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On-demand routing is a reactive approach in which a route is established only when it is needed. It describes how a routing protocol behaves, not one uniquely defined protocol. The standards use “reactive routing” for the same general approach and give examples including Dynamic Source Routing (DSR) and AODV-RPL.
What on-demand routing means
In RFC 9854, the IETF defines on-demand routing as “Routing in which a route is established only when needed.” The protocol responds to a requirement to send data instead of continually establishing routes for every possible destination. RFC 9854 also calls these “reactive” protocols because their operation is triggered when a new route is determined to be necessary. RFC 9854 (October 2025)
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How a route is discovered and maintained
DSR: discovery when data needs a path
Dynamic Source Routing (DSR) was designed for multi-hop wireless ad hoc networks of mobile nodes. When a node has data for a destination but no suitable known route, it begins Route Discovery. Route Request and Route Reply messages are used to find a path. RFC 4728 (February 2007)
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DSR: maintenance while the route is in use
Route Maintenance applies while the sender is using a source route. If a link on that route fails, the sender may switch to another route it already knows or discover a replacement. Thus, discovery finds a route on demand, while maintenance addresses problems that arise during its use. RFC 4728 (February 2007)
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AODV-RPL: discovery against application requirements
AODV-RPL is an example of the on-demand principle for low-power and lossy networks. Discovery can start when a node has data to deliver and existing routes do not satisfy the application’s requirements. The protocol can also establish separate routes in each direction when links are asymmetric, so the return path need not be the same as the forward path. RFC 9854 (October 2025)
Why use on-demand routing?
Its main potential advantage is less background routing activity. RFC 4728 specifies that DSR does not rely on periodic routing packets, advertisements, link-status sensing, or neighbor-detection packets. If the needed routes have already been discovered and nodes are approximately stationary relative to one another, DSR’s routing control overhead can fall to zero. That is a conditional behavior, not a guarantee for every network state: new destinations, broken links, or changing communication needs can trigger control traffic. RFC 4728 (February 2007)
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What varies between on-demand protocols
“On-demand” describes when routes are established; it does not mean all protocols use the same mechanism or support the same route behavior. Compare specific protocols by examining:
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- Discovery trigger: DSR begins discovery when data has a destination for which the sender lacks a route; AODV-RPL may initiate discovery when known routes fail application requirements.
- Failure handling: DSR’s Route Maintenance operates while a source route is being used and can lead to a known alternative or a replacement discovery.
- Target network: DSR is specified for mobile ad hoc networks; AODV-RPL addresses low-power and lossy networks.
- Directional paths: AODV-RPL can discover separate routes for forward and return traffic when link asymmetry requires them.
These are protocol-specific characteristics, not universal properties of every on-demand routing scheme. RFC 4728 (February 2007); RFC 9854 (October 2025)
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- Bright, high-resolution 5” glass capacitive touchscreen display lets you easily view your route
- Get more situational awareness with alerts for school zones, speed changes, sharp curves and more
- View food, fuel and rest areas along your active route, and see upcoming cities and milestones
- View Tripadvisor traveler ratings for top-rated restaurants, hotels and attractions to help you make the most of road trips
- Directory of U.S. national parks simplifies navigation to entrances, visitor centers and landmarks within the parks
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- Road trip–ready features include the HISTORY database of notable sites, a U.S. national parks directory, Tripadvisor traveler ratings and millions of Foursquare POIs
- Driver alerts for things such as school zones, sharp curves and speed changes help encourage safer driving and increase situational awareness
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