Introduction

Question 1

Describe which steps a mobile device have to perform when it wants to attach to a different point in the network

Answer 1

• 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

Question 2

Differentiate node and network mobility

Answer 2

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)

Question 3

Differentiate mobile and nomadic connectivity

Answer 3

Nomadic: on/off behaviour; larger devices; Stationary while active

Mobile: Striving for continous network attachment & uninterrupted use; usually phones; may be mobile while active

Question 4

What are seamless, fluctuating and intermittent connectivity?

Answer 4

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)

Question 5

What is a handoff?

Answer 5

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)

Question 6

What are soft and hard handovers?

Answer 6

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

Question 7

Differentiate handover and roaming:

Answer 7

Handover: technical side

Roaming: authentication & subscription of nodes from foreign networks