TD5: IP et TCP

1
TD5 IP et TCP

• Thomas Watteyne

Décembre 2007
2
Layer 4 (TCP) issues
Application
?

• reliable and ordered delivery
• flow control
• congestion control

Présentation
?
Session
?
Transport
?
Réseau
?
Liaison de DonnéesMAC
?
Physique
?
3
1

• IP Header

4
IP header
IP Header length, number of 32 bit words. Min5.
Simple QoS management
IPv4/v6
0 Normal Delay, 1 Low Delay
0 Normal Reliability,1 High Reliability
0 Normal Throughput,1 High Throughput
5
IP header
In bytes, including header and data
To assemble fragments
0 Last Fragment,1 More Fragments
0 May Fragment,1 Don't Fragment
6
IP header
L4 protocol ID
In number of 8 bytes.0 for first fragment.
Avoid loops
Header only. Recalculated at each hop (TTL
changes)
7
2

• TCP

8
TCP overview

• reliable and ordered delivery
• flow control
• congestion control

9
TCP overview

• Stream Data TransferFrom the application's
  viewpoint, TCP transfers a contiguous stream of
  bytes.
• ReliabilityTCP assigns a sequence number to
  each byte transmitted, and expects a positive
  acknowledgment (ACK) from the receiving TCP. If
  the ACK is not received within a timeout
  interval, the data is retransmitted. The
  receiving TCP uses the sequence numbers to
  rearrange the segments when they arrive out of
  order, and to eliminate duplicate segments.
• Flow ControlThe receiving TCP, when sending an
  ACK back to the sender, also indicates to the
  sender the number of bytes it can receive beyond
  the last received TCP segment.
• MultiplexingA pair of sockets uniquely
  identifies each connection.
• Logical ConnectionsThe reliability and flow
  control mechanisms described above require that
  TCP initializes and maintains certain status
  information for each data stream.
• Full DuplexTCP provides for concurrent data
  streams in both directions.

• reliable and ordered delivery
• flow control
• congestion control

10
TCP header
Identify the connection (with IP address)
Next seqNum(only if ACK1)
Rank of the first byte in the stream
Number of 32 bit words
If urgent part of message
Establish a connection
End a connection
Headerdata
Where does the non-urgent start ?
11
(No Transcript)
12
Sliding Window
MaxRxBuffer
MaxTxBuffer
13
Congestion control