Introduction to Networking Chapters 1 and 2
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
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
Sample Computer Network
Networks Defined by Geography LAN: Local-Area Network WAN: Wide-Area Network
LAN 802.3 802.11x
WAN Two geographically dispersed locations MPLS ATM Frame Relay
Networks Defined by Geography Network Category MAN CAN PAN WPAN Description Covers an area equivalent to a city or other municipality. Covers an area equivalent to an academic campus or business park. A CAN is typically owned or used exclusively by an entity. Connects two to three computers with cables and is most often seen in small or home offices. 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.
Physical Star 1 The computers are physically connect to a centralized device (MAU) 5 2 4 3
Logical Ring 1 The traffic flow actually loops round-and-round the network. 5 2 4 3
Physical Bus Nodes are arranged in a linear format 1 2 3 Terminator T-connector
Physical Ring Traffic flows in a circular fashion around a closed network loop (that is, a ring). 1 Flow of data is unidirectional to avoid collisions 5 2 Has upstream and downstream neighbors 4 3
Logical Bus Hub
Hub and Spoke A WAN link from each remote site (that is, a spoke site ) to the main site (that is, the hub site.
Full Mesh Directly connects every site to every other site. Highly fault tolerant n(n-1)/2
Partial - Mesh Hybrid 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.
Networks Defined by Resource Location Centralized Client/Server Peer-to-Peer
Centralized Hosts Terminals Connect to the host via terminals or terminal emulators
Client/Server Commonly used by businesses. Administration is easier.
Peer to Peer Allow interconnected devices (for example, PCs) to share their resources with one another. Commonly seen in smaller businesses and in homes
OSI Reference Model Sender Application Presentation Session Receiver Transport Network Data link Physical Please Do Not Throw Sausage Pizza Away
OSI 7 Layer Model (encapsulation)
OSI 7 Layer Model (encapsulation)
Application To provide services and utilities so that applications can access the network.
Presentation Encode (Format) Compress (LZMA) Encrypt (SSL, TLS)
Session 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
Transport 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
TCP Windowing/ Buffering 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
UDP Header
Network Primarily concerned with forwarding data based on logical addresses.
Packet Header
Data Link Concerned with packaging data into frames and transmitting those frames on the network.
Frame Header
Physical Concerned with the transmission of bits on the network along with the physical and electrical characteristics of the network.
Physical - Current State Modulation
Physical - Transition Modulation
Physical - Wiring Connectors
Bandwidth Usage BROADBAND - ANALOG Divides the bandwidth into different channels BASEBAND - DIGITAL Uses all available frequencies
Multiplexin g Strategy Time-division multiplexing (TDM)
Multiplexing Strategy Statistical time-division multiplexing
Multiplexing Strategy Frequency division multiplexing
OSI TCP/IP
Port Numbers
Application Layer Protocols Pt 1 Protocol Description TCP Port UDP Port FTP SSH SFTP SCP Telnet File Transfer Protocol: Transfers files with a remote host (typically requires authentication of user credentials) Secure Shell: Securely connect to a remote host (typically via a terminal emulator) Secure FTP: Provides FTP file-transfer service over a SSH connection 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 Telnet: Used to connect to a remote host (typically via a terminal emulator) 20 and 21 22 22 22 23
Application Layer Protocols Pt 2 Protocol Description TCP Port UDP Port rsh DNS NetBIOS SMB TFTP Remote Shell: Allows commands to be executed on a computer from a remote user Domain Name System: Resolves domain names to corresponding IP addresses Network Basic Input/Output System: Provides network communication services for LANs that use NetBIOS Server Message Block: used to share files, printers, and other network resources Trivial File Transfer Protocol: Transfers files with a remote host (does not require authentication of user credentials) 514 53 53 139 137, 138 445 69
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 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 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 443 110 67, 68
Application Layer Protocols Pt 4 Protocol Description TCP Port UDP Port IMAP4 NNTP NTP LDAP RTSP Internet Message Access Protocol Version 4: Retrieves e-mail from an e-mail server Network News Transport Protocol: Supports the posting and reading of articles on Usenet news servers Network Time Protocol: Used by a network device to synchronize its clock with a time server (NTP server) Lightweight Directory Access Protocol: Provides directory services (for example, a user directory including username, password, e- mail, and phone number information) to network clients Real Time Streaming Protocol: Communicates with a media server (for example, a video server) and controls the playback of the server s media files 143 119 389 123 554 554
Application Layer Protocols Pt 5 Protocol Description TCP Port UDP Port RDP SNMP SIP MGCP Remote Desktop Protocol: A Microsoft protocol that allows a user to view and control the desktop of a remote computer Simple Network Management Protocol: Used to monitor and manage network devices Session Initiation Protocol: Used to create and end sessions for one or more media connections, including Voice over IP calls Media Gateway Control Protocol: Used as a call control and communication protocol for Voice over IP networks H.323 H.323 is a signaling protocol that provides multimedia communications over a network RTP Real-time Transport Protocol: Used for delivering media-based data over networks, such as Voice over IP 3389 161 5061 5060 1720 2427, 2727 5004, 5005 5004, 5005
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
Introduction to Networking Chapters 1 and 2