Date 09.03.2023

Time: 70 min
60 Points


- Online exam on ISIS. They have a big pool of tasks and questions where the exam tasks are chosen from randomly.
- All material from the course was allowed, but the time was limited, so it was not really possible to look up a lot.
- Overall I'd say the questions are all not too hard, the biggest problem is to do them all in the limited time.

There were three different types of questions and tasks: 

    16 questions à 1 point
    12 questions à 2 points
    4 questions à 5 points 

I'll try write down the points as well, if I remember them.

The following questions are the ones that I can remember: 

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How is the time between the sending of a TCP segment and the arriving of a corresponding ACK called?

Answer: RTT (Round-Trip-Time)
Points: 1 

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An exercise about Dykstra Algorithmn. The graph was given and the outline of the table. The values inside of the table had to been filled.

Points: 5

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A link with a bandwidth of 45 MBit/s is to be used by several users. Each user needs 2 MBit/s
to send, but is only in 10% of the time active. How many users can be connected if circuit
switching is used?

Answer: 22 Users
Points: 1 or 2?

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A packet with a length of 250 bytes shall be transmitted via a link that has a capacity of 100Mbps whar is the transmission delay? (To answer in milliseconds)

Points: 1

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An IPv6 adress has how many octets?

Answer: 16 octets
Points 1

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Routing table and IP-address were given. It had to be stated to which interface the packet would be routed next (using longest prefix match).

Points: 2

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Network topologie with multiple switches + routers was given. Question: How many colliding domains and how many broadcast domains? (With differentiation between half-duplex and full-duplex).

Points: ? I'm not sure anymore, but I'm guessing 2.

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Network topo with two private networks both using NAT. Packet is being send from one host from frist network to a host from the second network. In a selected segment between the networks, which are the destination and which source address of the packet?

Answer: If segment after first NAT-router, the source address is changed from local to NAT address + dest. address is the public ip of the second networks NAT router before and is then changed to the private ip of host after NAT-route number two.

Points: 2

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Which tranport layer protocol to choose for a drone with live transmission?

Answer: I said UDP, not 100% sure though.
Points: 1

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Why moving average for TCP RTT instead of just always take the last obsereved RTT?

Points: 1

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Shorten a given IPv6 address as much as possible.

Points: 1

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Something with SDN networks and if a new routing protocol would be on data plane or control plane.

Points: ?

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A graph of several autonomous sytems was given. The AS were split in three hierachies. On the same hierachy they had pairing relations, on different hierachies there were customer relations. 

Something kinda like that:
 
Tier 1			| AS 1 |-------	| AS 2 |-------	| AS 3 |
		 	 /    \ 	 /    \          /    \
		        /      \        /      \        /      \
		       /        \      /        \      /        \
Tier 2	  	| AS 4 |-------	| AS 5 |-------	| AS 6 |-------	| AS 7 |
		 /    \  	 /    \          /    \		 /     \
		/      \        /      \        /      \        /       \
	       /        \      /        \      /        \      /         \
Tier 3    | AS 8|	| AS 9 |	| AS 10 |	| AS 11 |	| AS 12 |


Questions were always like: 

Sending a packet from host in AS X to a host in AS Y. Which possible routes would be taken? (Considering aspects like which paths would be advertised, considering e.g. finacial aspects and relations).

Points: 5

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