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Network Addressing

Level 2 Diploma Unit 10 Setting up an IT Network. Network Addressing. OSI Layers 1 to 4. OSI Physical layer 1 Network media – the cables/wireless and adapters OSI Data link layer 2 Method of transferring data between network adapters Organises data streams into frames Uses MAC addresses

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Network Addressing

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  1. Level 2 Diploma Unit 10 Setting up an IT Network Network Addressing

  2. OSI Layers 1 to 4 • OSI Physical layer 1 • Network media – the cables/wireless and adapters • OSI Data link layer 2 • Method of transferring data between network adapters • Organises data streams into frames • Uses MAC addresses • OSI Network layer 3 • Routes packets between networks • Uses IP addresses

  3. OSI (Open Systems Interconnect) model • 7 layers • Each layer provides a service for the layer above and uses the services of the layer below • Each layer (except the physical) attaches a header • Headers provide control information

  4. Frames • Address used is the 48 bit unique MAC (Media Access Control) address hard coded into the adapter

  5. Network Layer 3 • Data messages are split into smaller packets • Better chance of successful delivery • Easier to resend if lost or damaged • Routers • Choose the path that packets take around the network • Packets are given a time to live (TTL) to prevent them travelling for ever • Internet Protocol (IP) and IP addressing • Provides network identification and addressing • An IP address is a 32 bit binary value expressed as dotted decimal 00001010.00000001.1010000.00001100 is easier as 10.1.80.12

  6. Restricted addresses

  7. I. P Addresses 11000000101010000000000100000101 What is a ’bit’? 192.168.1.5 www.

  8. Network Address Translation • Private networks connect to the Internet via a router • Host’s private address is translated to a valid public address by the router using NAT • Easier IP configuration • Hosts protected from direct internet access • Can map 1:1 or use port addresses to map n:1

  9. ARP and ICMP • ARP (Address resolution protocol) • Network layer • Converts IP addresses to MAC addresses • Converts MAC addresses to IP addresses • ICMP (Internet control message protocol) • Used for diagnostic and troubleshooting tools • PING • TRACERT

  10. TCP and UDP Layer 4 • TCP Transmission Control Protocol • Reliable • Connection oriented packet transfer • TCP/IP applications use a unique identification number called a port • An IP address and a port make a socket • Socket to socket connections make a path • http:215.58.254.252:80 where 80 is the port number

  11. Common port numbers

  12. HTTP and HTML • Hypertext transfer protocol • Web browsers request resources from web servers by • connecting to port 80 • Using a Uniform Resource Identifier (URI) • Common web servers are • Apache (open source) • Microsoft Internet Information Server (IIS) • HTTP is used to serve HTML (Hypertext MarkUp language) pages which describe how the text should be displayed

  13. SSL/TLS • HTTP is not encrypted and does not authenticate • SSL (Secure sockets layer) and TLS (Transport Layer Security) • Provide cryptographic security • Used with HTTPS • Uses port 443 • Puts https:// in the URI • Adds a padlock icon in the browser

  14. E-mail • Plain text • File attachments encoded in MIME (multipurpose internet mail extensions) • Send mail out using SMTP • Simple mail transfer protocol • Receive mail using • POP3 or IMAP4 • Can be secured using PGP (Pretty Good Privacy or Secure MIME

  15. FTP • File transfer protocol • More efficient then e-mail • Plain text transfer • Most browsers include an FTP client • ftp://ftp.microsoft.com/

  16. Instant Messaging • Exchange of text messages with contacts

  17. Domain names • Every host on the internet has a unique, 32 bit IP address • For convenience each host also has a Fully Qualified Domain Name (FQDN) • Domain Name Servers cross reference between domain names and IP addresses • An FQDN is hierarchical • www.google.comwww as a local domain indicates the resource is a web server • A Subdomain has to be registered and identifies a company, organisation or individual Top level domain local domain Subdomain

  18. Top level domain names

  19. Uniform Resource Identifier • A URI (sometimes known as a URL): • Has all the information to identify a resource • http://news.bbc.co.uk/1/hi/sci/tech/8013709.stm • http:// is the protocol being used • News.bbc.co.uk is the FQDN • /1/hi/sci/tech/8013709.stm is the file path on the server

  20. email address • An email address consists of: • The user name • A separator symbol (@) • A domain name • prossert@hct.ac.uk

  21. Task (criteria P5) • You have been asked by a friend to explain how network communications work in a company. Describe how hardware, software and addressing combine to use a web browser to send an e-mail to another system. • Include a diagram making sure you show how the components are connected together • Make sure you explain: • NIC, cable, switches, routers, modems, servers • NOS, E-mail client, web browser • IP and MAC addresses

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