VL 19 - 16.06.25
process scheduling (cont.)
- scheduling is relevant for the process group “ready”
- Scheduling in Interactive Systems
- reactive and fast
- concurring processes have to be managed fairly
- round-robin scheduling:
- a queue for process scheduling
- quantum: the
- adventages of short quanta: higher reaction time
- disadvantages of short quanta: process switching is costly
- modern OS’s: 10 - 100 ms
- multiple queues - multilevel queue scheduling
- Lottery-Scheduling
- scheduling in real time systems (RTS)
- evaluating scheduling strategies:
- we need an evalution criteria
- throughput
- turnaround time
- cpu efficiency
- \(\Rightarrow\) queuing theory / server theory:
- basic:
- arrivals
- queue
- server
- departures
- variations
- multiple queues,
- some clients leave the system before being served
- …
- definitnions:
- T1 < T2 < T3 < … < Tn are the random arrival times of the clients
- we define a random variable tk := Tk - T_{k - 1}. it’s called the interarrivel time, IAT
- what is the distribution of this random variable? poisson-distribution (?)
- Service or processing time S1, S2, …
- which configuration is the best according to scheduling theory?
I/O Hardware
- modern chips have special chips for communication between components
VL 20 - 18.06.25
Internetworking
- introduction and terms:
- hosts
- communication lines
- router and switches
- protocolls
- tcp, ip, http, ethernet, skype
- internet-standards
- format rfc: request for comments
- ietf: internet engineering task force
- internet applications
- dns
- History of Internet
- various networks needed to be connected which lead to the internet:
- principles of internetworking:
- minimalism, autonomy
- best effort model
- stateless router
- decentralized control
- tcp, udp, ip
- ethernet
- ftp - a simple file transfer protocol
- OSI
- packet switching vs ‘leitungsvermittlung’
- protocoll stack