Voice over IP (VoIP), a recent advance in networking technology

Table of Contents

1. Introduction and brief overview of Voice over IP

2. Integration of Voice over IP in current networks of organisations and in the current networking scene

3. The effect of Voice over IP on the current technology used by organisations

4. Critical examination of the benefits of Voice over IP for organisation

5. Conclusion

References

1. Introduction and brief overview of Voice over IP

Voice over IP (VoIP) is at the moment one of the most discussed topics in the current network scene. Besides the theoretical interest in network development, there is always the practical relevance which is of high importance for advances in network technology. One major proof, that VoIP research and its technology has a high impact on businesses is the fact that VoIP it is already implemented in a number of companies in the United States of America, UK, Ireland and South Korea, according to Cherry (2005). The following graphic shows the importance of VoIP for companies according to a recent international study conducted by Network Computing.

illustration not visible in this excerpt

Fig.1: VoIP use and implementation survey

Source: Morrisey (2005), p.36

30% of all participants in the study confirmed a current implementation and usage (chart 1: 30% - VoIP is in production) of VoIP technology. This indicates the high investment activity which is currently happening in the field of VoIP. Regan (2005) for example states that the Department of Defense (DoD) of the United States of America established in the beginning of 2005 an over US$ 20 Mil. contract with Nortel Networks to upgrade the current network of DoD to support VoIP services. The main reasons for implementing VoIP are flexibility, control of communication and cost reduction. (Regan, 2005)

To assess these benefits and to evaluate the risks of VoIP, a sound understanding of VoIP’s functionalities and principles is necessary.

The following report will provide the reader in the first part with an introduction and a brief overview of VoIP. In the second part of the report it is analysed how VoIP can be integrated in the current network scene and environment. Parts three and four of the essay deal with the effect of VoIP on the current technology used by organisations and the benefits resulting from VoIP. Finally in the fifth part of the report a conclusion is given to summarize the findings.

It is not easy to analyse VoIP because there isn’t an industry wide definition for it. Hence, it means different things to different people. For this research paper I will focus on the definition of VoIP as the transmission of voice over a LAN or a WAN network by using the TCP/IP protocol suite. The transmission of voice over the public internet became also very fashionable but for complexity reasons and the reason of focusing the topic on WAN and LAN networks, I will only concentrate only on voice transmission over a WAN or LAN network and not on wireless networks. Concerning protocols, I will concentrate on the TCP/IP protocol suite and the other main standard protocols (H.323 and SIP) which are likely to become industry standards for VoIP.

However, I am a keen user of the various VoIP solutions over the public internet (which I access with a wireless LAN router) and recommend to the reader to try them out (as it is a cheap possibility of experience VoIP). Popular applications for VoIP over the public internet are in particular Skype (www.skype.com), Microsoft Netmeeting and Microsoft Messenger, Yahoo Messenger and the Apple Macinthosh iChat. There are also a number of applications available for using VoIP for UNIX and Linux platforms. (Morrissey, 2005)

The basic functionality of VoIP can be explained in a few sentences. The spoken voice gets digitized and converted into packets. Then it is transported over a network by using the Transmission Control Protocol / Internet Protocol (TCP/IP) protocol suite together with other protocols (mainly the H.323 or SIP umbrella protocols) and the sent data is reprocessed again by the receiver to hear the voice of the other person.

TCP/IP is a protocol family which covers all layers of the OSI reference model. Different layers in the OSI model are responsible for certain functionalities. For instance in the case of IP, higher layers are responsible for the retransmission and the correction of errors. In addition to that it can be said that IP is a connectionless protocol (whereas ATM for example is connection oriented). The implication of a connectionless protocol is the fact that the destination address is included in every IP packet. This means that there isn’t one defined network path for all data grams. There are in most cases different network routes which can be used for data grams to arrive at the receiver. This leads to the coordination problem of these data grams as they may appear in different order at the receiver. I will focus later on the problem of managing network paths for data packages in circuit switched and packet switched networks. The coordination and management of these data grams is realized by other OSI layers.

Nevertheless, a pure IP protocol is no longer used in most VoIP implementations. Other more efficient and secure protocols were developed; also with an improvement of quality of service in mind.

According to Kuhn, Walsh & Fries (2005), the two leading protocol architectures and families which are used for most VoIP implementations are H.323 and SIP. However, according to Wikipedia Encyclopedia’s entry for SIP retrieved on 16 May, 2005, SIP will become the leading standard for VoIP. Experts in the field of VoIP characterise the main benefits of SIP over H.323 in its simpler architecture. (Kuhn, Walsh & Fries, 2005) Due to the fact that H.323 is already used in a high number of VoIP implementations, I will also explain the basic principles of H.323.

H.323 was originally developed for multimedia communication and its standard and architecture is managed by the International Telecommunication Union (ITU). (Mitchell, 2005) It can be seen as a standard including several other protocols, e.g. H.225 and H.245. (Kuhn, Walsh & Fries, 2005)

The main functionalities which are realised by the use of H.323 and the underlying protocols are initializing and ending voice calls as well as forwarding them. (Mitchell, 2005)

The following illustration shows how a voice call is setup with H.323 with an underlying TCP network connection.

[...]