Network technology explanation: a detailed analysis of the router foundation
Router (Router) is one of the most important devices on the Internet. It is the tens of thousands of routers all over the world that constitute the "bridge" of the Internet, a huge information network that runs around us day and night. The core communication mechanism of the Internet is a data transmission model called "store-and-forward". Under this communication mechanism, all data flowing on the network is sent, transmitted, and received in the form of packets. Any computer connected to the Internet must have a unique network "address" to communicate with other machines and exchange information. The data is not directly transmitted from its "starting point" to the "destination", on the contrary, the data is divided into fragments of a certain length according to specific standards before transmission-data packets. Each data packet is added with the network address of the destination computer. This is like putting an envelope with the address of the recipient on it, so that the data packet will not be "lost" when it is transmitted online. These data packets must be forwarded and relayed by numerous communication devices or computers on the Internet before reaching their destination. The operation of the ancient post is an image metaphor of this process. On the Internet, the router plays the role of "post" for forwarding packets.
Most popular routers exist in the form of hardware devices, but in some cases programs are also used to implement "software routers". The only difference between the two is the efficiency of execution. The router is generally connected to at least two networks, and determines the transmission path of each data packet according to the status of the connected network. The router generates and maintains a table called "Routing Information Table", which tracks and records the address and status information of neighboring other routers. The router uses the routing information table and determines the best transmission path for a particular data packet based on optimization algorithms such as transmission distance and communication cost. It is this characteristic that determines the "intelligence" of the router. It can automatically select and adjust the transmission of data packets according to the actual operating conditions of adjacent networks, and do its utmost to transfer the data packets with the best route and the smallest cost. Pass it out. Whether the router can operate safely and steadily directly affects the activities of the Internet. Regardless of what causes the router to crash, denial of service, or a sharp drop in operating efficiency, the result will be disastrous.
The method of hacking the router is similar to that of attacking other computers on the Internet, because in a strict sense, the router itself is a computer with a special mission, although it may not have the appearance of a PC that people are usually familiar with. Generally speaking, hacker attacks against routers are mainly divided into the following two types: one is to obtain management authority through some means or way to directly invade the inside of the system; one is to use a remote attack method to cause the router to crash or run Efficiency has dropped significantly. In comparison, the former is more difficult.
In the first intrusion method mentioned above, hackers generally use the carelessness of the system users or known system defects (such as "bugs" in the system software) to gain access to the system, and finally through a series of further actions Obtain super administrator rights. It is generally difficult for a hacker to gain control of the entire system from the beginning. Under normal circumstances, this is a gradually escalating intrusion process. Because routers do not have many user accounts like ordinary systems, and often use special software systems with relatively high security, it is much more difficult for hackers to obtain the management rights of the router system than to invade ordinary hosts. Therefore, most of the existing hacking attacks against routers can be classified as the second type of attack means. The ultimate purpose of this attack is not to directly invade the system, but to send a large number of "junk" packets to the system by sending offensive data packets to the system or within a certain time interval, thereby consuming a lot of system resources of the router , Making it not work properly, or even completely collapsed.
Introduction to routing technology
STUN technology:
That is serial tunnel technology. The technology is to send the SNA software package from the serial port of FEP (3745/6) to the router, package it into an IP data packet by the router, and then transmit it in the network formed by the router to the target router, and then disassemble it by the router The packet is restored to the SNA SDLC data packet and sent to the SDLC interface device.
DLSw technology:
It is an international standard technology, which can package the SNA software package by IP and then transmit it to any router node on the IP network from the IP network, and then send it to the SDLC interface device through the serial port of the router in SDLC mode or via the Ethernet interface ( Or TOKEN RING) interface device to the LLC2 link layer protocol to transmit SNA data packet SNA node (such as RS6000).
An E1 interface of MIP:
It can provide 30 64Kbps sub-channels, and the channels can also be combined into a larger sub-channel of N × 64K, which is enough to meet the bandwidth requirements of connecting with local and municipal banks for a long time.
CiscoWorks:
Network management applications are a series of SNMP-based management application software that can be integrated on SunNet Manager, HP OpenView, IBM NetView / AIX, and Windows95 / NT platforms. The main functions provided are:
Allows the use of adjacent routers to remotely install new routers to provide a wide range of dynamic status, statistics, and configuration information to Cisco's Internet products, visually and graphically display Cisco equipment, and basic troubleshooting information. Audit and record configuration file changes, detect unauthorized configuration changes on the network, facilitate configuration of similar routers in the network, record contact details of a specific device, view status information of a device, including buffer memory, CPU load, and availability Memory, the interfaces and protocols being used to collect historical data of the network, analyze network traffic and performance trends, and graphically display the establishment of an authorization check program to protect CiscoWorks applications and network devices from unauthorized users. Especially need to explain is In order to manage the SNA interconnection network well, Cisco specially developed the CiscoWorks Blue network management application for IBM network management. In addition to supporting the above functions, SNA-type MIBs in routers have been added to support NMVT and LU6.2 management methods. SNA management related functions, such as:
Know the state of each SNA resource in the network and use it to change the state of the SNA resource; help detect problems related to the delay of network data flow and can be used to measure the response time from the host to the LU.
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