Session 1: Background and core concepts Flashcards
What are the oldest forms of networks?
Networks have been utilized for long range communication for thousands of years. Beacons, i.e., lighting fires atop hills/elevated terrain was frequently utilized to signal the approach of enemies in ancient times.
More recently, in the 19th century semaphore lines were built in several countries. This is essentially a line of towers placed on elevations with a simple mechanical device with arms put on top. The configuration of the arms determined message being relayed. These towers were usually placed several km apart since all towers were equipped with a telescope.
What are considered the three general types of network topology?
Centralized networks is often the simplest to construct, where all nodes are directly connected to a main hub/master node, through which all network traffic flows. This is the cheapest type since it only requires N-1 direct links for a network with N links. Centralized networks are also considered the weakest as a failure on the central node makes the entire network collapse.
Decentralized networks do not solely rely on one central node. Instead, some of the load is distributed to other nodes. This implies that not all communication breaks down if the most important node in the network fails. Consequently, distributed networks can be significantly more robust. In terms of costs, decentralization can be achieved with the same number of connections/links between nodes, i.e., we can achieve decentralization for a network containing N nodes while only needing N-1 links.
Distributed networks (also known as mesh) allow each node to connect to several others, which makes such networks superior in terms of robustness. However, a distributed network topology will quickly require many more links, which makes them much more expensive.
What is the OSI reference model?
The OSI model is an attempt of structuring network communication into different layers. The intent is to make the computer networking a better organized domain. The OSI model has 7 distinct layers where a given layer only directly interacts with the layer above and below.
What are the layers in the OSI model?
If we start at the top we have:
Application layer which handles communication at the level of application tasks.
Presentation layer is responsible of handling the encoding and decoding of the data from the application layer (may be used to encrypt application data).
Session layer manages logical connections between systems to establish, terminate and restart sessions between end points.
Transport layer handles the end-to-end transport of data. This can be carried out in different classes, i.e., connection-oriented or connection-less. There are also different grades of guarantee of delivery.
Network layer handles addressing and transmitting/routing data end-to-end.
Data link layer handles the bits and bytes from the physical layer and structures them into frames or packets.
Physical layer handles the physical interfaces and electrical/optical specifications (mainly just all the cables and devices involved during transmission).
List the threat categories provided by ENISA
Physical attack - Attacks involving physical manipulation or access to media devices.
Unintentional damage - E.g. human error leading to information leaks,
integrity breaches.
Disaster - E.g. fire, dust, water, unfavourable climate.
Malfunction - E.g. hardware, power faults, RF interference.
Outages - E.g. key staff absence, network infrastructure faults.
Interception - Includes data in flight and at rest, active attacks.
Abuse - E.g. malware, social engineering.
Legal - E.g. failure to comply with legal, regulatory requirements.
(Not exclusive for network security, but important for the field)
How is Quality of Service (QoS) handled within networking?
QoS is difficult to implement in networks and is therefore mostly handled on a best effort basis. Protocols trying to better enable QoS have largely proven inadequate. Ensuring sufficient performance is mostly handled by over provisioning the networks.
