Transcript unit1 - WCU Computer Science

CSC 600
Internetworking
with
TCP/IP
Unit 1: Introduction
(Ch. 1, 11)
Dr. Cheer-Sun Yang
Spring 2001
What is communication and
networking ?
• Communication: Different machines, (which are
also referred to as hosts, communication entities,
or stations), running different operating systems
transferring text, voice, image data between them.
• Networking: the communication entities being
“connected” together indirectly via another
communication entity or entities. This results in a
communication network.
Motivation for Networking
• Different machines, (which are also referred
to as hosts, communication entities, or
stations), running different operating
systems need to communicate.
• Computer users need to exchange data.
• Users need to access information stored
remotely.
What is internetworking?
• The technology, called internetworking,
accommodates multiple, diverse underlying
hardware technologies by providing a way to
interconnect heterogeneous networks and a set of
communication conventions that makes them
interoperate.
• Internetworking provides hardware and software
techniques and protocols for interconnecting
heterogeneous networks.
Communication Protocols
• Communication is achieved through the
cooperation of hardware and software.
• Two parties engaged in communication must
comply with a set of rules which governing the
timing of exchanging messages, the message
format, the meaning of each message content.
• Protocol – a set of rules which governs the
exchange of information.
• For example, TCP is a protocol, IP is another.
Types of Computer Networking
Systems
• Intranetworking—a communication system
for connecting homogeneous networks
together.
• Internetworking—a communication system
for connecting heterogeneous networks
together.
Internetworking vs. the Internet
• Internetworking—the communication of
heterogeneous computers.
• Internet—a specific kind of network
system.


Internetworking  Internet
The Internet
 U.S Government agencies realized the
importance and potential of internetworking
technology many years ago, and have
funded research that has made possible a
global Internet.
 An example of Open System
Interconnection.
Open vs. Proprietary
• Open Systems – the specifications are
publicly available; supported by almost all
venders
• Proprietary Systems –only supported by
specific venders. For example, IBM’s
SNA, APPLE’s AppleTalk, Datapoint’s
ARCNet.
Internet Services
• Application-Level Internet Services
– World Wide Web
– Electronic mail
– File transfer
– Remote login (telnet)
– Voice on IP: Internet Telephony
– Videoconferencing: using Internet to transmit
text, image, and voice data.
– Mobile IP: accessing Internet from within a car
Internet Services(cont’d)
• Network-Level Internet Services
– Connectionless Packet Delivery Service
– Reliable Stream Transport Service
Summary of Internet Services
• Each layer provides services to the layer
above it.
• Each layer uses the services provided by the
layer below it.
• This resulting protocol architecture is called
a protocol stack.
Application Layer Services
•
•
•
•
•
Virtual Terminal
File Transfer
Remote Login or Telnet
E-mail
World Wide Web
Transport-Level Services
• Connectionless Packet Delivery Services
• Reliable Connection-oriented Stream
Transport Service
• Provided by TCP and UDP, respectively
Network-Level Services
• Connectionless Packet Delivery Services
• Fragmentation and Assemble
• Provided by Internetworking Protocol(IP)
software
Media Access-Level Services
•
•
•
•
Framing of data bit streams
Error detection and recovery
Could be implemented in the NIC.
The driver implements some device
accessing functions for IP software to use.
Why is so special about the
Internet?
• Network technology independence:
Although TCP/IP is based on conventional
packet switching technology, it is
independent of any particular vender’s
hardware. In contrast, SNA only runs on
IBM hardware.
• Universal Interconnection: IP address
identifies a host from another.
Why is so special about
Internet?(cont’d)
• End-to-end acknowledgements: The TCP/IP
protocols only provide acknowledgements
between the source and the destination
instead of between successive machines
along the path. In contrast, X.25 provides
acknowledgements between any two nodes.
• Application Protocol Standards.
History of the Internet
• Late 60s—The government-funded
Advanced Research Projects
Agency(DARPA) created ARPANET in
1969.
• Mid 1970’s – ARPA began to work on
connecting computers in all associated
agencies. The early Internet had emerged.
History of the Internet(cont’d)
• Mid 1980’ – the Internet split into
ARPANET and MILNET.
• 1986 – NSFNET began to work; the
National Science Foundation funded a new
wide area network that connected all of its
supercomputing centers.
Other Names of the Internet
• ARPANET : the U.S. Department of
Defense Advanced Research Projects
(ARPA)
• The TCP/IP Internet
• The (Global) Internet
Who run the Internet?
• No one person, group or organization owns. The
backbone of it is funded by the National Science
Foundation in the U.S.
• In addition, a reorg of the Internet Advisory Board
(IAB) occurred in 1986. Now, there is an Internet
Engineering Task Force (IETF) and Internet
Research Task Force (IRTF) who help to set
standards (TCP/IP) for those who wish to connect
to, and use, the Internet.
• The IAB makes its standard available via
documents called RFC (Request for Comment).
Standards
• Required to allow for interoperability between
equipment
• Advantages
– Ensures a large market for equipment and software
– Allows products from different vendors to
communicate
• Disadvantages
– Freeze technology
– May be multiple standards for the same thing
Standards Organizations
• ISO (International Organization for
Standardization)
• Internet Architecture Board (IAB)
• ITU-T (formally CCITT)
• ATM forum
Internet Standards Organizations
•
•
•
•
Internet Activities Board (IAB): 1983
Internet Research Task Force (IRTF)
Internet Engineering Task Force (IETF)
Internet Society: replaced IAB around 1992.
Request For Comments(RFCs)
• Documentation of work on the Internet, proposals
for new or revised protocols, and TCP/IP protocol
standards all appear in a series of technical reports
called Internet Request For Comments(RFCs).
• Please check my Web Page for accessing RFCs.
• TCP: RFC 793
• UDP: RFC 768
• IP: 791, 760
The Internet Now
• In 1992, as the Internet moved away from the U.S.
government roots, a society was formed to
encourage participation in the Internet. A new
organization called Internet Society (ISOC)
becomes the host \for the IAB.
• Explosive growth –
– Now, it spans 82 countries and has millions of nodes.
– It has been growing exponentially since its inception.
• Used in all Venues-government, education, private
companies
(END OF CHAPTER 1)
Chapter 11
Protocol Layering
• Open Systems vs. closed systems
• SNA vs. TCP/IP
The Need of Multiple Protocols
• Open Systems vs. closed systems
• SNA vs. TCP/IP
What is TCP/IP?
• TCP/IP stands for Transmission Control
Protocol/Internet Protocol and is actually a set of
standards that describe how data is to be
transferred between computers.
• TCP/IP is the common tongue that all computers
must speak to communicate via Internet.
• There are implementations for UNIX, Windows,
Macintosh, and just about any computer operating
systems you can think of.
• TCP/IP is implemented as part of an Operating
System.
Connecting Two PCs
• Applications run on top of OS with
communication software implemented in it.
• Operating system communicates with
network driver that is another software.
• Network driver talks to communication
hardware including Network Interface Card
(NIC) and modem.
Connecting Two PCs(cont’d)
• Both parties must agree on the format of the
data unit being exchanged.
• Both parties must agree on how to initiate
the connection and when the send and
receive operations can be conducted.
• When to disconnect and how.
Keys
• Both parties must use the same data format.
• Both parties must see eye to eye on the
meaning of the content.
• Both must agree on the timing for
exchanging information.
The three factors constitute the core of a set
of rules which is called a communication
protocol.
Communication Protocol
• Definition – all parties involved involved in
the communication must comply with a set
of rules when exchanging messages. Thus,
the set of rules which both the sender and
the receiver all comply with is called
protocol.
• A protocol specifies the message format,
meanings, and the procedures
Key Elements of a Protocol
• Syntax
– Data formats
– Signal levels
• Semantics
– Control information
– Error handling
• Timing
– Speed matching
– Sequencing
applications
Comm.
software
applications
TCP
TCP
IP
IP
device driver Network Driver
Network interface card
Network Driver
Network interface card
Communication Reference
Models
• In summary, we need a communication reference
model to describe the relationship between various
software and hardware.
• There are two well-known reference models:
TCP/IP and OSI.
• A reference model describes the layering
relationship of software and hardware involved in
the communication.
• Let’s take a look at TCP/IP model.
The Need for Layered Protocols
• Complex data communication systems do not use
a single protocol to handle all transmission tasks.
• The require a set of cooperative protocols,
sometimes called a protocol family or protocol
suite..
TCP/IP Protocol Architecture
• Developed by the US Defense Advanced Research
Project Agency (DARPA) for its packet switched
network (ARPANET)
• Used by the global Internet
• No official model but a working one.
–
–
–
–
–
Application layer
Transport layer: host-to-host (application to application)
Internet layer: network routing and congestion control
Network access layer: access transmission medium
Physical layer
Physical Layer
• Physical interface between data
transmission device (e.g. computer) and
transmission medium or network
• Characteristics of transmission medium
• Signal levels
• Data rates
• etc.
Network Access Layer
• Exchange of data between end system and
network
• Destination address provision
• Invoking services like priority
Internet Layer (IP)
• Systems may be attached to different
networks
• Routing functions across multiple networks
• Implemented in end systems and routers
Transport Layer (TCP)
• Reliable delivery of data
• Ordering of delivery
Application Layer
• Support for user applications
• e.g. http, SMPT
TCP/IP Protocol Architecture
Model
Protocol Data Unit (PDU)
• An OSI term for the smallest data unit each layer
handles.
• TCP/IP terms are:
–
–
–
–
Data link layer: data frame
IP Layer: IP datagram
TCP: segment (p. 223) or TCP packet(p 184)
UDP: datagram
• Usually, datagram is used with connectionless
service; packet is used with connection-oriented
service.
Layering Principle
Layered protocols are designed so
that layer n at the destination
receives exactly the same object
sent by layer n at the source.
Layering
in a
Point-toPoint
Network
Layering in a TCP/IP Internet Environment
Layering in the Presence of Network Substructure
Two Important Boundaries in the TCP/IP Model
OSI Model
• Open Systems Interconnection (OSI)
• Developed by the International
Organization for Standardization (ISO)
• Seven layers
• A theoretical system delivered too late!
• TCP/IP is the de facto standard
OSI Layers
•
•
•
•
•
•
•
Application
Presentation
Session
Transport
Network
Data Link
Physical
Physical Layer
• Corresponds to basic hardware.
• Example: NIC, modem, cable
• Topics include transmission media, error
detection, correction.
Data Link Layer
• Specifies how to organize data into frames
and how to transmit frames over a network.
• Detail topics include the format of a data
frame, flow control.
Network Layer
• Specifies how to assign addresses and how
to forward packets to its destination.
• Detail topics include the format of a data
frame, flow control.
Transport Layer
• The basic function of the transport layer is
to accept data from the session layer, split it
up into smaller units, if needed, pass them
to the network layer, and ensure that the
pieces all arrive correctly at the other end.
• The transport layer also determines the type
of services, connection-oriented or
connectionless.
Session Layer
• Allows users on different machines to
establish sessions between them.
• Major functions include managing dialog.
• Session layer determines whether traffic
can only go in one direction or both
directions at the same time.
Presentation Layer
• Controls the encoding and decoding of data.
Application Layer
• Controls the interface with users.
• Application, presentation, session layers are
usually implemented together instead of
using laying architecture.
Nested Protocol Headers
Disadvantage of Layering
• The software that results from strict
layering can be extremely inefficient.
• The TCP layer will not understand the
format of the IP datagram.
• The TCP layer will not know how the
network will route the datagram.
• The packet size cannot be optimized.
applications
Comm.
software
WHAT
IS
THIS?
applications
TCP
TCP
IP
IP
device driver Network Driver
Network interface card
Network Driver
Network interface card
What’s Next? – TCP/IP Over
What?
• Two issues—
– Medium and connection
– Hardware addressing
• But…..
Do I
really
need
CSC600?
When is he
going to
stop?
Reading Assignment
• Chapters 1, 2, 3, 11 (ignore 2.5, 2.6, 2.10,
2.11)