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Lesson 9-Network Fundamentals . Introduction. The Internet is a giant network consisting of interconnected PCs, servers, routers, and switches. This presentation focuses on a widely accepted definition of a network to mean any series of interconnected information systems and devices.

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introduction
Introduction
  • The Internet is a giant network consisting of interconnected PCs, servers, routers, and switches.
  • This presentation focuses on a widely accepted definition of a network to mean any series of interconnected information systems and devices.
background
Background
  • Network has different meanings.
    • This presentation focuses on an accepted definition of a network to mean any series of interconnected information systems and devices.
background1
Background
  • Networks enable computers to interact – exchanging information on everything, from credit card transactions to the latest news and weather.
background2
Background
  • The Internet is a giant network consisting of interconnected PCs, servers, routers, and switches.
  • Though data networks vary widely in size and scope, they are generally defined in terms of their architecture, topology, and protocol.
objectives
Objectives
  • Upon completion of this lesson, the learner will be able to:
    • Describe the basic network architectures.
    • List and describe basic network protocols.
    • Explain routing and address translation.
network architecture1
Network Architecture
  • LANs – Local Area Networks
    • Are smaller in terms of size and geographic coverage.
    • Consist of two or more connected devices.
network architecture2
Network Architecture
  • WANs – Wide Area Networks
    • Are larger, covering more geographic area.
    • Consist of two or more systems in geographically separated areas connected by:
      • Leased lines
      • Radio waves
      • Satellite relays
      • Microwaves
      • Dial-up connections
wan and lan interconnection
WAN and LAN Interconnection

Example of a corporate network with interconnected LANs and WANs

other terms for networks
Other Terms for Networks
  • Other terms classify networks based on size and use.
    • CAN
    • Intranet
    • Internet
    • MAN
    • SAN
    • VLAN
    • Client-Server
    • Peer-to-Peer
network topology
Network Topology
  • Topology describes how the network is physically or logically arranged. The network’s topology is one of the major components of every network architecture.
  • The various network topologies are:
    • Star
    • Ring
    • Bus
    • Mixed
slide13
Star
  • Star – Network components are connected to a central point.

Star topology

slide14
Bus
  • Bus – Network components are connected to the same cable, often called “the bus” or “the backbone.”

Bus topology

slide15
Ring
  • Ring – Network components are connected to each other in a closed loop with each device directly connected to two other devices.

Ring topology

mixed topology
Mixed Topology
  • Larger networks, such as those inside an office complex, may use more than one topology at the same time.

Mixed topology

topology definitions
Topology Definitions
  • With recent advances in technology, these topology definitions often break down.
    • Notes Area:
    • To avoid confusion, many people use topology definitions to apply only to the physical layout of the network, focusing on how the devices are connected to the network.
network protocol
Network Protocol
  • A protocol is a format for exchanging or transmitting data between systems.
  • It defines parameters such as:
    • Data compression method
    • Error checking
    • Mechanisms for systems to signal when they have finished receiving or transmitting data
common protocols
Common Protocols
  • AppleTalk –
    • The communications protocol developed by Apple to connect Macintosh computers and printers.
common protocols1
Common Protocols
  • Asynchronous Transfer Mode (ATM) –
    • A protocol based on transferring data in fixed size packets, which helps to ensure that no single data type monopolizes the available bandwidth.
common protocols2
Common Protocols
  • DECnet –
    • The protocol developed by Digital Equipment Corporation and used to connect PDP and VAX systems.
common protocols3
Common Protocols
  • Ethernet –
    • The LAN protocol developed jointly by Xerox, DEC, and Intel – the most widely-implemented LAN standard.
common protocols4
Common Protocols
  • Fiber Distributed Data Interface (FDDI) –
    • The protocol for sending digital data over fiber optic cabling.
common protocols5
Common Protocols
  • Internet Protocols (IP) –
    • The protocols for managing and transmitting data between packet-switched computer networks.
common protocols6
Common Protocols
  • Internetwork Packet Exchange (IPX) –
    • The networking protocol used by Novell NetWare operating systems.
common protocols7
Common Protocols
  • Netware –
    • The LAN protocol developed by Novell Corporation.
common protocols8
Common Protocols
  • Signaling System 7 (SS7)
    • The telecommunications protocol used between PBXes to handle tasks such as call setup, routing, and teardown.
common protocols9
Common Protocols
  • Systems Network Architecture (SNA) –
    • A set of network protocols developed by IBM, originally used to connect IBM’s mainframe systems.
common protocols10
Common Protocols
  • Token Ring –
    • The LAN protocol developed by IBM where systems must possess the network “token” before transmitting data.
common protocols11
Common Protocols
  • Transmission Control Protocol/Internet Protocol (TCP/IP)
    • The collection of communications protocols used to connect hosts on the Internet.
common protocols12
Common Protocols
  • X.25 –
    • A protocol developed by the Comité Consultatif International Téléphonique et Télégraphique (CCITT) for use in packet-switched networks.
iso osi reference model
ISO/OSI Reference Model
  • Communications protocols were developed using the Open System Interconnection (OSI) model.
  • The OSI Reference Model is an ISO standard for worldwide communications.
  • It defines a framework for implementing protocols in seven distinct layers.
the seven layers
The Seven Layers

The OSI Model

packets
Packets
  • When data is broken into smaller pieces for transmission, the smaller pieces are called packets.
standard packets
Standard Packets
  • A standard packet is crucial in protocol definition.
  • Without a standard packet structure, systems would not be able to interpret the information coming to them from other systems.
ip packets
IP Packets
  • IP packets (datagrams) have two sections:
    • Header
    • Data section payload
the header
The Header
  • The header section contains all the information needed to describe the packet.
    • What kind of packet it is
      • (Protocol version number)
    • How large the header of the packet is
      • (Packet header length)
    • How to process this packet
      • (Type of service – Whether or not to use options (minimize delay, maximize throughput, maximize reliability, and minimize cost)
    • How large the entire packet is.
    • A unique identifier so that the packet can be distinguished.
the header1
The Header
  • The header section contains all the information needed to describe the packet.
    • Whether or not the packet is part of a longer data stream and should be handled relative to other packets.
    • A description of where the packet fits into the data stream as compared to other packets.
    • A checksum of the packet header:
      • To minimize data corruption during transmission.
the header2
The Header
  • The header section contains all the information needed to describe the packet.
    • Where the packet is from.
      • Source IP address such as 10.10.10.5
    • Where the packet is going.
      • Destination IP address such as 10.10.10.10
the header3
The Header
  • The header section contains all the information needed to describe the packet.
    • Option flags that govern security and handling restrictions:
      • Record the route this packet has taken.
      • Record timestamps.
    • The data in the packet.
packet illustrated
Packet Illustrated

Logical layout of an IP packet

tcp versus udp
TCP versus UDP
  • Transmission Control Protocol User Datagram Protocol
tcp versus udp1
TCP versus UDP
  • As separate protocols, TCP and UDP have their own packet definitions, capabilities, and advantages, but the most important difference between TCP and UDP is the concept of “guaranteed” reliability and delivery.
connectionless udp
Connectionless UDP
  • UDP is a “connectionless” protocol.
    • Very few error recovery services.
    • No guarantee of packet delivery.
udp unreliable
UDP – Unreliable
  • UDP is an unreliable protocol.
    • Used for network services not affected by the occasional lost or dropped packet.
udp efficient
UDP – Efficient
  • More time and space of a UDP session is dedicated to content or data delivery.
tcp connection oriented
TCP – Connection-Oriented
  • TCP was designed to allow a reliable connection between two hosts exchanging data.
  • TCP was designed to ensure that packets are processed in the order they were sent.
tcp packet sequence
TCP Packet Sequence
  • Each packet has a sequence number to show where the packet fits into the conversation.
    • Using sequence numbers, packets can arrive in any order and at different times.
    • The receiving system will still know the correct order for processing the packets.
tcp packet sequence1
TCP Packet Sequence
  • The sequence numbers let the receiving system know if packets are missing.
    • The receiving system can then request re-transmission of packets from the sender to fill any gaps.
tcp three way handshake
TCP Three-Way Handshake

TCP’s three way handshake

  • The TCP protocol requires that systems follow a specific pattern to establish communications.
    • The “three-way handshake” consists of a sequence of steps.
tcp three way handshake1
TCP Three-Way Handshake
  • Three-Way Step One
    • The originating host (client) sends a SYN (synchronize) packet to the destination host (server).
  • This tells the server:
    • What port the client wants to connect.
    • The initial packet sequence number of the client.
tcp three way handshake2
TCP Three-Way Handshake
  • Three-Way Step Two
    • Next, the server sends a SYN/ACK (synchronize/acknowledge) packet to the client which tells the client “I received your request.”
    • It contains the server’s initial packet sequence number.
tcp three way handshake3
TCP Three-Way Handshake
  • Three-Way Step Three
    • The client responds to the server with an ACK packet.
    • This completes the connection establishment process.
slide54
ICMP
  • ICMP or Internet Message Protocol is a control and information protocol, which is used to to determine:
    • Remote network’s availability.
    • Length of time to reach a remote network.
    • The best route for packets for that remote network.
icmp and traffic flow
ICMP and Traffic Flow
  • ICMP can handle the flow of traffic, telling other network devices to “slow down” transmission speeds if packets are coming in too fast.
icmp connectionless
ICMP – Connectionless
  • ICMP, like UDP, is a connectionless protocol.
    • Designed to carry small messages quickly.
    • Has minimal overhead.
    • Has minimum impact to bandwidth.
packet delivery
Packet Delivery
  • Local delivery applies to packets being sent out on a local network.
  • Remote delivery applies to packets being delivered to a remote system, such as across the Internet.
packet delivery1
Packet Delivery
  • The biggest difference in local vs. remote delivery is how packets are addressed.
    • These addresses are usually called MAC addresses for local packet delivery and IP addresses for remote packet delivery.
local packet delivery
Local Packet Delivery
  • Packets delivered on a local network are sent using the destination system’s hardware address or Media Access Control (MAC) address.
mac addresses
MAC Addresses
  • MAC address is a unique hardware address assigned to a device by the manufacturer.
    • Each manufacturer is assigned a specific block of MAC addresses.
    • No two devices can share the same MAC address.
mac address and arp
MAC Address and ARP
  • For one system to send data to another on the local network, it must first find out the destination system’s MAC address.
  • To find a MAC address, the Address Resolution Protocol (ARP) is used.
    • It is the computer’s way of finding out “who owns the blue convertible with license number 123JAK.”
using the arp
Using the ARP
  • Systems know the IP address of the computer to which they want to send data, but not the MAC address.
  • Using an ARP request, the sending system will send out a query – “who is 10.1.1.140”?
resolving the arp request
Resolving the ARP Request
  • This broadcast query is examined by every system on the local network, but only the system whose IP address is 10.1.1.140 will respond.
  • That system will send back a response that says “I’m 10.1.1.140 and my MAC address is 00:07:e9:7c:c8:aa.”
  • The sending system will then format the packet for delivery and drop it on the network media, with the MAC address of the destination workstation.
remote packet delivery
Remote Packet Delivery
  • Local packet delivery is accomplished with MAC addresses.
  • Remote packet delivery is usually accomplished using Internet Protocol (IP) addresses.
    • IP addresses are 32-bit numbers that we usually see expressed as a group of four numbers (such as 10.1.1.132).
dns role
DNS Role
  • The Domain Name Service (DNS) protocol translates names into IP addresses.
    • The DNS server handles DNS queries by examining its local records to see if it knows the answer.
    • If it does not, the DNS server queries higher level domain servers. They check records or query the server above them and so on until a match is found.
dns success
DNS Success
  • The name for the matching IP address is passed to the computer.
    • The user’s computer can create the Web request, stamp it with the right destination IP address, and send it.
local or remote
Local or Remote?
  • Before sending the packet, the system will first determine if the destination IP address is on a local or remote network.
    • This is done by sending the packet to a network gateway.
gateway
Gateway
  • Network Gateways (Routers):
    • Interconnect networks.
    • Move packets from one network to another.
  • The process of moving packets from one network to another is called routing.
packet reaches router
Packet Reaches Router
  • When a packet reaches a router:
    • It examines the destination address to determine where to send the packet.
    • If the router’s forwarding tables know where the packet should go, the router sends the packet out along the appropriate route.
router and unknown destination
Router and Unknown Destination
  • If the router does not know where the destination network is:
    • It will forward the packet to its defined gateway which will repeat the same process.
    • After traversing various networks and routers, the packet will come to the router serving the network with the Web site.
the destination router
The Destination Router
  • The destination router determines the MAC address of the destination system and forwards the packet accordingly.
subnetting
Subnetting
  • IP addresses are 32-bit numbers.
    • Some bits are used for the network portion of the address.
    • Some are used for the host portion of the address.
  • The network portion is called the subnet.
  • The process of dividing that 32-bit space into networks is called subnetting.
subnetting1
Subnetting
  • Subnetting tells the system how much of the 32-bit space is used for the network of the address and how much is used for the host portion of the address.
interpreting the subnet
Interpreting the Subnet
  • To interpret the 32-bit space, use a subnet mask.
    • The subnet mask describes how much of the space is the network portion and how much is the host portion.
example subnet mask
Example Subnet mask
  • IP address 10.10.10.101 with a subnet mask of 255.255.255.0.
  • Convert to binary
    • Subnet Mask: 11111111.11111111.11111111.00000000
    • IP Address: 00001010.00001010.00001010.01100101
bitwise and to get subnet
Bitwise and To Get Subnet
  • The bitwise AND operation examines each set of matching bits from the binary representation of the subnet mask and the binary representation of the IP address.
  • For each set, where both the mask and address bits are 1, the result of the AND operation is 1, otherwise if either bit is 0, the result is 0.
bitwise and to get subnet1
Bitwise and To Get Subnet
  • For each set, where both the mask and the address bits are 1, the result of the AND operation is 1, otherwise if either bit is 0, the result is 0.
  • This yields a subnet address: 00001010.00001010.00001010.00000000In Decimal 10.10.10.0 (The subnet address)
final interpretation
Final Interpretation
  • The subnet address and mask determine that the first three parts of the address are network-related.
    • The last part of the address is the host portion.
  • In the example, the network portion of the address is 10.10.10 and the host portion is 101.
classes of subnets
Classes of Subnets
  • Class A addresses:
    • 16 million hosts on each of the 127 networks.
      • Subnets: 0.0.0.0 to 126.255.255.255 (127.0.0.0 to 127.255.255.255 is reserved for loopback and is not included in the class A range)
  • Class B addresses:
    • 65,000 hosts on each of the 16,000 networks.
      • Subnets: 128.0.0.0 to 191.255.255.255
  • Class C addresses:
    • 254 hosts on 2,000,000 networks.
      • Subnets: 192.0.0.0 to 223.255.255.255
additional reservations
Additional Reservations
  • In addition, certain subnets are reserved for private use and are not routed across public networks.
    • 10.0.0.0 to 10.255.255.255
    • 172.16.0.0 to 172.31.255.255
    • 192.168.0.0 to 192.168.255.255
rule for valid hosts
Rule for Valid Hosts
  • To determine the valid hosts that can be placed on a particular subnet, keep in mind the following:
    • “All 0s” address of the host portion is reserved for the network address.
    • “All 1s” address of the host portion is reserved for the broadcast address of that particular subnet.
network address translation
Network Address Translation
  • Network Address Translation (NAT) compensates for the lack of available IP address space.
  • NAT translates private (non-routable) IP addresses into public (routable) IP addresses.
example of nat
Example of NAT
  • In the figure, we see an example of NAT being performed.
    • An internal workstation (10.1.1.121) wants to visit the CNN Web site at www.cnn.com.

Logical depiction of NAT

decoding for nat
Decoding for NAT
  • A packet NAT device
    • The device translates the 10.1.1.123 source address to the globally routable 63.69.110.110 address.
    • This is the IP address of the device’s externally visible interface.
  • When the CNN Web site responds, it responds to the device’s address.
    • Just as if the NAT device had originally requested the information.
  • The NAT device must then remember which internal workstation requested the information and route the packet to the appropriate destination.
ip address assignment
IP Address Assignment
  • When administrators set up a network, they usually assign IP addresses to systems in one of the two ways:
    • Statically
    • Via a DHCP
static ip addresses
Static IP Addresses
  • Static IP address assignment is simple.
    • The administrator decides what IP address to assign to a server or PC and that IP address stays assigned to that system until the administrator decides to change it.
slide87
DHCP
  • When a system boots or is connected to the network, it sends out a query for a DHCP server.
    • If a DHCP server is available on the network, it will answer the new system and assign the new system an IP address from a pool of dedicated, available addresses.
slide88
DHCP
  • DHCP is an “as available” protocol.
    • If the server has allocated the available IP addresses in the pool, new systems will not receive an IP address and will not be able to connect to the network.
slide89
DHCP
  • A key feature of DHCP is the ability to limit how long a system may keep its DHCP-assigned IP address.
    • These DHCP addresses have a limited lifespan.
      • Once the ‘lease’ expires, the system using that IP address must either renew that address or request another address from the DCHP server.
    • The requesting system may have the same IP address, or it may be assigned a completely new address depending on how the DHCP server is configured and the current demand for available addresses.
slide90
DHCP
  • DHCP is very popular in large user environments where the cost of assigning and tracking IP addresses is large.
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