Common description of Zyxel Prestige 128L bridge-router

LABORATORY WORK №4

THEME: ACTIVE NETWORK EQUIPMENT BRIDGES-ROUTERS

PURPOSE OF WORK

Studying principles of the bridge and router operation, the network screen and acquiring practical skills of main modes operation and maintenance.

KEY PRINCIPLES

Practically in all cases, whether it is one computer or set of computers interconnected in a local area network, there is necessity to use external wide-area networks to apply to Internet resources and to exchange information with other local area networks. To do this, such active network equipment as modems, bridges and routers, network screens are used.

As it is known, modems are intended to convert digital signals into analogue ones with their successive transmission across telecommunication lines, and also to restore an initial digital signal at reception. As there is a variety of different media through which data exchange is performed, many types of modems are created. Depending on coordination of data transfer, modems can be divided into on two big categories:

• Synchronous;

• Asynchronous.

Asynchronous modems can lose to 25 % time for transmission and reception negotiation. Synchronous modems use accessible link speed more effective and provide faster communications than asynchronous modems.

Remote bridge. It is the bridge intended for data transfer of one local segment through a wide-area network to other local segment. It builds the table of MAC-ADDRESSES on the basis of the traffic passing through it and on the basis of it makes solution – to transfer frames to a remote segment or not. If usual bridges do not almost find applications today the remote ones are applied rather often. They do not need to be configurated and this property proves to be very useful at remote offices where there is no qualified serving staff.

Bridge. It works at a data link level. It’s a medium of frames transmission on the basis of the physical address between two segments using, as a rule, identical protocols of physical and link levels. Thus, bridges provide the extension of a network, which does not demand program modifications on workstations operating in local segments. All servers working in segments use unique addresses when interacting and do not have to distinguish obviously servers of an own segment and servers of other segments. Bridges care of it. The bridge should know, which addresses of the data link level (MAC-ADDRESS) belong to each segment to define which frames to skip, and which ones to return to its segment. For this purpose it has a scheme of operation with addresses. If some segments are linked by several bridges, each bridge should have the table of passing paths through bridges as well. To provide the operation in conditions when frames arrive faster, than they can be transferred, the bridge should have sufficient volume of the buffer.

Unlike the switch the router supports protocols not only physical and data link levels, but also network one. Network layer protocols provide collection of the information about topology of connections between logical networks and construction of tables of routing with paths to all logical networks known to a router. (Methods of paths definition, optimal after the given criteria are considered in following section). On the basis of routing tables the router fulfils transmission of packages from one network to another and can make of solution for choice of the most rational path of an information transfer in difficult topology (topology with closed loops).

It has some physical interfaces, including, various network technologies, and can also provide economic access to territorial networks as it isolates the local traffic more effectively. If the router is capable to support some protocols of a network layer, it is named a multiprotocol router.

The range of functional tasks of a router also includes buffering, filtering and a fragmentation of packages. Therefore it is a typical computer with one or even several processors and with complicated software of real time. Since each package is handled by a router separately, its productivity considerably loses to productivity of the switch. There can be a bottleneck, hindering the traffic passing if it is set at the kernel level.

The server computer can fulfill the router role in the case is the network layer of its operating system supports transmission of packages. Universal OS of Unix or Windows include the program unit providing setup of the mode "router".

Association of two remote local area networks by means of two Zyxel Prestige 128L modems (see Figure 2.1).

Figure 2.1 – Example of a remote local area network

Common description of Zyxel Prestige 128L bridge-router

Prestige 128L Zyxelmodel of a company-manufacturer represents the bridge-router for the physical dedicated symmetric digital line. Having united in itself the function of a router, a bridge and a network screen, Prestige 128Lpossesses variety of functions which provide flexible network solutions for the access to the Internet, interconnections of local area networks of large corporations subsidiaries and connection of remote individual users.

Prestige 128L functionality includes:

• Support of protocols of TCP/IP and Novell IPX stacks and transparent translation of protocols (in a bridge mode).

• Connection at 64 Kbit/with or 128 Kbit/s speed on a cooper pair of 0,4 mm section for a distance to 5,5 km.

• 2B1Q line code.

• The spectrum of a signal to 80 kHz.

• Support of the data link level protocol of "point-point" PPP connection.

• Static and dynamic assignment of IP-addresses.

• Network Address Translation, NAT.

• Routing according to RIP-2 protocol (the advanced version of RIP protocol).

• The network screen filtering packages according to different tags (type of the protocol of higher level, number of the destination port of the transport layer etc.).

In Figure 2.2 there is the back panel of the device.

Date: 2015-12-24; view: 1001