N4. Internet protocol Flashcards
Internetworking - what cannot be guaranteed by underlying technology
Reliability - transmission errors and lost packets
Ordering - packets may not be delivered in correct sequence
Delay - may not be a consistent end-to-end path
IP service is “Best Effort”.
Is IP connection-oriented or connection-less?
Connection-less (CL)
‘send and forget’
What are IP addresses used for?
- used for identification: allows hosts to be uniquely labelled
- used by transport protocols
- bound to interface on an IP host
- used for routing and forwarding
How many bits are there in an IPv4 address?
32 bits (2 reserved)
Special IP addresses:
127.x.x.x
Loopback, sent to yourself
Special IP addresses:
0.0.42.6
Host that doesn’t know its network prefix
Special IP addresses:
0.0.0.0
Used by a host that doesn’t know its IP address
What is a netmask used for?
Masks the address for routing
Router only needs network prefix (final part masked as only needed for final delivery)
DNS name resolution:
What is an authoritative answer?
Answer from domain server
DNS name resolution:
What is a non-authoritative answer?
Answer from cache at local server
What is TTL?
Time To Live
Lifetime of a result stored in cache before it is refreshed or removed.
What is the role of a Local (resolving) server in DNS name resolution?
- it is recursive
- it queries other servers to resolve requests
- stores results in cache to answer other queries quickly
What is the role of a Root server in DNS name resolution?
- it is iterative (for load and security reasons)
- it sends a referral to the requester (does not actually redirect/fetch just points requester in right direction)
- referral gets requester closer to actual server holding mapping
