Protocols for connecting bridges

**Allison** · 10-01-2011

Hello everyone, I am thinking of building a large LAN instead of connecting multiple LANs via bridges, but I am having a doubt. When a single LAN, a fault in an area, block the entire LAN. When connecting multiple LANs with bridges, the decision on a LAN does not imply fault on the other?! When you have two geographically separate LAN, is easier and cheaper to connect to a bridge that use coaxial cable for example.?! I am posting here, because everytime I have some doubt, you members have tried your best to solve it..

So I am expecting some more help from your side.

**AK_Chopra** · 10-01-2011

The bridge, connecting two LANs with the same MAC protocol does not change the content of the frames, its only function is to capture frames from a LAN and repeat on the other LAN, without modification. Bridges must have a temporary memory to hold the frames to exchange LAN. In addition, the bridges must know the address enough to know what frames go to a LAN and what other goes to another LAN. Bridges must be capable of connecting more than two LANs. From the point of view of each season, all other stations are on the same LAN and the bridge is responsible for routing frames. Other functions that can be bridges are referrals to other bridges, and thus may know the costs to get from one station to another. In addition, temporary bridges may have memories to store frames awaiting shipment when there is saturation in the lines.

**Kamran** · 10-01-2011

The bridges carry out their activity in the medium access layer. Therefore, their only function to route the frame to the destination LAN, without adding any additional information to the MAC frame provided by the issuer. IEEE 802.5 has created a standard in which the originating station and the plot includes routing, and the bridge should only read about whether to forward the plot or not. Its main features are:

Basic operation: the source station must choose routing D4E and include this information in the plot. Thus, the bridge should only keep information about your ID (since the sender must know the path forward for the plot) and on the LAN that connects.
Directives routing and addressing modes: there are 4 commands that can be concealed a frame from the source:
1. Zero: the story can only go to stations in the same LAN.
2. Without diffusion, describes only one possible route, the other can not be used.
3. Dissemination through all routes: the plot is broadcast to all possible routes (you can come back to the destination).
4. Diffusion through a single route: the plot is headed for all possible routes, but the use of spanning tree algorithm, only a frame arrives at the destination.

**Guns-n-Roses** · 10-01-2011

There are three possible ways that a source station and the plot can be routed to the destination:

Information is loaded manually at each station, which is simple but makes possible to automate the routing process and it is difficult to be operated when there are failures in the routing.
One station in each LAN routing information maintained on the outside, and the other stations on that LAN viewing only at this station on its routing information.
Each station must search its routing on your own.

The IEEE standard uses only option 3. Each source station sends a control frame to a destination station so that when it receives the frame, it responds to report on the path he has followed this pattern. In this way, all responses received by the source frame, select the most suitable and stores it in its database for the following frames.

**Zombi** · 10-01-2011

The most important features of a protocol are:

Direct / indirect: the links are direct point to point but the links between two entities in different networks are involved indirect and intermediate elements.
Monolithic / Structure: Monolithic is one in which the issuer has control in a single layer of the entire transfer process. Structured protocols, there are several layers that are coordinated and that divide the task of communication.
Symmetric / asymmetric: the symmetrical are those in which the two entities that communicate are similar in terms to both issuers and consumers of information. A protocol is asymmetrical if an entity has different functions of the other (eg clients and servers).
Standard / non-standard: non-standard are those created specifically for a particular case and will not be necessary to connect with external agents. Currently, many entities intercommunicate to standardization is required.