04/10/23

Find 10’s complement of 52520 using quick way.

rn– N = ( rn – 1 ) – N + 1 _________A

From equation A,10’s complement is just equal to the 9’s complement plus 1.

So, for 9’s complement of 52520,The result using quick way is 47479

10’s complement is 47479 + 1 = 47480

However, we can also find the 10’s complement by leaving all least significant 0’sunchanged, subtracting the first non-zero least significant digit from 10 and subtracting alhigher significant digits from 9. So, using the assumption above,

10’s complement of 52520 is 47480

Find 10’s complement of 52520 using quick way.

rn– N = ( rn – 1 ) – N + 1 _________A

From equation A,10’s complement is just equal to the 9’s complement plus 1.

So, for 9’s complement of 52520,The result using quick way is 47479

10’s complement is 47479 + 1 = 47480

However, we can also find the 10’s complement by leaving all least significant 0’sunchanged, subtracting the first non-zero least significant digit from 10 and subtracting alhigher significant digits from 9. So, using the assumption above,

10’s complement of 52520 is 47480

Open Systems Interconnection (OSI) Open Systems Interconnection (OSI) Reference Model for Networking Reference Model for Networking

COSC 513 Operating SystemsCOSC 513 Operating Systems

Instructor : Dr. Mort AnvariInstructor : Dr. Mort Anvari

Presented Presented by by

Cheng Chiang GohCheng Chiang Goh

ObjectiveObjective

The aim of this topic is to understand theoretical models for what networks are and how they work. The Open Systems Interconnection (OSI) reference model for networking, which explains how networks behave within an orderly seven-layered model for networked communications.

IntroductionIntroductionThe concept of networking is so essential in this fast-moving

world nowadays, for the purpose of sharing information and

resources. Open Systems Interconnection (OSI) reference

model proposed by the International Standards Organization

(ISO) has been so successful to create an intellectual

framework within which to clarify network concepts and

activities. Today, OSI reference model has become a key

part of networking. The IEEE 802 is an enhancement to the

OSI model. With OSI model, networking can be broken into

seven layers. Therefore, the complexity of networked

communications, from application to hardware is broken into

a series of interconnected tasks and activities. It creates a

method to solve big problem by deconstructing them into a

series of smaller problems, that can then be solved

individually.

TopicsTopics Open Systems Interconnection (OSI) Model IEEE 802 Model OSI Reference Model Structure Network Communications and Protocols in OSI

model Protocols in Layered Architecture TCP/IP Protocol

Devices at each OSI model

OSIOSI ModelModel Layer 7 AApplication Layer 6 PPresentation Layer 5 SSession Layer 4 TTransport Layer 3 NNetwork Layer 2 DData Link Layer 1 PPhysical

PProgrammers DDo NNot TThrow SSausage PPizza AAway

Layer 7Layer 7 ApplicationApplication Top layer of OSI model provides interfaces for application to obtain access to

networked services Services like file transfer, message handling, database

query processing Also handle general network access: movement of data

(flow control), error recovery Transfer information from program to program

LayerLayer 6 6 PresentationPresentation Handles data format for networked

communications ( outgoing and incoming messages)

protocol conversion, data encryption and decryption as well as graphics commands

compress data for transmission to reduce the volume of data ( then decompression)

Redirector (software facility)

Layer 5Layer 5 SessionSession Permits two parties to hold ongoing communication

across a network handles session setup, data or message exchanges

and tear-down when session ends permit only authorized parties to establish session

(security)

Layer 4Layer 4 TransportTransport Manages the conveyance of data from sender to

receiver across a network segment long data into chunks that match the

maximum packet size for networking medium acknowledges successful transmission and request

retransmission when packets do not arrive it make sure that long data payloads make their

destination across the network

Layer 3 Layer 3 NetworkNetwork Handles addressing messages for delivery translates logical network addresses and names into

their physical counterparts decides how to route transmissions from sender to

receiver also handles packet-switching, routing and congestion

control Fragmentation and Reassemble ( from dissimilar

media - downsizes packets

Layer 2Layer 2 Data LinkData Link

Sends data frames from Network layer to Physical Layer [data frame consists of destination ID, sender ID, control, data and CRC(cyclical redundancy check-mathematical function based on bit patterns)]

adds error-checking information and formats data for physical transmission

Layer 1Layer 1 PhysicalPhysical Its jobs is to convert bits into signals for outgoing

messages and via versa manage hardware connection cable, transmitter, receiver, repeater operate at this

layer.

IEEE 802 extensions to the OSI IEEE 802 extensions to the OSI reference modelreference model

Layer 7 Application Layer 6 Presentation Layer 5 Session Layer 4 Transport Layer 3 Network Layer 2 Data Link -----Logical link control

-----Media access control

Layer 1 Physical

IEEE 802 standard breaks the Data Link layer into two sublayer

Logical Link Control (LLC) Also known as IEEE 802.2 for error control correction and flow control

Media Access Control (MAC) for access control direct access with NIC and ensure error-free data

transmission

802.3 CSMA/CD 802.4 Token Bus 802.5 Token Ring 802.12 Demand Priority

Network Communications and Protocols Network Communications and Protocols in OSI modelin OSI model

Protocols are rules and procedures for communications many protocols used today TCP/IP, NetBIOS/, IPX/SPX,

AppleTalk, the higher the protocols in the OSI model or layer, the

more sophisticated the protocol is protocol stack TCP/IP, the Internet protocol suite,

IPX/SPX for Novell NetWare

Two methods of delivering data in a network

Connectionless fast but not reliable

(don’t waste time to establish, manage and tearing down connections)

Connection-Oriented slower but reliable

Network layer of the OSI model is responsible for moving data across multiple network

Routable Network Layer (4) protocols like TCP/IP,

IPX/SPX; suitable for large network

Nonroutable NetBEUI; for small

network

Protocols in a Layered ArchitectureProtocols in a Layered Architecture Layer 7 Application Layer 6 Presentation Application

Layer 5 Session Protocol

Layer 4 Transport Transport

Protocol

Layer 3 Network Layer 2 Data Link Network Layer 1 Physical Protocol

Network ProtocolsNetwork Protocols Provide addressing and routing information, error

checking, retransmission requests and rules for communicating in a particular networking environment

Protocols likes IP (Internet Protocol) IPX (Internetwork Packet eXchange and NWLink NetBEUI DDP (Delivery Datagram Protocol) DLC (Data Link Control)

Transport ProtocolsTransport Protocols Ensure reliable data delivery between computers

Protocols likes TCP (Transmission Control Protocol) SPX (Sequenced Packet eXchange) and NWLink NetBEUI/NetBIOS ATP (AppleTalk Transaction Protocol) and NBP (Name

Binding Protocol)

Application ProtocolsApplication Protocols Provide application-to-application services

Protocols likes SMTP (Simple Mail Transport Protocol) FTP (File Transfer Protocol) SNMP (Simple Network Management Protocol) NCP (NetWare Core Protocol) AFP (AppleTalk File Protocol)

OSI ModelOSI Model TCP/IP ProtocolTCP/IP ProtocolStackStack

Layer 7 Application Layer 6 Presentation Layer 5 Session

Layer 4 Transport

Layer 3 Network

Layer 2 Data Link

Layer 1 Physical

TelnetFTP

SMTP

TCP DNS UDP

IP ICMP ARP OSPF RIP

ODI or NDIS

NIC Driver

Physical Connection

TCP/IPTCP/IPAllows for easy cross-platform communications and is the

basic for Internet ICMP (Internet Control Message Protocol) --- network layer;

used to send control messages ARP (Address Resolution Protocol) --- network layer; used

to associate a logical IP address to a physical MAC address

TCP (Transmission Control Protocol) --- transport layer; connection-oriented; transport protocol

UDP (User Datagram Protocol) --- transport layer; connectionless; faster than TCP

DNS (Domain Name System) --- transport layer; name-to-address resolution protocol (for example www.Microsoft.com to 102.211.10.111)

FTP ( File Transfer Protocol) --- session, presentation and application layer; provides services for file transfer as well as directory and file-manipulation services

Telnet --- remote terminal emulation protocol; used to provide connectivity between dissimilar system

SMTP (Simple Mail Transport Protocol) --- used for messaging services and is the basic for e-mail across Internet

(RIP) Routing Information Protocol --- a distance-vector protocol used for route discovery

OSPF (Open Shortest Path First) --- a link-state routing protocol; used to determine the best path through a network

IP (Internet Protocol) --- network layer; responsible for addressing and routing; (32 bits, e.g. 120.255.123.0);

Advantages and Disadvantages of Advantages and Disadvantages of TCP/IPTCP/IP

AdvantagesAdvantages Suitable for WAN Direct Access to the Internet Supported by most of the

computer and operating system support routing support SNMP, DHCP

(dynamically assign client IP addresses),

support Internet Protocols like POP(Post Office Protocol), HTTP.

Centralized TCP/IP domain assignment to allow internetworking between organizations

IP address

DisadvantagesDisadvantages Difficult to administer global expansions of Internet has

limited the availability of unique domain numbers

difficult to set up high overhead slower than IPX and NetBEUI

DevicesDevicesDevices that allow expansion of network locally or

across the world and layer of the OSI model they operate.

RepeaterRepeater operate at Physical layer has no concern for the type of data being transmitted, packet

address and the protocol being used cannot perform filtering or translation of the data and does

not help to ease network congestion cannot connect different network architectures allows easy expansion of the network over larger distance

and connection between different media

BridgeBridge Operates at the Data Link Layer of the OSI model or

Media Access Control sublayer of the Data Link layer (has access to this address information)

can filter to ease network congestion can connect different media and network architectures slower than repeater

RouterRouter

Operate at the Network layer can connect different media and network architectures choose the best path for packet through an internetwork reduce network traffic by not forwarding broadcasts or

corrupt packets more expansive and complex than repeater and bridge only work with routable protocol (like TCP/IP, IPX/SPX,

AppleTalk and etc) dynamic routing updates create network traffic slower than bridge because need to perform more

calculation on the packet

BrouterBrouter

Combination of bridge and router good at hybrid network using mixture of routable and

nonroutable protocols routable packet -- function as router (choosing the best

path to forward packet) nonroutable packet --- function as bridge (forwarding

packet based on hardware address

GatewayGateway work at the Application layer of OSI model can translate information between two different

network architectures or data formats ( for example, allows network communication between a TCP/IP LAN and IBM mainframe system using SNA and also can convert Microsoft Mail to SMTP for transmission over Internet

hard to install and configure; slower and more expensive

SummarySummary

OSI reference model plays a vital role in networking. OSI

model. Networking can be broken into seven layers with

OSI model. Therefore, the complexity of networked

communications, from application to hardware is broken

into a series of interconnected tasks and activities. It

creates a method to solve big problem by deconstructing

them into a series of smaller problems, that can then be

solved individually.

References & Related WebsitesReferences & Related Websites Matthew Strebe, Charles Perkins and James Chellis.

“MCSE: NT Server 4 Study Guide” Second Edition. SYBEX Inc 1998.

Joe Casad. “MCSE: Windows NT Server & Workstation 4”. New Riders Publishing 1996.

TCP/IP Networking : Architecture, Administration and Programming,James Martin, Joe Leben / Prentice Hall / August 1994

MCSE:Networking Essentials (2nd Edition),James Chellis. Sybex / June 1998

http://www.cit.ac.nz/smac/winnt/pt1_9.htm#Start http://www.vcs-s.com/network_topology.htm http://dir.yahoo.com/Computers_and_Internet/Communicat

ions_and_Networking/ http://www.mcpmag.com/