Network Switching & Routing

Switching & Routing

The purpose of this paper is to provide a better understanding of switching and routing used in a network environment and familiarize the reader with various hardware and software associated with there functions. This paper will look at some switching concepts that will include store and forward switching, cut through switching, fragment free switching, and V-Lan. This paper will also cover routing concepts, along with some comparisons including routed vs. routing protocols, Classful vs. classless protocols, and distance vector vs. link state protocols.

Switching

The definition of a switch or network switch is a small device that joins multiple computers together, working on layer two of the OSI, to form a local area network or LAN. Network switches are also known as smart hubs. Rather than simply dispersing the data evenly across a network the switch actually inspects the data packets for destination information, and then forwards the data to a specific location. By forwarding the data to its intended location bandwidth on the network is better controlled (Mitchell, 1999).

Store-and-Forward switching refers to a switching method that, after inspection, stores data packets for delivery. The data is received from the sender and passes a cyclic redundancy check along with a check to be sure it fits the required size limitations. After inspection and the check for errors the data is stored or held in physical storage until network availability allows the data to be sent to its destination (Cisco Systems, 2008).

Cut-through switching is a method of switching which uses only the destination information to switch data packets to a specific destination or destination segment. Although previous store-and-forward switches that examine the whole packet took longer to process the data than did the cut-through switching method with today’s technology the difference in speed has become minimal (Lantronix).

There are hybrid switches available today that combine both store-and-forward and cut-through switching methods. These hybrids are known as runtless or fragment-free switches. Fragment-free switches were designed to solve the late-collision problem and are primarily used in the backbone of congested networks. These hybrids check both the source and destination MAC address of a packet then make the appropriate switching to send the packet to its corresponding destination (Javvin Technologies,Inc., 2008).

VLANs

VLANs or Virtual Local Area Networks are logical local area networks that extend beyond the traditional LAN architecture. Because a VLAN is a logical entity, creating and configuring a VLAN is done completely in software. The advantages to using this type of LAN include but are not limited to the ability to conserve the network resources, to bridge geographical drawbacks, and to better manage the movement of personnel and equipment. To understand the need for VLANs you must first understand the Local Area Network (LAN). The definition of a LAN started as a group of computers that were connected in the same area, but today’s LAN is defined as a single broadcast domain. This is explained easily by looking at a large organization where each department would be on a separate LAN found behind a router or switch. With today’s expanding networks it has become important for these groups to cover a more defined grouping of people who need access to specific information without being limited to a geographical location. This is accomplished thru the use of a VLAN. Although a user can be in one physical location or LAN, by use of VLAN technology that user can now be connected to their department or group without further congesting the physical LAN. This in turn eliminates geographical limitations found in earlier network topology. Data from a workstation in a VLAN is tagged with a VLAN identifier. This tagging is called explicit tagging. Tagging of this type will ensure that the data sent is only distributed to the specific VLAN it is intended for thus limiting network traffic and data collisions. There are various types of VLAN membership including classification be MAC address, protocol type or port. Advantages to using VLANs include better network performance, simplified administration, reduced equipment costs and added security (Varadarajan, 2006).

Routing

The process of moving data packets through a network is the definition of routing. This is accomplished by the use of a router, which like a switch filters network traffic. The downside of this type of device is the latency or the delay the data packets experience. Routers unlike bridges work at layer 3 or the network layer of the OSI.

Routed vs. Routing Protocols

When looking at Routed verses Routing Protocols, a routed protocol can be routed by a router then forwarded to other routers. A routed protocol contains data elements required for a packet to be sent outside the host network or routed. The protocols used when a router communicates to another router are called Interior Gateway Protocols (IGP).Examples of these protocols are RIP and IGRP. These are considered routing protocols, but nor routed protocols. Examples of routed protocols are IP, Apple Talk, and IPX. Routed protocols are also known as layer 3 or Network Layer protocols.

Classful vs. Classless

The major difference in Classful and Classless protocols is