π Routing Protocols: IGP and EGP
Routing protocols implement routing algorithms in real-world networks, classified based on their administrative domain:
π IGP (Interior Gateway Protocol)
Used within a single autonomous system (AS).
RIP (Routing Information Protocol)
- Distance-vector protocol using hop count.
- Max hop count = 15 (limit to small networks).
- Periodic full-table updates β bandwidth-heavy.
OSPF (Open Shortest Path First)
- Link-state protocol using Dijkstra’s algorithm.
- Each router constructs full network map.
- Faster convergence, supports variable-length subnet masks (VLSM), and areas.
IS-IS (Intermediate System to Intermediate System)
- Similar to OSPF.
- Scales better in large ISPs; TLV-based structure.
π EGP (Exterior Gateway Protocol)
Used between autonomous systems.
- BGP (Border Gateway Protocol)
- Path-vector protocol.
- Considers AS-path, policy, and multiple attributes.
- Foundation of the global internet routing.
- Maintains table of paths; avoids loops via AS path tracking.
- Highly scalable, supports CIDR and route aggregation.
π§ Insights
- IGP optimizes for speed and simplicity inside a domain.
- EGP focuses on policy-based routing and inter-AS stability.
- BGPβs robustness is essential for the resilience of the internet.
π Comparison Table
| Feature | IGP (e.g., RIP, OSPF) | EGP (e.g., BGP) |
|---|---|---|
| Scope | Within AS | Between ASes |
| Convergence Speed | Faster | Slower (policy checks) |
| Complexity | Lower | Higher |
| Policy Control | Limited | Extensive |
| Loop Avoidance | Hop Count (RIP), Topology | AS Path |
π Links
- Previous: Routing Algorithms
- Next: Encapsulation and Tunneling