Cisco – Chapter 2

1. Cisco – Chapter 2 LAN

2. LAN Teaching Topology • physical topology is the actual layout of the wire (media) • logical topology defines how the media is accessed by the hosts • Logical topologies are Broadcast (Ethernet) and Token-passing. • Broadcast - each host sends its data to all other hosts on the network medium – CSMA/CD • Token Passing -Pass electronic token sequentially to each host.

3. LAN Topologies • Physical – how the network is wired • Bus • Ring single and dual • Star and Extended Star • Hierarchical • Mesh • Logical – how medium is accessed by hosts for sending data • Broadcast (Ethernet), token ring,

4. LAN Devices • 2 NICs • 1 Media • 1 Repeaters • 1 Hubs • 2 Bridges • 2 Switches • 3 Routers • 1-7 Clouds • 1 Network Segments

5. NICS – Layer 2 • printed circuit board that fits into the expansion slot of a bus on a computer’s motherboard or peripheral device • also called a network (LAN) adapter • Layer 2 devices because each individual NIC carries a unique code(looks at MAC – physical address) • Controls the host's access to the medium.

6. AUI • AUI does not always match (Cisco 2500 router) • transceiver (transmitter/receiver) is used to connect – Layer 1 • transceiver converts one type of signal or connector to another • convert electrical signals to optical signals • considered a Layer 1 device, because it only looks at bits

7. Security Devices • Firewalls – combination of hardware and software to protect internal network • Examines each packet to determine whether to discard or forward • AAA Server – authenticates, authorizes, and provides accounting information • Kerabos, TACACS+, RADIUS • VPN Concentrator –used with VPNs

8. Wireless • Wireless NICs – client adapter; available as PCMCIA and PCI cards • Wireless Access Points – WAPs, a transceiver that connects wireless to wired networks • Wireless Bridges – high speed, long-range line-of-sight wireless connectivity

9. Media Layer 1 • basic functions of media are to carry a flow of information, in the form of bits and bytes, through a LAN • networking media confine network signals to a wire, cable, or fiber and wireless • PAN (Personal area network) – uses human body as medium

10. Media 2 • Selection criteria include: • Cable length • Cost • Ease of installation • Total number of hosts • Most common medium is Cat 5 UTP

11. Repeaters – Layer 1 • Extend length of cable run beyond maximum length for that medium • Concept originated from early form of visual communication when signals were sent from hill to hill visually • Purpose is to regenerate (amplify) and retime signals • Single-port in and single-port out device • Act only on bit level

12. Hubs – Layer 1 • Regenerate (amplify) and retime network signals • Create a central connection point for the wiring media • Increase in the reliability of the network (one connection point) • Active hubs extend signal length; passive hubs do not extend length • Role in Token ring is played by MAU, a.k.a. concentrator • A.K.A. multi-port repeater

13. Bridges – Layer 2 • designed to connect two LAN segments • filters traffic on a LAN to keep local traffic local • allows connectivity to other parts (segments) of the LAN • Uses MAC address to make filtering decision • Are being replaced by switches & routers

14. Switches – Layer 2 • Called a multi-port bridge • Make decisions based on MAC addresses • Switch data only out port to which proper host is connected • Part of function is connectivity concentration (allow many devices to connect to one point in network) • Can provide each port with full bandwidth

15. Routers – Layer 3 • Makes decisions based on groups of network addresses (logical addressing) • Can also connect different layer 2 technologies, such as Ethernet, Token-ring, and FDDI. • Have become the backbone of the Internet, running the IP protocol. • Choose best path and switch to proper port • Primary functions – path selection & switching

16. Cloud – Layer 1- 7 • Reminds us there is a way to connect but does not supply details of connection or network • Represents a large group of details that are not pertinent to the situation

17. Network Segments – Layer 1 • Identifies the layer 1 media that is the common path for data transmission in a LAN; sometimes called WIRE • Each time an electronic device is used to extend the length or manage data on the media a new segment is created • It means segments of the network here; it does have a different meaning at Layer 4

18. Network Milestones • 1950s – Mainframe computers • 1960s – Mini computers • 1970s – Advent of personal computers • 1970s – Beginning of Internet • 1980s – Gateways – special purpose computers to interconnect LANs • 2000 – Convergence of voice, video, and data into one information stream

19. Encapsulation • Top three layers prepare data for transmission by creating a common format • Transport layer breaks data up into units called segments & assigns sequence #s • Network layer encapsulates segment into a packet & adds IP addresses • Data-Link Layer encapsulates packet into a frame and adds MAC addresses • Physical Layer sends out binary bits on media

20. Encapsulation 2 • Bottom three layers are primary movers of data • Physical, Data Link, and Network • Exception is a Gateway – a device designed to convert data from one format to another • Gateway uses all 7 layers of OIS model • Data – Segments – Packets – Frames - Bits