test after being down maximum opening rates should be greater than 7Mbit/s, when the test data is less than this value describes the DSLAM user port higher noise floor or on-line distribution cable attenuation. So on ADSL faults user maintenance should first ensure that the test in the measurement of indicators is normal, thereby avoiding blind outside line test.

To sum up, in order to ensure the normal use of ADSL users, reducing the failure rate of complaint, the user should pay attention to the user to install cabling, avoid some can cause users to fail the wiring in the future.

On the other hand, as the ADSL business of large-scale, past PSTN line maintenance tools and test methods have been insufficient to find the cause of the failure of broadband users, the need to introduce some new test method, for example, the background noise power spectral density test, broadband noise testing, performance testing of longitudinal balance line, cable crosstalk specifications testing, etc. Only through extensive testing to find the real obstacles to ADSL users.

【 Weak current College 】 LAN optimization of six of the cheats

Reasonable to set the server's hard disk

Use the LAN Office users, often using the network to print materials and access to the file. For some reason, network access may not be working properly at this time, we tend to be incorrectly believe that result in reduced network speed may be a network bottleneck happened some equipment, such as network cards, switches, hubs, etc, in fact, the greatest impact on the network or server hard disk speed. Therefore properly configured network server's hard disk, the entire LAN network performance is greatly improved.


According to the rules for connection

We all know that connect LAN every computer is achieved with twisted pairs, but does not use twisted pair to two computers simply connect each other, we can achieve the communication objectives, we must follow certain rules for wired connections. I have tried two are 100 metres away from the computer to connect with twisted pairs, enabling communication, but no matter what efforts does not connect successfully, then the expert advice, twisted pair connection distance must not exceed 100 m. In addition, if you need to connect more than 100 meters of the two computers, you must use a conversion device. In the connect conversion devices and switches, we also have a jumper. This is because Ethernet is used in General for two pair, arranged in 1, 2, 3, 6, if you are not using two pairs of lines, but the original pairing using separate use of the line, they would form crosstalk, network performance has a greater impact. 10M network environment the situation is not apparent, 100M network environment if the flow is large or long distance, the network will be unable to Unicom.

Proper use of the "bridge"-type equipment

The "bridge"-devices are usually used in the same segment of network devices, routers are used for different sections of the network devices. I have installed the unit to which a microwave networking equipment, physical device after online debugging, Unicom Server always prompts the current segment number should be the other side of the segment number. The server network segments, and each other to consistent, Server alarm disappeared. ! This is set to have a bridge in the nature of the device. Later and another place for installation of microwave networking equipment, swap the other a manufacturer's product, in the connection before we could be on either side of the segment number changed to consistent, when loaded on the device, server and alert: current routing errors. Modify the side segments, alarm disappeared. This shows that distinguish the "Routing" and "bridge" of the device, set the network parameters is important.

The strict implementation of grounding requirements

As a result of the transfer in the local area network are some of the weak signal, if the operation is slightly improperly or not in accordance with the network device specific operational requirements to do so, it may appear in the networking, serious interference information can cause the entire network is blocked. Especially some network switching equipment, as it involves a remote line, on the ground of the very strong, otherwise the network devices will not reach the required connection rate, resulting in a networking process produces a variety of inexplicable symptoms. Had no intention of the router's power plug in the AC outlet, the result is not 128KDDN hotline and Internet connectivity. The Bureau to examine the lines are quite normal, check the router's zero voltage, found no, change back to the socket on the UPS, everything returned to normal. In addition, the router's power plug grounding-broken, causing packet loss, often do Ping connection is good and bad, replace the power supply cable is all normal. Thus, we use a network device, be sure to the conditions provided for in the device, it will give our work brings a lot of trouble.

Use good quality and speed of network card

In the local area network, between the computer and the computer cannot communicate is quite normal, causing the failure cause there may be many. I have statistics, LAN failures related to most of the network card or adapter is not correctly installed or the network cable is bad, but may be older network cards, could not be properly recognized by the computer and also have a network adapter installed on the server, and withstand the impact of large capacity data, end-of-life, etc. Therefore, in order to avoid this phenomenon, we must be willing to invest, if the network card is installed on the server, be sure to use good quality network card, because the server is not run continuously, only the quality of the network card to work for "for a long time," because the server transmit data capacity is large, so we purchased card capacity must match in order to achieve "good horse with good saddle."

Reasonable set switches

Switch is a LAN an important data communications equipment, correct use of switch reasonably also can improve network performance in data transmission. I had to switch ports configured for full duplex, and the server 100M installed a model for the network card, install later Intel100MEISA all normal, but in large discharge load data transfer, the speed becomes very slow, and finally found this card does not support full duplex. The switch ports to half-duplex, fault disappears. This shows the switch port and network card speed and duplex mode must be consistent. There are many adaptive network adapter and the switch, follow the principle that should be properly adapted to the speed and duplex mode, but in fact, due to the inconsistency of the brand, are often not correctly to achieve full-duplex mode. Obviously the server network card to full-duplex, but switch duplex lamp is not lit, the only manual force setting. Therefore, we set up a network device parameters, be sure to reference the server or other network device on the workstation to enable parameters of each device matching jobs.

【 Weak current College 】 what is an optical burst switching technology

Introduction--current optical network switching technology there are three main: optical switching OCS (OpticalCircuitSwitching), optical packet switching OPS (OpticalPacketSwitching), OBS OBS (OpticalBurstSwitching).

Three optical switching technology

Current optical network switching technology there are three main: optical switching OCS (OpticalCircuitSwitching), optical packet switching OPS (OpticalPacketSwitching), OBS OBS (OpticalBurstSwitching).

One of the most mature of the light path switching OCS, network needs to establish a connection request from the source to the destination of the light path (each link will need to assign a professional wavelength). Exchange process is divided into three phases: ① link establishment phase is bi-directional bandwidth application process, you need to pass requests and responses confirmed that the two processes. ② link remains stage, the link is always communication both in use, do not allow the other communicating party sharing the link. ③ link demolition phase, any party disconnect signal, first issued in another party received disconnect signal after confirmation, resources are truly free.

In the long run, all-optical packet switching OPS is optical switching direction of development. OPS is a connection-oriented way, using a one-way exchange of booking mechanism for data transfer without need for routing and distribution of resources. Packet payload closely follow the group header in the same transmitting light path, a network node caching payload, waiting for the grouping with packet destination header processing to determine the routing. Compared to OCS, OPS has a very high level of resource utilization, and a strong ability to adapt to unexpected data. But also the existence of two near insurmountable obstacles: the optical buffer technology has not developed; the second is in OPS Exchange node, the more input the exact synchronization groups. So optical packet switch is difficult to achieve in a short period of time.

In 1997, by ChunmingQiao and J.STunnor respectively a new optical switching technology — — optical burst switching OBS as from circuit-switched to packet-switched technology transition technologies. OBS combines circuit-switched and packet-switched their benefits and overcome some shortcomings of both, has attracted more and more people's attention.

Burst

OBS in "burst" can be considered by the number of smaller with the same export edge node address and same QoS requirements of data grouping consisting of very long data is grouped, the data group can come from traditional IP network in the IP packet. Burst is optical burst switched networks in basic Exchange unit, it consists of a control group (BCP, BurstControlPacket, functions as a packet-switched in the group header) and burst BP (NET load) made up of two parts. Burst data and control groups on the physical channel is a separate group for each control corresponds to an unexpected data, this is also the core optical burst switching design concept. For example, in WDM systems, control group consumed one or several wavelength, burst then consume all other wavelengths.

The control group and burst data separation is control group can be the first to burst data transfer to compensate for the control group in the Exchange node in the processing of O/E/O converter and power processing delay. Then a burst in all-optical switching node in exchange for transparent transmission, thereby reducing on optical buffer needs, even reduced to zero, to avoid the current optical buffer the shortcomings of the technology was not ready. And, because of the control group size much less than the size, you need to burst O/E/O converter and electronic processing of data greatly decrease, reducing processing delays, greatly improving the exchange rate. This process is similar to an outbound tours, team before departure, carrying a staff members with relevant information, arrived one day earlier border clearance procedures and ticket, etc., before departure, then tours the visitors of the time also simplifies the process.

Edge and core node

Because optical fiber to the home network in the bottlenecks are now mainly used for backbone and metropolitan area networks, and user-end remains the traditional electric IP network. Optical burst switched network mainly by light core node and edge nodes of electricity. Edge nodes are mainly responsible for IP packet access, classification, packaging and dispatch, and reverse burst of receiving and remove frames. Entrance to the edge node data input through the line card, depending on the IP packet's destination address sorting after Assembly, forming burst data, and extract the corresponding group header generation control group, which breaking data cache to the burst queue waiting for scheduling. When a sudden burst of data in the send queue on the queue head, calculation of burst data with the appropriate control packet offset between time and feedback to control packet generator, and then issue the control group, the control group including time offset, burst length and specific route information. When the offset of the time expires, the issue of the burst. Export edge node simply burst apart, and which IP data extraction.

Core node functionality is to control the Group find, Exchange, burst monitor (such as blocking probability, delay, etc), it is assumed that each wavelength optic support for K + 1 (single wavelength used for transmission control block BCP, K a wavelength used for transmission burst). BCP for transmission wavelength in core nodes need to be O/E converter and power routing table lookups, light switching matrix control, last update BCP data for E/O converter. The rest of the k-wave transmission burst data in core node does not need O/E/O transform, the entire Exchange transmission in optical domain, ensuring the transparency of the data. Figure in optical switching matrix of fiber delay line is used to cache burst data (you can only cache a finiteLong time), wait for the control group, by setting the appropriate offset time offsettime can make sudden data does not need to be cached in the intermediate nodes, directly through the OBS networks, which in turn can cancel the optical delay lines. Besides optical delay lines can also be used to resolve competition issues, reducing conflict and achieve WDM layer of QoS (quality of service). When the burst into optical switching matrix, the control unit control of optical switching matrix to select the corresponding output wavelength.

【 Weak current College 】 802.11 context

June 12, 2003, IEEE802.11g official as technical standards publication, one month later, Wi-Fi Alliance certification for the first use of standard products. 802.11g IEEE802.11g can be viewed as IEEE802.11b, high-speed version, but in order to achieve 54Mbit/s of transfer rate, 11g adopted and 11b different OFDM (orthogonal frequency division multiplexing) modulation, it supports 54Mbps transfer rate.
IEEE802.11 standard was introduced in 1997, on this basis, in September 1999, the proposed standard and IEEE802.11b standard IEEE802.11a.
Boost wireless LAN standardization organization WECA (TheWirelessEthernetCompatibilityAlliance, also known as "Wi-Fi Alliance") was announced in November 2001, will follow the "IEEE802.11a" product identification tag to "Wi-Fi5" (this is because IEEE802.11a utilizes 5GHz band); WECA organizations previously will use 2.4GHz band wireless LAN IEEE802.11b "known as" "Wi-Fi".

Along with many other manufacturers a comprehensive intervention now 802.11 series wireless network product prices have reduced a lot. The newly launched TP-Link network card plus AP entry-type wireless network package, the price is less than $ 1000. The market and some integration of routers, switches, and other features of multifunctional ADSLModem AP sales for home users and SOHO family, this product has greatly reduced the CTO, is very attractive. From the compatibility and interoperability to consider the purchase of WLAN equipment, it is important to note that view ID, check whether the adoption of Wi-Fi certified integrated wireless network function notebook is no exception. Visit the official website of the WECA http//www.weca.net, online queries through the "Wi-Fi" certification of wireless networking products.
Currently on WLAN support best stand-alone operating system is WindowsXP, it will control on a wireless network interface integrated in a unified "wireless link" function, in the "Control Panel" to find it. For notebook users, do not use a wireless network, recommendations will be integrated wireless adapter off or external wireless network card removal; because the wireless adapter will continue to detect the surroundings have a wireless connection and the connection attempt, not only electricity, consume system resources, but also is a security risk.

In the midst of cheers, wireless network attracts everyone's attention, however our wireless network soft ribs should have an understanding. As a historical and a long history of technology, the wireless network has a variety of defects is inevitable and this is also the direction of its future efforts.
Bluetooth transmission distance less than is its Achilles heel. From a cost analysis, Bluetooth may not, however various patent fees and market speculation that Bluetooth got lost. A few years ago, it is Bluetooth universal opportunity, unfortunately we see various Bluetooth product price. Although today's Bluetooth is already down the altars, but in the transmission distance of more powerful Wi-Fi was established the advantages for Bluetooth in the competition very passive, basically giving up wireless LAN market, focused on bandwidth and transmission distance requirements lower mobile devices. In addition, the transmission distance of more recent infrared technology continues to develop, as a practical, low-cost solution.
Of course, Wi-Fi also is not perfect, security issues are bearing the brunt. In the commercial market, Wi-Fi eager to show in the wireless LAN, which had security problems on the breakthrough. Although in developing initial Wi-Fi will security problems in a certain height, but at least so far, many users still cannot be assured, especially those in low-priced universal product. In addition, the power consumption issues is by Wi-Fi must face, and this is its most than Bluetooth, lead in mobile device competition faced unfavorable situation.

【 Weak current College 】 wireless technology "WiMAX"?

Maximum transmission speed 75Mbit/seconds, the maximum transmission distance of up to 50km & high speed for long distance transmission of wireless communication technology "WiMAX" in the United States redoubled, much better than wireless LAN.

This technique is what will be applied in the fields of application will be how to? WiMAX Vision uses completely different with the wireless LAN. Wireless LANs are generally applied to a hundred meters of distance communication, namely, "LAN". While WiMAX is several kilometres to dozens of kilometers of wide application.

WiMAX standard based on the IEEE802.16. Generally can be divided into 2 types of IEEE802.16-2004 June this year to develop standards for basic IEEE802.16a. Envisaged maximum transmission distance of 7km ~ 10km fixed region. Another is being developed in IEEE802.16e, mobile terminal, the maximum transmission distance of 3km ~ 5km. Currently, there is a particular concern is the specification determined by 802.16-2004. It is expected that the first half of 2005, there will be a related product, it is used primarily to connect to the Internet service access lines. The alternative of using a telephone line, ADSL and so will the communication operators and users.

WiMAX in the United States's award-winning attention largely depends on the situation of the United States. Vast United States, even if you use a phone line or ADSL signal is transmitted to the distant suburban housing. This is also the hopes of WiMAX. WiMAX adoption and wireless LAN standard 802 .11A and 11g same OFDM modulation (OrthogonalFrequencyDivisionMultiplexing). The bandwidth of each channel to 20MHz. This also and 11a and 11 g is almost the same. But because you can outdoor fixed antenna and receiving radio waves in a stable way, so the radio waves can host the number of bits of higher than 11a and 11 g. Therefore, you can achieve 74.81Mbit/s maximum transfer rate. In addition, by location, very high the antenna transmitting power strong signal, and long-distance communication possible. WiMAX standards using 2G ~ 11GHz within a band. In the United States and Europe, plans assigned to WiMAX relative idle 2.5GHz, 3.5GHz and 5.8GHz band.