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The Internet Protocols. COMT 429. History. 1969First version of a 4 node store and forward network, the ARPAnet 1972Formal demonstration of ARPAnet with 20 packet switches and 50 hosts - PowerPoint PPT Presentation
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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
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.
COMT 429
Protocol Overview
Ethernet, X.25, HDLC etc.
IP ICMP ARP RARP (Auxiliary Services)
TCP UDP
E-Mail HTTP (WWW) Remote LoginFile Transfer
X.25 PacketLayer
COMT 429
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
COMT 429
Connection Types in TCP/IP
Data Link Layer and Physical Network
Network Layer
Transport Layer TCP: Connection Oriented
UDP: Connection-less
Connection-less
Depends on the network
COMT 429
IP HeaderVersion
Timeout Protocol Header Checksum
Source Address
Destination Address
Header Len Class of Service
Total Length
Identification
D M Fragment Position
COMT 429
TCP Header
Source Port Destination Port
Sequence Number
Acknowledgement Number
Window (flow cntrl)misc Flags
Checksum Urgent
Options
COMT 429
Addressing
IP Addresses are 32 bits long, originally using one of threeformats:
0NNNNNNN HHHHHHHH HHHHHHHH HHHHHHHH
or
10NNNNNN NNNNNNNN HHHHHHHH HHHHHHHH
or
110NNNNN NNNNNNNN NNNNNNNN HHHHHHHH
N = Network Address Bit
H = Host Address Bit
COMT 429
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
COMT 429
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?
OUInternet
132.235.0.0CS (Morton)
RTVC
COMT 429
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
COMT 429
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”
COMT 429
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.
COMT 429
HTTP Message
The browser assembles a text message:
First line:– GET index.htm
Optional additional lines:– Browser type– HTTP version number– Transmission option negotiation
COMT 429
Request to TCP
Browser makes a call to TCP, asking to open a connection to the numeric browser address
COMT 429
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
COMT 429
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.
COMT 429
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.
COMT 429
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.
COMT 429
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.
COMT 429
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.
COMT 429
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
COMT 429
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.
COMT 429
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.