Here’s a clear explanation of source routing in computer networking:
🧭 What Is Source Routing?
Source routing is a technique where the sender of a data packet specifies the exact path the packet should take through the network to reach its destination. This is different from traditional routing, where each router along the way decides the next hop based on the destination address.
🧠 Key Concepts
- Sender-controlled path: The source node embeds routing information directly into the packet.
- Overrides default routing: Instead of relying on routers to choose the path, the sender dictates it.
- Used for testing, diagnostics, or specialized routing needs.
🛣️ Types of Source Routing
There are two main modes in IP source routing:
| Mode | Description |
|---|---|
| Strict Source Routing | The packet must follow the exact path specified—no deviations allowed. |
| Loose Source Routing | The packet must pass through specified routers but can take intermediate hops as needed. |
🧪 How It Works
Imagine sending a package with instructions like:
“Go from Nashville → Atlanta → Charlotte → Raleigh.”
Each router checks the next hop in the packet and forwards it accordingly.
In IP networking, this path is embedded in the options field of the IP header.
🔐 Security Implications
While source routing can be useful for:
- Network diagnostics
- Load balancing
- Route testing
…it also poses security risks, such as:
- Spoofing attacks: Malicious users can manipulate return paths.
- Bypassing firewalls: Packets may avoid security checkpoints.
Because of these risks, many networks block source-routed packets by default.
🧰 Use Cases
- Traceroute enhancement
- Network troubleshooting
- Custom routing in software-defined networks (SDNs)
- High-performance interconnects like Myrinet or SpaceWire
