The Wan Switching Technologies

Published Date: 02 Nov 2017

INTRODUCTION

Wide Area Network is a data communication that covers a large or broad area and telephone lines or radio waves transmit data communication. Switch is a network device that filters and forwards packets between LAN segments. A switched network allows many users to benefit from the same line and therefore making WAN technology to be cheaper than the dedicated lines. Moreover, switched networks gives companies an easy to expand or scalability because remote sites can be connected to the switched network. WAN switching technologies are circuit switching, virtual switching, cell switching, and packet switching. These different methods contribute to the network performance and reliability. In this report, I looked at only three switching technologies which are packet switching, virtual switching and lastly the circuit switching.

ACKNOWLEDGEMENT

I would like to thank my coordinator Mr.Murugesh for explaining to me these project concepts and also extent my gratitude to the institution for providing the school library where I had access to the resources available in it.

PACKET SWITCHING NETWORKS

Packet switching network transport data through the network packet by packet. The data is divided into small size packets and thus making the data delivery efficient and fast the packets are sent out individually. When the packets reach the destination, they are reassembled in an appropriate manner or recompiled into the original message(Black, 2007). Also a packet switching transmit data over a channel which for the duration of the packet’s transmission is dedicated to that packet alone and is not interrupted to transmit other packets. The packet switching technologies protocols are frame relay and asynchronous transfer mode and X.25.

FRAME RELAY

This networking protocol works at the Physical and Data Link Layers of the OSI model specification that provides high performance. It is a successor of the X.25 protocol which was slow in performance due to the main role it played of error checking and Frame Relay discarded some of these functions of error checking to boost performance. It enables end stations to dynamically that has its end nodes connected share network resources and also offer connections between LANs and WANs.

it falls into the following two general categories:

Data terminal equipment (DTEs), which include terminals, personal computers, routers, and bridges

Data circuit-terminating equipment (DCEs), which transmit the data through the network and are often carrier-owned devices (although, increasingly, enterprises are buying their own DCEs and implementing them in their networks)

Frame Relay networks transfer data using one of the following two connection types:

Switched virtual circuits (SVCs), which are temporary connections that are created for each data transfer and then are terminated when the data transfer is complete (not a widely used connection)

Permanent virtual circuits (PVCs), which are permanent connections are actually created between two points on the WAN by configuring devices such as routers (that terminate a LAN that is which are created by the WAN) with a number that is provided by the service provider. This number, the Data Link Connection Identifier (DLCI), designates the PVC that will connect the two LANs via the WAN. Logical addresses such as IP addresses are then mapped to the PVC, providing a path through the for the movement of data between the connected LANs.(Joe, 2003)

ASYNCHRONOUS TRANSFER MODE (ATM)

ATM is based on sending data in packets of a fixed size. The fixed sizes are moderately small and allow ATM equipment to transmit video, audio and computer data over the same network, and guarantee that no single type of data dominates the line. Moreover, it generates a fixed route between the source and the destination whenever data transfers initiate.

X.25

X.25 operates at the Physical, Data Link, and Network layers of the OSI model. To allow large scale of WANs, X.25 uses PSTN and Integrated Service Digital Network. In older environments, X.25 was used with remote terminals which were connected via PSTN modem. It was mainly based on error-checking making connections more reliable since the older telephone lines were prone to error. The subscribers paid for the bandwidth they used depending on how many times they’ve used the telephone line.

VIRTUAL CIRCUITS

Virtual circuits switching technologies provider network provide a connection to the endpoints logically. Identities are assigned to these logical paths not the physical locations. These identities can either be permanent or switched. Virtual circuits can be switched meaning temporarily connected or permanent which means there will be no termination after data transfer is complete.

SWITCHED VIRTUAL CIRCUITS

Switched virtual circuits (SVCs) are temporary connections used in periodic sessions for transferring data between DTE devices across the Frame Relay network. A communication session across an SVC consists of the following four operational states:

CALL SETUP – This is the establishment of the virtual circuit between two Frame Relay DTE devices.

DATA TRANSFER –virtual circuit transfer data between the DTE devices.

IDLE - this is a state where SVCs will be terminated and PVCs excluded and there is no data transfer though the connection between DTE devices is active.

CALL TERMINATION – This is a state where virtual circuit between DTE devices is terminated.

If there is additional data to be switched over after the termination of a virtual circuit the DTE device establish a new switched virtual circuit which will be maintained and terminated using the same signaling procedure used in ISDN.

PERMANENT VIRTUAL CIRCUITS

Permanent virtual circuits (PVCs) are permanently established connections used for regular and constant data transfers between DTE devices across the Frame Relay network. Call setup and termination states which are used with switched virtual circuits are not required for communication across the PVCs. PVCs always operate in one of the following two operational states:

DATA TRANSFER – the transmission of data is done between the DTE devices over the virtual circuit.

IDLE - this is a state where SVCs will be terminated and PVCs excluded and there is no data transfer though the connection between DTE devices is active.

CIRCUIT SWITCHING

Circuit switching is a WAN switching method in which a dedicated physical circuit is established, maintained, and terminated through a carrier network for each communication session (www.NetworkTutorials.info). According to Joe (2003) Circuit switching accommodates two types of transmissions: datagram transmissions and data-stream transmissions. Circuit switching operates much like a normal telephone call in telephone company networks. An example of circuit-switching WAN technology is Integrated Services Digital Network (ISDN) which is more like a phone call setup. Data transfer cannot occur before the establishment of the end-to-end connection. It uses dial-up modems and ISDN and it is also used for low-bandwidth data transfers.

DIGITAL SUBSCRIBER LINE

Offers voice and data communication and can happen simultaneously on the very same phone line. Thus one can send data while receiving a call on the line.

ISDN

Integrated Services Digital Network is a set of digital services that transmit voice and data over existing phone lines.  ISDN can offer a cost-effective solution for remote users who need a higher-speed connection than an analog dial-up link offer.  ISDN is also a good choice as a backup link for other types of links such as Frame Relay or a T-1 connection (Joe, 2003). This service is provided by local phone providers and the charge is determined by how much one uses the line for data transfer.

CONCLUSION

WAN switching technologies play an effective role in a network for data transfer. In these switching technologies data can be transferred via packets or cells depending on the protocols used. These technologies operate at the lowest layers of the OSI model which are the network, data link and physical layers. The successors came along with new features which enhance performance of data transfers. Packet switching and circuit switching technologies used for communication methods are used in large companies.