INTERNETWORKING I
CHAPTERS 12-14 STUDY GUIDE
What are the primary duties
of the Transport Layer (Layer 4)?
1. transport of data
2. reliable and accurate
transport (error control)
What are the two main Layer
4 protocols we use?
TCP, UDP
What are four or more
characteristics of TCP?
creates virtual circuit
between sender and receiver
connection-oriented
reliable
divides outgoing messages
into segments
reassembles segments at
receiving end
re-sends anything not
received
reassembles messages from
incoming packets
What are four or more
characteristics of UDP?
transports data
unreliably
connectionless
unreliable
transmits messages
(datagrams), not segments
no error control
does not reassemble
incoming messages
no acknowledgements
no flow control
What layer does IP work on?
How does it work with TCP?
Layer 3; since IP is
connectionless, it works with TCP for error control (TCP is
connection-oriented)
What is the difference
between TCP and UDP?
TCP offers error control;
UDP does not.
What are the parts of a TCP
segment? Give a brief description of each part.
1. source port number
of the calling port
2. destination port
number of the called port
3. sequence number used
to ensure correct sequencing of arriving data
4. acknowledgement number
next expected TCP octet
5. HLEN number of
32-bit words in the header
6. reserved set to 0
(zero)
7. code bits control
functions (such as setup and termination of session)
8. window number of
octets that the sender is willing to accept
9. checksum calculated
checksum of the header and data fields
10. urgent pointer
indicates the end of the urgent data
11. option-one option
maximum TCP segment size
12. data upper-layer
protocol data
List four protocols that use
UDP. Briefly describe each one.
1. TFTP Trivial File
Transfer Protocol: kind of like FTP, but you have to be on the same network
segment for it to work.
2. SNMP Simple Network
Management Protocol: checks how the network is running
3. DHCP Dynamic Host
Configuration Protocol: assigns IP addresses to devices dynamically
4. DNS Domain Name
Service: maps names to IP numbers
What do TCP and UDP use to
pass information to upper layers?
port numbers
What do port numbers do?
They keep track of
different conversations that are crossing the network at the same time.
What port numbers are used
for public applications? Are assigned to companies? Are unregulated?
Public below 255
Companies 255-1023
Unassigned over 1023
What is a three-way
handshake?
it is the open sequence
that synchronizes a connection at both ends before data is transferred.
What is PAR?
Positive Acknowledgement
and Retransmission. It is an error-checking technique used by many protocols.
What is windowing?
flow control mechanism
requiring that the source device receive an acknowledgement from the sending
device after transmitting a certain amount of data.
What is window size?
the amount of data that
can be transmitted at one time before receiving an acknowledgement from the
destination device
What happens if a transmission
using TCP fails to deliver one segment out of a multi-segment file?
The destination device
lets the sending device know, and the segment is retransmitted.
How does the receiving
device know that theres a segment missing?
datagrams are numbered.
If a number is missing, the receiving device knows a segment is missing.
What is the definition of
the Session Layer (Layer 5)?
it establishes, manages,
and terminates sessions between applications.
What is dialogue control?
This is how the Session
Layer manages conversations on the network. Each device, whether sending or
receiving, acts like both a client a host at different times during the
transmission process. Dialogue control lets each device know which it is at any
time during the transmission process.
What is the difference
between two-way alternate communication and two-way simultaneous communication?
Which one is prone to collisions?
Two-way alternate
communication is when the sending and receiving devices take turns during the
transmission of the data on the network. This is like half-duplex
conversations.
Two-way simultaneous
communication is when the sending and receiving devices can both transmit at
the same time on the network. This is like full-duplex. This communication mode
is more prone to collisions.
What is dialogue separation?
the orderly process of
establishing, managing, and terminating communication.
List six important Layer 5
protocols.
1. NFS Network File
System
2. SQL Structured Query
Language
3. RPC Remote Procedure
Call
4. X-Window System
5. ASP Appletalk
Session Protocol
6. DNA SCP Digital
Network Architecture Session Control Protocol
What is the definition of
the Presentation Layer (Layer 6)?
The layer responsible for
presenting data in a form that the receiving device can understand.
Name 3 important functions
of this layer:
1. data formatting
2. data encryption
3. data compression
Name two types of text
formatting. What is the difference between the two?
ASCII and EBCDIC. ASCII
is simple text format. It is the computer standard today. EBCDIC was created by
IBM and is similar to ASCII, but doesnt use any sophisticated formatting. It
is primarily used on mainframes.
Name at least 4 standards
for graphic images.
1. PICT Picture format:
used on Mac OS systems
2. TIFF Tagged Image
File Format: high-resolution, bit-mapped images
3. JPEG Join
Photographic Experts Group: used to compress graphic images
4. GIF Graphic
Interchange Format: standard for uncompressed graphic images
Which if the above are used
on the Internet?
JPEG, GIF
Name at least 3 standards
for sound and movies.
1. MIDI Musical
Instrument Digital Interface: digitized music
2. MPEG Motion Picture
Experts Group: compression and coding of video for digital storage
3. QuickTime handles
audio and video for both Mac and PC operating systems
What is the definition of
streaming audio?
sound files that start to
play before completely downloading.
What is HTML?
Hypertext Markup Language
it is the tagging system used to create Web pages. The language of the
Internet.