As a company courtesy from ShadowTech, we have created this Networking Essentials section as a network help page. You will find networking information on many various subjects here. We hope that you will benefit from what we know.

Basic Networking Knowledge - Networking Standards/OSI Model/Protocols

• Standards are documented agreements containing precise criteria that are used as guidelines to ensure that materials, products, processes, and services suit their purpose.

ANSI (American National Standards Institute) is an organization composed of more than a thousand representatives from industry and government who together determine standards for the electronics industry and other fields, such as chemical and nuclear engineering, health and safety, and construction.

ANSI also represents the United States in setting international standards.

EIA (Electronic Industries Alliance) is a trade organization composed of representatives from electronics manufacturing firms across the United States.

TIA (Telecommunications Industry Association) Focuses on standards for information technology, wireless, satellite, fiber optics, and telephone equipment.

TIA/EIA alliance are its guidelines for how network cable should be installed in commercial buildings, known as the “TIA/EIA 568-B Series.”

IEEE (Institute of Electrical and Electronics Engineers), or “I-triple-E,” is an international society composed of engineering professionals.

IEEE goals are to promote development and education in the electrical engineering and computer science fields.

ISO (International Organization for Standardization), headquartered in Geneva, Switzerland, is a collection of standards and organizations representing 148 countries

ISO’s goal is to establish international technological standards to facilitate global exchange of information and barrier-free trade.

The ITU (International Telecommunication Union) is a specialized United Nations agency that regulates international telecommunications, including radio and TV frequencies, satellite and telephony specifications, networking infrastructure, and tariffs applied to global communications/

ISOC (Internet Society), founded in 1992, is a professional membership society that helps to establish technical standards for the Internet.

ISOC oversees groups with specific missions, such as the IAB and IETF

IAB (Internet Architecture Board) is a technical advisory group of researchers and technical professionals interested in overseeing the Internet’s design and management.

IETF (Internet Engineering Task Force), the organization that sets standards for how systems communicate over the Internet—in particular, how protocols operate and interact

IANA and ICANN.

Every computer / host on a network must have a unique address

Internet Assigned Numbers Authority (IANA) kept records of available and reserved IP addresses and determined how addresses were issued out.

Internet Corporation for Assigned Names and Numbers (ICANN), a private, nonprofit corporation and is now ultimately responsible for IP addressing and domain name management.

The OSI Model

• ISO’s OSI Model divides networking architecture into seven layers.

• • Each OSI layer has its own set of functions and interacts with the layers directly above and below it. Two hosts communicating with their peer layers. Each layer has its own Protocol Data Units. What are Protocol Data Units or PDUs? For data packets to travel from the source to the destination, each layer of the OSI model at the source must communicate with its peer layer at the destination. This form of communication is referred to as Peer-to-Peer Communication. During this process, each layer’s protocol exchanges information, called PDUs, between peer layers. Each layer of communication, on the source computer, communicates with a layer specific PDU, and with its peer layer on the destination computer. Data packets on a network originate at a source, and then travel to a destination. Each layer depends on the service function of the OSI layer below it. To provide this service, the lower layer uses encapsulation to put the PDU from the upper layer into its data field. It then adds whatever headers and trailers the layer needs to perform its function. As the data moves down through the layers of the OSI model, additional headers and trailers are added. After layers 7, 6, and 5 have added their information, layer 4 adds more information. This grouping of data, the layer 4 PDU, is called a segment. For example, the network layer provides a service to the transport layer, and the transport layer presents data to the network layer, which has the task of moving data through the internetwork. It accomplishes this task by encapsulating the data and attaching a header creating a packet or a datagram (the layer 3 PDU). The header contains information required to complete the transfer, such as source and destination logical addresses. The data link layer provides a service to the network layer. It encapsulates the network layer information in a frame (the layer 2 PDU). The frame header contains information (for example the physical address) required to complete the data link function. The data link header information is local and is meaningful only to the directly attached devices. The physical layer also provides a service to the data link layer. The physical layer encodes the data link frame into a pattern of 1s and 0s (bits) for transmission on the medium at layer 1. the bits are then transmitted to the next directly connected device in the end-to-end path. The destination host receives the bits and begins to de-encapsulate the data. Bits are passed to the data link layer for frame manipulation. When a data link layer receives a frame, it reads the physical address and other control information provided by the peer layer, it strips the control information from the frame, creating a datagram (packet), and then it passes the datagram up to the next layer, following the control instructions of the frame. This process of de-encapsulation continues up the layers.

  
   

In the early 1980s, ISO began work on a universal set of specifications that would enable computer platforms across the world to communicate openly.

This model, called the Open Systems Interconnection (OSI) Model, divides network communications into seven layers:

• APPLICATION LAYER

• Communicate between software (devices) and lower layer network services. Application program interfaces (a set of routines making up part of the software –APIs or DLLs) are created to interface with specific protocols, such as HTTP, FTP, or TFTP. On the test you will be asked to designate which protocols work with the Application Layer. This layer provides application services for file, print, message, database, World Wide Web, email (SMTP), and a variety of applications, such as MS Word, Excel, etc.

• PRESENTATION LAYER

• Translator between on application and host and another application and host.

• Graphics – GIF, TIFF, JPG are protocols which encode and compress graphics.

• Audio and video – Mpeg and QuickTime encode and compress audio and video data.

• ASCII and EBCDIC are examples for encoding and compressing text.

• Encryption/decryption

• SESSON LAYER

• Coordinates and maintains communication between nodes on a network.

• Synchronizes dialog and secures communications.

• Responsible for starting, maintaining, and terminating communications.

• Ensures that only authorized nodes can communicate.

• TRANSPORT LAYER

• Manages end-to-end delivery of data.

• Responsible for error checking.

• Responsible for flow control.

• Responsible for sequencing (segments).

• Maintains connection-oriented connections. Connects before transmitting and then requests acknowledgements upon sending data. TCP is connection-oriented.

• Connectionless connections are used whenever the data is live – video for example. UDP is connectionless.

• Breaks data into segments when the systems MTU (Maximum Transmission Unit) default is smaller than the data to be sent. For example. Ethernet packets are 1500 plus bits in size. If the data is larger, it is segmented before being sent to the Network layer. Segments are sequenced to facilitate reassembly.

• NETWORK LAYER

• Addressing and routing packets or datagrams.

• Network Layer addresses are also called logical addresses of virtual addresses.

• Physical addresses are MAC addresses burned into a NIC. The NIC has 12 hexadecimal numbers. The first 6 (Bock ID) represent the vendor and the last 6 Device ID) represent the node.

• IP addresses are logical. For example, 206.150.9.34.

• MAC and IP numbers are both used by routers.

• The Network Layer fragments the segments into smaller units called packets.

• DATA LINK LAYER

• Divides data received from the Network Layer into frames.

• A frame is a structured package for moving data. Contained within the frame are payload, source and destination addresses, error checking, and control information. The payload is the raw data.

• Error checking uses a 4 byte Frame Check Sequence (FCS). This field assures that the data being sent is the same at the destination as it was at the source. The FCS is 4 byte field which is constructed by taking the values of all other fields in the frame – Cyclic Redundancy Check (CRC).

• The Data Link Layer has two sublayers: the Logical Link Control and Media Access Control.

• The Media Access Control (MAC) appends physical addresses to a frame. The Logical Link Control (LLC) interfaces with the Network Layer protocols, manages flow control, and issues requests for transmission for data that has suffered errors.

• PHYSCIAL LAYER

• The Physical Layer accepts frames from the Data Link Layer and generates voltage to be able to send signals over a medium.

• Manages the transmission rate and monitors the data error rate.

• Hubs and repeaters operate at the Physical Layer.

The four lower layers are primarily responsible for data flow and control. The three upper layers are more oriented towards applications.

Applying The OSI Model

Communication Between Two Systems

At each layer of the OSI Model, some information is added to the original data

Frame Specifications

Two major categories of frame types

Ethernet

developed at Xerox in the early 1970s

Token Ring

developed by IBM in the 1980s

UNDERSTANDING 802.2, 802.3, 802.5, AND 802.11b

• These are the most common IEEE standards used in LANs.

• 802.2

• The 802 standard applies to the LLC sublayer of the Data Link Layer

• The recommendations of the IEEE are contributed to ANSI.

• The 802 committee was formed in 1980.

• 802.3, 802.5, and 802.11 are MAC sublayer specifications which work with 802.2.

• 802.2 ensures appropriate flow control for a group of data frames.

• The Data Link Layer was broken into two sublayers, LLC and MAC, to account for the variety of functions required for point-to-point data communications.

• 802.3

• IEEE 802.3 defines CSMA/CD as its network access method. When a node wants to send on a cable, it checks or senses if a carrier wave has been modulated. If it has then the cable is busy. The node backs off and waits a short time to again check to see if the medium is free. Because more than one node could be trying to send at the same time, collisions happen. This is normal. If a collision is detected, then the nodes back off, wait a random amount of time and then try to resend.

• 802.3makes use of both the bus and star topologies.

• 802.3 operates at the MAC sublayer of the Data Link Layer.

• The NIC is the network component which is responbible for applying the 802.3 standards to an electrical signal.

• 10baseT, 10base5, and 100baset all use the 802.3 standard.

• 802.3 has a transmission speed of 100Mbps on most modern systems.

• 802.5

• 4 and 16Mbps are both used on 802.5 networks

• Token-passing is the access method for the 802.5 standards.

• Earlier networks with 4 and 16Mbps speeds used coaxial cable. The newer 802.5 with a speed of 100Mbps runs on UTP, STP, and single-mode fiber.

• 802.5 standards operate at the MAC sublayer.

• The NIC is the network component which is responbible for applying the 802.5 standards to an electrical signal.

• 802.3 is preferred, for it is cheaper and can command greater speed.

• 802.5 uses the star-wired ring topology.

• 802.11b, (There are other standards, including 802.11a or 802.11g. 802.11n is in planning stages and will do 100Mbps or more. 802.11i is a reference to a level of security using AES)

• The NIC is the network component which is responbible for applying the 802.11b standards to an electrical signal.

• Direct infrared is the least secure.

• The general overall speed of 802.11b is 11Mbps. A wireless LAN probably will transmit at an overall rate of 2Mbps.

• 2.4GHz is the accepted frequency for 802.11b, because it is license free. Transmission is spread spectrum.

• 802.11b uses CSMA/CA. CA is for collision avoidance, which is the opposite of 802.3 with CD or collision detection.

• 802.11b is more appropriate for LANs not WANs.

• 802.11b is located at the MAC sublayer.

• Token Ring, 10BaseT, 100BaseT can integrate wireless devices.

• The NIC must have an antenna.

• Access points, with which the node needs to contact is also call the base station.

• Nodes may communicate directly without going to the base station.

• Wireless nodes use broadcast transmission methods.

 

• UNDERSTANDING ETHERNET CONNECTIONS

• 1.10BaseT has a maximum segment length of 100 meters. 10BaseT uses CAT3 and CAT5, baseband, RJ-45 connectors, a star topology with a central hub, a throughput of 10Mbps, access method is CSMA/CD, and runs on the same network with 100BaseT. Follows the 5-4-3 rule. 5 network segments, 3 populated segments, and 4 repeating services (hubs).

• 100BaseT uses 3 segments and 2 hubs (2 segments are populated), baseband, RJ-45 connectors, a star topology with a central hub, a throughput of 100Mbps, and runs on the same network with 10BaseT, upgrades easily from 10BaseT, CAT5 and higher, access method is CSMA/CD, and maximum segment length of 100 meters. 100BaseT is referred to as Fast Ethernet.

• 100BaseTX uses 3 segments and 2 hubs, baseband, RJ-45 connectors, a star topology with a central hub, a throughput of 100Mbps, and runs on the same network with 10BaseT, upgrades easily from 10BaseT, CAT5 and higher, access method is CSMA/CD, and maximum segment length of 100 meters. 100BaseTX is referred to as Fast Ethernet. 100BaseTX is ten times faster than 10BaseT. 100BaseTX uses two of four wire pairs and full-duplexing.

• 10Base2, or RG-58, has a maximum segment length of 185 meters per segment. Transfers data at 10Mbps and uses thinnet coaxial cable. Because of the black color of the cable, 10Base2 is referred to as black network cable. Uses a Bus topology, BNC connectors, barrel BNC connectors to connect two thinnet segments, CSMA/CD access method where one signal is share by all nodes, and must be terminated on both ends to eliminate signal bounce. 10Base2 can accommodate 30 stations per segment. All nodes must be separated by at least .5 m.

• 10Base5 or yellow Ethernet, has a maximum segment length of 500 meters per segment with 100 nodes. Transfers data at 10Mbps and uses thicknet coaxial cable. Uses RG8 thick coaxial cable or thicknet. Workstations on yellow Ethernet must be separated by 2.5 m. Thicknet requires a combination of a vampire tap to connect to a transceiver (media access unit) on the backbone plus a drop cable to connect network devices (node). Uses an AUI connector with 15 pins. The connection between the transceiver and node has a male connection at the transceiver and a female connection at the node. The total maximum length for a network is 1500 meters.

• 100BaseFX uses 100Mbps throughput with fiber-optic cabling. Usually uses SC or ST connectors. 100BaseFX networks requires multimode fiber containing two strands of fiber, one strand is used for transmission and one for reception, allowing full-duplex. Uses a star topology with a maximum segment length of 400 meters. 100BaseTX and 100BaseFX are compatible on the same network. This technology is highly scalable and fault tolerant. The problem is the cost, which is very high, due to fiber cable.

• Gigabit Ethernet can run on UTP but works best on multimode fiber-optic cable. This IEEE standard is 802.3z. A segment length can span 550 meters. 1 Gigabit Ethernet uses SC and ST connectors with fiber cable. The access method for Gigabit Ethernet is CSMA/CD. This technology uses star physical topology with full duplexing. This technology is also competing with ATM. This technology is usually used on the backbone.

Users

Network performance

Availability

Scalability

Integration

Security

Setting Project Goals

Project goals help keep a project on track

Evaluating whether a project was successful

A popular technique for setting project goals is to begin with a broad goal, then narrow it down into specific goals that contribute to the larger goal

Project goals should be attainable

Feasibility study should help determine whether you can achieve the project goals within the given time, budgetary, and resource constraints

If project goals are not attainable from the outset, you risk losing backing from project participants, users, and the managers who agree with the project’s goals and who will strive to help you achieve them

Managers and others who oversee resource allocation are called sponsors

Project Planning

Project plan organizes the details of a managed project

Small projects may take the form of a simple text or spreadsheet document

Larger projects, however, you typically take advantage of project management software such as Microsoft Project or PrimaVera Project Planner

Project management software facilitates project planning by providing a framework for inputting tasks, timelines, resource assignments (identifying which staff are responsible for each task), completion dates, and so on

Tasks and Timelines

Project should be divided into specific tasks

Break larger tasks into smaller subtasks

Identify tasks, you can assign a duration, start date, and finish date to each task and subtask in the project plan

Designate milestones, task priority, and how the timeline might change depending on resource availability or dependencies

A Gantt chart is a popular method for depicting when projects begin and end along a horizontal timeline

Communication

Communication is necessary to ensure that all participants understand the project’s goals

It helps keep a project’s budget and timeline on track, encourage teamwork, avoid duplicate efforts, and allows learning from previous mistakes

Project manager is responsible for facilitating regular, effective communication among project participants

Project managers must ensure consistent communication with all project stakeholders

A stakeholder is any person who is affected by the project; for example, in the Wyndham School District upgrade project, stakeholders include:

Teachers

Administrators

Technical staff

Students, because students are also network users

Contingency Planning

Unforeseen circumstances

Contingency planning

Include at least one of each type of device (whether a critical router or a client workstation) that might be affected by the change

Use the same transmission methods and speeds as employed on your network

Try to emulate the number of segments, protocols, and addressing schemes in your network.

Implement the same server and client software and configurations on your pilot network as found in your current network (unless they are part of the change you’re testing)

Once you have established the pilot network

Test it for at least two weeks to verify that its performance, security, availability, or other characteristics meet your criteria

Network Management

Network management refers to the assessment, monitoring, and maintenance of all aspects of a network

Baselining is the practice of measuring and recording a network’s current state of operation

Baselining

Baseline assessment should address the following Questions:

Access method

Protocols

Devices

Operating systems

Applications

Performance and Fault Management

Performance management (monitoring how well links and devices are keeping up with the demands placed on them)

Fault management (the detection and signaling of device, link, or component faults)

To accomplish both performance and fault management, organizations often use enterprise-wide network management software

Polling

Network management agent

Management information base (MIB) by definition are where managed objects and their data are collected

Agents communicate information about managed objects via any one of several Application layer protocols

Once data is collected, the network management program can present an administrator with several ways to view and analyze the data

Network Management

Network Status

One of the most common network management tools used on WANs is the Multi Router Traffic Grapher (MRTG)

MRTG is a command-line program that uses SNMP to poll devices, collects data in a log file, then generates HTML-based views of the data

MRTG is freely distributed software originally written by Tobias Oetiker

MRTG can be used with UNIX- and Windows-based operating systems and can collect and graph data from any type of device that uses SNMP

Network Management Graphs

Asset Management

A key component in network evaluation is identifying and tracking the hardware and software on your network, a process called asset management

Asset management is to take an inventory of each node on the network

Inventory should include the total number of components on the network, and also each device’s configuration files, model number, serial number, location on the network, and technical support contact

Software Changes

1. Determine whether the change (whether it be a patch, revision, or upgrade) is necessary

2. Research the purpose of the change and its potential effects on other programs

3. Determine whether the change should apply to some or all users and whether it will be distributed centrally or machine-by-machine

4. If you decide to implement the change, notify system administrators, help desk personnel, and users. Schedule the change for completion during off hours (unless it is an emergency)

5. Back up the current system or software before making any modifications

6. Prevent users from accessing the system or part of the system being altered (for example, disable logons)

7. Keep the upgrade instructions handy and follow them during installation of the patch or revision

8. Make the change

9. Test the system fully after the change

10. If the change was successful, reenable access to the system and if it was unsuccessful, revert to the previous version of the software

11. Inform system administrators, help desk personnel, and users when the change is complete. If you had to reverse it, explain why

12. Record your change in the change management system.

Patches

A general rule, upgrading or patching software according to a vendor’s recommendations is a good idea and can often prevent network problems

Patches is a correction, improvement, or enhancement to a particular piece of a software program

Differs from a revision or software upgrade in that it changes only part of a software program, leaving most of the code untouched

Are often distributed at no charge by software vendors in an attempt to fix a bug in their code or to add slightly more functionality

Client Upgrades

Software upgrade is a major change to a software package’s existing code

An upgrade to the client program replaces the existing client program

Upgrades are designed to add functionality and fix bugs in the previous version of the client

A client upgrade may be transparent to users, or it may completely change the appearance of the network logon interface

Application Upgrades

Application upgrades, apply to software shared by clients on the network

Back up the current software before upgrading it

Prevent users from accessing the software during the implementation

Keep users and system administrators informed of all changes.

Network Operating System Upgrades

Most Critical

Involves significant, potentially drastic, changes to the way your servers and clients operate

Have a project plan covering the upgrade procedure

How will the upgrade affect user IDs, groups, rights, and policies?

How will the upgrade affect file, printer, and directory access, applications or client interactions on the server?

How will the upgrade affect configuration files, protocols, and services running on the server?

How will the upgrade affect the server’s interaction with other devices on the network?

How accurately can you test the upgrade software in a simulated environment?

How can you take advantage of the new operating system to make your system more efficient?

What is your technical support arrangement with the operating system’s manufacturer if you need help in the midst of the upgrade?

Have you allotted enough time to perform the upgrade? (For example, would it be more appropriate to do it over a weekend rather than overnight?)

Have you ensured that the users, help desk personnel, and system administrators

Understand how the upgrade will affect their daily operations and support burdens?

The following steps demonstrate how careful planning and a methodical process can help you accomplish an NOS upgrade

Research

Proposal

Evaluation

Training

Pre-implementation

Implementation

Post-implementation