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Internet Protocols

Internet Protocols IP TCP http: Domain Name Services The internet is a network of networks Internet Protocols Problem: How do I seamlessly and securely move data from one computer to another, different computer Over a variety of network connections Without losing data Quickly?

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Internet Protocols

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  1. Internet Protocols • IP • TCP • http: • Domain Name Services The internet is a network of networks

  2. Internet Protocols • Problem: How do I seamlessly and securely move data from one computer to another, different computer Over a variety of network connections Without losing data Quickly?

  3. Application Layer Presentation Layer Session Layer OSI Model Transport Layer Network Layer Data Link Layer Physical Layer Internet Protocols • The OSI Model • Open Systems Interconnection • A STANDARD, not a specific protocol • Each layer provides a SERVICE to the layer above, passes or receives data • One layer’s implementation is transparent to the layer above but layers agree on the interface format

  4. Application Layer Presentation Layer Session Layer OSI Model Transport Layer Network Layer Data Link Layer Physical Layer Internet Protocols • IP • Internet Protocol • Defined in 1974 (Cerf & Kahn) as part of “TCP” • Independent of OSI model, yet remains consistent with it

  5. Internet Protocols Application Layer Browser Using http: Presentation Layer Session Layer OSI Model TCP/IP Model Transport Transport Control Protocol (TCP) Layer Network Internet Protocol (IP) Layer Data Link Network Interface (ppp) Layer Physical Physical Layer Layer

  6. Internet Protocols • IP • Handles Routing of Internet Packets • Packets are routed based on IP address • Based on Packet-switching • Routing Work is done by ROUTERS

  7. Internet Protocols • Routers are computers that connect networks • Routers contain configuration tables of known addresses, maintained by network administrators • Routers • DON’T send packets where they’re NOT needed • Send packets where needed by the fastest route • Process: • Scan the configuration table for the destination address • Check that path’s performance • Select an alternative path if busy

  8. Internet Protocols Structure of the IP Address • 4 bytes (octets), 32 bits • Values up to 232 (4,294,967,296) • Each 8-bit octet can range from 0 to 255 • Two portions: Network and Host • Length of the “Network” portion depends on the value of the first octet nnn.nnn.nnn.nnn

  9. Internet Protocols nnn.nnn.nnn.nnn • First Octet: • 1- 126 = Class “A” network (8 bits network, 24 bits host) • - 191 = Class “B” network (16 bits network, 16 bits host) • 192 – 223 = Class “C” network (24 bits network, 8 bits host) • 136 class A networks can each have up to about 16 million hosts attached – first bit = 0 • 16,384 class B networks can each have up to about 65,000 hosts each – first 2 bits = 10 • 2 million class C network can have up to 254 hosts each – first 3 bits = 110

  10. Internet Protocols nnn.nnn.nnn.nnn • Routers first check for “local” routing • If the destination is on the same SUBNET as the source, the packet need not leave the local network • Uses a “subnet mask” to decide • Example: • Source and destination have a subnet mask of 255.255.255 • The first 24 bits of both IP addresses are equal • Therefore, the router keeps it on the local network

  11. Internet Protocols • Topics for further research • IP version 6 • CIDR – Classless Inter-Domain Routing • VLSM – variable length subnet masking • Routing protocols – • Updating routing tables • Determining the best route

  12. Internet Protocols • TCP (Transport/Transmission Control Protocol) • “Certified Mail” -- guaranteed delivery • Runs on each host (part of your browser) • Manages packets passed to or received from IP • Breakdown and reassembly • Resend if needed

  13. Internet Protocols • Domain Name Services • A network of servers • Translate host names into IP addresses • Invented in 1984 • “Distributed Database” of translation tables • Often uses the BIND (Berkeley Internet Name Domain) software • Two components: Name Server & Resolver

  14. Internet Protocols • Domain Name Services • Top level = ZONE (rightmost) • .com, .gov, .mil, .net, .edu, .org, .biz, .info, .name • Second level DOMAIN (description PLUS zone) • Must be registered via a “registrar” • Dozens, governed by ICANN • Must be unique • Host name (leftmost) • Identifies a unique machine within that domain

  15. Internet Protocols • When my browser requests a DNS translation: • Goes to my assigned (primary or secondary) DNS server • If the domain I seek is cached, it returns the IP address • If not cached, it passes the request to one of many redundant ROOT servers for the top level domain • Root points to one of many redundant master name servers for that TLD • Which point to one of many redundant name servers containing the requested domain • IP Address is returned through my DNS server

  16. Internet Protocols • Tracing your Route: • Launch a “DOS” window (command prompt) • At the prompt enter “tracert” followed by a domain name

  17. Internet Protocols • http: • Governs the activity between web servers & browsers • Defined by Tim Berners-Lee in 1991 (birth of WWW), formalized in 1996 • Browser requests resources in URL format • Server returns requested document [protocol]://[domain name]/directory/filename

  18. Internet Protocols • http: REQUEST – RESPONSE - DISCONNECT • Client contacts host by URL or IP address (plus a port number.) • Client sends a text string, no spaces. • Web server software “listens” on port 80 for incoming http requests. Port 80 is assumed if no other is specified. • Connection is broken by the server when the entire page has been sent. May be aborted by the client. • Client-Server interaction is “stateless”

  19. Internet Protocols • http: • Most common = GET request followed by page requested • PUT request stores string on server at URL location • POST request passes the string as a subordinate to the specified URL – should be executable • Typically used to pass data from an HTML FORM to a server-side script for processing • Returns a “404” if URL is not found

  20. http://hotwired.lycos.com/webmonkey/ Many, many resources for web developers Including good, high-level overviews computer.howstuffworks.com Abundant explanations of how stuff works www.tcpipprimer.com/section.cfm Excellent primer on tcp/ip www.internic.net Overseers of DNS registration www.ietf.org Oversees all internet protocol definitions www.networksolutions.com Domain name registrar www.icann.org Define DNS standards Internet Protocols References:

  21. Internet Protocols References: http://www.dns.net/dnsrd/ Good DNS reference site Governs assignment of various numbers used by internet protocols http://www.iana.org/numbers.html

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