NOTES: FTP 20/21 SSH 22 Telnet 23 SMTP 25 DNS 53 DHCP 67/68 TFTP 69 HTTP 80 POP3 110 NetBios 137/139 IMAP 143 SNMP 161/162 LDAP 389 HTTPS 443 SMB 445 RDP 3389 Mail protocols: SMTP is the only protocol used to send emails over TCP 25. POP3 and IMAP are used to receive emails. The post office protocol (POP3) is used to access email messages stored in a mailbox on a remote server over TCP 110. The server usually deletes messages once the client has downloaded them. The internet message access protocol (IMAP) is used to access email messages stored in a mailbox on a remote server using TCP 143. Unlike POP3, messages persist on the server after the client has downloaded them. IMAP also supports mailbox management functions, such as creating subfolders and access to the same mailbox by more than one client at the same time. Network Troubleshooting notes: It's Broke! Identify the Problem (gather info) Establish a Theory (question the obvious) Test the theory (confirm it is the issue) Establish a Plan of Action and Implement the Plan Verify Full System Functionlity Document Findings It works! LCD (Liquid Crystal Display) technologies: TN (Twisted Nematic) LCD- The original LCD, fast response time, poor viewing angles- color shift IPS (In Plane Switching) LCD- Excellent color representation, more expensive than TN VA (Vertical Alignment) LCD- Good color representation, slower response than TN (in-between TN and IPS) LCD monitors require a backlight. Older backlights were CCFL- Cold Cathode Fluorescent Lamp. New backlights are LED, can be an array of LED's behind the screen or around the edge. LCD displays need an inverter for the CCFL backlights. The inverter turns DC into AC. Troubleshoot display issues by looking closely and using a flashlight. If you can make out an image the issue may be with the inverter. OLED (Organic Light Emitting Diode): Organic compound emits light when receiving an electrical current. Thinner and Lighter, flexible and mobile- no glass needed. No backlights, the organic compound provides the light. Found on Tablets, phones, and smart watches. Very accurate color representation but higher cost than LCD. SDN (Software Defined Network): Infrastructure layer/Data plane- Process the network frames and packets; forwarding, trunking, encrypting, NAT Control layer/Control plane- Manages the actions of the data plane; routing tables, session tables, NAT tables; Dynamic routing protocol updates Application layer/Management plane- Configure and manage the device; ssh, browser, API DHCP: DORA- Discover, Offer, Request, Acknowledge Discover- find a DHCP server Offer- get an IP address offer from the DHCP server Request- accept the offer from the DHCP server Acknowledge- DHCP server confirms request and assigns IP address Hard Drive (HDD) Speeds: 5,400rpm 7,200rpm 10,000rpm 15,000rpm Raid (Redundant Array of Inexpensive Drives): Type Drives Raid 0- striping Raid 1- mirroring Raid 5- striping w/ parity Failure Condition 2 or more A single drive failure breaks the array with data loss 2 or more 3 or more Raid 10- striping w/ mirroring 4 or more DVI (Digital Visual Interface) cables: Array will work as long as one drive is operational Need all drives operational but one Can lose all but one from each set of mirrors DVI-A this is an Analog cable 3.7 Gbps HDTV up to 60fps DVI-D this is a Digital cable (dual link available at 7.4 Gbps HDTV up to 85fps) DVI-I this is an Integrated cable providing both Analog and Digital (dual link available) PCIe slot size: PCIe x1 - NIC or WI-FI network cards PCIe x4 - M.2 NVMe drives PCIe x16 - Graphics Cards Motherboard form factors: ATX- standard-ATX size 12 x 9.6 mATX- micro-ATX size 9.6 x 9.6 mITX- mini-ITX size 6.7 x 6.7 OS tech: 32-bit (x86) cannot run 64-bit apps 64-bit (x64) can run 32-bit apps ARM- Advanced RISC Machine; less power needed, less heat, mostly IoT and mobile devices Multithreading: Hyper-Threading Technology (HTT)- one CPU core acting like 2 CPU cores; Not actually as fast as 2 but gives at 15-30% performance improvement Printers: MFD- multifunction devices; these devices can be printers/scanners/fax/network/phone line/web print PCL- Printer Command Language; created by Hewlett-Packard very common across the industry, faster output with lower quality PostScript- created by Adobe Systems, popular with high end printers, higher quality with slower output Duplex- saves paper and prints on both sides of the paper Laser printer- combines a laser, high voltage, charged ions, powdered ink, heat, and paper Imaging drum- image is drawn onto a photosensitive drum with a laser, picks up toner and transfers to the paper, can be separate from the toner cartridge or combined Fuser assembly- heat and pressure to melt plastic toner powder and permanently bond toner to the paper Transfer belts and roller- used for multi color laser printers; usually 4 separate cartridges (cyan, yellow, magenta, black). The image is transferred from all cartridges to the single belt and then to the single transfer roller Pickup rollers- pickup paper; should be a single page picked up, should be cleaned periodically during maintenance process Separation pad- pull just the top sheet from the paper tray, small and inexpensive; used with the pickup rollers Duplexing- able to print on both sides; printing on one side then turning page over without intervention to print second side 7 steps for laser printing: Step 1: Processing (nothing moving; sending data to printer and prints after job has completely rendered in memory) Step 2: Charging (A corona wire or charge roller applies a negative charge to imaging drum) Step 3: Exposing (The laser applies a positive charge; writing the image to the imaging drum) Step 4: Developing (a negatively charged toner is applied to the positively charged sections on the photo sensitive drum) Step 5: Transferring (toner is transferred from the photo sensitive drum to the paper) Step 6: Fusing (the paper passes through the fuser and it melts the toner to the paper permanently) Step 7: Cleaning (removes any excess toner from the drum) Inkjet printer- relatively inexpensive, quiet, high-resolution, ink is usually proprietary and expensive. Fades rapidly overtime (not good for archiving) and can clog easily. 4 colors CMYK: cyan, magenta, yellow, key (black) Print heads- drips the ink onto the paper; some printers combine the inkjet cartridge with a print head Feed rollers- pick up and feed paper Carriage and belt- ink cartridges are moved over the paper via the carriage (which may have its own print head), the belt moves the carriage back and forth inkjet calibration- align nozzles to the paper, lines should be crisp and colors should align. Thermal printer- special coated white paper turns black when heated; no ink required, very quiet, fades overtime (not good for archiving) Feed assembly- pulls paper through the printer via a cylinder feed assembly Heating element- full-length heating element, no moving print head Thermal paper- paper covered with a chemical; thermochromic paper Impact printer- Dot-matrix printers are impact printers. print heads with a small matrix of pins press against a ribbon to make a mark on the paper, great for carbon/multiple copies. poor graphics with low cost but very loud Dot-matrix printer head- moves back and forth, pins hit the ribbon and paper. print head includes are large heat sink due to heat generated from strikes of the pins on the paper Printer ribbon- very long ribbon, made of fabric and easy to replace; proprietary sizes for each model Tractor feed- continuous paper feed with perforations between pages, paper can be pulled through holes on the sides instead of using friction 3D printers- "print" in three dimensions, create a 3D item based on electronic model; additive manufacturing builds in layers to create the object, no machining process required. Used in rapid prototyping, design and create relatively quickly and inexpensively. Can be used anywhere in the world and in space Filament printing- Fused Deposition Modeling (FDM), melt filament to print 3D objects. Most common form of 3D printing; Print a layer, move up, print another, and so on. Good all-around printer with larger print bed than resin printers, easy to manager filament, minimum mess, and fewer disposal issues Resin printing- Stereolithography (SLA) 3D printing, smooth and finely detailed 3D prints. Resin is hardened using a light source. Ultraviolet light or a laser hardens the resin, layers are added to the bottom. The entire print hangs from the build platform and is lowered into the resin. Resin must be handled properly, wear protective gear and take unused resin to hazardous material disposal. Print Bed- a flat adhesive surface, the foundation of 3D printing. Must be level and clean. Virtualization: Type 1 hypervisor, also known as bare metal, uses a specialized hypervisor OS to run the virtual machines (such as VM Ware's ESXi) Type 2 hypervisor runs on top of an existing operating system. VM escaping- Malware recognizes it's on a VM, Malware compromises the hypervisor, Malware jumps from one guest OS to another Rogue VM's- bad actors try to install their own system VM sprawl- VM sprawl is the uncontrolled deployment of more and more VMs. Resource pooling- Resource pooling refers to the concept that allows a virtual environment to allocate memory and processing capacity for a VMs use. Rapid elasticity can be a security threat to your organization's data due to data remanences. Data remanence is the residual representation of digital data that remains even after attempts have been made to remove or erase it. So, when a cloud resource is deprovisioned and returned to the cloud service provider, it can be issued to another organization for use. If the data was not properly erased from the underlying storage, it could be exposed to the other organization. For this reason, all cloud-based storage drives should be encrypted by default to prevent data remanence from being read by others. Virtual Network Requirements: Shared network address- The VM shares the same IP address as the physical host, uses a private IP address internally, Uses NAT to convert to the physical host IP Bridged network address- The VM is a device on the physical network, each VM gets its own IP address Private address- The VM does not communicate outside of the virtual network. Troubleshooting: "OS not found" - The "OS not found" error at boot time is an indication that the MBR (Master Boot Record) or GPT (Globally Unique ID Partition Table) is corrupted or faulty. If this occurs, you should reboot into the Windows recovery mode and use the 'bootrec /fixboot' command to fix the GPT. This issue may occur if one or more of the following conditions are true: (1) the basic input/output system (BIOS) does not detect the hard disk, (2) the hard disk is damaged, (3) sector 0 of the physical hard disk drive has an incorrect or malformed master boot record (MBR), (4) an incompatible partition is marked as Active, or (5) a partition that contains the MBR is no longer active. LCD Burn in- image sticking can be removed by displaying a white screen for an extended period ipconfig /flushdns - The ipconfig /flushdns command provides you with a means to flush and reset the contents of the DNS client resolver cache. During DNS troubleshooting, if necessary, you can use this procedure to discard negative cache entries from the cache, as well as, any other dynamically added entries. Resetting the cache does not eliminate entries that are preloaded from the local Hosts file. To eliminate those entries from the cache, remove them from the hosts file instead Additional notes: VRAM- video RAM Virtual Memory- Virtual memory is an area on the hard disk allocated to contain pages of memory. When the operating system doesn't have sufficient physical memory (RAM) to perform a task, pages of memory are swapped to the paging file. This frees physical RAM to enable the task to be completed. When the paged RAM is needed again, it is re-read into memory. Digitizer- use a stylus or finger to draw on a screen by converting analog input into digital signals for the computer. Bluetooth- Bluetooth is a wireless technology standard used for exchanging data between fixed and mobile devices over short distances using UHF radio waves in the industrial, scientific, and medical radio bands from 2.402 GHz to 2.480 GHz and building a personal area network (PAN). Jitter- time between frames, excessive jitter from variable intervals between frames can cause "choppy" voice calls Latency- a delay between the request and the response NFC- Near-field communication (NFC) is a set of communication protocols that enable two electronic devices, one of which is usually a portable device such as a smartphone, to establish communication by bringing them within 4 cm of each other. This is commonly used for contactless payment systems, transferring contacts, or transferring a file from one device to another. SAN- Storage Area Network; looks and feels like a local storage device, block-level access, very efficient reading and writing. Inverters- turn DC power for laptop into AC power for LCD displays. These power the backlight, one way to determine if the inverter is not working is to shine a flashlight on the screen and see if you can make out any of the image being displayed. Perimeter network- (formerly called a Demilitarized Zone or DMZ) is a portion of a private network connected to the Internet and protected against intrusion. Certain services may need to be made publicly accessible from the Internet (such as a web, email, or Minecraft server) and they should be installed in the perimeter network instead of in your intranet. If communication is required between hosts on either side of a perimeter network, then a host within the perimeter network will act as a proxy to take the request. If the request is valid, it re-transmits it to the destination. External hosts have no idea about what is behind the perimeter network so that the intranet remains secure. A perimeter network can be implemented using either two firewalls (screened subnet) or a single three-legged firewall (one with three network ports)
