Page 33 - CITS - Computer Software Application -TT

COMPUTER SOFTWARE APPLICATION - CITS

• At the sending end, TCP divides the whole message into smaller units known as segment, and each segment
contains a sequence number which is required for reordering the frames to form an original message.

• At the receiving end, TCP collects all the segments and reorders them based on sequence numbers
Congestion Control
Congestion control in computer networks is a set of techniques and strategies used to manage and relieve
network congestion, ensuring that the network operates efficiently and effectively even during periods of high
traffic.
Congestion can happen when the demand for network resources, such as bandwidth and processing capacity,
exceeds the available supply, leading to degraded performance, increased latency, and packet loss.
Here are some key aspects of congestion control in network environment.
1 Traffic Policing and Shaping
• Traffic Policing- Network devices, such as routers and switches, can enforce traffic limits by discarding or
marking packets that exceed specified rate limits. This prevents excessive traffic from entering the network.
• Traffic Shaping Rather than discarding excessive traffic, traffic shaping smooths out traffic bursts by buffering
and releasing packets at a controlled rate. This helps in avoiding sudden spikes in network congestion.
2 Quality of Service (QoS)
• QoS mechanisms prioritize certain types of traffic over others based on predefined rules. This ensures that
critical or real-time traffic (e.g., VoIP, video conferencing) receives better treatment than less time-sensitive
traffic.
3 Window-Based Congestion Control (TCP)

• In the Transmission Control Protocol (TCP), which is widely used for reliable data transmission, window-
based congestion control mechanisms adjust the rate at which a sender transmits data based on feedback
from the network.

• TCP uses techniques like the Slow Start, Congestion Avoidance, and Fast Recovery algorithms to
dynamically adapt the sender’s transmission rate to the network’s congestion level.
4 Explicit Congestion Notification (ECN):

• ECN allows routers to mark packets as they pass through congested areas of the network. The sender
receives this feedback and can adjust its transmission rate accordingly, avoiding further congestion.
5 Random Early Detection (RED) and Active Queue Management (AQM):

• RED is a queue management algorithm that helps routers manage congestion by dropping or marking
packets when the queue length exceeds a certain threshold. This encourages sources to reduce their
sending rates.
• AQM extends RED by actively managing the queue length to maintain an optimal balance between low
latency and high throughput.

6 Load Balancing:
• Distributing incoming network traffic across multiple paths or resources helps prevent any single point of
congestion. Load balancers ensure that no individual component becomes overwhelmed.
7 Multipath Routing

• Using multiple paths for data transmission can help avoid congestion on a single path. Multipath routing
algorithms dynamically select paths based on current network conditions.
8 Congestion-Aware Routing:

• Some routing algorithms take congestion into account when selecting paths for data transmission. They
avoid routes with high congestion and prefer paths with lower traffic loads.

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CITS : IT&ITES - Computer Software Application - Lesson 01-17