IEEE802.3/Ethernet was accepted in 1985 for standardizing by the LAN IEEE (Institute of Electrical and Electronics Engineers) committee and appeared under the title “IEEE 802.3 Carrier Sense Multiple Access with Collision Detection (CSMA/CD) Access Method and Physical Layer Specifications” (Freer 1996). This standard sets common rules of data transfer in local networks. IEEE 802.3 is a collection of “IEEE standards defining the Physical Layer and Data Link Layer’s media access control (MAC) sublayer of wired Ethernet. This is generally a LAN technology with some WAN applications. Physical connections are made between nodes and/or infrastructure devices (hubs, switches, routers) by various types of copper or fiber cable” (Freer 1996). Actually, Ethernet is a modification of IEEE 802.3 and it gains more popularity due to its cheap installation and easy support. Hubs and switches exist today in different forms and don’t cost a lot. IEEE 802.3 based network can be built with the help of either hubs or switches. It depends only on the wish of the network administrator. But there are some differences in the behavior of hubs and switches in the network of such kind.
Layer 2 switches or L2 switches are switches that work with the second Data Link Level of the OSI model. They transfer data and frames between nodes on the local network segments, and in some cases correct the errors that may have occurred on the Physical Level of the OSI model. They are ruled by Ethernet, and PPP protocols and work with dual node connections. Layer 2 is divided into two sublevels, but here we care about MAC-sublevel. Network Bridge that operates at this sublevel can interconnect between a small number of computers. “Classic bridges may also interconnect using a spanning tree protocol that disables links so that the resulting local area network is a tree without loops. In contrast to repeaters, spanning tree bridges must have topologies with only one active path between two points” (Osterlon 2001). “Once a bridge learns the topology through a spanning tree protocol, it forwards data link layer frames using a layer 2 forwarding method” (Froehlich 1994). There’s better organization of sending frames through switches. For example, broadcasting frames are redirected to all segments connected to the switch, except the segment from which the broadcasting frame was received. Also, the switch doesn’t transfer the state of collision which allows to segment collision in the domain. If a frame is to be sent through a port that is occupied at the moment, then switch spools this frame in its memory and send when the port is free. This was achieved due to the interconnection of the switch and MAC sublevel of the Data Link Level. Switch finds the certain addressee in its table of MAC addresses and frames are sent only to the receiver. If the receiver’s port is occupied, the frame will be stored in special network storage, while in hubs they would be lost.
The network concentrator or hub is a multiport repeater. Bit impulses arrive on the port of a hub, hub restores and transfers to all other ports. Also, the hub transfers a collision condition to all ports. Physical segments united by means of hubs and repeaters are called the divided environments of data transmission. Network constructed only on hubs and repeaters is one big domain of collisions with its own disadvantages. (Stallings 2008). Modern IEEE 802.3/Ethernet networks are constructed mainly on switchboards.
The main difference between networks based on switches without using hubs is the absence of collisions and the opportunity of full-duplex work. In IEEE 802.3/Ethernet networks which use twisted-pair wires as a transmission medium, passing data and received data go through different pairs. In IEEE 802.3/Ethernet networks using fiber optic as a transmission medium, passing data and received data go through different fibers. Network, where each computer is connected to a separate switch port, avoids collisions and provides the possibility of simultaneous passing and receiving of data (full-duplex work). In this case, data transfer between 2 PCs through the switched network can be regarded as a creation of a virtual connection of the Peer-to-Peer type, which is called micro-segmentation.
But hubs or IEEE 802.3/Ethernet repeaters have one good advantage. As switch networks can be interconnected within a rather small territory, allowing access to the network only to a small number of computers and it needs a special type of topology, hubs provide a bigger area for the network. Being connected via twisted pair cables or coaxial cable they allow covering bigger territory connecting a greater number of computers.
The main difference between using switches and hubs in the IEEE802.3 network is the speed allowed to connect PCs and users. For example, in a network constructed in hubs where network capacity equals 100 Mbps and one of the connected users has a client adapter that allows only 10 Mbps, then network speed will be equal to 10 Mbps. and if the same network is constructed in switch, network capacity will be 100 Mbps. Hub transfers frames to the target user, and other computers do not see them. This is very useful for hackers as it is much easier to track the way of the frame and then send some virus software program. Though, switch broadcasts frames. That’s why networks constructed with the help of switches are safer and provide faster internet access.
From the given information it is clear that a network based on switches works faster and allows no collisions, provides faster internet access for users and makes the network safer from hackers and other abusers.
References
Freer, John R. (1996). Computer Communications and Networks. London: Pitman Publishing.
Froehlich, Fritz E. (1994). Encyclopedia of Telecommunications. New York, NY: Marcel Dekker.
Osterlon, H. (2001). IP Routing Primer Plus. USA: Sans Publishing.
Stallings, W. (2008). Data and Computer Communications. Upper Saddle River: Prentice-Hall.