x Software Networks
transmitter to a receiver, the data for transmission are grouped
together in one or more packets, depending on the total size of the
message. For a short message, a single packet may be sufficient;
however, for a long message, several packets are needed. The packets
then pass through intermediary transfer nodes between the transmitter
and the receiver, and ultimately make their way to the end-point. The
resources needed to handle the packets include memories, links
between the nodes and sender/receiver. These resources are shared
between all users. Packet-switched mode requires a physical
architecture and protocols – i.e. rules – to achieve end-to-end
communication. Many different architectural arrangements have been
proposed, using protocol layers and associated algorithms. In the early
days, each hardware manufacturer had their own architecture (e.g.
SNA, DNA, DecNet, etc.). Then, the OSI model (Open System
Interconnection) was introduced in an attempt to make all these
different architectures mutually compatible. The failure of
compatibility between hardware manufacturers, even with a common
model, led to the re-adoption of one of the very first architectures
introduced for packet-switched mode: TCP/IP (Transport Control
Protocol/Internet Protocol).
The second revolution was the switch from hardwired mode to
wireless mode. Figure I.1 shows that, by 2020, terminal connection
should be essentially wireless, established using Wi-Fi technology,
including 3G/4G/5G technology. In fact, increasingly, the two
techniques are used together, as they are becoming mutually
complimentary rather than representing competition for one another.
In addition, when we look at the curve shown in Figure I.2, plotting
worldwide user demand against the growth of what 3G/4G/5G
technology is capable of delivering, we see that the gap is so
significant that only Wi-Fi technology is capable of handling the
demand. We shall come back to wireless architectures, because the
third revolution also has a significant impact on this transition toward
radio-based technologies.
www.it-ebooks.info
transmitter to a receiver, the data for transmission are grouped
together in one or more packets, depending on the total size of the
message. For a short message, a single packet may be sufficient;
however, for a long message, several packets are needed. The packets
then pass through intermediary transfer nodes between the transmitter
and the receiver, and ultimately make their way to the end-point. The
resources needed to handle the packets include memories, links
between the nodes and sender/receiver. These resources are shared
between all users. Packet-switched mode requires a physical
architecture and protocols – i.e. rules – to achieve end-to-end
communication. Many different architectural arrangements have been
proposed, using protocol layers and associated algorithms. In the early
days, each hardware manufacturer had their own architecture (e.g.
SNA, DNA, DecNet, etc.). Then, the OSI model (Open System
Interconnection) was introduced in an attempt to make all these
different architectures mutually compatible. The failure of
compatibility between hardware manufacturers, even with a common
model, led to the re-adoption of one of the very first architectures
introduced for packet-switched mode: TCP/IP (Transport Control
Protocol/Internet Protocol).
The second revolution was the switch from hardwired mode to
wireless mode. Figure I.1 shows that, by 2020, terminal connection
should be essentially wireless, established using Wi-Fi technology,
including 3G/4G/5G technology. In fact, increasingly, the two
techniques are used together, as they are becoming mutually
complimentary rather than representing competition for one another.
In addition, when we look at the curve shown in Figure I.2, plotting
worldwide user demand against the growth of what 3G/4G/5G
technology is capable of delivering, we see that the gap is so
significant that only Wi-Fi technology is capable of handling the
demand. We shall come back to wireless architectures, because the
third revolution also has a significant impact on this transition toward
radio-based technologies.
www.it-ebooks.info