Networking Concepts

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Networking Concepts
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LAN

• Concepts
• Attenuation, Noise
• Hardware
• Repeater, Amplifier
• Bridge, Router, Gateway, Switch, Hub
• Twisted pair, Coaxial cable, Fiber optics
• Server, Workstation
• Wireless access point
• Topology
• Bus, Tree, Star, Ring

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LAN

• Standard
• OSI (Open Systems Interconnection)
• IEEE (Institute of Electrical and Electronic
  Engineers)
• ITU-T (Intl Telephone Union Telecom. Sector)
• ISO (International Standards Organization)
• EIA (Electronic Industries Association)
• ETS (European Telecom. Standard)

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Communications Hardware

• Repeater
• Extends distance limitation on networks (both
  voice and data)
• Filters noise
• Regenerates signals
• For twisted pair wire, repeaters are placed every
  100 meters
• Amplifier
• Extends distance limitation on networks (both
  voice and data)
• Amplifies both signal and noise

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Communications Hardware

• Bridge
• Connects two LANs using same protocol
• Single path between LANs
• Minimal sophistication
• Router
• Connects multiple LANs using same protocol
• Choice of paths between LANs
• Mainstay of internetworking

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Communications Hardware

• Gateway
• Connects multiple LANs using any protocol
• Very sophisticated
• Supports todays internet by providing access
  points to several networks
• Hub
• Connects nodes to a network
• Sometimes acts as repeater

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Communications Hardware

• Switch
• Connects multiple LAN segments using the same
  protocol
• Connections may use twisted pair, coaxial cable,
  or fiber optics wiring
• Faster than bridges
• Enables simultaneous communication between
  multiple network segments

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Ethernet

• Ethernet was developed jointly by Xerox, Intel,
  and DEC in 1980
• DEC (Digital Equipment Corporation) a computer
  company that specialized in mini-computers in the
  1970s. It was acquired by Compaq and Compaq
  merged with HP.
• This was the first commercial LAN system
• Ethernet is a simple protocol to implement
• Ethernet addresses the layers 1 and 2
  functionality for the OSI model
• Ethernet standard is very close to IEEE 802.3
  standard, but has some minor differences

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Ethernet

• Ethernet uses bus topology (which we will discuss
  next)
• Ethernet transmits a baseband signal at 10 Mbps
• Baseband signals are digital and bidirectional
• Ethernet allows the user data to have a variable
  length up to 1500 bytes
• Unlike HDLC and SDLC protocols, ethernet uses a
  length field in the header to identify the length
  of the user data in bytes. Because of this, no
  special bit pattern is needed to recognize the
  start and end of the user data.

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Ethernet frame format
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Ethernet diagram
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Bus topology

• It is a contention-based topology, which means
  that each node on the network must contend for
  access
• Each node listens to traffic on the network
• When a node has packets to transfer and the bus
  is not busy, then the packets are put on the bus
  in both directions, with the destination address
  marked on the packets
• All nodes listen to traffic on the network and
  the node that has packets addressed to it,
  receives the packets
• No routing or switching is involved in data
  transfer

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Bus topology diagram
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Tree topology

• Tree topology is a variation on bus topology
• A special node is designated as root
• The primary reason for this topology is to
  segment nodes so that not all nodes need to
  listen to packets broadcast on a segment
• This adds a layer of security in the form of
  unwanted nodes not listening to the network
  traffic
• Speeds up data transfer since there will be fewer
  nodes on each segment

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Tree topology diagram
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Star topology

• This is another variation on bus topology
• This has a central hub, a passive device
• Star is a logical bus and a physical ring
• Hub has ports in multiples of 8. Multiple hubs
  can be connected in a daisy chain format
• Easy to add nodes to the network and remove nodes
  from the network
• Central node does switching between nodes
• Multiple nodes can communicate simultaneously
  without collision
• Potential problem is the single point of failure
  for the network when the central node fails

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Star topology diagram
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Ring topology

• The nodes are connected in a ring pattern
• Unlike bus topology, each node on the ring acts
  as a repeater on the network
• Nodes access the network using a token, which
  eliminates the need for contention as in bus
  topology
• Token is a series of bits that identifies the
  node that has the right to transmit at any given
  time
• Example of a token Assume that there are 6 nodes
  on the network. The nodes are labeled 1 through
  6 and the token would consist of 3 bits. The
  token 100 will indicate that node 4 has the
  token.
• Tokens circulate in a single direction from a
  node to its neighbor

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Ring topology diagram
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OSI 7-layer model
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IEEE 802

• 802.1 General LAN management of OSI
• layers 3 through 7
• 802.2 LLC sublayer
• 802.3 Ethernet
• 802.4 Token bus
• 802.5 Token ring
• 802.6 MAN
• 802.7 Broadband, in general

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IEEE 802

• 802.10 Network Security
• 802.11 Wireless LAN
• 802.12 100VG-AnyLAN (Voice Grade)
• 802.13 unused
• 802.14 Cable Modem

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WAN

• Concepts
• Gateway, Frame Relay, ATM, DSL, T1, T3, STS
  (Synchronous Transport Signal)
• Standard
• TCP/IP (Transmission Control Protocol /Internet
  Protocol)
• IETF (Internet Engineering Task Force)
• ATM Forum (Asynchronous Transfer Mode)

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STS, STM, OC equivalencies
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ATM VPI and VCI
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TCP/IP functions

• Establish a connection between nodes
• Manage data flow on the network
• Handle transmission errors
• Terminate connection at the end
• TCP is a connection-oriented protocol, meaning
  that a packet sent to the next node is monitored
  for proper receipt
• IP is a connection-less protocol, meaning that a
  packet sent to the next node is not monitored for
  proper delivery
• Since TCP and IP work together, the packet
  delivery is reliable
• Connection-less mode is known as User Datagram
  Protocol (UDP)

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TCP/IP 5-layer model

• TCP/IP protocol is divided into 5 layers
• Application layer
• Transport layer
• Network layer
• Data link layer
• Physical layer

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IP Addressing

• IP address consists of 4 octets n.n.n.n where n
  is in the range 0 to 255
• This form of IP address is known as IPv4,
  denoting IP address Version 4
• A new form of IP address known as IPv6, denoting
  IP address Version 6, has been proposed. It uses
  128-bit addressing instead of 32-bit addressing.

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IP Address Hierarchy

• There are 3 main classes of IP addresses in use
  and two additional classes of IP addresses
  available for multicast and testing
• Class A First octet range 1 126
• IBM, ATT, HP, Merck, Stanford University
• Class B First octet range 128 191
• U of L and most other universities
• Class C First octet range 192 223
• IGLOU, Louisvilles first ISP

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UDP

• User Datagram Protocol is a best effort
  protocol
• best effort means no guarantee of delivery
• This is a connection-less protocol
• UDP does not provide reliability
• UDP sends out packets without first establishing
  a connection
• RFC 768 describes UDP
• UDP header consists of source port, destination
  port, length, checksum
• Example of UDP TFTP (Trivial File Transfer
  Protocol). TFTP is used when bootsrapping
  diskless system
• TFTP is on UDP port 69