BEN IT

My name is Ben IT, and these are my notes on Networking, Programming, and General Computing. Currently Working on: Cisco CCENT/CCNA Certification CompTIA A+ Certification Certifications: None.

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Storage Devices

FDD - Floppy Disc Drives -1.44MB on a single 3.5" Floppy

HDD - Hard Disc Drives -SATA, PATA, SCSI (All 3.5") -SSD (Solid-state Drives) No moving parts

Parts of an HDD -Platter -Spindle -Actuator -Arm -Head

HDD Facts -Multiple Platters and Arms/Heads -Many tracks on each platter -Head is on same track on each platter -Many sectors on each track

MBR - Master Boot Record -First sector of HDD -Usually only 512 Bytes -Contains: Table for primary partitions, disk signature, directions for starting OS

Storage Technology Interfaces SATA - Serial Advanced Technology Attachment PATA - Parallel AT Attachment -formerly known as ATA ATAPI - AT Attachment with Packet Interface IDE - Integrated Drive Electronics -Western Digital original standard SCSI - Small Computer Systems Inferface

Optical Formats CD - Compact Disc -700MB capacity DVD - Digital Versatile Disc -4.7GB for single layer -8.5GB for dual-layer Blu-ray -25GB for single layer -50GB for dual-layer

Removable Storage Flash memory - USB drives, SD cards, compact flash cards External Hard Drives Tape Drives

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Intro to PCs

The Complete PC -Monitor -Keyboard -Mouse -Speakers/Headphones -Printer

Inside The Computer -Power Supply -Motherboard --CPU (Central Processing Unit) AKA Processor --RAM (Random Access Memory) AKA Memory --CMOS/BIOS -Cooling Fans -Floppy Drive (Legacy) -Hard Drive

Computer Operation Primer Input->Processing->Output              ^StorageV

CMOS - Complementary Metal-Oxide Semiconductor BIOS - Basic Input/Output System

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LANs (Part 3)

Ethernet Data Link Protocols -Ethernet LAN addressing identifies either individual devices or groups of devices on a LAN -Each address is 6 bytes long and is usually written in hexadecimal -Unicast ethernet addresses identify a single LAN card -The IEEE requires globally unique MAC addresses on all LAN interface cards -First half of address identifies the manufacturer 

OUI - Organizationally Unique Identifier

OUI -Size in Bits: 24 Bits -Size in Hex Digits: 6 Hex Digits -Example: 00 60 2F Vender Assigned (NIC Cards, Interface) -Size in Bits: 24 Bits -Size in Hex Digits: 6 Hex Digits -Example: 3A D7 BC

BIA - Burned-in Address UAA - Universally Administered Addresses

Unicast Address AKA -LAN Address -Ethernet Address -Hardware Address -Physical Address -MAC Address

Group Addresses - Identify more than one LAN interface card -Broadcast Addresses - The most often used of the IEEE group MAC addresses, the broadcast address, has a value of FFFF.FFFF.FFFF. The broadcast address implies that all devices on the LAN should process the frame. -Multicast Address - Used to allow a subset of devices on a LAN to communicate. When IP multicasts MAC addresses used by IP follow this format: 0100.5exx.xxxx, where any value can be used in the last half of the address.

LAN MAC Address Terminology and Features -MAC - Media Access Control. 802.3 (ethernet) defines the MAC sublayer of the IEEE ethernet. -Burned-in Address - The 6-byte address assigned by the vendor making the card. -Unicast Address - A term for a MAC address that represents a single LAN interface. -Broadcast Address - An address that means "all devices that reside on this LAN right now." -Multicast Address - On ethernet, a multicast address implies some subset of all devices currently on the ethernet LAN.

Ethernet Framing - Defines how a string of binary numbers is interpreted (Layer 2, Data Link)

IEEE 802.3 Ethernet Header and Trailer Fields (Data Link Layer) Preamble (7 Bytes) - Synchronization Start Frame Delimiter (SFD) (1 Byte) - Signifies that the next byte begins the Destination MAC field Destination MAC Address (6 Bytes) - Identifies the intended recipient of this frame Source MAC Address (6 Bytes) - Identifies the sender of this frame Length (2 Bytes) - Defines the length of the data field of the frame (Either length or type is present, but not both). Type (2 Bytes)  Defines the type of protocol listed inside the frame (Either length or type is present, but not both). Data + Pad (46-1500 Bytes) - Holds data from a higher layer, typically an L3 PDU (generic), and often an IP packet. Frame Check Sequence (FCS) (4 Bytes) - Provides a method for the receiving NIC to determine if the frame experienced transmission errors.

Note: FCS only in the trailer, and is NOT used for error recovery.

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LANs (Part 2)

Ethernet UTP Cabling -The three most common are 10BaseT (ethernet), 100BaseTX (fast ethernet), & 1000BaseT (gigabit ethernet). -Uses RJ-45 connectors. -8 wires, Slightly wider, but similar to RJ-11 phone cable.

GBIC - Gigabit Interface Converters SFP - Small Form Pluggables

UTB Cabling Pinouts for 10BaseT & 100BaseTX -IEEE doesn't define an official standard -Telecommunications Industry Association (TIA) and Electronics Industry Alliance (EIA) define standards.

T568A Pinouts 1. Green/White 2. Green 3. Orange/White 4. Blue 5. Blue/White 6. Orange 7. Brown/White 8. Brown

T568B Pinouts 1. Orange/White 2. Orange 3. Green/White 4. Blue 5. Blue/White 6. Green 7. Brown/White 8. Brown

Sending and Recieving -Ethernet NICs send data using the pair connected to 1 and 2 -Ethernet NICs receive data using the paid connected to 3 and 6 -Hubs and Switches do the opposite

Straight Through Cable - wired the same on both ends Crossover Cable - wired the opposite at both ends

Devices that transmit on 1 and 2, receive on 3 and 6 -PC NICs -Routers -Wireless Access Points -Networked Printers

Devices that transmit on 3 and 6, receive on 1 and 2 -Hubs -Switches

1000BaseT Cabling (requires 4 wire pairs)

Crossover Cable Wiring 1 > 3 2 > 6 3 > 1 4 > 7 (Gb Only) 5 > 8 (Gb Only) 6 > 2 7 > 4 (Gb Only) 8 > 5 (Gb Only)

How Hubs Work 1. The NIC sends a frame. 2. The NIC loops the sent frame into its receive pair internally on the card 3. The hub receives the electrical signal, interpreting the signal as bits so that it can clean up and repeat the signal 4. The hub's internal wiring repeats the signal out all other ports, but not back to the port from which the signal was received 5. The hub repeats the signal to each receive pair on all other devices

Switches - a layer 2 device -Significantly reduce, or even eliminate collisions -Do not create a single shared bus -Interpret the bits in the received frame so that they can typically send the frame out the one required port, rather than all the ports If a switch needs to forward multiple frames out the same port, the switch buffers the frames in memory, sending one at a time, therefore avoiding collisions

Advantages of Switches -If only one device is cabled to each port of a switch, no collisions can occur -Devices connected to one switch port do not share their bandwidth with devices connected to another switch port. Each has its own separate bandwidth, meaning that a switch with 100Mbps ports has 100Mbps of bandwidth per port

Full-duplex - an ethernet card can send and receive concurrently -LAN switches with only one device per port can operate at full-duplex.

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LANs (Part 1)

IEEE - The Institute of Electrical and Electronics Engineers

Most Common Types of Ethernet Ethernet -Speed: 10Mbps -Alt Name: 10BaseT -IEEE Standard: IEEE 802.3 -Cable Type/Max Length: Copper, 100m Fast Ethernet -Speed: 100Mbps -Alt Name: 100BaseTX -IEEE Standard: 802.3u -Cable Type/Max Length: Copper, 100m Gigabit Ethernet -Speed: 1000Mbps or 1Gbps -Alt Name: 1000BaseLX, 1000BaseSX -IEEE Standard: 802.3z -Cable Type/Max Length: Fiber, 550m(SX), 5Km (LX) Gigabit Ethernet -Speed: 1000Mbps or 1Gbps -Alt Name: 1000BaseT -IEEE Standard: 802.3ab -Max Length: 100m

LAN Functions -File Sharing -Printer Sharing -File Transfers -Gaming

MAC - Media Access Control (802.3) LLC - Logical Link Control (802.2)

CSMA/CD - Carrier Sense Multiple Access with Collision Detection -Ensures data doesn't collide -One device sends traffic at a time

CSMA/CD Algorithm -A device that wants to send a frame waits until the LAN is silent - in other words, no frames are currently being sent - before attempting to send an electrical signal. -If a collision still occurs, the devices that caused the collision wait a random amount of time and then try again.

Attenuation: As distance increases, the signal gets weaker.

Repeaters: Takes signal, interprets the bits (as 1s and 0s), and generates a brand new, clean, strong signal out on the other end. -Because repeaters do not interpret what the bits mean, but examines and generates electrical signal, a repeater is considered to operate on Layer 1.

Key Points Relating to Today's LANs -The original ethernet LANs created an electrical bus to which all devices connected. -Because collisions could occur on this bus, ethernet defined the CSMA/CD algorithm, which defined a way to both avoid collisions and take action when collisions occured. -Repeaters extended the length of LANs by cleaning up the electrical signal and repeating it - a layer 1 function - but without interpreting the meaning of the electrical signal.

Hubs: essentially repeaters with multiple physical ports.

More Key Points -10Base2 and 10Base5 repeaters extend the length of LANs by cleaning up the electrical signal and repeating it - a layer 1 function - but without repeating it.

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The OSI Reference Model

OSI - Open System Interconnection

OSI Layers 7. Application 6. Presentation 5. Session 4. Transport 3. Network 2. Data Link 1. Physical

OSI vs. TCI/IP -The Application Layer (TCP/IP) contains the Application (OSI), Presentation (OSI), and Session (OSI) layers. -The Transport Layer (TCP/IP) contains the Transport Layer (OSI). -The Internet Layer (TCI/IP) contains the Network Layer (OSI). -The Network Access Layer (TCI/IP) contains the Data Link and Physical (OSI) layers.

OSI Layers and Their Functions 7. Application - The Application layer provides an interface between the communications software and any applications that need to communicate outside the computer on which the application resides. It also defines processes for user authentication. 6. Presentation - The Presentation layer's main purpose is to define and negotiate data formats, such as ASCII text, EBCDIC text, binary, BCD, and JPEG. Encryption also is defined by OSI as a presentation layer service. 5. Session - The session layer defines how to start, control, and end conversations (called sessions). This includes the control and management of multiple bidirectional messages so that the application can be notified if only some of a series of messages are completed. This allows the presentation layer to have a seamless view of an incoming stream of data. 4. Transport - The Transport layer provides a large number of services. Although layers 5-7 focus on issues related to the application, layer 4 focuses on issues related to data delivery on another computer - for instance, error recovery and flow control. 3. Network - The Network layer defines three main features: logical addressing, routing (forwarding), and path determination. The routing concepts define how devices (typically routers) forward packets to their final destination. Logical addressing defines how each device can have an address that can be used by the routing process. Path determination refers to the work done by routing protocols by which all possible routes are learned, but the best route is chosen for use. 2. Data Link - The Data Link layer defines the rules (protocols) that determine when a device can send data over a particular medium. Data link protocols also define the format of a header and trailer that allows devices attached to the medium to send and receive data successfully. The data link tailer, which follows the encapsulated data, typically defines a frame check sequence (FCS) field, which allows the receiving device to detect transmission errors. 1. Physical - The Physical later typically refers to standards from other organizations. These standards deal with the physical characteristics of the transmission medium, including connectors, pins, use of pins, electrical currents, encoding, light modulation, and the rules for how to activate and deactivate the use of the physical medium.

Layer Protocol and Device Examples Layers 5-7 -Protocols: Telnet, HTTP, FTP, SMTP, POP3, VoIP, SNMP -Devices: Firewall, Intrusion Detection System Layer 4 -Protocols: TCP, UDP Layer 3 -Protocols: IP -Devices: Router Layer 2 -Protocols: Ethernet (IEEE 802.3), HDLC, Frame Relay, PPP -Devices: LAN Switch, Wireless Access Points, Cable Modem, DSL Modem Layer 1 -Protocols: RJ-45, EIA/TIA-232, V.35, Ethernet (IEEE 802.3) -Devices: LAN Hub, Repeater

Acronyms for Remembering OSI Layers All People Seem To Need Data Processing (7-1) Please Do Not Take Sausage Pizzas Away (1-7) Pew! Dead Ninja Turtles Smell Particularly Awful (1-7)

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TCP/IP Protocol Architecture

Layer..........................Example Protocols Application.................HTTP, POP3, SMTP Transport...................TCP, UDP Internet......................IP Network Access..........Ethernet, Frame Relay

Application Layer -interface between software on a computer and a network -web browser requests the page using Hypertext Transfer Protocol

Transport Layer -TCP: Transmission Control Protocol -UDP: User Datagram Protocol

Internet Layer -postal service of networking -IP: Internet Protocol

Network Access Layer -Defines the protocols and hardware required to deliver data across some physical network -Ethernet, Frame Relay, PPP

Same layer interaction on different computers -The 2 computers use protocol to communicate with the same later on another computer. The protocol defined by each layer uses a header that is transmitted between the computers, to communicate what each computer wants to do.

Adjacent layer interaction on same computer -On a single computer, one layer provides a service to a higher layer. The software or hardware that implements the higher layer requests that the next lower layer performs the function.

Data Encapsulation Terminology 1. Create and encapsulate the application data with any required application layer headers. 2. Encapsulate the data supplied by the application layer inside a transport layer header. 3. Encapsulate the data supplied by the transport layer inside an internet layer header (IP). 4. Encapsulate the data supplied by the internet layer inside a network access layer header and trailer. 5. Transmit the bits.

Vocabulary: segment - transport layer [TCP][Data] packet - internet layer [IP][Data] frame - network access layer [LH][Data][LT]