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49 Cards in this Set

  • Front
  • Back

What are the seven layers of the OSI protocol stack? briefly explain each

1. Physical - Physical cable and electrical signalling

2. Data Link - Error free (kind of) media access for datagrams.

3. Network - Provides a path through the network data

4. Transport - Reliable (usually) flow of datagrams between nodes.

5. Session - Synchronizes dialogue between two programs

6. Presentation - Converts data between two formats used by programs.

7. Application - Applications that use the network or something...

What are layers 1-4 and layers 5-7 of the OSI protocol stack referred to as?

Layers 1-4: transmission - how data moves through the network.

Layers 5-7: understanding - how data appears to applications and users.

What are three transmission attributes?


Electrical Interference (noise)

Attenuation (signal decay)

What is the difference between baseband and and broadband?

Baseband - One channel (most LAN connections)

Broadband - Multichannel (i.e. cable)

Name the three access methods

Carrier sense, multiple access and collision detection (CSMA/CD)

Token Passing (Token Ring)

Point-to-point (PPP) (bae caught me SLIPin)

Name three media types


Twisted Pair

Optical Fibre

Which parts of the OSI protocol stack are considered "gateway" protocols

layers 4-7

What do the following do? (give an example of each)

Physical gateway

Datalink gateways

Network gateways

Physical gateway - Allows network beyond standard cable length limits ex. a repeater, hub

Datalink gateways - Uses link-level address to determine passing of packets ex. a bridge, switch

Network gateways - Transmits packets based on IP address ex. router

Fun fact: UNIX systems can act as routers if packet forwarding is enable though this is not recommended (let routers do router and UNIX do ... UNIX stuff)

Name the IP protocol family

TCP: Transmission Control Protocol

UDP: User Datagram Protocol

IPv4: Internet Protocol

ICMP: Internet Control Messaging Protocol

ARP: Address Resolution Protocol

Fun fact: a list of protocols can be found on UNIX under /etc/protocols

What address is used at the link level? and what is the UNIX command to view the current machines address?

MAC(and chese) address

lanscan or ifconfig

What are the different classes of IP addresses

Class A - 1-126

Class B - 128-191

Class C - 192-223

Class D - 224-239 (multicast)

Reserved/Experimental - 240-255

What are the private networks that are not allowed on the public IP range and how are they connected to the internet? - -

They connect using NAT

What are subnets?

Subnets break up networks into smaller more manageable chunks. A group in a subnet can communicate without having to pass through a router.

What are subnet masks?

Subnet masks determine the subnet lengths (I know this shish)

What is the command to view or set a host name in UNIX?

hostname or uname -n

Name the three host naming systems


»Flat name space

»Does more than just hosts: users, groups, protocols, home directories,etc.



»Internet standard

»Does mainly hostnames and email routing


»combines features of NIS and DNS, adding secure authentication

What are the five main shells in UNIX?

Bourne Shell

Bash (Bourne again) Shell

C Shell

T Shell

Korn Shell

What are several features that make UNIX popular?

UNIX is:

- portable

- multiuser

- multitasking

- networking

- organized file system

- device independence

- utilities- services

What are the three different computing environments used in UNIX?

- stand-alone : personal environment

- time-sharing : multiple users connected to a computer

- client/server: users get clients and computing is shared

What is the kernel and shell?

The kernel contain the OS's process control and resource management

The shell receives and interprets commands

what are the different wildcards that can be used when browsing the file system

? : replaces any single character

[...] : any single character set

* : 0 or more character

what command is used to change directories and what is used to view files in the current directory

cd - change directory

ls - view files in current directory (-l for long list)

what can be used to change to home directory and what can be used to change to parent directory

~ : home directory

.. : parent directory

what is the difference between relative pathname and absolute pathname

a relative pathname is a path that is contained in the current directory and does not begin with '/'an absolute pathname is a path that starts from the root and starts with a '/'

what is the difference between a directory and a file

a directory cannot be run and contains other files and directoriesa file contains content that can be viewed or run

what is the command to remove a directory and make a new directory

rmdir : remove directorymkdir : makes new directory(bonus: directory cannot be removed unless empty)

what are the commands to copy, move and remove files

cp : copy

mv : move / rename

rm : remove

what command can be used to change permission on a file


what is the syntax for chmod

chmod -option mode file/directory


$ chmod u=rwx file.doc

$ chmod a+w this.txt

what are the octal values for chmod

r w x

4 2 1 4 = r--, 2 = -w-, 1 = --x, 6 = rw- etc...

user group all


776 file1.doc = u: rwx, g: rwx, a: rw-

what is the command to change owner and change group

chown: change owner (must be superuser)

chgrp: change group

what command can be used to find the current shell

echo $0

what are the three standard streams

input (0), output (1) and error (2)

how do you use a file as the input instead of the keyboard

command < file

how do you copy the output to a file (3 types)

command > file (new file)

command >| (overwrite file)

command >> file (append file)

how do you copy errors to a file (3 types)

command 2 > file (new)

command 2 >| (overwrite)

command 2 >> (append)

what does the pipe operator do and how do you call it

pipe (|) takes the output of the previous command and uses it as input for the next command

ex: $echo 3+3 | bc

> 6

how do you call a sequence of commands on the same line

commands can be executed in sequence by using ";" between each command

what are the conditional commands that can be used

&& - and

||- or

what is needed to use meta keys as normal characters


how do you start a background job


how can you stop, start, kill and move a background job to the foreground

stop 'job number' - suspend

bg 'job number' - resume

kill 'job number' - kill

fg 'job number' - move to foreground

what is the difference between job number and process ID

job numbers are for commands are different for each user whereas processes are for the entire OS

what is UNIX written in


what happens when you try to copy a file to one that already exists

the existing file is overwritten

how can you tell if a path name is relative or absolute

absolute path names have a / at the beginning whereas relative starts with a folder or file name

should you start your file names with a (.)? why?

no because normally hidden files start with a dot

How do you generate a random number in korn shell


Every time you echo RANDOM it will generate a new number between 0 and -32767

How do you create an alias? How do you remove an alias?

alias 'command' - creates an alias

unlais 'command' - removes alias name