introduction to networking.… · presentation session transport network data link physical ......

Introduction to NetworkingChapters 1 and 2

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Outline

• Computer Network Fundamentals• Defining a Network

• Networks Defined by Geography

• Networks Defined by Topology

• Networks Defined by Resource Location

OSI Reference Model

• The TCP/IP Stack

• Common Application Protocols

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Computer Network Fundamentals

• The Purpose of Networks• …is to make connections

• File sharing between two computers

• E-mail

• Voice over IP (VoIP), to replace traditional telephony systems

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Sample Computer Network

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Networks Defined by Geography

• LAN: Local-Area Network

• WAN: Wide-Area Network

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LAN

802.3

802.11x

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WAN

Two geographically dispersed locations

MPLS

ATM

Frame Relay

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Networks Defined by Geography

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Network Category Description

MAN Covers an area equivalent to a city or other municipality.

CANCovers an area equivalent to an academic campus or business

park. A CAN is typically owned or used exclusively by an entity.

PANConnects two to three computers with cables and is most often

seen in small or home offices.

WPAN

Connects wireless devices in very close proximity but not through

a Wireless Access Point (WAP).

Infrared and Bluetooth are some technologies used for connecting

devices in a WPAN.

Networks Defined by Topology

• Physical VS. Logical • The way components are physically interconnected determines the physical topology.

• The actual traffic flow determines the logical topology.

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Physical Star

The computers are physically connect to a centralized device (MAU)

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1

2

34

5

Logical Ring

The traffic flow actually loops round-and-round the network.

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1

2

34

5

T-connectorTerminator

Nodes are arranged in a

linear format

Physical Bus

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31 2

Physical Ring

Traffic flows in a circular fashion around a closed network loop (that is, a ring).

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1

2

34

5

Flow of data is unidirectional

to avoid collisions

Has upstream and

downstream neighbors

Logical Bus

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Hub

Hub and SpokeA WAN link from each remote site (that is, a spoke site ) to the main site (that is, the hub site.

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Full Mesh

Directly connects every site to every other site.

Highly fault tolerant

n(n-1)/2

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Partial -MeshHybrid of the previously described hub-and-spoke topology and full-mesh topology.

Designed to provide an optimal route between selected sites, while avoiding the expense of interconnecting every site to every other site.

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Networks Defined by Resource Location

• Centralized

• Client/Server

• Peer-to-Peer

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Centralized

Hosts

Terminals

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Connect to the host via

terminals or terminal emulators

Client/Server

Commonly used by businesses.

Administration is easier.

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Peer – to –Peer Allow interconnected devices (for example, PCs) to share their resources with one another.

Commonly seen in smaller businesses and in homes

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OSI Reference Model

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Please Do Not Throw Sausage Pizza Away

Application

Presentation

Session

Transport

Network

Data link

Physical

Sender Receiver

OSI 7 Layer Model (encapsulation)

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OSI 7 Layer Model (encapsulation)

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Application

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• To provide services and utilities so that applications can access the network.

Presentation

Encode (Format)

Compress (LZMA)

Encrypt (SSL, TLS)

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Session

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• A session can be thought of as a conversation that needs to be treated separately from other sessions to avoid intermingling of data from different conversations.

Session

netstat -a

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Transport

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• Messages are taken from upper layers (Layers 5–7) and are encapsulated into segments for transmission to the lower layers (1–3)

Transport

• TCP

• Connection

• Sequential Numbering

• Windows

• ACK

• UDP

• Connectionless

• Single Segments

• Streaming

• No ACK

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TCP – Windowing/Buffering

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• One or more segments are sent at one time, and a receiver can acknowledge the receipt of all the segments in a window with a single acknowledgment.

TCP Header

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UDP Header

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Network

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• Primarily concerned with forwarding data based on logical addresses.

Packet Header

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Data Link

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• Concerned with packaging data into frames and transmitting those frames on the network.

Frame Header

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Physical

Concerned with the transmission of bits on the network along with the physical and electrical characteristics of the network.

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Physical - Current State Modulation

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Physical - Transition Modulation

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Physical - Wiring Connectors

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Bandwidth Usage

BROADBAND - ANALOG

• Divides the bandwidth into different channels

BASEBAND - DIGITAL

• Uses all available frequencies

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Multiplexing Strategy

Time-division multiplexing (TDM)

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Multiplexing Strategy

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Statistical time-division multiplexing

Multiplexing Strategy • Frequency division multiplexing

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OSI – TCP/IP

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Port Numbers

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Application Layer Protocols – Pt 1

Protocol Description TCP Port UDP Port

FTP File Transfer Protocol: Transfers files with a remote host (typically requires authentication of user credentials)

20 and 21

SSH Secure Shell: Securely connect to a remote host (typically via a terminal emulator)

22

SFTP Secure FTP: Provides FTP file-transfer service over a SSH connection

22

SCP Secure Copy: Provides a secure file-transfer service over a SSH connection and offers a file’s original date and time information, which is not available with FTP

22

Telnet Telnet: Used to connect to a remote host (typically via a terminal emulator)

23

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Application Layer Protocols – Pt 2

Protocol Description TCP Port UDP Port

rsh Remote Shell: Allows commands to be executed on a computer from a remote user

514

DNS Domain Name System: Resolves domain names to corresponding IP addresses

53 53

NetBIOS Network Basic Input/Output System: Provides network communication services for LANs that use NetBIOS

139 137, 138

SMB Server Message Block: used to share files, printers, and other network resources

445

TFTP Trivial File Transfer Protocol: Transfers files with a remote host (does not require authentication of user credentials)

69

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Application Layer Protocols – Pt 3

Protocol Description TCP Port UDP Port

DHCP Dynamic Host Configuration Protocol: Dynamically assigns IP address information (for example, IP address, subnet mask, DNS server’s IP address, and default gateway’s IP address) to a network device

67, 68

HTTP Hypertext Transfer Protocol: Retrieves content from a web server 80

HTTPS Hypertext Transfer Protocol Secure: Used to securely retrieve content from a web server

443

SMTP Simple Mail Transfer Protocol: Used for sending e-mail 25

POP3 Post Office Protocol Version 3: Retrieves e-mail from an e-mail server

110

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Application Layer Protocols – Pt 4

Protocol Description TCP Port UDP Port

IMAP4 Internet Message Access Protocol Version 4: Retrieves e-mail from an e-mail server

143

NNTP Network News Transport Protocol: Supports the posting and reading of articles on Usenet news servers

119

NTP Network Time Protocol: Used by a network device to synchronize its clock with a time server (NTP server)

123

LDAP Lightweight Directory Access Protocol: Provides directory services (for example, a user directory— including username, password, e-mail, and phone number information) to network clients

389

RTSP Real Time Streaming Protocol: Communicates with a media server (for example, a video server) and controls the playback of the server’s media files

554 554

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Application Layer Protocols – Pt 5

Protocol Description TCP Port UDP Port

RDP Remote Desktop Protocol: A Microsoft protocol that allows a user to view and control the desktop of a remote computer

3389

SNMP Simple Network Management Protocol: Used to monitor and manage network devices

161

SIP Session Initiation Protocol: Used to create and end sessions for one or more media connections, including Voice over IP calls

5061 5060

MGCP Media Gateway Control Protocol: Used as a call control and communication protocol for Voice over IP networks

2427, 2727

H.323 H.323 is a signaling protocol that provides multimedia communications over a network

1720

RTP Real-time Transport Protocol: Used for delivering media-based data over networks, such as Voice over IP

5004, 5005 5004, 5005

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Analyze a scenario and determine the corresponding OSI layer

Layer Function Hardware / Other PDU

7. Application To provide utilities so that applications can access the network.

Content Switches, Proxy Servers

6. Presentation Encode, Compress, Encrypt PDF, jpg, ASCII, TIFF

5. Session Establish and maintain communications Sockets

4. Transport Ensure reliable delivery of data Gateway / TCP, UDP Segment

3. Network Find the best route Routers / RIP, OSPF, EIGRP, BGP Packet

2. Data Link Addressing, Error Detection, Carrier Sense Switches / Vlans / STP, VTP Frame

1. Physical The electrical characteristics or voltage Hubs, Media Bits

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Introduction to NetworkingChapters 1 and 2

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