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ISOC : Internet SOCiety IAB : Internet Architecture Board IRSG : Internet Research Steering Group IRTF : Internet Research Task Force IESG : Internet Engineering Steering Group IETF : Internet Engineering Task Force
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Bonjour
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Demande d’ouverture de connexion TCP
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GET http://www.upn.fr
Où est la gare ? Deuxième rue à gauche
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2. Using a common syntax. If necessary, the data are converted to a form expected by the destination. This may include a different character code, the use of encryption, and/or compression.
Peer−to−peer dialogue. Before data are sent, the sending and receiving applications agree on format and encoding and agree to exchange data.
Application
Data
3. Segmenting the data. TCP may break the data block into a number of segments, keeping track of their sequence. Each TCP segment includes a header containing a sequence number and a frame check sequence to detect errors.
Peer−to−peer dialogue. The two TCP entities agree to open a connection.
TCP
4. Duplicating segments. A copy is made of each TCP segment, in case the loss or damage of a segment necessitates retransmission. When an acknowledgment is received from the other TCP entity, a segment is erased.
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Data Peer−to−peer dialogue. Each IP datagram is forwarded through networks and routers to the destination system.
5. Fragmenting the segments. IP may break a TCP segment into a number of datagrams to meet size requirements of the intervening networks. Each datagram includes a header containing a destination address, a frame check sequence, and other control information.
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6. Framing. A frame relay header and trailer is added to each IP datagram. The header contains a connection identifier and the trailer contains a frame check sequence
1. Preparing the data. The application protocol prepares a block of data for transmission. For example, an email message (SMTP), a file (FTP), or a block of user input (TELNET).
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7. Transmission. Each frame is transmitted over the medium as a sequence of bits.
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LLC 9. Processing the frame. The frame relay layer removes the header and trailer and processes them. The frame check sequence is used for error detection. The connection number identifies the source.
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10. Routing the packet. IP examines the IP header and makes a routing decision. It determines which outgoing link is to be used and then passes the datagram back to the link layer for transmission on that link.
Peer−to−peer dialogue. The router will pass this datagram onto another router or to the destination system.
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11. Forming LLC PDU. An LLC header is added to each IP datagram to form an LLC PDU. The header contains sequence number and address information. 12. Framing A MAC header and trailer is added to each LLC PDU, forming a MAC frame. The header contains address information and the trailer contains a frame check sequence. M ##L#### I
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13. Transmission. Each frame is transmitted over the medium as a sequence of bits.
8. Arriving at router. The incoming signal is received over the transmission medium and interpreted as a frame of bits.
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20. Delivering the data. The application performs any needed transformations, including decompression and decryption, and directs the data to the appropriate file or other destination.
Application
19. Reassembling user data. If TCP has broken the user data into multiple segments, these are reassembled and the block is passed up to the application.
Data
18. Processing the TCP segment. TCP removes the header. It checks the frame check sequence and acknowledges if there is a match and discards for mismatch. Flow control is also performed.
TCP
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IP 17. Processing the IP datagram. IP removes the header. The frame check sequence and other control information are processed.
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16. Processing the LLC PDU. The LLC layer removes the header and processes it. The sequence number is used for flow and error control.
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15. Processing the frame. The MAC layer removes the header and trailer and processes them. The frame check sequence is used for error detection.
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14. Arriving at destination. The incoming signal is received over the transmission medium and interpreted as a frame of bits.
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