TCP/IP Lecture 1 - Basics

7/25/2019 TCP/IP Lecture 1 - Basics

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Introduction to communication network

Lecture 1 - Basics

Jens Myrup Pedersen

Associate ProfessorAalborg University

[email protected]

Figures by Matija and Kardi (mst,[email protected]), and to limited extend Andrew S. Tananbum, Co


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The purpose of this lecture is for you to

Understand the principles of layered packet-based network ar

Obtain an overview of the TCP/IP protocol stack and the OSmodel, and to understand the differences between them.

Get an understanding of connectionless and connection-orien

protocols.

Get to know the units used for network speeds and bandwidt

It is highly recommended for you to take notes during the lecturfocusing on these learning points.


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First a little about procotol stacks:

Example of a protocol stack.

Each layer has its ownfunctionality.

Each layer offer services to the

layer above.

Transparency: A layer dont seewhat is underneath it, but virtuallyspeaks to the corresponding layerat the other machine.


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First a little about procotol stacks:

Typical one protocol per layer Between each layer there is a well defined functionality The layered architectures allows for:

A modular design

Layers can be re-used for different protocols

Easier to change implementations (or add new protocols)

Easier to develop applications

Independency of the physical medium


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So, how does it look from a message point of A message is sent from one application to another. This is do

packet: A sequence of bits.

In the different layers, diffferent kinds of control information (and/or tails) are added. This control information can for examaddresses or different kinds of protocol information.

There can also be limitations to packet sizes, so packets may b

This also means that in addition to the mssage being sent, eacadding additional information (or overhead): How much is addlayer depends on the protocols being used.


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Let us look at an example


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Connection-oriented or connection-less

Important: connection-oriented and connection-less protocols.

The simplest is a connection-less protocol. Here packets are simon the network, usually marked with an address, and we hope tHowever, there are no guarantees that all packets will arrive, anhas no way of telling whether this has happened.

For a connection-oriented protocol, a connection is first set upare send, and eventually the connection is torn down. Acknowlbe used to assure the arrival of all packets, and the protocol canmechanisms for re-transmissions and re-orderings of packets thor arrive in the wrong order.


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Connection-oriented or connection-less


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Two important models

The OSI reference model, developed by ISO

The TCP/IP Protocol stack, used in the Internet


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The OSI reference model

Open Systems Interconnection, suggested by ISO Designed as it should be done. The reference-model is made prior to the standards for each 7 layers.


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The OSI reference model

L7: Application layerL6: Presentation layerL5: Session layerL4: Transport layerL3: Network layer

L2: Data link layerL1: Physical layer

In the following, lets have a look at the functionality of the differWe focus on the layers which are also used in the TCP/IP stack.


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OSI: The physical layer

Defines the physical transmission, e.g. voltage, frequency etc. For example: Electricity, laser, radio waves Set-up and tear-down of connections Offering services for the data link layer.


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OSI: The data link layer

The data link layer receives data from the network layer, whicbroken into smaller frames. The size of these frames dependsnumber of issues, for example the error rate.

At the physical layer, transmission errors can occur of many dreasons. It can be because of disturbance due to noise, weathconditions (especially for wireless), worn equipment and many

things. This error control is can be done in the data link layer The data link layer takes care of physical addressing, error co

control, and Medium Access Control (MAC). The data link layer can also contains mechanisms such as slidin

for controlling the sending speed, and thus avoid congestion. Examples: Ethernet, Token ring, PPP, HDLC, Frame Relay, ISD


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OSI: The network layer

Most important functionality is routing Quality of Service can also be handled here, for example by gi

packets a higher priority. Elements of congestion control can done.

Gateway-functionality between different networks is also typihandled at the network layer. Yet another example of the stre

layered protocols. Many networks use dynamic hop-by-hop routing, but source r

static routing can also be used. Static routing is usually used osmall or very reliable network (certain multi processor system

Examples: IP, ICMP, IGMP, X.25, CLNP, ARP, RARP, BGP, OSIPX, DDP


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OSI: The transport layer

The layer between applications and network layer. Offer end-communication.

Split and join packets before they are sent to and from the ne Decides which connection should be available for the upper la

Connection set-up and tear-down

Error correction can be done here

Acknowledgements and retransmissions

Handling out-of-order packet arrivals Some protocols such as TCP also have traffic/flow control Examples: TCP, UDP, RTP, SCTP, SPX, ATP


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OSI: The session layer

Handles sessions


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OSI: The presentation layer

Handles data structures


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OSI: The application layer

The upper layer, which can be used directly by the user applic(such as web browsers, email clients, ssh clients etc.)

Examples: HTTP, SMTP, SNMP, FTP, Telnet, Ssh and Scp, NFS


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OSI vs. TCP/IP


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TCP/IP

The protocols of layer 2,3 and 4 will be treated more in-deptcoming lectures.

In the following, a few differences to the OSI model will be higand some examples of protocol design given.


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TCP/IP Host-to-Network

Corresponds to layer 1+2 from the OSI model

Among the data link layers, Ethernet is probably the most knois also possible to run IP over ATM.

Example: Ethernet.


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TCP/IP Internet layer

Corresponds to the network layer of the OSI model

IPv4 is probably the best known.


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TCP/IP Transport layer

Corresponds to the transport layer of the OSI model Most used/known protocols:

TCP: Reliable, connection oriented

UDP: Unreliable, connectionless

These protocols will be treated in more details in coming


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TCP/IP Application layer

Corresponds to session, presentation and application layer in HTTP, FTP, mail, news etc. Example: HTTP


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TCP/IP an overview of protocols


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To sum of this lecture just a few facts

One bit is a single 0 or 1 1 byte is 8 bit 1Gbit/s = 1000Mbit/s = 1.000.000 Kbit/s = 1.000.000.000 bit/s

If written as e.g. 1MB/s, this usually means one megabyte per should be avoided to avoid confusion..

So: Bandwidth or throughput is often measured as bit/s (oMbit/s, Kbit/s).

When sending data from A to B, the time it takes to transmessage depends on the bandwidth as well as the latency.


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End of lecture

Please dont hesitate to send questions or comment

Jens Myrup PedersenAssociate ProfessorAalborg University

[email protected]

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TCP/IP Lecture 1 - Basics