Web Science/Part1: Foundations of the web/Transmission Control Protocol/Port numbers

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Port numbers

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Learning goals

  1. understand the concept of a socket in a TCP/IP package
  2. understand that ports are part of the TCP header
  3. be able to explain the difference between solicited and unsolicited TCP/IP traffic
  4. understand how ports can be used for multiplexing internet connections
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Video

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Quiz

1 How many port numbers are placed in a TCP package?

1
2
3
4

2 A TCP port number consists of how many bits?

8
16
32
64
128

3 What is a network socket?

a pair consisting of port numbers
a pair consisting of ip addresses
a pair consisting of an IP address and a port number
a quadruple consisting of 2 port numbers and two IP addresses

4 What kind of incoming TCP packets are usually accepted by a host?

all packets where the destination port is the same as an open port of the host.
all packets where the source port is the same as an open port of the host.
all packets where the destination port corresponds to solicited traffic.
all packets where the source port corresponds to solicited traffic.

5 What port number is chosen as the source port of outgoing TCP packets?

a random number that is not used as source port for any established connection of the host
a random number that is not used as source port for any established connection of the host and is not an reserved port
if possible the destination port. If this is used it for any other connection it is increased by one until it becomes available.
the host does not choose a source port number. A number bigger than 1000 is assigned by the server in his SYN ACK Message during the three way handshake.

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