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Discover the fundamentals of networking, including protocols, mediums, LAN vs. WAN, OSI model, TCP/IP, and more. Learn how computers communicate and exchange data effectively within networks.
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What is a Network? A connection between two or more computers so they may exchange information/resources. Using a network ‘medium’, computers pass information from one to another in an organized fashion using communication rules governed by ‘protocols’.
Network Medium Refers to the tool used to carry the transmitted signals from one computer to the next. Typically Unshielded Twisted Pair cabling is the most common (aka 10BaseT or 100BaseT).
Protocol • The ‘language’, or set of rules, that govern the communication between two devices. • The protocol determines the following: • the type of error checking to be used • data compression method, if any • how the sending device will indicate that it has finished sending a message • how the receiving device will indicate that it has received a message TCP/IP, IPX/SPX, Apple Talk, NetBEUI, etc.
Network Types 1. LAN The most common type of network is the Local Area Network in which computers situated in a common physical enclosure are connected together. A typical office scenario would be the most common example.
Network Types 2. WAN When two buildings need to be connected together a Wide Area Network is needed. Typically joining two LANs together creates a WAN. How do we join them?
Traditional Methods T1 T3 Fiber DSL Modem
WaveRider Methods Wireless Wireless
Our NCL family of products is used to join two LANs and create a WAN…
…while our LMS product line provides a wireless Last Mile Solution for ISPs and home/small business users.
WaveRider Product Two Network Interfaces: RF Interface (SMA connector) Ethernet Interface (10BaseT)
RF Perspective Issues such as antenna selection, cabling, distance, Line of Sight, configuration, etc. must all be considered. These topics covered in the RF Networking section. Ethernet Perspective Issues such as what type of protocol to use, medium and configuration must be considered.
How to Implement? • Two options: • Bridge Mode • Route Mode How do I choose??
Bridge Mode Used when connecting two segments of the same network together via the wireless link. In Bridge Mode, the NCL product supports all protocols. TCP/IP NetBEUI IPX/SPX AppleTalk
Route Mode Used when connecting two different networks together. The NCL/LMS products support TCP/IP when functioning in Route Mode. Take advantage of Route Tables to route packets from one network to another. TCP/IP Network ID: 192.168.10.0 Network ID: 10.32.0.0
TCP/IP: The Internet Protocol Due to the popularity of the Internet and internet services such as e-mail and web pages, the TCP/IP protocol has become the protocol of choice for most networks. It also allows the network administrator to use SNMP, DHCP and other services to help manage the network. TCP/IP Transmission Control Protocol/Internet Protocol
What is TCP/IP? Suite of protocols that, when used together, allow computers to pass data between one another. Each protocol in the suite performs a specific function in the communication process. - used for connection based communication TCP - used for resolving IP addresses to MAC addresses ARP - used for remotely monitoring network devices SNMP - used for addressing and routing data to the destination IP DHCP, RIP, ICMP, UDP, FTP, HTTP, etc….
In 1978 the International Standards Organization introduced an architectural model that would allow all networks to be able to communicate with each other. This model is called the Open Standards Interconnect Reference Model (OSI). All manufacturers have developed their product according to this standard. Understanding the OSI model will help you to understand how communication on a network happens.
The OSI Reference Model Represents a layered approach to networking. Each layer of the model handles a different portion of the communications process. The OSI Model simplifies how hardware and software work together, as well as providing a specific method of how components should function. The OSI model consists of 7 Layers.
Physical Layer (Layer 1) Converts incoming signals into bits and converts outgoing bits into signals by managing the interface between the computer and the network medium. Data Link (Layer 2) Responsible for creating the frame type used on the network (ie. Ethernet vs. Token Ring). Also provides error checking to determine when data needs to be re-transmitted. Network Layer (Layer 3) Defines protocols for routing data by opening and maintaining a path on the network between systems to ensure that data arrives at the correct destination node.
Transport Layer (Layer 4) Controls the movement of data between systems, defines protocols for structuring messages, and supervises the validity of transmissions by performing error checking. Session Layer (Layer 5) Coordinates communication between systems, maintaining sessions for as long as needed and performing security, logging, and administrative functions. Presentation Layer (Layer 6) Defines how information is formatted for display or printing, how data is encrypted, and translation of other character sets.
Application Layer (Layer 7) The highest layer of the model, defines the way applications interact with the network. As data is sent through the model, a header is added at each layer. On the receiving end the data is passed from Layer 1 to Layer 7 with the headers being stripped off as they go until the Application receives the data to be processed.
OSI TCP / IP Application (Layer7) Application Presentation (Layer6) Session (Layer 5) Transport (Layer 4) Transport Network (Layer 3) Internet Data Link (Layer 2) Network Interface Physical (Layer 1) TCP/IP Model TCP/IP has it’s own reference model which relates to the OSI Model. By understanding the two models it is easy to see how the various protocols participate in the communication process. FTP, SNMP, HTTP, SMTP, Telnet, PING TCP UDP ICMP IP ARP
Network Addressing For a packet of information to reach it’s destination it must be addressed with the destinations address, much the same way a regular mail letter needs an address before you put it into the post box. Where peoples homes have street addresses, with IP networking each computer has an IP address. 10.32.0.24 255 Consumers Road
On any given network (or street) no two computers (or homes) can have the same address. If so, then where would the packet (or mail) be delivered!?!? 260 Consumers Road 255 Consumers Road 265 Consumers Road 10.32.0.10 10.32.0.24 10.32.0.100
An IP address consists of two parts: a NetID portion and a HostID Portion A house address consists of two parts: a street name and a house number 255Consumers Road 10.32.0.24
Obviously there could be two similar addresses in the world, the only difference being the cities each is located. Identifying the city tells the mail carrier how to handle the packet. In the computer world the same holds true. The Subnet Mask associated with the computer defines which network it belongs to. 255 Consumers Road Toronto, Canada 265 Consumers Road Melbourne, AUS
IP: 10.32.0.24 SM: 255.255.255.224 IP: 10.32.0.100 SM 255.255.255.224 Network 10.32.0.96 Network 10.32.0.0 The Subnet Mask determines what NetID the computer has.
IP Rules…so far • All computers on a given network must have same NetID • No two computers can have the same HostID • All computers on the same network must have the same subnet mask
IP Address Every device on a TCP/IP network requires a unique IP address. The IP address is commonly represented in ‘Dotted Decimal Notation’. 207.23.175.2 In reality, the IP address is really a 32-bit binary number. A computer would view the above IP address as: 11001111.00010111.10101111.00000010 Each ‘quarter’ of the IP address is called an Octet, because each quarter is made up of an 8-bit binary number.
Binary Numbers Each bit in a binary number is assigned a decimal value. The more bits available in a binary number, the larger the decimal value of the number becomes. 128 64 32 16 8 4 2 1 = 207 1 1 0 0 1 1 1 1 Tip: When converting from decimal to binary, always start from the left and add bits to the right.
Movie Warriors of the Net
HTTP FTP Telnet SNMP Remember: the Application Layer of the TCP model is responsible for interacting with applications. Many applications have a certain protocol they rely on to get the job done. Some common applications and their associated protocols would be: Web Browser – HTTP SNMP Manager – SNMP E-Mail Program – SMTP
Hyper Text Transfer Protocol (HTTP) is the protocol used to transfer the data used to create Web Pages in your browser. To the end user the use of the protocol goes unnoticed, but to the application it is very important. Another common protocol is the File Transfer Protocol (FTP). When transferring files over the Internet this protocol is used to create a connection oriented session to transfer the data. TCP is used to create the session and guarantee delivery of packets.
Telnet is a protocol commonly used to remotely administer Routers and other network devices from a remote location. It allows you to establish a session with the other machine and emulate keystrokes on the machine from your remote computer. All components of the LMS are manageable through Telnet sessions. The LMS and NCL products are both configurable through a Telnet session to the unit.
Simple Network Management Protocol (SNMP) is used to remotely monitor or modify devices on your IP network. Unlike Telnet where you are actually emulating keystrokes on the unit, with SNMP you are polling devices for information. Depending on the security you set the units up with you can: 1. View information on the unit 2. View and edit information on the unit SNMP relies on a Management Station to ask questions to Agents which respond to the questions appropriately.
The data that a Management station requests from an agent is held in a MIB (Management Information Base). Basically it is a list of questions that the management system can ask an agent. Managers and Agents use the MIB tables as a lookup to send data back and forth. Both the LMS and the NCL both have their own MIBs which are installed at the management station. That way the management station will know what information it can poll the agent for.
TCP UDP • Remember: the Transport Layer of the TCP model is responsible for delivery and movement of packets. • There are two ways in which a packet can be delivered to another computer. • Guaranteed with some sort of acknowledgement of delivery (ie. Registered Mail) • Non-Guaranteed with no acknowledgment of delivery (ie. Regular Mail)
When the delivery of packets needs to be guaranteed the Transmission Control Protocol (TCP) is used at this layer to establish a ‘connection oriented’ session between the two computers. The session tracks packets by monitoring when a packet is sent, in what order it is sent, and by notifying the sender when it is received. If for some reason packets are lost, the sending machine will resend the data. All of this ‘chatter’ between the two computers causes TCP to have more overhead than it’s counterpart UDP.
The User Datagram Protocol (UDP) is a non-connection based protocol that does not require a session to be established before transmitting data. Packets are not guaranteed and are also not retransmitted if lost in transit. Because of the low overhead of UDP it is most commonly used with applications that depend on speed and where the guarantee of delivery is not very important. SNMP applications and real-time audio/video applications are good examples of applications that use UDP as a carrier.
TCP is typically used for transferring large amounts of data, where the application requires acknowledgement that the data has been received. SNMP applications and real-time audio/video applications are good examples of applications that use UDP as a carrier.
IP ARP DHCP ICMP Remember: the Internet Layer of the TCP model is responsible for addressing and routing of packets. Every packet a computer generates must be addressed with an IP address. There are two possible ‘types’ of destination IP addresses a packet could possibly have: • Local • Remote
Local When a computer is sending data to a computer on the same logical network as it is located on, the two computers are said to be ‘local’ to each other. Remote When a computer is sending data to a computer on a different logical network than the one it is located on, the two computers are said to be ‘remote’ to each other. In this case, a router must be present on each network to allow data packets to travel back and forth between the two.
NetID The NetID is what the sending computer looks at to determine if the destination is local or remote to it. IF (Destination NetID) = (Local NetID) then destination is local IF (Destination NetID) < > (Local NetID) then destination is remote How do we determine the NetID?
ANDing Upon boot up, all computers determine their own NetID by ANDing their IP address and their Subnet Mask. IP: 200.100.10.140 SM: 255.255.255.224 11001000.01100100.00001010.10001100 11111111.11111111.11111111.11100000 11001000.01100100.00001010.10000000 1 & 1 = 1 1 & 0 = 0 0 & 0 = 0 200.100.10.128 a Network ID