About Computer Network Bridges (ACNB)


ACNB:   SOLD       



Substance:

  1. UNDERSTANDING
  2. BACKGROUND
  3. FUNCTION AND HOW BRIDGE WORKS
  4. TYPES OF NETWORK BRIDGE
  5. BRIDGE CHARACTERISTICS
  6. BRIDGE ADVANTAGES
  7. WEAKNESSES IN BRIDGE


Computer Network Bridge

1. Definition

Bridge is a network device used to break up a large network. Bridge works at the data-link layer of the OSI model. Bridge works by recognizing the MAC address of the originator that transmits data to the network and automatically builds an internal table. This table serves to determine which segment the packet will be routed to and provides filtering capabilities.

2. Background

Many organizations/companies have more than one LAN and want to connect their LANs. LANs can be connected with a device called Bridge, which operates in the data link layer. This statement means that Bridge does not examine the network layer header and can then copy IP, IPX and OSI packets equally well, in contrast to pure IP and IPX or OSI routers can only handle packets originating from themselves.

There are six reasons why an organization/company uses several LANs, namely:

  1. Many departments in a university or company have their own LAN. This is mainly intended to connect their own personal computers, workstations and servers. Since the objectives of the various departments are different, different departments will choose different LANs, regardless of the LANs chosen by other departments. Sooner or later there will be a need to interact, therefore a Bridge is needed. In this example, several LANs are formed due to the autonomy of each owner.
  2. An organization may be geographically spread across several buildings that are quite far apart. It may be cheaper to have a separate LAN in each building and connect them with bridges and infrared links than to run coaxial cable connecting all the LAN locations.    
  3. It may be necessary to split what is logically a single LAN into separate LANs to accommodate the load. For example, many universities have thousands of workstations for use by students and faculty. Typically, files reside on a file server, and are downloaded to the user's machine on request. The sheer size of these systems precludes storing all the workstations on a single LAN, and the total bandwidth required is too large. Therefore, multiple LANs are used, connected by bridges. Each LAN contains a cluster of workstations that have their own file servers, so that most traffic is confined to a single LAN and does not add to the backbone.
  4. In some situations a single LAN will be sufficient in terms of its load, but the physical distance between the two farthest machines is too great. Even if the cabling is easy enough, the network will not work because of the large round-trip delays. The only solution is to segment the LAN and install bridges between the segments. By using bridges, the total physical distance covered will be increased.
  5. There are reliability issues. On a single LAN, a failed node that keeps sending out a continuous stream of garbage will bring the LAN to a standstill. Bridges can be inserted at critical locations, such as emergency exits in buildings, to prevent a single, uncontrollable node from bringing the entire system to a standstill. Unlike a repeater, which simply copies everything it sees, a bridge can be programmed to train some policies about what to pass on and what not to pass on.
  6. Bridges can contribute to an organization's security. Most LAN interfaces have a nondiscriminatory mode, in which all frames are forwarded to a computer, not just those addressed to that computer. Spies and other nosy people love this feature. By inserting bridges in several places and being careful not to forward specific traffic, it is possible to isolate parts of the network so that traffic does not get lost and fall into the wrong hands.

3. Function & How Bridge Works

Bridge, also known as layer 2 switch, from its definition bridge is a hardware device used to create a connection between two separate computer networks or to divide one network into two. Both computer networks usually use the same protocol; Ethernet is an example of this protocol.

The function of this Bridge is not limited to Personal Computers (PC), printers, routers, switches and hubs. Devices connected to the network via an Ethernet adapter card have what is known as a Media Access Control (MAC) address, also called the physical address of the hardware. This is what uniquely identifies the device to the address that can then determine which network the device is connected to.

The primary function of a Bridge is to forward data based on the MAC addresses of the sending and receiving devices. This operation helps to eliminate what is known as a collision domain. One way to define a collision domain is a network in which one device, also called a node, forces all other devices to accept while it is sending a data packet. Another definition states that a collision domain occurs when two or more devices attempt to transmit information at exactly the same time. A network running Carrier Sense Multiple Access/Collision Detection (CSMA/CD) should, in theory, be protected from collisions occurring, but CSMA/CD can fail.

Every time a collision occurs, efficient data packet transmission is greatly compromised. The more devices on a network trying to transmit data, the greater the chance of a collision occurring. A Bridge Function can be used to segment one network into two, thereby reducing the number of devices competing for transmission rights. For example, if network A has 20 devices, it is likely that two or more of them will try to transmit data at the same time and cause a collision. If a Network Bridge is added, it can split network A into networks A and B with 10 devices each.

Once the Network Bridge is inserted, it will begin to "set up" data transmission in devices on the two networks. The Network Bridge accomplishes this by recording the MAC addresses of the devices in a table that is automatically generated without being programmed to do so. When the first device transmits data, the Network Bridge will add the MAC address as a forwarding table for future reference. The Network Bridge also looks at the MAC address of the destination or receiving device. If it does not appear in the table, the Network Bridge will broadcast the data packet to all devices on both networks to find the destination.

The forwarding table is built directly, Network Bridge does not have to wait until it receives a transmission from a device before it can learn the MAC address. The MAC address of the receiving device must also learn the channel, search for the destination location. Once the destination responds, its address is also added to the forwarding table of Network Bridge. Finally, all MAC addresses will be captured and the packet data will be efficiently routed directly to the destination. This will happen without all devices having to queue for the transmission process.

4. Types of Network Bridges

  • Local Bridge : a bridge that can connect local network segments. It is a bridge that connects one cable media to another cable media, examples of its use can be seen in hubs, switches, or modems.
  • Remote Bridge : can be used to create a connection (link) between LANs to create a Wide Area Network.
  • Wireless Bridge : a bridge that can combine wired LAN networks and wireless LAN networks or several media whose connections are wireless media. Its application can be seen in the Access Point function for Hostpot implementation.

5. Bridge Characteristics

  • Bridges can control broadcasts on networks connected through them.
  • Like the switch function, Bridge can also learn the received frame packets and the destination MAC address to perform data/packet transmission.
  • Bridges can help make large network segments smaller so they are easier to monitor.
  • Bridges can also perform routing.

6. Benefits of Using Bridge

  • Moving data across intermediate networks with different protocols.
  • Can reduce collisions or crashes when sending packets in the network.
  • Allows connection to different types of networks.
  • Can expand network capacity and reduce the risk of traffic congestion.

7. Disadvantages of Using Bridge

  • Bridge cannot block broadcast packets
  • Adds delay to the network.
  • If the received address is not recognized by the bridge, then the message can be broadcast to other network segments and this can result in a broadcast storm which can cause the entire network to crash.
  • Even though they can have different collision domains, bridge equipment only has one broadcat domain.
  • Bridging techniques can consume a lot of bandwidth.

Netizens

Q1:

  1. YUDHAARGA GROUP 14 Oct 2015, 21:31:00 = the post is very useful, bro, don't forget to visit the Computer Network Devices and Their Functions portfolio of Arga Yudha Adhiprama, thank you
  2. EKA ISWARA Jul 29 2016, 11:14:00 = great blog, complete bro, permission to bookmark
  3. CAO YUNCHANG Nov 2 2016, 09:09:00 = IH IH THANK YOU LA YE.....,CAM TU RUPENYE PAK CIK BARU KNOW... THANK YOU LA YA SON YE......! 🙂🙁

A1:

  1. Hello YUDHAARGA GROUP, ready with pleasure, thanks
  2. Yup, please go ahead Eka, it's also okay to follow our social media 😃
  3. Yoa, CAO YUNCHANG, you are welcome

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