台北科技大学：《计算机网络》（英文版） NP04 3 CONTENTS

Underlying Technologies Chuan-Ming Liu CSIE NTUT Spring 04, TAIWAN CS旧E.NTUT. TAWAN

CSIE, NTUT, TAIWAN 1 Underlying Technologies Chuan-Ming Liu CSIE, NTUT Spring ’04, TAIWAN

CONTENTS ·LANS · POINT-TO- POINT WANS SWITCHED WANS CONNECTING DE VICES CSIE NTUT TANAN

CSIE, NTUT, TAIWAN 2 CONTENTS • LANS • POINT-TO-POINT WANS • SWITCHED WANS • CONNECTING DEVICES

Internet model Point-to-point WAN LAN Point-to-point WAN Switched WAN CSIE NTUT TANAN Figure 3-1

CSIE, NTUT, TAIWAN 3 Figure 3-1 Internet model

3.1 LOCALAREA NETWORKS (LANS) CSIE NTUT TANAN

CSIE, NTUT, TAIWAN 4 LOCAL AREA NETWORKS (LANS) 3.1

Local Area networks (LANS) Data communication system in a limited geographic area such as a single department, a single building, or a campus ° Popular LaNs include Ethernet Lans Token Ring LANs WireleSs lans ATM LANS CSIE NTUT TANAN

CSIE, NTUT, TAIWAN 5 Local Area networks (LANs) • Data communication system in a limited geographic area such as a single department, a single building, or a campus. • Popular LANs include – Ethernet LANs – Token Ring LANs – Wireless LANs – ATM LANs

Ethernet Most widely used lan protocol Bus or star topolos Traditional ethernet 10 Mbps Carrier Sense Multiple Access with Collision Detection(CSMA/CD) Minimum frame length Transmission rate Collision domain(maximum network distance) CSIE NTUT TANAN

CSIE, NTUT, TAIWAN 6 Ethernet • Most widely used LAN protocol • Bus or star topology • Traditional Ethernet – 10 Mbps – Carrier Sense Multiple Access with Collision Detection (CSMA/CD) • Minimum frame length • Transmission rate • Collision domain (maximum network distance)

CSMA/CD A B A's frame Collision Z's frame Collision signal Collision signal Time Time Figure 3-2 CSIE NTUT TANAN

Figure 3 CSIE, NTUT, TAIWAN 7 -2 CSMA/CD

Note Minimum frame length Transmission rate is proportional to Collision domain /Propagation speed CSIE NTUT TANAN

CSIE, NTUT, TAIWAN 8 Minimum frame length/Transmission rate is proportional to Collision domain / Propagation speed

Ethernet Data Link Layer Logical link control (LlC) Flow control Error control Media access control(MAC) operation of the CSMA/CD access method CSIE NTUT TANAN

CSIE, NTUT, TAIWAN 9 Ethernet Data Link Layer • Logical link control (LLC) – Flow control – Error control • Media access control (MAC) operation of the CSMA/CD access method

Ethernet Layers OSI Model Ethernet Logical link Control LLC) Data link layer Media access Control (MAC) Physical layer Physical layer T ransmission medium CSIE NTUT TANAN Figure 3-3

CSIE, NTUT, TAIWAN 10 Figure 3-3 Ethernet Layers