Transcript Week 4b

Data Link Control Protocols
& Transmission Media
Unit 4, Chapter 7 & Chapter 18 pp 531-573
Subnets & Subnetting
Default Subnet Masks
– Class A = 255.0.0.0
– Class B = 255.255.0.0
– Class C = 255.255.255.0
Bits in the host octets are used to define subnet(pg
388)
– Class C address 206.11.20.81
– Subnet mask 255.255.255.224 or /27
• 11111111.11111111.11111111.11100000
• 81 =
0101 0001
– Subnet Number 2
– Host ID 17
Transmission Control Protocol
Can communicate between hosts with diverse
hardware and operating systems
Developed by Defense Advanced Research Projects
Agency (DARPA)
Direct or point-to-point communications
Connection oriented communication
Full Duplex – communication in both direction
3 way hand shake to start communications & End
Communications
– Start:->SYN,<-SYN+ACK,->ACK
– End: ->FIN+ACK,<-FIN+ACK,->ACK
TCP HEADER
TCP Header Information
TCP/IP Header:
Stop-and-Go (left) versus Sliding Window Flow Control
(right)
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TCP/IP Header:
Sliding Window Flow Control in
Operation
Copyright ©2005 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
User Datagram Protocol
Simple protocol
Connectionless
No error checking
No sequencing
No Handshaking
Examples: Ping, DNS, VOIP, TFTP
UDP Header:
UDP Diagram Format
Cisco Learning Institute
Network+ Fundamentals and Certification
Copyright ©2005 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
UDP Header:
IP Header Field Information
Cisco Learning Institute
Network+ Fundamentals and Certification
Copyright ©2005 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
TCP/UDP Port Number:
Selected Well-Known Port Numbers
Well known port numbers
Cisco Learning Institute
Network+ Fundamentals and Certification
Copyright ©2005 by Pearson Education, Inc.
Upper Saddle River, New Jersey 07458
All rights reserved.
Internet Tools
Name Server Lookup (nslookup)
– Determine IP address of a host system
Whois
– Determine name from an IP address
Ping
– Troubleshooting tool
– Is the node there, is it alive, how much time ….
Traceroute
– Determine route packet takes to remote host
Data Link Layer Functions
Data Link
– Communication Startup
• How will communications be started
– Character Identification and framing
• What constitutes a character and what is a control character
– Message (PDU) identification
• What is a message
– Line Control
• signaling for successful transmission, line turn around,
whether receiving terminal can accept more data
– Error Control
• What scheme to use, what to do when an error is detected
– Termination
Communication Parameters
Established prior to communications taking place
Predetermined
Settings on a device (Modem)
– Parity
– Transmission Speed
Line Access
Definition: Data Terminal Equipment (DTE) - That part of a data station that
serves as a data source, data sink or both and provides data communication control
functions
Methods to attain access to a circuit (Line Access)
– Contention Systems
• Listen,,wait/send
• Small systems, few nodes or fast circuit
– Polling
• Roll Call Polling
– Master with polling list
– Queries stations if they need to transmit
• Fast Select Polling
– Polls several stations at one time, only stations waiting to send respond
• Hub Polling
– Each DTE does part of the Master Station function
– Nothing to send, pass on to the next stations
– Token Passing
• Similar to Hub Polling, includes token
Flow Control
Stop-and-Wait (left) versus Sliding Window Flow
Control (right)
Asynchronous Data Link
Protocols
Point to Point Protocol
– Over dial-up lines
– Authentication, data compression error detection,
correction, packet sequencing
– 6 frames
•
•
•
•
•
•
Flag
Address
Control
Protocol
Data
Frame check sequence
X MODEM
Synchronous Data Link
Protocols
Dealing with blocks of data
Divided into 3 types according how they start/end
messages
– Character-oriented
– Byte-count oriented
– Bit-oriented
High-Level Data Link Control
(HDLC)
Originally IBM’s SDLC, then modified by ISO and
other standards organizations to make HDLC
IEEE 802.2 protocol
Bit-oriented protocol that supports both half
duplex and full-duplex
– What’s the difference?
3 Configurations pg 176
High-Level Data Link Control (HDLC)
Frames 3 types
– Supervisory (Control)
– Information (Data)
– Unnumbered
2 Frame Formats
– Normal
– Extended
Flag field 01111110 must be unique
Address Field – 8 or 16 bits
Frame Flow (Page 180)
– Initiation Phase
– Data Transfer Phase
– Disconnect Phase
Review Questions
1. Predetermined communication parameters are
those that are set __________ by switches or
specified as parameters in software.
a. dynamically
b. historically
c. manually
d. inherited
Review Questions
2. Polling systems require several stations on the
circuit to act as master stations.
a. True
b. False
Review Questions
3. The simplest form of flow control is
called___________________.
a. stop and wait flow control
b. give and get flow control
c. first in first out flow control
d. first in last out flow control
Review Questions
4. Background noise (white noise) on a circuit
______________________.
a. is rarely a problem because it is a known, predictable
phenomenon
b. is one of the most difficult problems to work around
c. occurs in spikes
d. delays some frequencies more than others
Review Questions
5. What does the term “sliding window” relate to?
a.
b.
c.
d.
e.
Multiplexing
Stop and wait
Flow control
Full duplex
None of the above
Review Questions
6. How “big” is an IPv6 Internet address?
a. 32 bits
b. 32 bytes
c. 20 octets
d. 128 bits
e. 128 bytes
Review Questions
7. What is the main objective of the IPv6 proposal to
the TCP/IP protocol suite?
a. Reduce user response
b. Update TCP/IP to remain compatible with new
technology
c. Allow for more Internet addresses
d. Add a fiber optic specification to TCP/IP suite
e. Force the acceptance of the hexadecimal numbering
system
Review Questions
8. What is the size , in bits, of the Net_ID field in a
Class B Internet address?
a. 8
b. 16
c. 14
d. 32
Review Questions
9. What does the “time-to-live” field (8bits) do in an
IP header?
a. Prevents infinite loops
b. Sets Frame Priority
c. Records the transmission time for tracert functions
d. Error checking
e. Frame sequence numbering
Review Questions
10. The part of the message that contains the
destination address is called the ______ .
a. Zip
b. Text
c. Trailer
d. Header
e. Flag
Homework
Assignment: Due Next Week
–
Review:
•
•
–
Chapter 7, pp. 158-182
Chapter 18, pp. 531-538
Read:
•
•
–
Chapter 10, pp. 248-282
Chapter 11, pp. 286-314
Complete:
•
•
•
Assignment 4.1: Chapter Multiple Choice; Chapter 18 Multiple Choice
Assignment 4.2: Subnet Homework B
Assignment 4.3 Draw OSI Model again, this time include the Hardware
of each layer.