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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 l.jpg
Internet Protocols

  • IP

  • TCP

  • http:

  • Domain Name Services

The internet is a network of networks


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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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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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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


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Internet Protocols

  • Tracing your Route:

  • Launch a “DOS” window (command prompt)

  • At the prompt enter “tracert” followed by a domain name


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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


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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”


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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


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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:


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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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