Sidevõrgud IRT 4060/ IRT 0020 vooruloeng 3 / 29. sept 2004 Avo Ots telekommunikatsiooni õppetool, TTÜ raadio- ja sidetehnika inst. avo.ots@ttu.ee

Backbone network design layers

Layering

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

Andmeülekanne (loogiline) application transport network link physical data ack

Andmeülekanne (füüsiline) application transport network link physical data

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

Vahekihid Telnet FTP packet radio coaxial cable fiber optic HTTP HTTP

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

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

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

Routed Backbone

Collapsed backbone

Central Parking’s collapsed backbone

ATM Virtual Circuits

ATM Encapsulation

Protokollid http://www.private.org.il/tcpip_rl.html http://www.eix.co.uk/Ethernet/