1. Sidevõrgud IRT 4060/ IRT 0020 vooruloeng 3 / 29. sept 2004
Avo Ots telekommunikatsiooni õppetool,
TTÜ raadio- ja sidetehnika inst.

2. Backbone network design layers

3. Layering

4. Ülemise ja alumised kihid
Lower three layers are hop-by-hop
Next two layers are end-to-end
Application
Transport
Network
Datalink
Physical
Physical medium

5. Andmeülekanne (loogiline)
application
transport
network
link
physical
data
ack

6. Andmeülekanne (füüsiline)
application
transport
network
link
physical
data

7. Sõnumiülekanne source destination application transport network link
datagram
application
transport
network
link
physical
source
destination M H t n l
message
segment
frame

8. Vahekihid Telnet FTP packet radio coaxial cable fiber optic HTTP HTTP

9. Funktsioonijaotus
The application knows the requirements best, place functionality as high in the layer as possible
If the application can implement a functionality correctly, implement it at a lower layer only as a performance enhancement
Think twice before implementing a functionality that you believe that is useful to an application at a lower layer

10. Töökindlus
router
sender
receiver L2 L2 L1 L1 L1
Solution 1: make each step reliable, and then concatenate them
Solution 2: end-to-end check and retry

11. Töökindluse tagamine The receiver has to do the check anyway!
Thus, full functionality can be entirely implemented at the upper layer; no need for reliability from lower layers
Is there any need to implement reliability at lower layers? L1 L2
sender
receiver

12. Routed Backbone

13. Collapsed backbone

14. Central Parking’s collapsed backbone

15. ATM Virtual Circuits

16. ATM Encapsulation

17. Protokollid http://www.private.org.il/tcpip_rl.html