Tutorial 1: 26th September 2019 Flashcards
IP Mobility
How is IP mobility presently implemented?
Independently in the application layer, as opposed to any standard approach in a lower layer. No mobile IP technologies like ILNP or Mobile IP are implemented.
How do the packets received over time change when changing networks in IP and in ILNP?
Complete drop and then increase when disconnecting from 1st and then connecting to 2nd; ILNP smoothes this to no change
What is an application presence mechanism?
Methods by which users of a service inform others that they are present and available and willing to communicate.
When does ILNP need to update the locator DNS value?
If and only if you expect traffic to an old network and there is no presence mechanism at the application level.
How will DNS’ architecture delay the propagation of updates?
Its caching mechanisms mean that DNS records for ILNP addresses will propagate less slowly, only each hop when the cache times out.
How can we avoid DNS’ architecture delaying the propagation of updates?
Eliminate caching, especially in clients, by setting TTL to 0 or mostly by setting it to 1.
What effect will setting the TTL of DNS records and DNS record caches to ~ 0 have?
Update propagation will be faster but there will be a large increase in load on the network and even large reductions in TTL in IP networks don’t affect load that much.
Why does DNS need to be updated with an authentication mechanism?
Because at present anybody can claim they are Google on it.
Why would adding an authentication mechanism to DNS increase network load?
Secure updates to DNS would increase network load by taking more and larger packets.
Why can you maintain IP connections on 4G when moving between different towers but not when going from Wifi to 4G?
Different towers are on the same underlying network, at the link and network layer, but wifi is on a different underlying network (at the network layer).
How can switching between networks affect QoS and QoE?
QoS can drop completely while moving between networks and be poorer on the new network. This can degrade QoE, e.g. lower bandwidth so lower quality video/more buffering/live feed delays/etc.
How could we adapt network load to the conditions of the network?
Reduce the bandwidth needed by applications when performance decreases, such as reducing the video resolution and frame rate on Skype.
What are the major problems of ILNP?
Fast DNS updates increasing network load, resilience to adoption, and requiring adaptability of applications
