Computer Networks · TEE · papers
Q5(b)(ii) · Ethernet physical media
2022-11-16 · AI-only Sem V
Exact historical variant. Current-syllabus questions solved; excluded topics and source limitations stated.
Q5(b)(ii). What physical media can Ethernet run over? Explain in detail. [5 marks]
Answer
Guided media constrain signals to a physical path: twisted pair, coaxial cable and optical fiber. Unguided media carry electromagnetic waves through free space: radio, microwave and infrared. Wireless bandwidth and reach depend on frequency, power, antenna, obstacles and regulations; media names alone do not fix a speed.
| Medium | Two key characteristics | Limitations / use |
|---|---|---|
| Twisted pair | Electrical signal; pairs twisted to reduce interference | Low-cost LAN access; distance/noise limits depend on category and design |
| Coaxial cable | Shielded central conductor; greater shielding than basic unshielded pair | Bulkier; cable broadband and legacy shared LANs |
| Optical fiber | Light in glass/plastic; high capacity with immunity to electromagnetic interference | Transceivers and careful splicing/bend control needed; backbone links |
| Radio waves | Wireless propagation; many bands support broad/non-line-of-sight coverage | Interference, shared spectrum and security configuration matter; Wi-Fi/mobile |
| Terrestrial microwave | Directional antennas; typically line of sight | Alignment and obstructions matter; point-to-point backhaul |
| Satellite microwave | Wide coverage through relay in space | Cost and latency depend strongly on orbit/system; remote connectivity |
| Infrared | Short-range light; usually blocked by walls | Limited coverage; short-range indoor/remote-control links |
Yaad rakho: Guided = cable path; unguided = free-space waves.
Transmission media are classified into guided media (twisted pair, coaxial cable, optical fiber) and unguided media (radio, microwave, infrared).
Optical fiber carries data as light in a core surrounded by cladding. It is a guided medium. Single-mode fiber supports one main propagation mode and is used for long/high-capacity links; multimode supports multiple modes and is often used over shorter distances.
| Advantages | Disadvantages / design costs |
|---|---|
| High data capacity and low attenuation over suitable links | Optical transceivers, connectors and splicing add cost/skill requirements |
| Immune to electromagnetic interference; no electrical crosstalk | Tight bends, dirty connectors and poor installation increase loss |
| Electrical isolation between buildings | Fiber is mechanically sensitive and requires appropriate protection |
| Harder to tap casually than an unprotected radio channel | It is not automatically confidential; encryption/access control remain necessary |
Yaad rakho: Fiber light carry karta hai; immunity means no EMI, not no security risk.
Ethernet can use balanced twisted-pair copper (e.g.100BASE-TX/1000BASE-T), optical fiber (e.g.1000BASE-SX/LX), and historical coaxial cable (10BASE2/10BASE5). Twisted pair is economical for typical building runs; fiber supports longer reach and immunity to electromagnetic interference. The exact reach and rate depend on the Ethernet standard, not simply the word “fiber”.