Cisco

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 computers
  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