Understanding Networking Protocols
Not only can IP packets simply fail to arrive at
their destination on occasion, but sometimes they arrive out of sequence due to
other Internet traffic and other reasons. This is fine for transmitting things such
as files, because the packets can be reassembled on the other end in the proper
sequence once they are all received. For a real-time application such as voice,
however, having packets arrive out of sequence results in a hopelessly jumbled,
and thus useless, transmission.
QoS not widely implemented
Real-time uses of the Internet, such as VoIP
or multimedia streaming and time-sensitive transmissions, should be given
priority over transmissions that are not particularly time-sensitive, such as
the transmission of an e-mail message. Fortunately, IP has a quality of service
(QoS) field that enables the user to prioritize traffic for such reasons. However,
QoS is not widely implemented in all parts of the Internet.
VoIP is a hot, emerging technology that is virtually certain to become an important
part of the Internet and most companies' networks. However, there is still much work
to be done toward actually implementing this technology widely and solving the
problems outlined in this section. In other words, if you're learning about networking,
you should be aware of VoIP--what it is and what it does--although the technology is
still relatively early on the adoption curve.
There are a number of companies offering VoIP services for residential customers, including
AT&T, Vonage, Verizon, and Time Warner Cable. These companies provide packages that allow
virtually unlimited calling over an existing high-bandwidth Internet connection for as little as $30
additional per month. They often package the necessary VoIP hardware with a subscription agreement.
Comparing Important Proprietary Protocols
While Microsoft-based, Novell-based, and Apple-based networks can work with
TCP/IP and all the previously discussed protocols, each type of network got its start
supporting proprietary protocols unique to the company, and each of these protocols
can still be found in current networks. All these companies have embraced TCP/IP and
support it fully, both for servers and for network clients.
Microsoft and Novell networks (as of Windows NT 4 and Novell NetWare 5) can
be easily deployed using only TCP/IP. In theory, you could do the same thing with
an Apple-based network, but you would lose a good deal of the Macintosh's network
functionality if you did so. Because of this, an Apple-based network should support
both AppleTalk (Apple's proprietary protocol) and TCP/IP.
Novell networks originally used the Internetwork Packet Exchange/Sequenced
Packet Exchange (IPX/SPX) protocols. These are not the same as TCP/IP, but they are
comparable. IPX is analogous to IP, and SPX is analogous to TCP.