Computer Networks Week 1

Name the layers of the TCP/IP reference model

4. Application Layer 3. Transport Layer 2. Internet Layer 1. Link Layer

Name the layers of the OSI/ISO reference model

7. Application Layer 6. Presentation Layer 5. Session Layer 4. Transport Layer 3. Network Layer 2. Data-Link Layer 1. Physical Layer

What is a protocol Stack?

A list of the protocols used by a certain system, one protocol per layer, is called a protocol stack.

What is a network?

A network is a set of autonomous computers that provide information exchange and each machine operates based on dedicated hardware and software

What is a "network protocol"?

A network protocol is a set of established rules that determine how data is transmitted between different devices in the same network.

What is a service?

A service is a set of primitives (operations) that a layer provides to the layer above it. The service defines what operations the layer is prepared to perform on behalf of its users, but it says nothing at all about how these operations are implemented. A service relates to an interface between two layers, with the lower layer being the service provider and the upper layer being the service user.

What is a distributed system?

A set of geographically distributed, autonomous, and interconnected computers, which offer a service based on cooperation

What is a network architecture?

A set of layers and protocols is called a network architecture. Neither the details of the implementation nor the specification of the interfaces is part of the architecture because these are hidden away inside the machines and not visible from the outside.

What is Unicast?

A transmission method in which data is transferred from a specific source address to a specific destination address. (One-to-one)

What is Anycast?

An anycast communication flow is a one-to-nearest flow. (Incoming request can be routed to a variety of different locations and "nodes". Typically routes to the nearest data center)

What is the Link Layer (TCP/IP) and what is it responsible for?

First TCP/IP Layer Passes data to the physical network. It can work with any media such as copper wire, optical fibre and wireless. Like the combination of physical layer and data-link layer of the iso/osi modell. (not end-to-end)

What is the Physical Layer (OSI) and what is it responsible for?

First layer in OSI. In charge of transmitting raw bits over a communication channel. The Physical Layer defines electrical and physical specifications for devices. The physical layer defines the relationship between a device and a transmission medium, such as a copper or optical cable.

What is the Transport Layer (OSI) and what is it responsible for?

Fourth Layer in the OSI model Accepts Data from above and splits it into smaller units and makes sure that those pieces all arrive correctly at the desitnation. (First end-to-end layer) Transport Layer provides transparent transfer of data between end users, providing reliable data transfer services to the upper layers. The transport layer controls the reliability of a given link through flow control, segmentation and desegmentation, and error control.

What is GAN

Global Area Network

What does HTTP stand for ? And in what layer is it used? What is it most commonly used for?

Hypertext Transfer Protocol (Application layer). It is mainly used to load web pages from the World Wide Web into a web browser.

What is a partial mesh topology and what is a full mesh topology?

In a meshed network, each network node is connected to one or more others. The network is connected (zusammenhängend), and there is a path from each node to every other node. Full Mesh topology is a setup wherein each device is connected directly to every other device on the network. number of needed links: n(n-1) / 2

What is a signal?

Is a physical representation of data by well-defined space- or time-based changes of physical parameter

what is internetworking?

Solutions for different limitations of networks. Ex.:not all communication channels preserve the order of messages sent on them, leading to solutions that number messages. Another example is differences in the maximum size of a message that the networks can transmit. This leads to mechanisms for disassembling, transmitting, and then reassembling messages.

What is DNS?

The Domain Name System (DNS) converts domain names or host names into IP addresses. Instead of having to remember a host's IP address, DNS allows you to use a friendly name to access the host. For example, it is easier to remember cisco.com than 198.133.219.25.

What are peers in a Layer Network?

The entities comprising the corresponding layers on different machines are called peers. The peers may be software processes, hardware devices, or even human beings. In other words, it is the peers that communicate by using the protocol to talk to each other.

What is WAN?

Wide Area Network

What is an interface in a layer network?

Between each pair of adjacent layers is an interface. The interface defines which primitive operations and services the lower layer makes available to the upper one.

Application Layer (TCP/IP)

Contains all the higher-level protocols such as HTTP, DNS,SMTP

What is the Application Layer (OSI) and what is it responsible for?

Layer 7 of the OSI model Contains protocols which are often needed by clients/users E.g. HTTP The Application Layer interface directly interacts with application and provides common web application services.

What is LAN

Local Area Network

What is PAN

Personal Area Network

Internet Layer (TCP/IP)

Second TCP/IP Layer Determines the best path through the network (routing). Equivalent to the network layer of the OSI model. Defines an official packet format and protocoll called IP(Internet Protocol) ICMP (Internet Controll Message Protocol) assists IP and makes sure that IP packets arrive at the right destination.

What is SMTP?

Simple Mail Transfer Protocol: Standards used for directing mail around the internet

What is the Session Layer and what is it responsible for?

The fifth layer in the OSI model. This layer establishes and maintains communication between two nodes on the network. It can be considered the "traffic cop" for network communications. -> offers dialog control(who's turn it is) ,token management (preventing two parties to attempt the same critical operations synchronously) and synchronization.

What is Multicast?

The process of sending a packet from a host to selected groups of hosts (ip range). Possibly in different networks

What is the Data-Link Layer (OSI) and what is it responsible for?

The second layer in the OSI model. This layer bridges the networking media with the Network layer. Its primary function is to divide the data it receives from the Network layer into frames that can then be transmitted by the Physical layer. Data Link Layer provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the physical layer.

What is the Presentation Layer (OSI) and what is it responsible for?

The sixth layer of the OSI model. The Presentation layer translates between the application and the network. Here, data are formatted in a schema that the network can understand, with the format varying according to the type of network used. The Presentation layer also manages data encryption and decryption, such as the scrambling of system passwords.

What is the Network Layer (OSI) and what is it responsible for?

The third layer in the OSI model. This layer translates network addresses into their physical counterparts and decide how to route data from the sender to the receiver. Make sure different networktypes can communicate together

What is the Transport Layer (TCP/IP), what are its functions and what protocol does it contain?

Third TCP/IP Layer Contains Two Protocols: TCP and UDP Accepts Data from above and splits it into smaller units and makes sure that those pieces all arrive correctly at the desitnation. (end-to-end layer) -> providing reliable data transfer services to the upper layers. The transport layer controls the reliability through flow control, segmentation and desegmentation, and error control.

What does TCP stand for? In what layer is it used? connection based or connection less?

Transmission Control Protocol (Transport layer) -> reliable connection based communication -> Handles flowcontrol

What does UDP stand for? Which layer and connection based or connection less?

User Datagram Protocol(Transport Layer) -> unreliable connectionless communication -> faster than TCP -> used for e.g., for video and speech transmission

What is a Protocol?

a protocol is an agreement between the communicating parties on how communication is to proceed

What is a end-to-end layer/protocol? Which are the end to end layers of iso/osi and tcp/ip?

communication takes place completely between PC1 and PC2 - and not via router/switch & co as in the lower layers.

what is protocol layering?

dividing the overall problem into layers with protocols and hiding implementation details between the layers (using well defined interfaces)

Which choice lists the neccessary components to form a computer network? a) End systems, Intermediate systems b) intermediate systems connection connections(links) c) End systems connections d) Distributed systems, links e) end systems, intermediate systems, connections

e) end systems, intermediate systems, connections

What is routing?

finding a working path through a network.

what is addressing and naming?

identifying the senders and receivers that are involved in a particular message.

What is Broadcast?

it is the process of a host sending a packet to all hosts in the network.