The Internet
Last updated
Last updated
Administrative borders define:
Autonomous Systems (AS)
Intra-domain routing;
Individual internal policies;
May use different metrics between domains;
Protocols: RIPv2, OSPFv2.
AS interconnections
Inter-domain routing;
Connectivity information;
Protocols: BGP.
Self-organized set of interconnected autonomous components.
More than 60.000 autonomous domains (with more than 100K numbers allocated)
Single guarantee is running TCP-IP;
Works by packet switching;
More than 340 millions of registered domains (URL)!
Commercial traffic larger than non-commercial.
Exponential growth in all numbers (number of users, traffic).
Different machines (networks) can offer different services.
Each user can select what it uses.
Only bi-directional media that supports communications.
One to one (unicast, e.g. email); one to many (multi-cast, e.g., electronic news).
NB: Internet networks are operated AUTONOMOUSLY
After connecting to the Internet, the network becomes PART of the Internet.
Apparently hierarchical.
Backbone ISP provides service to increasingly smaller ISPs.
Smaller ISPs eventually providing service end users.
But hierarchy is not respected.
Private connection agreements;
Mechanisms for improvement of the network;
All companies provide service to (some) users;
Service providers connect to multiple connection providers;
Users connect to multiple ISPs.
Great for burst information.
Resource sharing;
No call setup time.
When excessive congestion: delays and losses.
Needs reliable data transfer protocols.
Providing circuit switching services ?
For multimedia applications we need bandwidth and delay.
Problem not yet completely solved.
Some apps (audio/video real time) handle losses.
Other applications (file transfer, telnet) require 100% of success in transmission.
Some applications (multimedia) need a minimum bandwidth to be effective.
Other applications (“elastic applications”, ex. email, file transfer) use the bandwidth available.
Some applications (Internet voice, multiuser games) require low delays to be effective.
Other applications (without real time requirements) do not have strict delays end-to-end.
Interactive data transfer (e.g. HTTP, FTP).
Sensitive to the medium delay, not to rare occurrences.
Bulk data transfer (e.g. mail, news).
Not sensitive to delay;
Best effort works.
Sensistive to packet delay (telephony, gaming).
Maximum delay may be limited.
Adapt to larger ranges of delays (streaming audio, video).
| Applications | Losses | BW | Timing |
|---|---|---|---|
File Transfer | lossless | elastic | no |
lossless | elastic | no | |
Web Documents | lossless | elastic | no |
Real time audio/video | supports | audio: 5k-1Mbps video: 10k-5Mbps | yes, 100's ms |
Streamed audio/video | supports | See above | yes, few secs |
Interactive gaming | supports | Some Kpbs | yes, 100's ms |
Finance applications | lossless | elastic | Yes and no |
