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The Internet Protocols. COMT 429. History. 1969 First version of a 4 node store and forward network, the ARPAnet 1972 Formal demonstration of ARPAnet with 20 packet switches and 50 hosts

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history
History

1969 First version of a 4 node store and forward network, the ARPAnet

1972 Formal demonstration of ARPAnet with 20 packet switches and 50 hosts

mid-70s UNIX distributed to academic and research sites. DEC PDP-11 systems gain wide acceptance. Initial research on TCP.

1980 DEC VAXs appear and replace PDP-11. Berkley UNIX provided with TCP implementation.

1983 ARPAnet goes to TCP full-time. Sun Computers incorporate TCP/IP.

protocol overview
Protocol Overview

E-Mail HTTP (WWW) Remote Login

File Transfer

TCP UDP

IP ICMP ARP RARP

(Auxiliary Services)

X.25 Packet

Layer

Ethernet, X.25, HDLC etc.

network hierarchy
Network Hierarchy

“Backbone”

“Gateway”

types of connections
Types of Connections
  • Connection-Oriented Protocols
    • Requires Set-Up and Termination
    • Provides Sequencing, Flow Control, Error Handling
  • Connection-Less Protocols
    • Also referred to as “Datagram” or “Best Effort” Delivery
    • Typically does include Error Detection
connection types in tcp ip
Connection Types in TCP/IP

Transport Layer

TCP: Connection Oriented

UDP: Connection-less

Connection-less

Network Layer

Data Link Layer and Physical Network

Depends on the network

ip header
IP Header

Version

Header Len

Class of Service

Total Length

Identification

D

M

Fragment Position

Timeout

Protocol

Header Checksum

Source Address

Destination Address

udp header
UDP Header

Source Port

Destination Port

Checksum

Length

tcp header
TCP Header

Source Port

Destination Port

Sequence Number

Acknowledgement Number

misc Flags

Window (flow cntrl)

Checksum

Urgent

Options

addressing
Addressing

IP Addresses are 32 bits long, originally using one of three

formats:

0NNNNNNN HHHHHHHH HHHHHHHH HHHHHHHH

or

10NNNNNN NNNNNNNN HHHHHHHH HHHHHHHH

or

110NNNNN NNNNNNNN NNNNNNNN HHHHHHHH

N = Network Address Bit

H = Host Address Bit

notation
Notation
  • Dotted Decimal:
    • 192.149.89.61 = 1100 0000 1001 0101 0101 1001 0011 1101 = C0 95 59 3D
    • 132.235.75.17
  • The Network:
    • 192.149.89.0
  • Broadcast on that network:
    • 192.149.89.255
routing in an autonomous system
Routing in an Autonomous System
  • Assign a network class that grants enough host addresses.
  • The internet routes based on one network number
  • Do we find a host inside the autonomous system?

OU

Internet

RTVC

132.235.0.0

CS (Morton)

subnetworks
Subnetworks
  • Divide the Host Section
  • Network 132.235.0.0
    • Use half of the host id as a subnetwork
    • 10NNNNNN NNNNNNNN SSSSSSSS HHHHHHHH
  • Network Mask 255.255.255.0
  • 132.235.75.17
    • Internet network 132.235.0.0
    • Internal Network 132.235.75.0
    • Host 17
an example
An Example

Web Server:

www.lerc.nasa.gov

Web Browser

“Backbone”

the request
The Request
  • User types into the browser:
  • “http://www.lerc.nasa.gov/index.htm”
browser interpretation
Browser Interpretation
  • “http://www.lerc.nasa.gov/index.htm”
  • Protocol to use is HTTP (HyperText Transfer Protocol); the transport protocol is TCP
  • The requested server is named www.lerc.nasa.gov
  • The SAP address is 80
  • The requested file is “index.htm”
name resolution
Name Resolution
  • www.lerc.nasa.gov is not an actual address
  • Make a call to the “resolver” (or, in most PCs, the “stub resolver”) to get a numeric address.
  • The answer may come from local storage, or may itself require a network transmission using the Domain Name System (DNS) protocols.
  • The name space and the address space are unrelated, except that they can be translated into each other.
http message
HTTP Message
  • The browser assembles a text message:
  • First line:
    • GET index.htm
  • Optional additional lines:
    • Browser type
    • HTTP version number
    • Transmission option negotiation
request to tcp
Request to TCP
  • Browser makes a call to TCP, asking to open a connection to the numeric browser address
request to ip
Request to IP
  • TCP creates a header with the origin and destination SAPs
  • TCP sets a “flag” (bit) to request a new connection (SYN)
  • TCP may set other parameters and options
locate the gateway
Locate the Gateway
  • IP needs to find a way to get the TCP PDU (called a segment) to the destination address.
  • Since the destination is on a different network, it needs a gateway.
locate the physical gateway address
Locate the Physical Gateway Address
  • IP knows the global (IP) address of the gateway.
  • To make a request of the data link layer, it needs the physical (MAC - Media Access Control) address of the gateway.
  • The ARP protocol is used to broadcast a request for the “owner” of the IP gateway address.
  • The gateway responds to the broadcast; IP learns the MAC address from the response.
dispatch the syn packet
Dispatch the SYN Packet
  • IP creates one or more packets (usually one in this case).
  • The header has the origin and destination IP addresses and other options.
  • The packet goes to the Ethernet driver, which attaches the MAC (Ethernet origin and destination), and sends the packet to the gateway.
routing
Routing
  • The gateway receives the packet, and determines that it is not:
    • addressed to the gateway itself (at the IP level)
    • addressed to any networks the gateway is attached to
  • The gateway examines its routing table, and selects a circuit to send the packet out on.
receipt
Receipt
  • www.lerc.nasa.gov receives the packet.
  • IP removes its headers after error-checking the header
  • TCP removes its headers, after error-checking the entire packet.
  • TCP consults the owner of SAP 80, and determines that the web browser is willing to create the connection.
response
Response
  • TCP creates an empty packet
  • The packet acknowledges the receipt of the SYN
  • TCP responds to any options that may have been requested in the SYN
request transmission
Request Transmission
  • The browser is informed that the connection has been created.
  • The actual text message (the GET…) is now handed to TCP
  • TCP attaches its header and contacts IP
  • IP attaches its header and uses the Ethernet driver to send the packet to the gateway
  • etc.
response1
Response
  • The packet is received and checked by IP and TCP; they each remove their headers.
  • TCP notifies the web server
  • The web server reads the GET request
  • The server creates a header with responses to the options requested by the browser
  • The server adds a line to the header indicating the format of the file (MIME)
  • The header is followed by a blank line and the actual file content.
standards setting
Standards Setting

ISOC

IANA

IESG

IAB

IETF

Area Directors

Internet

Routing

General

User Services

Applications

Areas

Operations and Management

Security

Transport

Working Groups