Remote Connectivity–Advanced IP Networking–NETWORKING, SECURITY, & MORE ESSENTIALS—CompTIA Network+ (N10-007) NETWORK-PLUS Certification Prep Course Notes

Remote Connectivity

Telephony Technologies
- Original telephone systems used frequency division multiplexing; today they use time division multiplexing.
- T1 = 24 DSOs = runs at 1.544 (~1.5) Mbps
- T3 = 28 DS1s = runs at 44.736 (~45) Mbps [DS1–Digital Signal 1]
- E1 and E3 are European carriers
- 64 Kbps
- Frequency Division Multiplexing
- Time Division Multiplexing
- A DS0 can carry 64 kilobits per second!
- DS1 (digital signal 1)–24 DS0 signals all going down the same wire.
  - this is not Frequency, but Time Division Multiplexing, it uses block & frames, not frequencies.
- DS1 is just a signal type that runs on something called “T1”.
- “T1” is a specific type of cabling system.
  - T1 runs at 1.5Mbps
    - ex: In Networking world we say “we have ethernet frames & ethernet cable”…Well in the Telephone world we say “DS1 frames but on a T1 system”.
- These are all “copper carriers”, btw.
- DS3–runs 28 DS1’s simultaneously.

CSU/DSU–acts as the endpoint; a permanent connection always running.
BERT (bit error rate testing); helps diagnose problems with a T1 line (to make sure the connection is good).
T1 crossover–can be used to emulate a full-blown T1 connection.

Optical Carriers:
- SONET (Synchronous Optical Networking)–main fiberoptic standard. SONET uses OC lines.
- OC1 = STS1 = 51.85 Mbps
- OC3 = STS3 = 155.52 Mbps
- OC12 = STS12 = 622.08 Mbps

SONET Optical Level	Line Speed	Signal Method–(Framing type)
OC-1 (Optical Carrier 1)	51.85 Mbps	STS-1
OC-3	155.52 Mbps	STS-3
OC-12	622.08 Mbps	STS-12
OC-24	1.244 Gbps	STS-24
OC-48	2.488 Gbps	STS-48
OC-192	9.955 Gbps	STS-192
OC-256	13.22 Gbps	STS-256
OC-768	39.82 Gbps	STS-768
*Tip: 51.85 multiplied by the OC number gives the Line Speed

DWDM (Dence wavelength division multiplexing)–“SONET on steroids!”

Packet Switching
- (Note: Circuit switching is the opposite of packet switching–it creates a hard wired circuit between 2 communicating nodes.)
- Know your types of telephony packet switching.
- Frame relay & ATM (Asynchronous Transfer Mode) are being replaced with MPLS (Multi-protocol Label Switching).
- ATM is limited to small 53 byte frames; Ethernet frames are 1500 bytes
- Frame relay–older technology
- ATM (Asynchronous Transfer Mode)–replacing Frame Relay; ATM is a complete networking solution. (Today even ATM is fading away.)
- MPLS (Multi-protocol Label Switching)–designed for IP-based networks.

Connecting with Dial-Up
- Dial-up is slow & not a reliable backup. Runs at 56k. (uses the same 64k DS0 that our voice uses for telephone calls, but due to overhead & maintenance, we can only use about 56 of the 64k to actually transfer data!)
- Dial-up requires a modem & an ISP connection (phone number).
- An ISP will give a username & password.
- Dial-up uses the PPP protocol.
- *Dial-up modems convert the computer digital signals into analog signals that can travel on a telephone line & then convert returned, analog signals back to digital signals so they can be passed into the computer!

Digital Subscriber Line (DSL)–lives on telephone lines.
- DSL is either in symmetric or asymmetric mode, (or Asynchronous DSL)
  - asymmetric is the common application (High download speed & slower upload speed.)
- DSL filtering is used to clear the phone line of the DSL noise (to make phone calls!)
- Takes RJ-11 connection & connects to an RJ-45 connection.
- VDSL (very-high-bit-rate DSL)

Connecting with Cable Modems
- Cable modems adhere to the DOCSIS cable connection standard!
- Cable modems come from the cable company.
- Cable rarely requires PPPoE. (DSL almost always uses a PPPoE!)
- Cable modems use F-type connectors.
- MAC address clone–used to “fool” cable modems.
- In general, cable is considered to be faster than DSL.

Connecting with Satellites
- Satellite modems enable connecting to the Internet through a satellite.
- Satellite connections have terrible latency.
- Run an RG-6 cable from the dish to the modem.

ISDN & BPL
- ISDN (Integrated Service Digital Network)
- BPL (Broadband over Power Lines)
- ISDN ran at two speeds: 64-kbps and 128-kbps
- ISDN has a telephone number
- BPL uses power line to move Internet data.
- ISDN uses a Terminal Adaptor

Remote Desktop Connectivity
- *TightVNC runs on port 5900 (free & easy to use, & cross-platform!)
- *Microsoft RDP runs on port 3389 (and Microsoft remote desktop tools)
- Use remote help to control the desktop of the user you are assisting.
- Remote connections (in general) don’t transfer files from the remote to local desktop; it’s just a way to show the GUI to do things.
- ex: Citrix is very dominant; Alternatives are (TightVNC-Port 5900) & Microsoft remote desktop tools.
- Remote desktop lets one computer remotely operate another computer by taking over its screen & keyboard.

Advanced Remote Control Systems
- Industrial control systems control machines with sensors & actuators connected to an ICS server.
- SCADA (Supervisory Control And Data Acquisition) systems handle ICS over a large area. ICS–(Industrial Control Systems)
- Key pieces: programmable logic controller, human machine interface, and remote terminal unit.
- ICS:
  - the ICS server is connected to Sensors on the machine.
  - the ICS server has Actuators (i.e.–pumps, lights, or motors).
  - The Interface is where humans talks to the ICS Server.
- DCS–Distributed Computer Systems
  - DCS is an extension of ICS.
  - DCS creates a hierarchy of ICS systems.
- SCADA:
  - is still ICS but designed for long distance things like oil-field pipelines or railroads, etc.
- The Programmable Logic Controller (PLC) is the actual ICS Server itself. PLC are usually “headless” PCs with CPUs, RAM, storage, & OSes.
- The interface is usually Human Machine Interface (dedicated interfaces).
- SCADA has a Remote Terminal Unit (really just a powerful PLC)
  - more autonomous; gathers more data;
- *Remember…SCADA is used to monitor & manage remote sites. ICS/DCS is usually used to monitor/manage single sites, or multiple sites in close proximity to each other & the monitor.