2.5.1 Traffic Conditioning Functions

Before a packet enters a high-speed core, it passes through a traffic conditioner which performs four main tasks:

1. Classification: Identifying the packet type based on Port, IP, or Protocol.
2. Metering: Measuring the current flow rate.
3. Marking: Setting the priority bits (DSCP/CoS).
4. Shaping/Dropping: Ensuring the flow stays within the SLA (Service Level Agreement).

2.5.2 Effective Bandwidth

In high-speed networks, we often calculate the Effective Bandwidth. It is a value between the average rate and the peak rate.

• If an app sends 1 Mbps average but 10 Mbps burst, the effective bandwidth might be 4 Mbps.
• If you reserve 10 Mbps, you waste space. If you reserve 1 Mbps, you lose data. Effective bandwidth calculation minimizes this trade-off.

2.5.3 The Impact of TCP Window Size on Throughput

Throughput of a TCP connection is limited by both the link speed and the Receive Window.

• Throughput <= WindowSize / RTT
• Example: If a window is 64KB and RTT is 100ms, max throughput is only 5.2 Mbps, even on 10 Gbps fiber! This is why "Window Scaling" is required for high-speed networks.

2.5.4 RED (Random Early Detection)

Instead of waiting for the buffer to be 100% full (Tail Drop), RED starts dropping packets randomly when the buffer is 50-80% full.

• Goal: This "signals" some TCP senders to slow down early, preventing global synchronization where all senders stop and start at the same time.

2.5.5 Fairness in Traffic Management

• Max-Min Fairness: No flow gets more than it requests, and all flows that are bottlenecked at the same point get an equal share of the leftover bandwidth.
• Weighted Fair Queuing (WFQ): Shares bandwidth based on a "weight" (e.g., Platinum users get 3x more than Bronze users).