Internet Congestion

The increase of the internet and intranet usage has introduced complications and hindrance of normal performance. The increase in the data sent to networks has resulted in congestion. The worldwide network of computer networks known as the Internet handles an enormous amount of traffic every day. At any given moment thousands of users are sending messages or browsing millions of pages of the World Wide Web. The current Internet features traffic from diverse applications; ranging from delay-sensitive web...

Congestion has become such a problem that some sites provide daily Internet "weather reports, " detailing average delays in reaching sites at different times in various parts of the world.

Groups monitoring Internet traffic have observed spikes of extremely high activity--or data storms--that appear quickly, then subside. A congestion spike may result from a specific event, such as the landing of a spacecraft or from network failures. At other times, however, a spike appears to have no discernible cause.

Many people suggest that intermittent congestion spikes punctuating routine traffic are inevitable because the Internet is essentially a public resource whose users are generally not charged fees according to the amount of data exchanged.

In the mathematical model it is observed that the usefulness of the Internet is proportional to the speed with which users can access information at remote sites. At the same time, because they usually do not pay costs linked to consumption, users don't differentiate between activities that require the transfer of large amounts of information, such as downloading graphic files and browsing Web sites, and those that require much less, such as electronic mail, or E-mail.

Typically, users who experience congestion tend to believe that others do so as well and expect that if they try again later, the network is likely to be less congested. The current Internet features traffic from diverse applications; ranging from delay-sensitive web... The frame relay and TCP/IP each have their own congestion and flow control mechanisms. Frame relay provides a cost effective way of transporting a variety of encapsulated...

There are many ways to classify congestion control algorithms:

• By the type and amount of feedback received from the network: Loss; delay; single-bit or multi-bit explicit signals


• By incremental deployability on the current Internet: Only sender needs modification; sender and receiver need modification; only router needs modification; sender, receiver and routers need modification.


• By the aspect of performance it aims to improve: high bandwidth-delay product networks; lossy links; fairness; advantage to short flows; variable-rate links


• By the fairness criterion it uses: max-min, proportional, "minimum potential delay"

Recommendations on Queue Management and Congestion Avoidance in the Internet states that:

• Fewer packets will be dropped with Active Queue Management (AQM).


• The link utilization will increase because less TCP global synchronization will occur.


• By keeping the average queue size small, queue management will reduce the delays and jitter seen by flows.

congestion avoidance can also efficiently be achieved by reducing the amount of traffic flowing into your network. When an application requests a large file, graphic or web page, it usually advertises a "window" of between 32K and 64K. This results in the server sending a full window of data. When you have many applications simultaneously requesting downloads, this data creates a congestion point at your upstream provider by flooding the queue much faster than it can be emptied. By using a device to reduce the window advertisement, the remote servers will send less data, thus reducing the congestion and allowing traffic to flow more freely. This technique can reduce congestion in a network by a factor of 40.

Groups monitoring Internet traffic have observed spikes of extremely high activity--or data storms--that appear quickly, then subside. A congestion spike may result from a specific event, such as the landing of a spacecraft or from network failures. At other times, however, a spike appears to have no discernible cause.

Many people suggest that intermittent congestion spikes punctuating routine traffic are inevitable because the Internet is essentially a public resource whose users are generally not charged fees according to the amount of data exchanged.

In the mathematical model it is observed that the usefulness of the Internet is proportional to the speed with which users can access information at remote sites. At the same time, because they usually do not pay costs linked to consumption, users don't differentiate between activities that require the transfer of large amounts of information, such as downloading graphic files and browsing Web sites, and those that require much less, such as electronic mail, or E-mail.

To avoid congestion, users ought to be charged in proportion to the amount of data transmitted. Such charges would make people more directly aware of their role in overtaxing the capacity of the Internet.

Pricing schemes are a wise and sound approach. Various network pricing schemes are now being tested.

ALTERNATE TECHNIQUES

Backpressure: A flow-control technique that avoids frame loss by impeding external traffic from sending frames to congested interfaces.

Full duplex: A transmission method that lets two network devices transmit and receive concurrently, effectively doubling the bandwidth of a half-duplex link, in which data flows one way at a time.

GBIC (gigabit interface converter): A type of hot-swappable, standards-based transceiver used with switches. It converts electrical signals to optical signals and vice versa, and it is usually used for connections on or to the backbone.

GVRP (Generic VLAN Registration Protocol): A specification defining parameters that switches use to exchange information for registering VLANs on a Spanning-Tree network and to facilitate direct communication.

IEEE 802.1p :A standard that provides quality of service (QoS) in Ethernet networks. It relies on packet tags and allows switches to transmit packets in order of priority.

IEEE 802.1q :A standard that defines Ethernet frame tags that carry VLAN identifiers.

IEEE 802.3ab: A standard that defines Carrier Sense Multiple Access/Collision Detect (CSMA/CD) methods and physical-layer specifications for 1, 000Base-T.

IEEE 802.3x :A standard that defines Ethernet frame start and stop requests and timers on full-duplex links.

Port mirroring: A transmission method in which frames transmitted and received on one port can be duplicated on another port for diagnostic purposes.

Port trunking :A link aggregation technique that creates a single, high-speed logical link from several lower-speed physical links.

RMON (remote-monitoring): A monitoring methodology for measuring traffic flow and setting alarms for error conditions. It doesn't require polling (as SNMP does).

SFP (Small Form Factor Pluggable): A specification for high-speed (up to 5-Gbps) electro-optical transceivers.

Sniffer: A software program that monitors and analyzes network traffic, allowing administrators to detect performance bottlenecks and transmission errors.

SNMP (Simple Network Management Protocol): A specification that governs network device monitoring and management.

Spanning Tree Protocol: A specification that lets network bridges exchange information while only one of them controls traffic between computers on a network.

TFTP (Trivial File Transfer Protocol): A simple TCP/IP file transmission specification with no authentication mechanism. It is often used for software downloads.

VLAN (virtual local area network): A logical grouping of network nodes, regardless of their physical locations

Lecturer, Dept of Informatics
Alluri Institute of management sciences, warangal.

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