Network Models Flashcards
what is a protocol?
A protocol defines the rules that the sender and receiver and all intermediaries need to follow to be able to communicate effectively
what is modularity in protocol layering?
Modularity means independent layers. A module (layer) is a black box with inputs and outputs, and as long as the inputs and outputs are the same they can be replaced.
what are some advantages of protocol layering?
- separates services from implementation
- intermediate steps do not need all layers
what is the first principle of protocol layering?
If we need bidirectional communication, we need to make each layer so that it is able to perform 2 opposite tasks one in each direction.
what is the second principle of protocol layering?
The objects under each layer at both sites (sender and receiver) should be identical
what is a logical connection?
an imaginary connection between identical objects at the same layer of different sites
what does TCP/IP stand for?
Transmission Control Protocol/Internet Protocol
what does the physical layer do?
It takes electrical signals from the transmission media and turns them into bits
what does the data-link layer do?
When a router choose the best link, the data- link protocol moves the datagram across the link.
what does the network layer do?
chooses and routes the packet through possible routes.
what does the transport layer do?
provides signals to the application layer adds a transport header and information on ports etc, and the type of program to be used
What does the application layer do?
Logical connection between two applications. Sends the message between applications, usually with no header
Identify the five components of a data communications system.
Message Sender Receiver Transmission medium Protocol
What are the three criteria necessary for an effective and efficient network?
Performance - throughput and delay
Reliability - frequency of failure, recovery time, robustness in a catastrophe
Security - access, damage, development, recovery
What are the advantages of a multipoint connection over a point to point connection?
Advantages of a multipoint over a point-to-point configuration (type of connection) include
ease of installation and low cost.
What are the two types of line configuration?
point to point
multi point
Categorise the four basic topologies in terms of line configuration
mesh - p2p
star - p2p
bus - multipoint
ring - p2p
what is the difference between half duplex and full duplex transmission modes?
half duplex - no transmission and receiving at the same time
full duplex both stations can transmit and receive simultaneously
for n devices in a network, what is the number of cable links required for a mesh, ring, bus and star topology?
mesh n(n-1)/2
ring n
bus n+1
star n
What is an RFC and what difference between a required RFC and a Recommended RFC?
Before a new Internet standard is adhered to it must be an Internet Draft (ID). Once the ID is endorsed, it becomes a Request for Comment (RFC). Required RFC must be adhered to for minimum conformance. Recommended RFC are recommended for their usefulness, e.g. FTP and TELNET.
What is the maximum number of symbols that can be represented by unicode?
2^(32) I think…
A color image uses 16 bits to represent a pixel. What is the maximum number of different colors that can be represented?
2^(16)
How many input/output ports are required on each device in a mesh topology
n-1
Which layers of the TCP/IP protocol suite are involved in a link-layer switch?
The link-layer switch is normally involved in the first two layers of the TCP/ IP protocol
suite:
a. the physical layer,
b. and the data-link layer
At what protocol layer is the main protocol IP?
Network layer
At what protocol layer is TCP and UDP?
Transport. Transmission Control Protocol and User Datagram Protocol.
At what layer protocol is HTTP and SMTP and FTP
application layer. Hypertext Transfer Protocol, Simple Mail Transfer Protocol, File Transfer Protocol
