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Networking Exam 1

QuestionAnswer
What does PDU stand-for? Protocol Data Unit
What does SOHO stand-for? Small Office / Home Office lan network
What does PSTN stand-for? Public Switched Telephone Network
What does NRZ-I stand for? Non-returned to zero inverted encoding. A type of encoding for data transmission. Starts at low-voltage. The one is always a difference in signal, and the zero is never encoded as a difference -- maintains.
What is ASK? Amplitude Shift Keying - is similar to frequency shift keying Design association. Uses four levels of amplitudes to represent two bits in each bit time or two bits per baud (one bit time).
What is FSK ? Frequency shift keying - use frequency changes to represent bit values.
What is PSK? Phase shift keying - uses phase shift alone to represent data bits. 4 at a time.
What is QAM? Quadrature Amplitude Modulation - QAM-64 different combinations. 6 bits transferred per symbol. QAM-16 has 16 different combinations.
What is a service? A major function of a network that it performs or provides.
What is communication in networking? Transmitting or receiving data between two connected machines.
What is networking? Technologies that connect >2 hosts together.
Why do we need to connect computers to form a computer network? So we can use the services provided by the network.
What is a protocol? A protocol is a set of rules both the sender and receive comply with to achieve the communication between them.
Describe three aspects of a protocol specifications? 1. Syntax - message format, i.e. the message header and payload 2. Semantics: the meaning of each field in the message header. 3. Timing: when to send what messages.
Define TCP / IP protocol stack A layered protocol. - Physical, Data Link, Network, Transport, and Application Layer.
PDU for the Physical Layer of the TCP / IP stack - and what that layer does? Bit - encoding, modulation, and Demodulation
PDU for Data Link Layer? Frame - frame footer and header. Handles error control and flow control.
PDU for Network Layer ? Datagram or Pack - Routing Congestion control, framentation and reassembly
Service vs. Protocol? The service is what you can do, the protocol is the means by which you can do it. The service defines what operation the layer is prepared to perform on behalf of the user, but nothing about how it's implemented.
Interface vs. Protocol An interface refers to point of interaction between components -- hardware or software -- that com with other components via protocol. A protocol is a convention or stand. that controls or enables that conn comm to endpoints or interfaces
Why do we need different addressing schema at different layer? Diff functions require diff format.
Give a quick definition of addressing scheme? Every layer needs a mechanism for identifying the senders and receivers that are involved in a message. The mechanism is called addressing or naming. Used in low and high layers.
What is a mac address? A media access control address (MAC address) of a computer is a unique identifier assigned to network interfaces for communications at the data link layer of a network segment.
What is an IP address? An Internet Protocol address (IP address) is a numerical label assigned to each device (e.g., computer, printer) participating in a computer network that uses the Internet Protocol for communication. - Network Layer Address scheme
What is a Port ID? a port is an endpoint of communication in an operating system. While the term is also used for hardware devices, in software it is a logical construct that identifies a specific process or a type of network service. Trasnport layer address scheme
What is a Domain name address scheme? An application layer address scheme -- The Domain Name System (DNS) is a hierarchical decentralized naming system for computers, services, or any resource connected to the Internet or a private network.
What are the three impairments in networking -- just name them? Attenuation, distortion and noise
What is attenuation? means a loss of energy. strength of a signal falls off with distance over any trans medium. For guided media, this loss in strength is generally logarithmic and is thus typically expressed as a constant number of decibels per unit distance.
What is distortion? Distortion means that the signal changes its form or shape. Delay dist is a phenomenon peculiar to guided transmission media. The distortion is caused by the fact that the velocity of propagation of a signal through a guided medium varies with frequency.
What is frequency? Frequency, conceptually, is the number of oscillations in one unit.
The process of converting between bits and signals that represent them is called ______________ digital modulation.
What is multiplexing? Channels are often shared by multiple signals. After all, it is much more convenient to use a single wire to carry several signals than to install a wire for every signal. This kind of sharing is called multiplexing.
Give a description of NRZ digital modulation. A common form of digital mod is to use a + voltage to rep a 1 and a - (neg) volt to rep a 0. For an optical fiber, the presence of light might represent a 1 and the absence of light might represent a 0. This scheme is called NRZ (Non-Return-to-Zero).
A common form of digital mod is to use a _____ voltage to rep a 1 and a ______ volt to rep a 0. This scheme is called NRZ (Non-Return-to-Zero). +, -
In the TCP / IP protocol stack, what is Encapsulation? When receiving PDU from layer above (at senders side), each layer will add a header in front of the upper layer PDU and a trailer.
What is the most common problem with just plain-old NRZ modulation? Polarity error - With NRZ, in which the symbols are simply voltage levels, a long run of 0s or 1s leaves the signal unchanged. After a while it is hard to tell the bits apart, as 15 zeros look much like 16 zeros unless you have a very accurate clock.
Switching and it's purpose? Switching exists to reduce number of connections to form a fully connected network.
Created by: aiur100