Traffic shaping

Traffic Shaping is a technique used to control the flow of data in a network to ensure smooth, consistent, and predictable transmission of packets. It is typically applied in the network layer to prevent congestion and to optimize bandwidth usage. The goal of traffic shaping is to smooth out bursts of traffic and ensure that the network resources are used efficiently, preventing packet loss and delays.

Key Points:

• Definition and Purpose:
• Traffic shaping involves delaying packets to ensure that they conform to a defined traffic profile, typically by regulating the data transmission rate.
• The main purpose of traffic shaping is to control data flow, prevent congestion, and ensure fair usage of bandwidth by all users or applications.
• It is commonly used to smooth out bursty traffic, which might otherwise overwhelm the network, especially when the data rate exceeds the available bandwidth.

How Traffic Shaping Works:

• Buffers and Queues: Traffic shaping uses buffers or queues to temporarily store packets that cannot be sent immediately. These packets are released gradually based on the allowed data rate.
• Rate Limiting: Traffic shaping defines a maximum allowable transmission rate, ensuring that data is transmitted at a constant rate over time, preventing sudden traffic bursts.
• Traffic Profiles: The traffic is usually shaped to conform to a profile, which defines how much data can be sent during certain time intervals (e.g., bytes per second).

Techniques Used:

• Token Bucket: The Token Bucket algorithm is often used for traffic shaping. Tokens are added to a "bucket" at a fixed rate, and a packet can only be sent if there is a token available in the bucket. If no tokens are available, the packet is delayed or discarded.
• Leaky Bucket: The Leaky Bucket algorithm ensures that data is sent at a constant rate, and any excess traffic is discarded. It smooths out traffic, preventing bursts.
• Policing and Shaping: Traffic policing drops packets that exceed a set rate, while shaping may buffer and delay packets to conform to the allowed rate.

Example of Traffic Shaping:

• Scenario: Traffic Shaping in a Corporate Network
• Imagine a corporate network that connects employees to the internet and internal servers. The network is shared by multiple departments, and certain applications (like video conferencing and VoIP) require guaranteed bandwidth to function properly without delays or quality degradation.

How Traffic Shaping Works:

• The network administrators set up traffic shaping rules that prioritize VoIP and video traffic because these applications require low latency and high reliability.
• During peak hours, employees may also be downloading large files, which causes bursts of traffic that can cause congestion and affect the quality of real-time communications like VoIP.
• Traffic Shaping Policy: The shaping policy ensures that large file downloads are delayed or throttled. For instance, non-essential file downloads might be limited to a maximum rate of 2 Mbps, while VoIP traffic is allowed a higher priority with 5 Mbps to maintain quality.
• Buffering and Delaying Traffic: The network equipment (e.g., routers or traffic shaping devices) temporarily buffers the excess packets from the file downloads and releases them at a controlled rate to avoid sudden spikes.

Outcome:

• Smooth Data Flow: The network traffic is controlled to prevent congestion, and large file downloads do not overwhelm the network, allowing critical services like VoIP to function smoothly.
• Improved Performance: By smoothing out bursty traffic, traffic shaping ensures that all applications receive the necessary bandwidth and that latency-sensitive services (e.g., video conferencing) remain unaffected.
• Fair Resource Allocation: All departments and users get a fair share of the available bandwidth, ensuring that no single user or service consumes all the resources.