Tutorial 3: 17th October 2019

Question 1

What factors should be considered during system design?

Answer 1

performance, cost, functionalitity, and scalability

Question 2

How does recovery compare between Reno and Cubic?

Answer 2

Reno recovers more slowly, especially at larger delays.

Question 3

Why was the cubic variant of TCP made?

Answer 3

Because of the slow recovery times of Reno TCP, especially at high delays, and in particular in the transmission of Physics test data.

Question 4

What has been the priority in the development of HTTP?

Answer 4

Performance

Question 5

What may you have to trade-off when designing protocols?

Answer 5

Some two properties, such as performance and scalability

Question 6

How do companies influence the development of new protocols?

Answer 6

Change or twist them to their interests (e.g. making their app faster) rather than for public interest as a whole

Question 7

What is IPSec?

Answer 7

IPSec = IP security = a suite of protocols that provide data authentication, integrity, and confidentiality.

Question 8

What is the difference between security and privacy on the Internet?

Answer 8

Privacy is the control one has over their data: who can see them and what they can do with them. Security is how information is protected: privacy is established.

Question 9

When could security be implemented but privacy not?

Answer 9

Encrypted packets are secure but not private since the sender and receiver are in plaintext headers. So can see URL you are at but not the POST/GET request data.

Question 10

What is TLS?

Answer 10

A cryptographic protocol implementing secure, encrypted communications over a network. It is at the transport and session layer and is on top of TCP, again providing an application interface for secure and encrypted communications.

Question 11

What is SSL?

Answer 11

A protocol that enables encrypted communications over a network (the Internet). SSL is at the transport layer, sitting on top of TCP, and provides an application interface for secure and encrypted communications.

Question 12

Where is TLS in the layered Internet protcol model?

Answer 12

A mixture of transport and session layers

Question 13

What does TLS do with HTTP?

Answer 13

Provides an interface to secure and encrypted comms.

Question 14

Which versions of HTTP can use TLS?

Answer 14

1.1 onwards.

Question 15

How does privacy and security change with HTTP3?

Answer 15

Forces the use of TLS and privacy and security features by default, giving a warning if not used.

Question 16

How does the comparison of nginx and Apache present an example of a tradeoff?

Answer 16

both better for different workloads: single v multi threading

Question 17

What important aspect of protocol/systems deployment do many university students and graduates fail to consider? Why?

Answer 17

deployment and scalability as never been issues with designs before as we control practicals

Question 18

What difficulties does the Interent add to protocol and service deployment?

Answer 18

Need to be interoperable with existing systems and protocols as well as number of devices to update

Question 19

What type of apps are particularly affected by firewall issues and NATs? Why?

Answer 19

real-time interactive apps. because they try to use new port numbers which interferes with NAT’s mapping mechanism (port number not global ID). So a presence/discovery mechanism is required on top of NAT due to a lack of global addresses.

Question 20

What are presence systems?

Answer 20

Methods by which users of a service inform others that they are present and available and willing to communicate.

Question 21

What are presence systems aka?

Answer 21

Discovery systems.

Question 22

When are presence systems required?

Answer 22

When there are no global IDs on a network so hosts can’t query other hosts themselves.

Question 23

Why may people want to use NAT with IPv6?

Answer 23

For privacy and to abstract a subnetwork connection.

Question 24

What is NPTv6?

Answer 24

NAT with IPv6.

Question 25

What unforeseen responsibility do staff in companies in the technology industry now have in regards to its development?

Answer 25

Ensuring it is in the best interest of the public and doesn’t take advantage of them or their influence.

Question 26

Can ILNP give NAT-like functionality? How?

Answer 26

Yes, in the rewriting mechanism. It gives NAT-like functionality whilst maintaining unique end-to-end identifiers.