Computer Networks
Non-Return to Zero Inverted
1 is transition, 0 is flat
Manchester
1 is up, 0 is down
Non-Retrurn to Zero (NRZ)
1 is up, 0 is flat
IP Address Class A Range
1 to 126
IP Address Class B Range
128 to 191
A port address in TCP/IP is ______ bits long.
16
IP Address Class C Range
192 to 223
IP Address Class D Range
224 to 239
__________ provides full transport layer services to applications.
TCP
________ is responsible for delivering data across networks with the desired reliability or quality
The Transport layer
UDP has no data-recovery features
True
Full-duplex link:
Used for transmission in both directions at once, e.g., use different twisted pairs for each direction
Wavelength Division Multiplexing (WDM)
WDM is a technique in fiber optic transmission for using multiple light wavelengths to send data over the same medium. WDM creates several different channels over the same fiber. WDM is conceptually the same as FDM, except that the MUX & DEMUX involve optical signals transmitted through fiber optic channels
Bipolar Alternate Mark Inversion (AMI)
0 is flat, 1 is a pulse
Differential Manchester Encoding
0 transition on the edge, 1 transition in the middle
Frequency-division multiplexing (FDM)
A scheme in which numerous signals are combined for transmission on a single communications line or channel. Each signal is assigned a different frequency (subchannel) within the main channel (modulation).
Multiplexing (MUX)
A technique to place multiple signals on a single communications channel by partitioning the channel into many separate channels.
Application Layer in TCP Model is equivalent to
Application, Presentation and Session Layer
TDM Receiver
At the receiver, the interleaved data are demultiplexed and routed to the appropriate destination buffer
Half-duplex link:
Both directions, but not at the same time, e.g., senders take turns on a wireless channel
Most modem IP networks today use a variety of different equipment, which statements are true about IP networks
Bridges to make forwarding decisions use MAC addressed : routers use IP addresses
3rd Function of the Physical Layer
Data Transmission and Reception: After encoding the data appropriately, the physical layer actually transmits the data, and receives it.
1st Function of the Physical Layer
Definition of Hardware Specifications: The details of operation of cables, connectors, wireless radio transceivers, Network Interface Cards (NIC) and other hardware devices are generally a function of the physical layer
Routing
Determines the route taken by packets from source to destination
What is the routing algorithm used by IGRP?
Distance vector
Time Division Multiplexing (TDM)
Each channel uses all of the bandwidth for part of the time
The Physical Layer:
Encode the bits that represent Data Link layer frames into signals and to transmit and receive these signals across the physical transmission medium.
2nd Function of the Physical Layer
Encoding and Signaling (methods): Transform the data from bits that reside within a computer or other device into signals that can be sent over the network. Key problem is to send (digital) bits using only (analog) signals This is called modulation
Select ALL analog multiplexing techniques
FDM , WDM
How many layers in TCP/IP Model
Four
In TDM, slots are further divided into
Frames
Types of Multiplexing (Physical Layer)
Frequency / Wavelength / Time
Which of the following layers from the TCP/IP model corresponds to the network layer in OSI model
Internet
Synchronous TDM
Items from different sources sent over a shared medium in a round-robin fashion (an item from sender 1 followed by an item from sender 2, and so on)
Bandwidth
Measures the amount of information that can flow from one place to another in a given amount of time.
Forwarding
Moves packets from routers inputs to appropriate router output
Physical Layer and Data Link Layer are Equivalent to _____ in the TCP Model
Network Access Layer
Simplex link:
Only one fixed direction at all times; not common
Which of the following is a basic service of the transport layer?
Provides reliability by using sequence numbers and acknowledgments Segments upper-layer application data Establishes end-to-end operations
Nyguists theorem
Relates the data rate to the bandwidth and number of signal levels
Shannons theorm
Relates the data to the bandwidth and signal strength relative to the noise
What would be the proper command to set a DCE clock rate of 56k for a serial interface?
Router (config-if) #clock rate 56000
Demultiplexer (DEMUX)
Separates the stream back into its component transmissions (1-to-many) and directs them to their corresponding receivers
How many layers in OSI model
Seven
In a cyclic redundancy check
The divisors one bit more than the CRC
Which of the following is true about IP routing?
The frame changes at each hop.
Throughput
The measure of the transfer of bits across the media over a given period of time.
Goodput
The measure of usable data transferred over a given period of time.
Time Division Multiplexing (TDM)
The process of taking a group of bits from each input line for multiplexing is called interleaving
Two main types of logical topologies
Token based, shared media
4th Function of the Physical Layer
Topology and Physical Network Design: It is also considered the domain of many hardware-related network design issues, such as LAN and WAN topology.
The physical layer is concerned with the movement of _______ over the physical medium.
bits
In _________, the message is first divided into manageable packets before being sent.
circuit-switching
In _________, the whole packet is sent from the source to the destination without being divided into packets.
circuit-switching
______ control in a network means handling a situation in which too many packets are present in an area of the Internet.
congestion
The ______ layer is responsible for moving frames from one hop (node) to the next.
data link
_________ control means including a mechanism for detecting corrupted, lost, or duplicate packets.
error
_________ control means regulating the amount of data a source can send without overwhelming the destination.
flow
Information in a computer is stored in __________ byte order.
host
An interface is a set of ___________ designed to facilitate interaction between two entities.
instructions
The ______ layer adds a header to the packet coming from the upper layer that includes the logical addresses of the sender and receiver.
network
A bridge has access to the _______ address of a station on the same network.
physical
Repeaters function in the _______ layer.
physical
The ________ address. also known as the link address... is the address of a node as defined by its LAN or WAN.
physical
Bridges function in the _______ layers.
physical and data link
PPP is a _______ layer protocol.
physical and data link
Frame Relay operates in the _______.
physical and data link layers
Which layer is concerned with the movement of bits over the physical medium?
physical layer
Routers function in the _______ layers.
physical, data link, and network
In the OSI model... encryption and decryption are functions of the ________ layer.
presentation
In the OSI model... what is the main function of the transport layer?.
process-to-process message delivery
In a URL, the _______ is the client-server program used to retrieve the document.
protocol
In the OSI model... as a data packet moves from the lower to the upper layers... headers are _______.
removed
A _______ is a program providing services to the ______ program.
server; client
In the OSI model, when data is transmitted from device A to device B, the header from A's layer 5 is read by B's _______ layer.
session
Why was the OSI model developed?
standards were needed to allow any two systems to communicate
The_________ layer is responsible for the delivery of a message from one process to another.
transport
In the OSI model, which layer functions as a liaison between user support layers and network support layers?
transport layer
In the OSI model... which layer functions as a liaison between user support layers and network support layers?
transport layer
