--- title: "Static and dynamic routing algorithms" subject: "Telecommunications" chapter: 8 key: "semester_8/telecommunications:static-dynamic-routing" source: https://www.bctengineer.com/q/semester_8/telecommunications/static-dynamic-routing site: BCT Engineering --- # Static and dynamic routing algorithms Telecommunications · Chapter 8: Data Communication - Asked in: 2076 Chaitra, 6 marks - Video: [Difference between Static and Dynamic Routing | CCNA 2018](https://www.youtube.com/watch?v=da_63I7MuPo) — NETWORKING PLUS - Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14 - Page: https://www.bctengineer.com/q/semester_8/telecommunications/static-dynamic-routing - Whole chapter: https://www.bctengineer.com/md/semester_8/telecommunications/chapter-8 ## Question Explain static and dynamic routing algorithms used in data communication. ## Short answer Static routing uses precomputed routes loaded by an administrator; it cannot react to failures, and includes shortest path, flooding and flow-based routing. Dynamic routing changes routes automatically via protocols; distributed examples are distance-vector (RIP) and link-state (OSPF), while centralized and isolated also exist. Dynamic reacts to failures but has overhead. ## Answer A **routing algorithm** decides the output line on which a router forwards each packet so that it reaches its destination. Routing algorithms are of two main kinds: **static (non-adaptive)** and **dynamic (adaptive)**. #### Static (non-adaptive) routing Routes are computed in advance and loaded into the routers (by the administrator or an offline program). They do not change with traffic or topology until changed manually. - **Shortest path routing:** the network is drawn as a graph with link weights (distance, delay, cost); Dijkstra's algorithm finds the least-cost path, which is stored in the table. - **Flooding:** each packet is sent on all output lines except the input one; a hop counter limits copies. Very robust, used where reliability is vital or for broadcasting. - **Flow-based routing:** uses known average traffic between nodes and link capacities to pick routes with least average delay. Advantages: simple, no routing overhead, predictable, secure. Disadvantages: cannot react to failures or congestion; unsuitable for large changing networks. #### Dynamic (adaptive) routing Routers exchange information and change routes automatically when topology or load changes. - **Centralized:** one Routing Control Centre computes all tables. - **Isolated:** each node uses only local data (e.g. hot potato: shortest queue). - **Distributed:** - **Distance vector (Bellman-Ford):** each router sends its distance table to its neighbours periodically and updates using $D_x(y)=\min_v\{c(x,v)+D_v(y)\}$. Simple but slow convergence and count-to-infinity. Example: RIP. - **Link state (Dijkstra):** each router floods its link costs to all routers, builds the full map and computes shortest paths. Fast convergence. Example: OSPF. Example: if link B–C fails, a static router keeps sending packets over link B–C and they are lost; a dynamic router learns of the failure and shifts the traffic to another path. #### Comparison | Point | Static | Dynamic | |---|---|---| | Route set by | Administrator | Routing protocol | | Reaction to failure | None (manual) | Automatic | | Overhead | None | Control messages, CPU | | Suitable for | Small, stable networks | Large, changing networks | | Examples | Shortest path, flooding | RIP, OSPF | ## Check yourself The answer's key points as multiple-choice questions, with the correct option and why. 1. What characterises static (non-adaptive) routing? A. It uses RIP B. Routes change automatically with load C. Routers exchange tables D. Routes are computed in advance and do not change until changed manually Answer: D. Static routes cannot react to failures or congestion. (Key point: Static routing) 2. If link B-C fails, what happens under static and dynamic routing? A. Static keeps sending into the failed link; dynamic learns of it and shifts traffic B. Dynamic drops all packets C. Both reroute automatically D. Static recalculates instantly Answer: A. Dynamic routing adapts at the cost of control messages and CPU. (Key point: Failure reaction) 3. What is hot potato routing? A. Isolated adaptive routing sending the packet on the shortest output queue B. Link-state routing C. Flooding with hop counter D. Centralised routing with a control centre Answer: A. It uses only local information. (Key point: Hot potato) 4. Which network suits dynamic routing? A. Large changing networks B. Single-link networks C. Small stable networks D. Networks with no failures Answer: A. Static suits small stable networks; dynamic suits large changing ones. (Key point: Suitability) ## Related in Telecommunications - [Adaptive and non-adaptive routing algorithms](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aadaptive-nonadaptive-routing) — Telecommunications, chapter 8, asked 3× - [Short note: Routing algorithm in data communication](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Arouting-algorithm-data-comm) — Telecommunications, chapter 8, asked 2× - [Routing, flow control and dynamic routing](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Arouting-flow-control-dynamic) — Telecommunications, chapter 8 - [Switching techniques in data communication](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aswitching-techniques-data-comm) — Telecommunications, chapter 8, asked 3× - [Flow control mechanisms in data communication](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aflow-control-mechanisms) — Telecommunications, chapter 8 - [Flow control in data communication network](https://www.bctengineer.com/question.md?key=semester_8%2Ftelecommunications%3Aflow-control-network) — Telecommunications, chapter 8 ## Related in other subjects - [Static and dynamic data structures; array list](https://www.bctengineer.com/question.md?key=semester_4%2Fdata_structure_and_algorithm%3Astatic-dynamic-ds-array-list) — Data Structure and Algorithm, chapter 3 - [Static vs dynamic implementation of list](https://www.bctengineer.com/question.md?key=semester_4%2Fdata_structure_and_algorithm%3Astatic-vs-dynamic-list-example) — Data Structure and Algorithm, chapter 3, asked 2× - [Static vs dynamic implementation of stack](https://www.bctengineer.com/question.md?key=semester_4%2Fdata_structure_and_algorithm%3Astack-static-vs-dynamic) — Data Structure and Algorithm, chapter 2 - [Static vs dynamic list; getnode and freenode](https://www.bctengineer.com/question.md?key=semester_4%2Fdata_structure_and_algorithm%3Astatic-dynamic-list-getnode-freenode) — Data Structure and Algorithm, chapter 3