Unit 9 Computer Networks Topologies and Network Models

Unit 9: Computer Networks Topologies and Network Models

Defining Components of the Network Home Office Mobile Users Internet Branch Office Main Office

Defining Components of the Network (cont. ) Branch Office Floor 2 Server Farm ISDN Floor 1 Telecommuter Remote Campus

Network Topologies LAN • Physical Star • Physical Bus • Logical Bus (Hub and Spoke) Hub • Logical Star • Physical Star (Hub and Spoke) Switch • Logical Bus

Network Topologies LAN Full Mesh Partial Mesh

Network Topologies WAN Server 1 R 2 Larry R 1 Physical Star R 3 Logical Full Mesh Bob Server 1 R 2 Larry R 1 Physical Star Logical Partial Mesh R 3 Bob

Network Topologies LAN/WAN Physical Single Ring Logical Ring Token ring hub Physical Dual Ring Logical Ring Physical Star Logical Ring

Physical Topology types Physical topology types Function Description Bus This is a linear topology, with all devices connected to the cable Star Each device is connected to a central point, sometimes called hub-and-spoke Extended Star A star topology is in the centre, but instead of each point being a single device, it can be the centre of another star topology Full Mesh Each device has a direct connection to each other device Partial Mesh Each device does not have a direct connection to each other device Single Ring Each device is connected directly to two others so that the signal is repeated in one direction, creating a ring or loop Dual Ring . Two rings go through the same set of devices, allowing loops to be made upon failure, which continues the operation of a ring

OSI Model

Why a Layered Network Model? • Reduces complexity • Standardizes interfaces • Facilitates modular engineering • Ensures interoperable technology • Accelerates evolution

The Seven Layers of the OSI Model Examples Telnet - FTP

The Seven Layers of the OSI Model Examples Telnet - FTP ASCII - EBCDIC JPEG

The Seven Layers of the OSI Model Examples Telnet - FTP ASCII - EBCDIC JPEG Application Access Scheduling

The Seven Layers of the OSI Model Examples Telnet - FTP ASCII - EBCDIC JPEG Application Access Scheduling TCP – UDP - SPX

The Seven Layers of the OSI Model Examples Telnet - FTP ASCII - EBCDIC JPEG Application Access Scheduling TCP – UDP - SPX IP - IPX

The Seven Layers of the OSI Model Examples Telnet - FTP ASCII - EBCDIC JPEG Application Access Scheduling TCP – UDP - SPX IP - IPX 802. 3/802. 2 - HDLC

The Seven Layers of the OSI Model Examples Telnet - FTP ASCII - EBCDIC JPEG Application Access Scheduling TCP – UDP - SPX IP - IPX 802. 3/802. 2 - HDLC EIA/TIA-232 - V. 35

Data Encapsulation

Data De-Encapsulation

Peer-to-Peer Communication

TCP/IP Stack • Defines four layers • Uses different names for Layers 1 through 3 • Combines Layers 5 through 7 into single application layer work

TCP/IP Stack versus the OSI Model

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