Metropolitan Area Network (MAN)

Computer Networks and Internet Basics (9hrs) · Computer Fundamentals & Emerging Technologies

1. Definition

A Metropolitan Area Network (MAN) is a network that spans a city or a large metropolitan area, typically 5 to 50 km, linking many LANs of different organisations, offices and homes within one city. It is larger than a LAN but smaller than a WAN, is usually built on fibre-optic rings or leased high-speed links, and is often owned by a single entity — a telecom operator, an ISP, a cable company, a metro corporation or a consortium of organisations. A city-wide cable TV and internet service is the standard example.

2. Characteristics

Feature	Typical value
Coverage	A city, 5-50 km
Speed	10 Mbps to 10 Gbps (metro Ethernet, DWDM links)
Ownership	One operator, ISP, government body or consortium
Latency	A few milliseconds (city distances)
Error rate	Low to moderate — fibre is excellent, wireless/metro links vary
Media	Optical fibre (dominant), coaxial (HFC), microwave, WiMAX
Devices	Metro switches, routers, DWDM terminals, access points
Cost	High setup (fibre laying, right of way); often shared among customers
Administration	Centralised but crosses many sites — needs strong management and security

3. MAN Technologies

Technology	Nature	Use
Metro Ethernet	Carrier-class Ethernet over city fibre	Interconnecting offices and campuses across a city
SONET/SDH rings	Standard optical transmission with protection switching	Telecom backbone within a city
DWDM	Many wavelengths on one fibre	Very high-capacity metro backbones
HFC (Hybrid Fibre-Coaxial)	Fibre to the neighbourhood plus coax to homes	Cable TV + broadband internet
WiMAX (IEEE 802.16)	Wireless broadband over kilometres	Last-mile access where cabling is costly
FDDI / DQDB	Dual-ring legacy metro standards	Historical metro backbones
City Wi-Fi mesh	Many access points forming a mesh	Public Wi-Fi, smart-city services

4. How a MAN is Organised

          ┌──────────── CITY FIBRE RING (DWDM, self-healing) ─────────────┐
          │              │               │              │               │
      LAN-A           LAN-B          LAN-C          ISP POP        Data centre
   (corporate)      (college)      (hospital)     (internet)      / cloud
          │              │               │              │
      Office PCs     Campus PCs      Medical LAN     Customers

Because the ring is bidirectional/self-healing, a single fibre cut can be routed around, which is why carriers prefer ring topologies for metropolitan service. Each site still has its own LAN and a router/switch connecting it to the metro ring.

5. Advantages and Limitations

Advantages	Limitations
Covers an entire city — connects offices, campuses and homes	Very high initial cost — fibre laying and permits
Much higher speed than a WAN link	Complex to design, operate and secure
Cost shared by many customers, so cheaper than private long links	Depends on the provider's SLAs and infrastructure
Fibre ring gives reliability with protection switching	Right-of-way, digging permissions and civic hurdles
Enables city services: CCTV, smart traffic, e-governance	Traffic crosses public/carrier infrastructure — encryption needed
Good middle ground between LAN speed and WAN reach	Expansion may require significant re-engineering

6. MAN in Context

Basis	LAN	MAN	WAN
Coverage	Building/campus, ≤ 1 km	City, 5-50 km	Country/global
Speed	100 Mbps-100 Gbps	10 Mbps-10 Gbps	2 Mbps-10 Gbps per link
Ownership	Single organisation	Operator/consortium	Multiple carriers
Cost	Low, one-time	High, shared	High recurring
Example	College lab LAN	City cable broadband, metro Ethernet	Internet, bank branch network

7. Applications

Cable TV and broadband internet across a city (HFC) · interconnecting a university's several campuses · hospital and diagnostic-centre networks feeding a central records server · city-wide CCTV and traffic-control networks · metro rail signalling and ticketing systems · bank ATM networks inside a city · e-governance and municipal office connectivity · ISP metro backhaul between its own POPs · public Wi-Fi and smart-city sensor networks.

8. Exam Points

Define a MAN and list its characteristics — 5 marks, frequent.
Differentiate LAN, MAN and WAN (tabular) — 5 marks, almost certain.
Name any four MAN technologies and state one use of each — 5 marks.
Explain the applications of a MAN in a metropolitan city — 5 marks.
Why are fibre rings preferred for MAN backbones? — 3 marks.
Draw a labelled diagram of a MAN interconnecting several LANs — 5 marks.

Metropolitan Area Network (MAN)