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Chapter 6r

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Chapter 6r

  1. 1. Network Services Networking for Home and Small Businesses – Chapter 6
  2. 2. Network ServicesClients/Servers and Their InteractionClient Server Relationship Server – host running software application that provides information to other hosts on network – Example: Web Server Client – name given to a computer application that someone uses to access information held on a server – Example: Web browser • host uses web client software to request a web page Cisco Discovery Home & Small Business Chapter 6: Network Services 2/20
  3. 3. Network ServicesClients/Servers and Their InteractionClient Server Relationship Activity 6.1.1 DNS (Domain Name Server/System) – provides IP address of web site with the domain name Telnet – remote login E-mail – SMTP (Simple Mail Transfer Protocol) – POP3 (Post Office Protocol) – IMAP (Internet Message Across Protocol) DHCP Web – uses HTTP protocol FTP – used to download and/or upload files between clients and servers Cisco Discovery Home & Small Business Chapter 6: Network Services 3/20
  4. 4. Network ServicesClients/Servers and Their InteractionRole of Protocols in Client Server Communication Application Layer Protocols – determine the way in which a server and client interact – HTTP – way to convey information on the web Cisco Discovery Home & Small Business Chapter 6: Network Services 4/20
  5. 5. Network ServicesClients/Servers and Their InteractionRole of Protocols in Client Server Communication Transport Layer Protocols – manages individual conversations between client and servers – formats messages into segments (PDU) to be sent to destination – provides flow control – provides acknowledgments between hosts Cisco Discovery Home & Small Business Chapter 6: Network Services 5/20
  6. 6. Network ServicesClients/Servers and Their InteractionRole of Protocols in Client Server Communication Internetwork Layer Protocols – assigns logical addressing (IP) – encapsulates segments into packets – provides routing to the destination Cisco Discovery Home & Small Business Chapter 6: Network Services 6/20
  7. 7. Network ServicesClients/Servers and Their InteractionRole of Protocols in Client Server Communication Network Access Protocols –Primary functions • Data link management – takes IP packets and encapsulates them into frames – the frame reads the MAC address • Physical network transmissions – how bits are represented (1 and 0) – how bits are sent (media) Cisco Discovery Home & Small Business Chapter 6: Network Services 7/20
  8. 8. Network ServicesClients/Servers and Their InteractionTCP and UDP Transport ProtocolsTCP Protocols Provides acknowledgment of delivery of the packet – similar to sending a registered letter through the postal system How it works . . . – Message is broken into segments – Segments are then numbered in sequence – Keeps track of the number of segments – If sender not receive the segments within a period of time . . – The lost portion is retransmitted FTP and HTTP are examples of applications that use TCP to ensure delivery of data Cisco Discovery Home & Small Business Chapter 6: Network Services 8/20
  9. 9. Network ServicesClients/Servers and Their InteractionTCP and UDP Transport Protocols Activity 6.1.3UDP Protocols U = UNRELIABLE “Best effort delivery” No acknowledgment, no guarantee No retransmission Used by: – streaming audio – streaming video – VoIP Cisco Discovery Home & Small Business Chapter 6: Network Services 9/20
  10. 10. Network ServicesClients/Servers and Their InteractionTCP/IP Port Numbers Used by both TCP and UDP A port is a numeric identifier within each segment that is used to keep track of specific conversations and destination services requested Every message includes a source and destination port Destination port – sent by client in the segment to tell what service is requested • Port 80 = HTTP • Port 21 = FTP Cisco Discovery Home & Small Business Chapter 6: Network Services 10/20
  11. 11. Network ServicesClients/Servers and Their InteractionTCP/IP Port Numbers The source port number is randomly generated by the sending device to identify a conversation between two devices. This allows multiple conversations to occur simultaneously. The combination of the source and destination IP address and the source and destination port number is known as a socket. Cisco Discovery Home & Small Business Chapter 6: Network Services 11/20
  12. 12. Network ServicesClients/Servers and Their InteractionDomain Name Service Lab Activity 6.2.1 Associates a names with an IP address Some groups – .com – .edu Port 53 = DNS – used if clients wants an IP address of a web site or host Cisco Discovery Home & Small Business Chapter 6: Network Services 12/20
  13. 13. Network ServicesClients/Servers and Their InteractionFTP Clients and Servers Lab Activity 6.2.3 Host must run FTP client access to access the FTP server Two ports used to communicate – FTP Request = Port 21 – To transfer files when open = Port 20 Cisco Discovery Home & Small Business Chapter 6: Network Services 13/20
  14. 14. Network ServicesClients/Servers and Their InteractionEmail Clients and Servers Lab Activity 6.2.4Email Protocols SMTP (Simple Mail Transfer Protocol) – used by email client to send messages to local email server – Port #25 POP3 (Post Office Protocol) – receives/stores messages for the users – when client connects to email server messages are downloaded to the client; messages are removed from server – Port #110 IMAP (Internet Message Across Protocol) – receives/stores messages but keeps messages on the server unless deleted by user – Port #143 Cisco Discovery Home & Small Business Chapter 6: Network Services 14/20
  15. 15. Network ServicesClients/Servers and Their InteractionPort Numbers Activity 6.2.7 Client requests can be identified because the request is made to a specific destination port. Ports are assigned and managed by an organization known as the Internet Corporation for Assigned Names and Numbers (ICANN). Well-known ports – 1-1023 (destination ports) Registered ports – 1024-49151 – source and destination ports Private ports – 49152-65535 (source ports) Cisco Discovery Home & Small Business Chapter 6: Network Services 15/20
  16. 16. Network ServicesClients/Servers and Their InteractionProtocol Interaction Each upper layer relies on the layer below it Upper Layers – message content Lower Layers – help to move data Cisco Discovery Home & Small Business Chapter 6: Network Services 16/20
  17. 17. Network ServicesClients/Servers and Their InteractionProtocol InteractionWhy Use a Layered Model? Assists in protocol design Allows competition between vendors – can all work together One layer does not affect other layers Allows for a common language Cisco Discovery Home & Small Business Chapter 6: Network Services 17/20
  18. 18. Network ServicesClients/Servers and Their InteractionProtocol Operation of Sending and Receiving a MessageEncapsulation (sending data) From top to bottom Application data broken into segments – segments contain source and destination ports TCP segments sends it down to Internet layer – source and destination IP added (packet) Packet put into a frame – header and trailer added • header = source and destination MAC • trailer = error checking Broken into bits – encoded onto the media (cabling) Cisco Discovery Home & Small Business Chapter 6: Network Services 18/20
  19. 19. Network ServicesClients/Servers and Their InteractionProtocol Operation of Sending and Receiving a Message Activity 6.3.2De-encapsulation (receiving data) From bottom to top Bits are decoded from the media Frame removes header and trailer Packet removes the IP address – source and destination IP Segment is received and reassembled for the user – viewing a web page Cisco Discovery Home & Small Business Chapter 6: Network Services 19/20
  20. 20. Cisco Discovery Home & Small Business Chapter 6: Network Services 20/20

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