NE_YuR/network/tcpquiclab/README_LINUX.md

Computer Network Experiment: TCP vs QUIC (Linux Guide)

This guide adapts the Windows-based experiment manual for a Linux environment.

1. Prerequisites

Ensure you have the following installed:

• gcc (Compiler)
• quiche library (Headers and Shared Object installed)
• openssl (For certificates)
• tcpdump or wireshark (For packet capture)
• iproute2 (For tc traffic control)

2. Compilation

Compile all programs using the provided Makefile:

make

This will generate:

• tcp_server, tcp_client (Task 1)
• quic_server, quic_client (Task 2)
• tcp_perf_server, tcp_perf_client (Task 3 Performance)
• quic_perf_server, quic_perf_client (Task 3 Performance)

Note: If quiche is not in the standard system path, edit the Makefile to point to the include/lib directories.

3. Task 1: Basic TCP Client-Server

1. Start the Server:

   ./tcp_server
   

2. Run the Client (in a new terminal):

   ./tcp_client
   

   Expected Output: The client sends "Hello...", server receives it and replies.

4. Task 2: Basic QUIC Client-Server

1. Start the Server:

   ./quic_server
   

2. Run the Client (in a new terminal):

   ./quic_client
   

   Expected Output: QUIC handshake completes, client sends data on a stream, server echoes it back.

5. Task 3: Performance Analysis

3.1 Connection Establishment Time

1. Start capture on loopback:

   sudo tcpdump -i lo -w handshake.pcap
   

   (Or use Wireshark on the lo interface)

2. Run the TCP or QUIC client/server pairs again.

3. Open handshake.pcap in Wireshark to analyze the time difference between the first packet (SYN for TCP, Initial for QUIC) and the completion of the handshake.

3.2 Throughput Test (100MB Transfer)

Baseline (Normal Network):

1. Run TCP Perf Server: ./tcp_perf_server
2. Run TCP Perf Client: ./tcp_perf_client
3. Record the MB/s output.
4. Repeat for QUIC (./quic_perf_server, ./quic_perf_client).

Simulating Network Conditions (Packet Loss / Delay):

We use Linux tc (Traffic Control) with netem instead of clumsy.

Scenario A: 5% Packet Loss

1. Apply 5% loss to the loopback interface:

   sudo tc qdisc add dev lo root netem loss 5%
   

2. Run the perf tests again.
3. Important: Remove the rule after testing!

   sudo tc qdisc del dev lo root
   

Scenario B: 100ms Delay

1. Apply 100ms delay:

   sudo tc qdisc add dev lo root netem delay 100ms
   

2. Run the perf tests again.
3. Remove the rule:

   sudo tc qdisc del dev lo root
   

3.3 & 3.4 Advanced Tests

• Multiplexing: The current quic_perf_client uses a single stream (Stream ID 4). You can modify the code to launch multiple streams in parallel to test head-of-line blocking resilience.
• Network Recovery: Use tc to drop 100% packets (loss 100%) for 30 seconds during a long transfer, then remove the rule (del) to see if the connection recovers.