Download Ch05a

Chapter 5
Network and Transport Layers
Announcements and Outline
Assessment 1 Review Assignment – Due 2/15
Assessment 1 – 2/17 (multiple choice and short answer)
Recap
4 Data Link Layer
4.1 Media Access Control
4.2 Error Control
4.3 Data Link Protocols
Outline
5 Network and Transport Layers
5.1 Protocol
5.2 Transport Layer Functions
5.3 Addressing
5.4 Routing
5.5 TCP/IP Example
Copyright 2010
John Wiley & Sons, Inc
2
Chapter 5 Outline
Transport & Network Layer Protocols
 TCP/IP
Transport Layer Functions
 Segmenting
 Linking to the Application Layer
 Session management
Addressing
 Assigning addresses and address resolution
Routing
 Types of routing, routing protocols, and multicasting
TCP/IP Examples
3
Network Layers
Computer 1
Computer 2
4
Introduction
Transport and Network layers
 Responsible for moving messages from end-to-end in a network
 Closely tied together
 TCP/IP: most commonly used protocol
• Used in Internet
• Compatible with a variety of Application
Layer protocols as well as with many
Data Link Layer protocols
Application Layer
Transport Layer
Network Layer
Data Link Layer
5
Transport/Network Layer Protocols
TCP/IP (Transmission Control Protocol / Internet Protocol)
 Most common, used by all Internet equipment
Developed in 1974 by V. Cerf and B. Kahn
 As part of Arpanet (U.S. Department of Defense)
Most common protocol suite
 Used by the Internet
 Largest percentage of all backbone, metropolitan, and wide area
networks use TCP/IP
 Most commonly used protocol on LANs
6
Introduction - Transport layer
Responsible for end-to-end delivery of messages
Application Layer
Responsible for segmentation and
reassembly
Transport Layer
 Breaking the message into several smaller
Network Layer
pieces at the sending end
 Reconstructing the original message into a single whole at the
receiving end
Interacts with Application Layer
7
Transmission Control Protocol (TCP)
used in message
reassembly
TCP Header: 192 bits (24 bytes)
5-8
Introduction – Network Layer
Responsible for addressing and routing of messages
 Selects best path from computer to computer
until the message reaches destination
Transport Layer
Performs encapsulation on sending end
 Adds network layer header to
message segments
Network Layer
Data Link Layer
Performs decapsulation on receiving end
 Removes the network layer header at receiving end and passes
them up to the transport layer
9
Internet Protocol (IP)
Two versions in current in use
10
IP Packet Formats: IPv4 (24 bytes) vs. IPv6 (40 bytes)
IPv4 Header: 192 bits (24 bytes)
IPv6 Header: 320 bits (40 bytes)
5 - 11
Student Questions
What goes in the data field of an IP Packet in the Network
Layer? What about the previous layer’s packet?
https://db-ip.com/
12
TCP/IP’s 5-Layer Network Model
13
Efficiency
You want to transmit a 500 byte email message. What
would be the efficiency in transmitting this message?
Overhead:
• SMTP:
• TCP:
• IP:
• Ethernet:
What about an HTTP file of 4000 bytes?
14
Transport Layer Functions
Segmenting
Application Layer
Linking to the Application Layer
Transport Layer
Session management
Network Layer



15
5.2.1 Segmenting
Breaking outgoing messages from the application layer into
a set of smaller segments for transmission through
network.
When the transport layer is set up, it determines what size
segments will make best use of its data link protocols.
16
Packetization and Reassembly
sender
What size packet to use?
FTP
FTP
TCP
TCP
IP
IP
receiver
Delivers incoming packets
as they arrive (e.g., Web pages) or
to wait until entire message arrives
(e.g., e-mail)
17
5.2.2 Linking to Application Layer
TCP may serve several Application Layer protocols at the
same time
 Problem
 Solution
How do we know what number
the server uses?
HTTP FTP SMTP
80
21
25
TCP
What would be the other type of number used and why?
5 - 18
…
5.2.2 Application Layer Services
5 - 19
5.2.3 Session Management
A session can be thought of as a conversation between
two computers.
Types of Session Management
• Connection Oriented
• Connectionless Routing
• Quality of Service (QoS)
5 - 20
5.2.3.1 Session Management - Connection Oriented
Setting up a virtual circuit, or a TCP connection
 Packet deliveries are acknowledged
For which application layer packets does the transport
layer use a connection oriented session for?
5 - 21
5.2.3.1 Setting up Virtual Connections
B
A
SYN
SYN
Data 1
Data 2
ACK 2
Data 3
Data 4
FIN
not
busy
5 - 22
5.2.3.2 Session Management - Connectionless Routing
• Provided by UDP
 Sending packets individually without a virtual circuit
 Each packet is sent independently of one another, and will be
routed separately, following different routes and arriving at
different times
5 - 23
5.2.3.2 UDP - User Datagram Protocol
Protocol used for connectionless routing in TCP/IP suite
that uses no acks, no flow control
Uses only a small packet header
 Only 8 bytes containing only 4 fields:
• Source port
• Destination port
• Message length
• Header checksum
Can also be used for applications where a packet can be lost,
such as information rich video
5 - 24
5.2.3.3 Protocols Supporting QoS
Asynchronous Transfer Mode (ATM)
 A high-speed data link layer protocol
RSVP
RTSP
TCP/IP protocol suite
RTP
 Resource Reservation Protocol (RSVP)
• Sets up virtual circuits for general
UDP
purpose real-time applications
 Real-Time Streaming Protocol (RTSP)
IP
• Sets up virtual circuits for audio-video
applications
 Real-Time Transport Protocol (RTP)
• Used after a virtual connection setup by RSVP or RTSP
• Adds a sequence number and a timestamp for helping
applications to synchronize delivery
• Uses UDP (because of its small header) as transport
5 - 25
Network Layer Functions
Addressing
 Each device on the path between source and destination must
have an address
 Internet Addresses
Transport Layer
 Assignment of addresses
 Translation between network layer
Network Layer
addresses and other addresses
(address resolution)
Data Link Layer
Routing
 Process of deciding what path a packet must take to reach
destination
 Routing protocols
5 - 26
5.3.1 Types of Addresses
• Application Layer Address
Application Layer
• Network Layer Address
Transport Layer
Network Layer
Data Link Layer
• Data Link Layer Address
5 - 27
5.3.1 Types of Addresses
Address Type
Example
Example Address
Analogy
Application Layer URL
www.iub.edu
Name
Network Layer
IP address
129.79.127.4 (4 bytes) Zip code
Data Link Layer
MAC address
00-0C-00-F5-03-5A
(6 bytes)
Street
address
• These addresses must be translated from one type to another for a
message to travel from sender to receiver.
• This translation process is called address resolution.
5 - 28
5.3.1 Question: Addresses and Clients
How many addresses are assigned to the different
computers in this room?
 Desktop
 Laptop
5 - 29
5.3.2 Assignment of Addresses
Data Link Layer Address (MAC address)
 Unique hardware addresses placed on network interface cards by
their manufacturers ( based on a standardized scheme)
How are these set?
What do you they look like?
http://www.coffer.com/mac_find/
5 - 30
5.3.2 Assignment of Addresses
Application Layer address (URL)
 For servers only (clients don’t need it)
 Assigned by network managers and placed in configuration files.
 Some servers may have several application layer addresses
Network Layer Address (IP address)
 Assigned by network managers, or by programs such as DHCP, and
placed in configuration files
 Every network on the Internet is assigned a range of possible IP
addresses for use on its network
5 - 31
5.3.2 Internet Addresses
Managed by ICANN
 Internet Corporation for Assigned Names and Numbers
 Manages the assignment of both IP and application layer name
space (domain names)
• Both assigned at the same time and in groups
• Manages some domains directly (e.g., .com, .org, .net) and
• Authorizes private companies to become domain name
registrars as well
Example: UNCW
 URL that end in .uncw.edu
 IP addresses in the 152.20.x.x range (where x is any number
between 0 and 255)
5 - 32
5.3.2 How do you decide who gets what address?
Group of computers on the same LAN with IP numbers
using the same prefix
Assigned addresses
 For example:
• Subnet 152.20.234.x
– Computers in CIS labs (x is between 0 & 255)
• Subnet 152.20.244.x & 152.20.196.x
– Computers in CIS Offices (x is between 0 & 255)
• Subnet 129.79.125.x
– Computers in Cameron
Does anyone see a problem with the subnets above?
5 - 33
5.3.2 Subnets: Example
5 - 34
5.3.2 Subnets
How do you think UNCW handles assigning address?
How does the server know where to send the IP address if it
doesn’t have one?
5 - 35