Architecture · Lesson 04

How can a network route traffic without fixed infrastructure?

A mobile ad hoc network, or MANET, lets participating nodes forward traffic for one another while the topology changes around them.

Remove the fixed center

In a MANET, the nodes are the infrastructure.

A mobile ad hoc network has no permanently required access point, switch, or router at its center. Devices discover nearby neighbors and may forward packets for nodes that are outside direct radio range. A phone, vehicle, sensor, or field computer can be both an endpoint and a router.

MANET is a network architecture.The radio technology may be Wi-Fi, a specialized wireless link, or another medium. MANET describes how nodes organize and route, not one frequency or modulation.

Forward across neighbors

Reachability can require several changing hops.

Node A may reach node D through B and C even when A and D cannot communicate directly. Each forwarding node consumes airtime, battery, and processing capacity, so a longer path is not automatically a better path.

MULTI-HOP REACHABILITYABCDEA route is a sequence of forwarding decisions. When a node moves away, discovery and repair must find another sequence.
MANET routing turns local neighbor knowledge into an end-to-end path that may disappear at any time.

Choose when to discover

MANET protocols trade route freshness for control overhead.

01

AODV

On-demand distance-vector routing discovers a route when needed and maintains sequence information to reduce stale paths.

02

DSR

Dynamic Source Routing places the discovered route in packet headers, which can become expensive as paths grow.

03

OLSR

Optimized Link State Routing maintains routes proactively and reduces flooding with selected relay nodes.

04

Trade-off

Proactive knowledge costs periodic control traffic; reactive discovery costs setup delay and route repair time.

Expect churn

Mobility turns a stable route into a temporary hypothesis.

Nodes can move, sleep, lose radio visibility, exhaust battery, or become congested. A protocol must detect broken next hops, invalidate stale routes, limit broadcast storms, and avoid choosing paths that are technically reachable but operationally fragile.

Reachability is conditional.A MANET can be connected in one moment and partitioned in the next. Applications need timeouts, retries, buffering, and honest failure handling.

Keep the domains distinct

Telecommunications carries the radio; Networks decides the path.

The Telecommunications angle covers propagation, channel access, interference, range, modulation, and the physical wireless link. The Networks angle covered here is neighbor discovery, forwarding, addressing, route selection, repair, and end-to-end behavior.

A MANET may use Wi-Fi or another radio, but it is not the same thing as Wi-Fi. Wi-Fi describes a family of wireless LAN technologies; MANET describes a topology and routing model that can operate without fixed infrastructure.

Knowledge check

Test your MANET model

Answer five questions.

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