Routing. Point to point protocol (PPP) ETSF05 Internet Protocols Kaan Bür 1

Transcription

1 ETSF05 Internet Protocols PPP TDM Asynchronous Transfer Mode Synchronous Optical Networks WLAN Jens A Andersson (Kaan Bür) Routing Konsten att bygga least costtrees Från sändare till mottagare Från varje nod till varje annan nod Tre principer Distance Vector Link State Path Vector Policy based routing 2 Point to point protocol (PPP) Direct connection between two nodes Internet access Home user to ISP Telephone line Cable TV PPP ETSF05 Internet Protocols 3 Kaan Bür 1

2 State transitions in PPP We need more protocols LCP Link Control (LCP) Data Transfer Authentication Network Control (NCP) 4 PPP frame format Support for several (sub)protocols Address & control not used Maximum payload 1500 bytes ETSF05 Internet Protocols 5 Link control protocol (LCP) Establish Configure Terminate Options Maximum receive unit (payload size) Authentication protocol (none/pap/chap) Protocol field compression (on/off), Address and control field compression (on/off) ETSF05 Internet Protocols 6 Kaan Bür 2

3 Authentication protocols (AP) Password authentication (PAP) ETSF05 Internet Protocols 7 Authentication protocols (AP) Challenge handshake authentication (CHAP) ETSF05 Internet Protocols 8 Network control protocols (NCP) Preparations for the network layer IPCP for Internet ETSF05 Internet Protocols 9 Kaan Bür 3

4 IP datagram encapsulation in PPP ETSF05 Internet Protocols 10 PPP session example ETSF05 Internet Protocols 11 PPP session example (cont.) ETSF05 Internet Protocols 12 Kaan Bür 4

5 Transmission modes Parallell transmission ETSF05 Internet Protocols 14 Serial transmission ETSF05 Internet Protocols 15 Kaan Bür 5

6 Transmission modes Asynchronous Synchronous 16 Time division multiplexing (TDM) Sharing available bandwidth Actually, time sharing available bit rate 17 Synchronous TDM Outgoing link faster than incoming links At least n times 18 Kaan Bür 6

7 STDM for digital telephony (T 1) 19 STDM frame structure (T 1) 20 Digital hierarchy 21 Kaan Bür 7

8 Wide area networks (WAN) ATM SONET/SDH 22 Asynchronous Transfer Mode (ATM) Developed by ATM Forum, adopted by ITU T Wide area interconnectivity Connection oriented Uses fixed size cells as data unit Hardware implementation High data rates 23 Asynchronous TDM Statistical multiplexing Fixed cell size solves problem with variable frame size 24 Kaan Bür 8

9 ATM network architecture User to network interface (UNI) Endpoint switch Network to network interface (NNI) Switch switch 25 Virtual paths, virtual circuits Logical subunits of a physical transmission path 26 Virtual connections Identified by Virtual path no. Virtual circuit no. Unique combination 27 Kaan Bür 9

10 Routing with VPI, VCI at ATM switch 28 Virtual Circuit Networks Packet switching infrastructure Circuit switching logic 29 IP och ATM Hur funkar IP över ATM? Stora paket i små celler Effektivt? ATM är länkprotokoll Mappning IP adress länkadress behövs Eller? ETSF05 Internet Protocols 30 Kaan Bür 10

11 Synchronous Optical Networks SONET, developed by ANSI Synchronous Digital Hierarchy SDH, developed by ITU T 31 Digital hierarchy on optical links 32 Network architecture Devices and connections 33 Kaan Bür 11

12 Network architecture Devices and layers Data link layer Physical layer 34 SONET add/drop multiplexer Replaces a signal with another one Operates at line layer Similar to a switch 35 SONET frames Proportional to data rates 36 Kaan Bür 12

13 SONET frames in transmission 37 SONET frame structure (STS 1) 38 Encapsulation and offsetting STS 1 90 bytes x 9 rows 39 Kaan Bür 13

14 Pointers H1+H2 Where does the next frame start? 2 bytes to address 774 possibilities 40 Multiplexing and byte interleaving 41 Multiplexed SONET frame (STS 3) 42 Kaan Bür 14

15 Concatenated signal (STS nc) Data rate > STS 1 Put in an STS n signal Not demultiplexable Path overhead in single column 43 Virtual tributaries Backward compatibility with DS 1 and DS 3 44 Linear SONET topology Without add/drop multiplexer With add/drop multiplexer 45 Kaan Bür 15

16 Automatic protection switching Failure protection through line redundancy 46 Ring SONET topology 47 Mesh SONET topology Better scalability Multiplexing/demultiplexing at switches 48 Kaan Bür 16

17 Wireless LANs Basic Service Sets (BSS) Infrastructure AdHoc Extended service set (ESS) Hidden Node/Station Problem Kaan Bür 17

18 CSMA/CA and NAV NAV Frame format More complicated than threaded Ethernet! Addressing mechanisms Note! AP has address. Compare with Ethernet switch Kaan Bür 18

19 Exposed station problem Kaan Bür 19