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Communication Protocols

Course: CIS 3003Fundamental of

Information Technology

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Protocol

• Allow individuals to communicate with each other.

• Every day protocols:– Greeting – Writing order– Letter / address– Traffic signals and signs

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OSI Model

• Open Systems Interconnection (OSI)

• Allows computers to communicate

• Layer abstraction• Similar communication

functionalities in the same layer.

• Layer communicates through interface.

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Layer 1 – Physical Layer Protocols

• Define electrical, optical, and mechanical specification between a device and transmission medium such as fiber optical, coaxial, or twisted pair cables.

• Voltage level , transmission rate, signal timing, connection specification.

• Example protocols: T568A and T568B standards for Category 5 Ethernet cable, SDH and SONET for fiber optic cable.

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Cat-5 Ethernet cable• Standard organizations:

– Telecommunications Industry Association and Electronic Industries Alliance

• Protocols: TIA/EIA-568-A, TIA/EIA-568-B, TIA/EIA-568-C

• Specifications:– Cabling Type: unshielded 4

twisted pairs – Maximum distance: 100 meters– Bent at most 4 times the

diameter of the cable. – Connector– Cable termination standards– Performance characteristics – Methods of testing installed

cable.

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Layer 2 – Data Link Layer

• Describes how to access a particular physical medium such as Ethernet cable, fiber optic cable, and wireless.

• Collision detection, avoidance, frame format, channelization.

• Examples: CSMA/CD, Token Ring, IEEE 802.11 for Wi-Fi, TDMA/CDMA, IEEE 802.15 for Bluetooth, IEEE 802.16 for WiMAX.

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CSMA/CD & CSMA/CA

• Carrier Sense Multiple Access with

• Carrier sense: after detect a busy signal– 1-persistent: node sends

out immediately once the medium is free.

– p-persistent: node sends out frame or waits with a probability.

• Collision Detection:• Collision Avoidance

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IEEE 802.11

• Organization: – Institute of Electrical and

Electronics Engineers

• Frequency: 2.401-2.483• Channel width: 20 MHz• Uses CSMA/CA

• Data rates• MIMO: Multiple input

and output streams (i.e. antennas).

• Modulations: phase shift and frequency.

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IEEE 802.2

• Logical link control.• Provides interface to upper network layer

protocols to control a link layer protocol. • Allows a network layer to unicast, multicast, or

broadcast using several procedures– Broadcast MAC addrs: FF:FF:FF:FF:FF:FF– Multicast: 01:00:5e:00:00:00 - 01:00:5e:7f:ff:ff

• Offer several methods of sending data over a physical link.

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IEEE 802.2 Procedure Types

• Type 1: unacknowledged connectionless to single, multiple, or all nodes in the network

• Type 2: connection-oriented link to a node.

• Type 3: acknowledged connectionless supports only point-to-point connection.

• Connection-oriented– Validate link before send out

data and a failed link is communicated to upper layer.

– RTS/CTS.

• Connectionless– Link not validated first.

• Acknowledgement– Frame acknowledgment

with sequence number. – ACK/NACK

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Layer 3 – Network Layer

• Defines topology• Uses of routing table to route data• IP address• Wired and Wireless routing protocols

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Layer 4 – Transport Layer

• Provides end to end communication.• Provides an interface to application protocols

to send data over network. • Example protocols: TCP (Transmission Control

Protocol), UDP (User Datagram Protocol), etc.

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TCP vs. UDP• TCP: Transmission Control Protocol. UDP: User

Datagram Protocol. • TCP provides error checkings: UDP does not.

– Buffers out-of-order data– Discard duplicate packets– Resends erroneous data

• TCP provides congestion control; UDP does not.• TCP sets up and maintains connection; UDP does not. • TCP slower; UDP faster.

– Non-time critical applications: HTTP, HTPS, FTP, Telnet – Time critical applications: VoIP, IPTV, online gaming, DNS

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TCP Congestion Control

Slow start

Congestion Avoidance

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TCP Connection Setup

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TCP header

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UDP header

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Layer 5: Session Layer

• Opens, maintains, and closes a session. – Session: semi-permanent dialogue consists of

requests and responses that occur between applications

• Example protocols: RPC (Remote Procedure Calls), H.245 (Call Control Protocol for Multimedia Communication).

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H.245

• Conveys information needed for multimedia transmission such as such as encryption keys, flow control, jitter management, preference requests, as well as the opening and closing of logical channels used to carry media streams.

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Remote Procedure Calls (RPC)

• Allows one computer to call a procedure that resides on a remote computer

• Steps to use a RPC– A client calls the client stub

with a function and parameters.

– The stubs packs the function and parameters into a message and sends them to kernel.

– The kernel sends the message to server

– The kernel at the server end passes the function and parameters to the server stub.

– The server stub calls the procedure on the server and passes the parameter.

– The server stub sends result in a reverse direction.

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RPC Example

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Layer 6 – Presentation Layer

• Formats and encodes information from an application so that other computers using the same standard can understand

• Provides serialization; converts a complex data structure used by an application into a format such as XML to be sent over a network. – Java, .NET, and C/C++ provides serialization. – MPEG, ASCII, Unicode are example formats that

can be sent over network.

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JavaSerialization

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Java Serializable Object

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Java – Write Serializable Object

The text file can then be sent over a network to another computer.

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Java – Read Serializable Object

Receiver needs to understand the format to read the binary file.

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Same data in different formats

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Layer 7 – Application Layer

• Provides services to application programs so that the programs can communicate with each other.– Determines how to reach another party such as a

web site.– Authenticates an application program. – Determines what lower level protocols to use.

• Example protocols: HTTP, FTP (File Transfer Protocol, Telnet, BitTorrent, DHCP (Dynamic Host Configuration Protocol).

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HTTP

• Hypertext Transfer Protocol

• Organizations: – Internet Engineering

Task Force (IETF)– World Wide Web

Consortium (W3C)

• RFC 2616– Requests for Comments

• Request methods:– HEAD, GET, POST, PUT,

DELETE, TRACE, OPTIONS, CONNECT, PATCH

– Safe methods: retrieve information only, no unintended change on the server. Used by search engine.

– URL: Uniform Resource Locator. Points to an Internet resource.

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URL

• Uniform Resource Locator.• Points to an Internet resource. • A parameter to the HTTP methods. • URL Examples: http://www.google.com/,

https://my.ucf.edu/index.html.

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Various Internet browsers

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Browser and server

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Bit Torrent protocol

• Peer-to-peer file sharing protocol

• Describes how a node retrieves pieces of a file from other peers in a network.

• Uses a hash function to associate pieces to the corresponding file.

• TCP as the transport layer protocol.

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Various programs using Bit Torrent

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TCP/IP – Alternatives to OSI Model

• Four layers• Network layer is mainly

of Internet Protocol (IP). • Transport layer is mainly

Transport Control Protocol (TCP).

• Compared to OSI, there are no separated layers for session or presentation protocols.

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Organizations behind protocols

• No single organization, government, or company assumes responsibility for establishing the enormous number of standards required for network communications.

• A complex matrix of organizations assumes responsibility for setting standards in various areas– National, International, Professional organizations,

Consortia of technology companies, public.

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ANSI (an-see)

• American National Standards Institute– http://www.ansi.org/ – Founded in 1918. One of the oldest standards

institutions in the world– Private, nonprofit organization with participating

members from businesses, organizations, academic institutions, and governmental agencies

• Promotes and coordinates standards that are in the nation’s economic interest

• Protocol: ADSL

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EIA

• The Electronic Industries Alliance– http://www.ecaus.org/eia/site/index.html – Trade organization of more than 2500 companies

involved in manufacturing electronic systems and components

– Telecommunications Industry Association (TIA): http://www.tiaonline.org/

• Specifies electrical standards for a variety of networking components: TIA/EIA-568 for Ethernet cables.

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ISO (eye-so)

• International Organization for Standardization.– International standards-setting organization– Made up of national standards bodies from more than 150

countries– ANSI represents United States

• Protocol: – ISO 9660 or Compact Disc

File System: an image file standard of optical disk such as CD, DVD, or Blue Ray

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IEEE (I-Triple-E)

• Institute of Electrical and Electronics Engineers– http://www.ieee.org/publications_standards/

index.html – Nonprofit professional organization of engineers– http://www.ewh.ieee.org/r3/orlando/Osm112003/

student.htm IEEE Orlando Branch

• Important IEEE specifications include Ethernet, token ring, and wireless LAN standards

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IETF

• Internet Engineering Task Force: – Has no formal membership, but has more than 100

“working groups” that advance Internet standards http://www.ietf.org/

• Group most directly responsible for developing Internet protocol standards

• Since 1969, an electronically published archive known as the “request for comments,” or RFC series, has documented the Internet standards process. RFC 2988 specifies TCP.

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W3C

• World Wide Web Consortium– http://www.w3.org/ http://www.w3.org/standards/ – http://www.w3schools.com/html/ – Founded in 1994

• Promoting continued development of Web technologies and ensuring interoperable, vendor-independent Web standards.

• Standards: HTML, XML, Web service (in progress).

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ITU

• International Telecommunication Union– http://www.itu.int/en/Pages/default.aspx – International telecommunications standards

organization operating under the auspices of the United Nations

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NIST

• National Institute of Standards and Technology – http://www.nist.gov/index.html – United States– Dates back to 1901

• Standard: Encryption protocol such as Advanced Encryption Standard.

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Summary

• Computing devices can exchange information over a network if they adhere to standard rules called protocols

• Protocols perform a number of functions, including how to format information in binary code, how to indicate the initiation or termination of a connection, and how to append standard addressing information prior to transmission.

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Summary

• The OSI reference model is a framework that groups the many protocols and protocol functions required to exchange information over a network.

• The TCP/IP protocol suite is the group of communications protocols that exchange over the public Internet (and private TCP/IP networks)

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Summary

• Many standards-setting organizations establish communication protocols; organizations work for companies that have a stake in the outcome of protocol design and include ANSI, EIA, NIST, the IEEE, the IETF, the ITU, the ISO, and the W3C.

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Summary

• Protocols have economic implications because they represent a means of control over competing equipment and software manufacturers, determine how innovative markets can be, and sometimes even serve as barriers to trade in global IT markets