Transcript Introduction to Telecommunication Systems (Continued)

Chapter 5 - Transport and Network Layers
TCP/IP (Part 1)
Dr. V.T. Raja
Oregon State University
Chapter Objectives:
• Understand primary functions of transport and
network layers
• Understand the “big picture”
– Five-layer network model
Examples of Transport/Network Layer Protocols
• Examples:
– Two Popular transport/network layer protocols
– Example of transport/network layer protocol not used much in
North America
– Protocol for IBM compatible hardware/software and mainframe
environments
• Why TCP/IP?
• What is the expansion of TCP/IP?
• What are the major functions of TCP/IP?
TCP
• Main functions of TCP: Packetizing
– What is packetizing?
• At sender
• At final destination
TCP
• Thought Questions (with regard to the “big
picture”):
– With what layer(s) does TCP interface in the 5layer model?
– If more than two computers are involved in
message transmission, then is TCP involved in
all the computers? In how many computers is
TCP involved?
TCP (Continued)
• Some details on TCP header:
– TCP header containing 24 bytes (192-bit header) of
overhead information is enclosed along with user’s
data:
• Examples of overhead information added:
– Source and destination address
– Packet sequence number
• Thought Question (with regard to the “big picture”):
– Didn’t the data link layer already have the source and
destination address specified in the DLH? Is TCP
duplicating this function of DL?
Port Identifiers
• Source Port IDs refer to software used at
application layer of source computer
• Destination Port IDs refer to software to be used at
application layer of final destination computer
• With TCP/IP, each application layer software has a
unique port address/identifier.
• Every standard application layer software on the
Internet has a predefined (default) port number.
Port Identifiers
• Thought Questions:
– Could network managers choose not to
use the default port numbers?
– Why would a network manager not want
to use a default port number?
Internet Protocol (IP)
• What are IP’s main functions?
– Main functions:
• Thought Question:
– Is IP involved only at sender’s or final destination
computers? Or is it involved in all interim computers
that take part in the message routing as well?
IP (Continued)
• Different versions of IP
– IPv4 and IPv6
• IP creates a IP header
– IP header contains (among other
overhead information) source and
destination address!
• Network layer (IP) address
– Examples?
IP (Continued)
• Thought Question (with regard to the “big
picture”):
– In what order are the different headers combined with
the user data packet?
– If DL protocol is Ethernet, and NL protocol is TCP/IP,
then what is the maximum packet size for user data?
Assume DLH and DLT sizes sum to 26 bytes, TCP
header size is 24 bytes, and IP header size is 24 bytes
as well.
– Sample content in each header?
IPv4 Addressing
ICANN
• Every computer participating on the Internet
should use approved network layer (IP) addresses.
• IP Addresses are approved by ICANN or one of
several private companies authorized by ICANN
– Internet Corporation for Assigned Names and Numbers
– http://www.icann.org/
– FAQ on registration of IP addresses
– http://www.internic.net/faqs/
IPv4 Addressing
Dotted Decimal Notation
• Dotted Decimal Notation
– Four bytes (8 bits = 1 byte) per address
– Each byte separated by a dot
– Each byte expressed in decimal notation
• Example:
– Dotted Decimal Notation: 192.16.224.254
– Binary Notation?:
– What is the minimum decimal value any byte can be
assigned?
– What is the maximum decimal value any byte can be
assigned?
IPv4 Addressing
Class Based Address Structure
• IP Addresses were grouped into classes:
– Classes A, B, C, D and E
– Classes A, B and C - used for commercial purposes
• The class of the address - determined by
examining the first byte of the address and
mapping it to a range of values as follows:
– Class A: first byte is in the range 1 – 127
– Class B: first byte is in the range 128 - 191
– Class C: first byte is in the range 192 - 223
IPv4 Addressing
Network and Host Addresses
• Each IP address has two parts:
– Network Address (assigned/approved by ICANN)
– Host Address (assigned by host organization)
•
For a Class A IP address, the first byte is assigned/approved by ICANN
– Class A: Network.Host.Host.Host
•
For a Class B IP address, the first two bytes are assigned/approved by ICANN
– Class B: Network.Network.Host.Host
•
For a Class C IP address, the first three bytes are assigned/approved by ICANN
– Class C: Network.Network.Network.Host
• Restrictions for Host address: IP address cannot end in 0 or 255
IPv4 Addressing (Continued)
Subnets
• Subnets
– Part of a network that is logically grouped by IP addresses
– Example:
• Suppose ICANN assigned OSU a set of IP addresses as follows:
128.193.x.x
• OSU assigns the host part of the IP address
– 128.193.75.x; (CS subnet)
– 128.193.76.x; (BSG subnet)
– 128.193.76.x; (COB subnets)
• Can have one subnet for faculty: 128.193.76.____ (faculty subnet)
• Can have one subnet for IS staff: 128.193.76.____ (IS staff subnet)
– Every computer in a TCP/IP network is assigned a subnet mask
by the host organization – Why?
IPv4 Addressing
Subnet Masks
• Subnet Mask Applications:
Subnet mask applications (Continued)
Determining if sender and receiver are on same subnet
• How to determine if sender and receiver are
on the same subnet?
• Refer to algorithm provided on separate handout
• Examples:
– Are computer A (IP address: 128.193.78.3) and computer
B (IP address: 128.193.78.250) on the same subnet?
• Do you have sufficient information to answer the
above mentioned question?
– Class Participation Exercise # 2 (Question # 1)
Subnets (Continued)
Partial Subnetting
• Subnet mask default values
• Example: Class Participation Exercise # 2 (Question # 2)
• Partial Subnetting
– Subnet masks can also take values other than 0 or 255
• Example 1:
– Subnet mask: 255.255.255.224
– Sender’s IP: 120.192.40.16
– Receiver’s IP: 120.192.40.30
• Example 2: Class Participation Exercise # 2 (Question # 3)
Subnet Mask Applications (Continued)
• Subnet mask helps:
– Determine if sender and receiver are on same subnet
– Determine maximum number of computers per subnet
– Determine maximum number of subnets possible
• Example 1:
Background: Assume OSU is assigned a Class C address, and assume that
the network manager at OSU has selected the subnet mask value as:
255.255.255.248
Question: Find (a) maximum # of computers per subnet and
(b) maximum # of subnets possible
Number of Subnets and Number of Computers Per Subnet
Class C Addresses
Subnet Mask
255.255.255.224
(3-bit subnetting)
255.255.255.240
(4-bit subnetting)
255.255.255.248
(5-bit subnetting)
255.255.255.255
(CP # 2 - Q4)
# of Computers # of Subnets
per subnet
Class Participation Exercise # 2 – Question # 5
• Background Info: A firm has been assigned a class B
address by ICANN. Based on an estimation of future
network growth in the firm, the administration plans to
have 30 different subnets, and about 2040 computers in
each subnet.
• Question: What subnet mask value should the network
manager use in order to satisfy the planning needs (of the
administration) as specified above?