Describe which steps a mobile device have to perform when it wants to attach to a different point in the network
- Discover a point of attachment
- Obtain new or confirm old network address
- Dicover a local router
- Optionally reauthenticate
- Obtain authorization
- Optionally perfom location updates
- > continue or resume old connections
- > establish new connections
Differentiate node and network mobility
Node mobility: Directly attached individual nodes are mobile (per-node)
Network mobility: nodes are attached to a network which then is mobile (e.g. Bus)
Differentiate mobile and nomadic connectivity
Nomadic: on/off behaviour; larger devices; Stationary while active
Mobile: Striving for continous network attachment & uninterrupted use; usually phones; may be mobile while active
What are seamless, fluctuating and intermittent connectivity?
seamless: continously attached to network; fast change between access networks; always connected
fluctuating: may be attached to network all the time but quality varies substantially
intermitted: experience gaps in network attachement (similar to nomadic movement)
What is a handoff?
Moving from one attachment point to next.
2 issues:
- need 2 find a new attachment point
- who initiates? device (fading reception) or network (load balancing, qos)
What are soft and hard handovers?
soft - make-before-break: associate new network before diconnect from old; consumes more resources; may offer continuity
hard - break-before-make: disconnect first and then associate with new network; needs just one interface and nearly no support from network; introduces gaps
Differentiate handover and roaming:
Handover: technical side
Roaming: authentication & subscription of nodes from foreign networks
