Wednesday, October 12, 2011

Networks and Network Connections

As the Internet evolves, we can see specialization increasing in the portions of the systems providing communications support. In the mainframe era of the 1960s, communications were directly supported by the systems. This changed in the 1970s, as needs grew, and led manufacturers to produce semi-autonomous communications subsystems coupled to the main system. These were known as front-end processors, and examples include IBM’s 37xx series and Bull’s Datanet.

This trend increased with the rise of local area networks, with the emergence of a new generation of network equipment—routers, concentrators and so forth—that off-load a number of chores from the servers.

Nowadays, we do not expect a server to directly support a variety of communications interfaces, but rather to provide a number of high-bandwidth pipes that carry requests for it to operate on the data it owns.

We expect this trend to continue, especially with convergence resulting in the same network carrying voice (and video) along with data, from the point of view of provisioning sufficient physical resources as well as from the IP point of view. Forecasts suggest a continuing significant increase in data traffic, with voice traffic stagnating; thus, the effects of this convergence will likely be felt more in the telephony industry (makers of automatic telephone exchanges and switches) than in the data-processing industry.

Increased use of multimedia will impose further demands on servers, because of the need to observe and guarantee temporal properties. This might suggest deployment of specialized realtime operating systems as well as use of special peripherals, such as disks optimized for this type of use. The industry has at its disposal a number of technologies, particularly optical, which will allow it to support demand; increasing bandwidth; reducing latency; the address space increase offered by IPv6; the concept of quality of service, and so on.

A key issue, though, is driving new uses that will themselves make use of the possibilities available and allow these technologies to be deployed.

Cisco, the world leader in networking equipment, envisages the emergence of the intelligent network, whose components are:

» Interconnection with proprietary networks like SNA, DSA or others;

» Broadcast or multicast facilities, allowing one message to be sent to many destinations

» Video services (both video conferencing and video-on-demand)

» Cache services

» Administration

» Voice-related services

» QoS (quality of service)-related services

» Security services

Looking at these a little deeper:

» Interworking with proprietary networks is a necessity while these networks exist

» Some applications would benefit from a multicast capability—one message with multiple recipients (examples of such applications include videoconferencing, updating workstation software, Internet “push” technologies, information replication, and more)

» Expect videoconferencing to grow, since it can reduce travel and thus reduce costs and the polluting side-effects of vehicle usage; however, it is a new form of interaction, and there will need to be a learning curve as individuals adapt to it (video on demand, except for specialty niches such as within hotels, should grow at a much lower rate)

» Caching data in the network improves access to information

» It is difficult to overemphasize the requirements for good administration and security in networks

» The concept of QoS appeared a few years ago, and still needs time to develop fully. It is a fundamental parameter for the usability of a system. In use, the quality—in terms of bandwidth, or latency, for example—of a connection is negotiated, and then the network guarantees that level while the connection is open

When a number of disks are assembled within a single enclosure, but without any special organization (such as RAID) being implemented, the collection is known as JBOD (Just a Bunch of Disks).

Source of Information : Elsevier Server Architectures 2005
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