Remote Connectivity Chapter 13.

Remote Connectivity Chapter 13

Objectives Describe WAN telephony technologies, such as SONET, T1, and T3 Compare last-mile connections for connecting homes and businesses to the Internet Discuss and implement various remote access connection methods Troubleshoot various WAN scenarios

Historical/Conceptual
Remote Connections

Remote Connections Types of connections that predate the Internet
Connecting a local computer or network to distant computers Private interconnections of private networks Old ways were slow and expensive Technologies used to make private remote connections became the way the Internet interconnects

Telephony and Beyond

Telephony in Depth (1 of 2)
Revisit the tier 1 ISPs Most of the high-speed Internet backbone uses old technologies SONET signal type on most connections Conventional telephone system technologies Public Switched Telephone Network Telephone system of the 1970s and 1980s Note (p. 369): Even as you read this, more and more of the Internet interconnections are moving toward Gigabit and 10 Gigabit Ethernet. Telephone technologies, however, continue to dominate. Tech Tip: Telephony in Depth (p. 370) This section is just the lightest of overviews to get you through the CompTIA Network+ exam. The full history of long-distance communication is an incredible story, full of good guys, bad guys, crazy technology, and huge fortunes won and lost.

Telephony in Depth (2 of 2)
Figure The tier 1 Internet

The Dawn of Long Distance (1 of 3)
The telephone operator made the physical link The switchboard acted as a circuit switch Analog signals lost quality over distance Analog required many wires Exam Tip (p. 371): The various multiplexing and demultiplexing technologies and protocols, both analog and digital, are collectively referred to as modulation techniques, a term you might see on the CompTIA network+ exam. Modulation more technically means converting a digital signal to analog or pushing an analog signal to a higher frequency. Pay attention to the wording of any exam questions on modulation.

Figure Old-time telephone operator (photo courtesy of the Richardson Historical and Genealogical Society)

Figure Now that’s a lot of telephone lines!

More Efficient Methods (1 of 5)
A multiplexer combined signals onto one wire Local exchange A defined group of phone circuits served by a single multiplexer The central office housed one or more exchanges Dial-up appeared in the 1950s Connections between exchanges were carried over multiplexed trunk lines

Figure 13.4 Another problem of early long-distance telephone systems

Figure Multiplexers combine multiple circuits

Figure A central office building

Figure Interconnected central offices

The Same Lines (1 of 3) Frequency Division Multiplexing (FDM)
Telephone frequency ranges from 350 to 4000 Hz Designed to cover range of human speech A multiplexer adds a frequency multiplier to each call Each call is kept in its own unique frequency range Tech Tip (p.372): The Same Lines The long-distance lines used for voice calls are the same ones that carry our Internet data. There is no difference as far as the carriers are concerned.

The Same Lines (2 of 3) Long distance used a series of trunk lines
The operator had to connect each intersection Circuit switching Two phones physically on one circuit Only option for analog long distance

Figure 13.8 Multiplexed FDM
The Same Lines (3 of 3) Figure Multiplexed FDM

From Analog to Digital (1 of 3)
Analog was adequate through 1930s to 1950s A new digital system needed for heavier load New remote connections - precursor to Internet Digital repeaters made the system faster Trunk lines were digital Central office converted analog voice to digital Last mile Connection from the central office to users Note (p. 374): Attempts were made to convert the entire telephone system, including your telephones, to digital, but these technologies never took off (except in a few niches). See “ISDN” later in this chapter.

Figure Repeater versus amplifier

Figure Analog and digital

Test Specific Digital Telephony

Digital Telephony Digital technology was used in later computer networks Digital packets were first adopted for telephony First working topologies Telephony specifics Remote connections use a single type of cable One frame type One speed

It All Starts with DS0 (1 of 2)
DS0: basic digital data chunk A modem converts analog sound into 8-bit chunks Simplest digital telephony data stream 64 Kbps Slowest rate An analog call is converted into DS0 at the central office The signal is multiplexed onto larger digital circuits Tech Tip: Modems (p. 375) A modulator takes a digital signal and converts it into an analog signal. A demodulator takes an analog signal and converts it into a digital signal. You call a device that does both a modulator-demodulator, better known as a modem. Because many people refer to modern DSL and cable boxes as “modems,” you’ll hear the term analog modem to describe the old-style analog-to-digital devices. See “The Last Mile” later in this chapter for the scoop on all the ways to connect today.

It All Starts with DS0 (2 of 2)
Figure Analog to digital

Getting Digital Signals to the Phone
Need network technologies Types of interconnections include T1, OC-3, and more Need method to switch across network No longer use multiplexed circuit switching Now switching packets are used

Copper Carriers: T1 and T3 (1 of 2)
First digital trunk carriers T1: high-speed digital networking technology T1 line: specific shielded, two-pair cabling Channel Service Unit/Digital Service Unit (CSU/DSU) One at each end of a T1 connection CSU/DSU connects to customer equipment Two CSU/DSUs max on a single T1 line Note (p. 376): What does the “T” stand for in T1? The most common explanation is “trunk-level,” because T1 and later T-carriers functioned as trunk lines. The more definitive explanation is “terrestrial,” so named in the early 1960s to differentiate between ground-based and space-based communications when the first satellites went into orbit. Exam Tip (p. 376): You can connect two CSU/DSU boxes together directly by using a T1 crossover cable. Like the UTP crossover cables you’ve seen previously in the book, the T1 crossover cable simply reverses the send/receive pairs on one end of the cable. You’ll only see this in use to connect older routers together. The CSU/DSU connections provide convenient link points.

Copper Carriers: T1 and T3 (2 of 2)
Figure T1 line

DS1 Gets No Respect! T1 signaling method Relatively primitive frame
No addressing is necessary with point-to-point 25 pieces totaling 193 bits Framing bit 24 channels – each with a single 8-bit DS0

DS1 Defines Data Transfer Speed (1 of 2)
Frames transmitted 8000 times/sec Total throughput: Mbps Split into Kbps DS0 channels Time division multiplexing (TDM) Frames carry a portion of every channel in every frame sent on a regular interval Note (p. 376): Each 64-Kbps channel in a DS1 signal is a DS0.

DS1 Defines Data Transfer Speed (2 of 2)
Figure DS1 frame

T1 Analogy (1 of 3) Milk bottling factory
Crates with 24 bottles come down a conveyer belt Bottles are filled with milk at filling machine The crate continues to the other end to labeling and sorting machines If the filling machine uses only one type of milk, the process is simple An Ethernet frame works similarly: encapsulates a single set of data

T1 Analogy (2 of 3) Suppose a factory has different types of milk products Bottles are filled with the proper types Labeling and sorting machines provide the correct labels and place the bottles into the proper cases A DS1 frame can be used for multiple data sets CSU/DSU at the other end collects and separates the data streams to keep them separate Tech Tip: DS1 Gets No Respect! (p. 377) People rarely use the term “DS1.” Because T1 lines only carry DS1 signals, you usually just say T1 when describing the signal, even though the term DS1 is more accurate.

T1 Analogy (3 of 3) Two conveyer belts are running in opposite directions T1 connections can both send and receive

Fractional T1 access T1: dedicated phone connection leased on a monthly basis Always connected Entire bundle is expensive Can purchase individual channels

T3 Line Dedicated telephone connection 45 Mbps
672 individual DS0 channels Sometimes called DS3 lines Regional telephone companies and ISPs use to connect to the Internet

E-carrier level 1 (E1) European format for digital transmission
Can interconnect with T1 Carries signals at Mbps 32 channels at 64 Kbps E3 lines Carry 16 E1 lines Bandwidth is 34 Mbps Exam Tip (p. 378): E1 and SONET use a derivative of the High-Level Data Link Control (HDLC) protocol as the control channel.

CSU/DSU (1 of 3) Connects a leased T1 or T3 line to the customer’s equipment Has at least two connectors Performs line encoding and conditioning Often has a loopback function for testing Many newer routers have built-in CSU/DSUs

CSU/DSU (2 of 3) CSU protects from lightning strikes and other electrical interference DSU functions Supplies timing to each user port Converts the input signal into the specified line code Cross Check: Demarc (p. 378) You first read about the demarc—the spot where connections from the outside world come into a building—way back in Chapter 6, so check your memory and see if you can answer these questions. How does the demarc affect your wallet? What do you call the cable modem or DSL receiver that marks the demarc in many houses and offices?

CSU/DSU (3 of 3) Table 13.1 T-carriers Carrier Channels Speed T1 24
1.544 Mbps T3 672 Mbps E1 32 2.048 Mbps E3 512 Mbps

Fiber Carriers: SONET/SDH and OC
Early 1980s: fiber-optic became the primary cabling Primary fiber-optic carriers moved to a new international standard (with two names) United States: Synchronous Optical Network (SONET) Europe: Synchronous Digital Hierarchy (SDH) Allowed the Internet to expand worldwide Tech Tip: What’s in a Name? (p. 379) Students often wonder why two separate names exist for the same technology. In reality, SONET and SDH vary a little in their signaling and frame type, but routers and other magic boxes on the Internet handle the interoperability between the standards. The American National Standards Institute (ANSI) publishes the standard as SONET; the International Telecommunications Union (ITU) publishes the standard as SDH, but includes SONET signaling. For simplicity’s sake and because SONET is the more common term in the United States, this book uses SONET as the term for this technology.

SONET Remains the primary standard for long-distance, high-speed, fiber-optic transmission Defines the interface standards at the Physical and Link layers of the OSI model Can combine multiple DS1, DS3, and E1 signals and package them into single SONET frames for transmission Requires high-capacity fiber optics Exam Tip (p. 379): SONET is one of the most important standards for making all WAN interconnections—and it’s also the least likely standard you’ll ever see because it’s hidden away from all but the biggest networks.

Optical Carrier (OC) Standards
Denote optical data carrying capacity Escalating series of speeds Designed to meet the needs of medium-to-large corporations 51.8 Mbps (OC-1) to 39.8 Gbps (OC-768)

Dense Wavelength Division Multiplexing (DWDM)
Enables a single-mode fiber to carry multiple signals by giving each a different wavelength Wavelength specifies the color of laser light A single DWDM fiber can support about 150 signals Very popular for long-distance lines Note (p. 379): DWDM isn’t just upgrading SONET lines; DWDM works just as well on long-distance fiber Ethernet.

Coarse Wavelength Division Multiplexing (CWDM)
Can carry a signal fast over long distances Simpler than DWDM Seen in higher-end LANs Lower cost offers benefits

SONET Method (1 of 2) Synchronous Transport Signal (STS) signal method
Two parts STS payload (carries data) STS overhead (carries signaling and protocol information) STS-1 is defined as Mbps on OC-1 line STS-3 is defined as Mbps on OC-3 line

SONET Method (2 of 2) Table 13.2 Common Optical Carriers
SONET Optical Level Line Speed Signal Method OC-1 51.85 Mbps STS-1 OC-3 Mbps STS-3 OC-12 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

Packet Switching Connect the multiple point-to-point T1s, T3s, and OCs is required to create a mesh Packet switching is the answer Packet switching protocols are functionally identical to routable network protocols like TCP/IP Two forms dominate: Frame Relay and ATM Exam Tip (p. 380): The first generation of packet-switching technology was called X.25 or the CCITT Packet Switching Protocol. It enabled remote devices to communicate with each other across high-speed digital links without the expense of individual leased lines. Exam Tip (p. 380): Machines that forward and store packets using any type of packet-switching protocol are called packet switches.

Frame Relay An efficient packet-switching standard
Primarily used with T-carrier lines Effective for on-again/off-again traffic No guarantee of data integrity Discards frames if the network is congested T-carrier lines have low error rates In the United States, T1 lines use Frame Relay Note: (p. 380): Frame Relay works at both Layer 1 and Layer 2 of the OSI model, using frames rather than packets.

Asynchronous Transfer Mode (ATM)
Designed for high-speed LANs in the early 1990s Very popular for WANs Most SONET rings use ATM Integrates voice, video, and data

ATM Cells Short, fixed-length frames
Every cell with the same source and destination traveled the same route Fixed length cells: 53 bytes Handled data and voice/video to Mbps and beyond ATM was most common on OC lines

Multiprotocol Label Switching (MPLS)
An improved technology that replaces frame relay and ATM Adds an MPLS label between the Layer 2 header and Layer 3 information

MPLS Header Parts (1 of 4) Label Experimental Bits (Exp)
Unique identifier Used by MPLS-capable routers to determine how to move data Experimental Bits (Exp) Relative value defining the importance of the labeled packet for prioritization

MPLS Header Parts (2 of 4) Bottom of Label Stack (S)
Used when there are multiple labels Set to one (1) for the initial label Time to Live (TTL) Determines the maximum number of hops before the label is eliminated

MPLS Header Parts (3 of 4) Figure MPLS Header

Figure 13.15 MPLS header inserted in a frame
MPLS Header Parts (4 of 4) Figure MPLS header inserted in a frame

MPLS Process (1 of 2) Allows moving traffic more quickly and efficiently by providing network-wide QoS MPLS routers avoid running IP packets through full routing tables Use header information to route packets quickly Cross Check: QoS (p. 382) You learned about QoS back in Chapter 11, so see if you remember enough to answer these questions. What is the purpose of QoS? How does it speed up networks?

MPLS Process (2 of 2) Figure 13.16 MPLS routers talk to
each other about their overhead

MPLS Terms (1 of 5) Forwarding Equivalence Class (FEC)
A group of devices that tend to send packets to the same place, such as a router Label switching router (LSR) Forwards packets based on their MPLS label

MPLS Terms (2 of 5) Label edge router (LER)
MPLS router that adds MPLS labels to unlabeled packets LERs talk to each other to determine the best possible routes Label Distribution Protocol (LDP) Used to communicate state information

Figure 13.17 Sample MPLS network
MPLS Terms (3 of 5) Figure Sample MPLS network

Figure 13.18 MPLS initial routes added
MPLS Terms (4 of 5) Figure MPLS initial routes added

Figure 13.19 Data routing through an MPLS network
MPLS Terms (5 of 5) Figure Data routing through an MPLS network

MPLS in VPNs Label-stacking ability makes it a perfect candidate for end-user VPNs Permanent virtual circuit Can lease a fully functional connection to your network from an ISP using MPLS Exam Tip (p.383): Look for a question or two comparing packet-switched versus circuit-switched network technologies. Current networks use packet switching; ancient networks used circuit switching.

Real-World WAN (1 of 2) Telephony WAN connects the LAN to the Internet
Telephone company installs a line to a demarc ISP (often the telephone company) installs a CSU/DSU, connects to your router, and provides Internet access Test with the Bit Error Rate Test (BERT) Telephony WAN connects LANs

Figure 13.20 Old-school T-carrier setup
Real-World WAN (2 of 2) Figure Old-school T-carrier setup

Alternative to Telephony WAN
Ethernet is the biggest newer technology for WAN connectivity Superfast 10-Gbps Ethernet, 40-Gbps Ethernet, or 100-Gbps Ethernet Runs on single-mode fiber Connects to DWDM-capable switches Metro-Ethernet is available in larger cities Exam Tip (p.384): The CompTIA Network+ objectives use the full name for Ethernet throughout a city— metropolitan Ethernet—rather than the shorter, common term used here—metro Ethernet. It means the same thing. Exam Tip (p.384): Any kind of city-wide network is called a metropolitan area network (MAN). Expect either MAN or metropolitan Ethernet on the exam.

The Last Mile Data transfer technologies between central offices and individual users Dial-up DSL Broadband Cable Satellite Fiber Note (p.385): Cellular networking technology most definitely should be considered when discussing the Last Mile for many modern networks. It gets its own section in Chapter 16, “Mobile Networking.”

Dial-Up Dedicated lines Dial-up lines have phone numbers
Never hang up on each other Dial-up lines have phone numbers Dial-up technologies: PSTN and ISDN

Public Switched Telephone Network (1 of 2)
Also called Plain Old Telephone Service (POTS) A regular phone line Designed for analog sound data Waveforms cycle at 2400 times a second An individual cycle is a baud Baud rate is the number of bauds per second PSTN lines are 2400 baud Use RJ-11 connectors Exam Tip (p. 385): A company that provides local telephone service to individual customers is called a Local Exchange Carrier (LEC). A company that provides long-distance service is called an Interexchange Carrier (IXC). Classically, LECs owned the central offices and IXCs owned the lines and equipment that interconnected them. Over time, the line between LECs and IXCs has become very blurred.

Public Switched Telephone Network (2 of 2)
Figure RJ-11 connectors (top and side views)

Network Interface Unit (NIU) (1 of 2)
The interface between phone company lines and customer lines Typically a small box on the house that accepts incoming lines and splits them to different wall outlets Demarc describes large connections used in businesses

Network Interface Unit (NIU) (2 of 2)
Figure Typical home demarc

Modulator-Demodulator (Modem) (1 of 2)
Converts digital data into analog and back Universal Asynchronous Receiver/Transmitter (UART) Part of a PC’s internal modem Converts 8-bit-wide data to 1-bit wide data Note (p. 386): Modems and dial-up might seem 20th century to a lot of folks, but as of this writing, some 10 million Americans still use dial-up.

Modulator-Demodulator (Modem) (2 of 2)
Figure Internal modem

Baud Rates versus Bits Per Second
56 Kbps is not 56 kilobaud Baud rate and bps are the same up to 2400 baud A 2400-bps modem uses 1 analog baud to send 1 bit of data 2 x 2400 cycle rate per second = 4800 bps 4 x 2400 cycle rate per second = 9600 bps 24 x 2400 = 57,600 bps (56 Kbps)

V Standards CCIT-defined modem modulation speeds V Standard Speed V.22
1,200 bps V.22bis 2,400 bps V.32 9,600 bps V.32bis 14,400 bps V.34 28,000 bps V.90 57,600 bps V.92

V.92 Standard Has the same download speed as V.90
Upstream rate is as much as 48 Kbps Quick Connect implements faster handshaking Modem on Hold feature enables the modem to stay connected During an incoming call-waiting call During outgoing voice call Depends on server modem support

Additional CCIT (Now ITU) Standards
V Standard Topic V.42 Error checking V.42bis Data compression V.44 MNP5 Error checking and data compression Exam Tip (p. 388): Do not memorize these V standards—just know what they do.

Integrated Services Digital Network (ISDN)
PSTN characteristics Analog last mile was slow but phone lines are ubiquitous Customers demanded faster service Solution: ISDN Make the last mile digital with special equipment Achieve 64 Kbps rate over same copper wires used by PSTN Note (p. 388): ISDN also supports voice but requires special ISDN telephones.

Types of ISDN Channels Bearer channels (B channels)
Carry data and voice information using standard DS0 channels Can use one or two B channels Delta channels (D channels) Carry setup and configuration information at 16Kbps

BRI and PRI Basic Rate Interface (BRI) Primary Rate Interface (PRI)
Two B/one D on one physical line Each B channel sends 64 Kbps = 128 Kbps Primary Rate Interface (PRI) A full T1 line Carries 23 B channels

ISDN Physical Connections (1 of 2)
Similar to PSTN modems An ISDN wall socket looks like a standard RJ-45 network jack Line runs to a demarc (usually a second demarc separate from the PSTN demarc) An internal or external terminal adapter (TA) connects to the computer May also include a hub for a LAN connection Exam Tip (p. 389): Remember, a B channel is a DS0 channel.

ISDN Physical Connections (2 of 2)
Figure A TeleWell ISDN terminal adapter

Configuring ISDN (1 of 2) Must be within 18,000 feet of a central office The phone company/ISP provides information The phone number of the connection from the ISP A Service Profile ID (SPID) from the phone company

Figure 13.26 ISDN settings in an old version of Windows
Configuring ISDN (2 of 2) Figure shows a typical installation screen for an internal ISDN TA. Figure ISDN settings in an old version of Windows

Digital Subscriber Line (DSL)
Fully digital Dedicated (no phone number) Provided by telephone companies Great advance from ISDN Uses PSTN, RJ-11 jacks Several versions of DSL

DSL Versions Symmetric DSL (SDSL) Asymmetric DSL (ADSL)
Provides the same upload and download speeds Most ISPs offer 192 Kbps to 9 Mbps Relatively expensive Asymmetric DSL (ADSL) Uses different upload and download speeds Download speeds vary from 384 Kbps to 15 Mbps Tech Tip: VDSL (p. 389) AT&T (along with other telecoms) uses a very fast DSL version in some of its Internet offerings called very-high-bit-rate DSL (VDSL). The current version, VDSL2, can provide simultaneous upload and download speeds in excess of 100 Mbps, though only at short distances (~300 meters). Typical speeds using this technology are a lot slower, in the range of 8 to 16 Mbps down and 1 to 2 Mbps up. Try This! Comparing Options in Your Neighborhood (p. 390) So what do your local providers offer in terms of higher-speed service, if any? Try this! Call your local phone company or shop them on the Web ( is an excellent reference). Does the company offer DSL? What speed options do you have? If you want to compare with other parts of the United States, check one of the national speed test sites, such as MegaPath’s Speakeasy Speed Test ( speedtest/).

DSL Features Same phone lines carry data and voice
Distance restriction is a maximum 18,000 feet central office-to-end user DSL Access Multiplexer (DSLAM) Located at the central office Connects multiple customers to the Internet

Installing DSL Phone lines must be up to specification
Must filter out the DSL signal on the POTS line Information channels in a DSL line High-speed downstream Medium-speed duplex POTS A filter separates DSL channels from POTS Tech Tip: DSL POTS Filters (p. 390) If you install a telephone onto a line in your home with DSL and you forget to add a filter, don’t panic. You won’t destroy anything, although you won’t get a dial tone either! Just insert a DSL POTS filter and the telephone will work.

Common DLS Installation (1 of 3)
A DSL modem is connected to a telephone wall jack and to a standard NIC in computer RJ-11 connection to the wall jack CAT 5e patch cable to the router or NIC

Figure A DSL modem connection between a PC and telco

Figure DSL connection

DSL Installations (1 of 2)
First generation used a bridged connection No authentication required Simply connect and you are on the Internet Point-to-Point over Ethernet (PPPoE) Preferred by ISPs Requires name and password Most SOHO routers have PPPoE support

DSL Installations (2 of 2)
Figure PPPoE settings in SOHO router

Broadband Cable Added service from cable TV providers
Cable TV industry modified the infrastructure Cable modems are now very common Theoretical speed is 5 to 100 Mbps Actual service 5 to 30 Mbps for downloading 2 Mbps to 10 Mbps for uploading Exam Tip (p.391): You’ll see the term “cable broadband” on the CompTIA Network+ exam. I use the more common term here, “broadband cable.” Both terms refer to the same technology.

Cable Modem Installation (1 of 2)
A cable modem is connected to an incoming cable connection Separate (split) from cable TV outlet Connects to a PC using a standard NIC Connects to the head end via a coax cable

Cable Modem Installation (2 of 2)
Figure Cable modem

Data Over Cable Service Interface Specification (DOCSIS)
Cable network protocol Current specification: DOCSIS 3.1 Difference between cable modem and DSL modem Cable modem has coax BNC and RJ-45 connectors DSL modem has RJ-11 and RJ-45 connectors

Satellite (1 of 3) Only option for some remote locations One-way
Download from satellite Upload using a PSTN/dial-up connection Two-way Download and upload via satellite Note (p. 393): Companies that design satellite communications equipment haven’t given up on their technology. At the time of this writing, at least one company, HughesNet, offered download speeds up to 25 Mbps. You can surf with that kind of speed!

Satellite (2 of 3) Requires a satellite antenna
Connects to a satellite modem Modem connects to PC NIC or network Exam Tip (p. 393): Neither cable modems nor satellites use PPP, PPPoE, or anything else that begins with three Ps.

Figure 13.31 Satellite connection
Satellite (3 of 3) Figure Satellite connection

Fiber (1 of 2) Fiber-to-the-home/fiber-to-the-premises as an option to cable AT&T (U-verse) Verizon (FiOS) Google Fiber Speeds will increase above 100 Mbps

Fiber (2 of 2) Passive Optical Network (PON) architecture
Uses a single fiber to the neighborhood switch An individual fiber runs to each destination Uses WDM to enable multiple signals to travel on the same fiber Passively splits the signal at the switch Note (p. 393): Most municipalities in the United States have very tight deals in place with telephone and cable companies, allowing little room for any other high-speed Internet service. A few cities have bucked the regional monopolies and done pretty well, such as Chattanooga, Tennessee. Their publicly owned electric utility—EPB—rolled out fiber to every home and business by 2011 and currently offers Internet speeds up to 10 Gbps.

Which Connection? What services are available in your area?
How much bandwidth do you need? Start out slow Upgrade as needed Try This! Going Connection Shopping (p. 394) You’ve already checked the availability of DSL in your neighborhood, but now you have more choices! Try this! Do you have cable or satellite available? A great Web site to start your search is It has a handy search feature that helps you determine the types of service and the costs for DSL, cable, and other services. Which one makes sense for you?

Using Remote Access

Remote Access Common forms Dial-up to Internet Private dial-up
Virtual private network Dedicated connection Remote terminal VoIP Note (p. 394): You’ll see the term extranet more in books than in the day-to-day workings of networks and network techs. So what is an extranet? Whenever you allow authorized remote users to access some part of your private network, you have created an extranet.

Dial-Up to the Internet (1 of 2)
Oldest and least expensive method All operating systems support dial-up You will need: A modem and the ISP’s dial-up phone number Username and password (provided by the ISP) Type of connection (PPP) IP information (from the ISP—usually DHCP) Note (p.395): As you will recall from Chapter 10, the Point-to-Point Protocol (PPP) enables two point-to-point devices to connect, authenticate, and negotiate a network protocol.

Dial-Up to the Internet (2 of 2)
Figure Dial-up in Windows

Private Dial-Up Connects a remote system to a private network using dial-up connection Does not use Internet Requires two systems Remote access server (RAS) Client connection tool Note (p. 395): When you run Microsoft’s Routing and Remote Access Service on a server, you turn that server into a remote access server.

Setting Up Private Dial-Up (1 of 4)
Windows runs Routing and Remote Access Service (RRAS) Authenticates dial-in users RAS server Has at least one modem and accepts incoming calls Handles password authentication using standard methods Tech Tip: RAS (p. 396) Remote access server refers to the hardware component (servers built to handle the unique stresses of a large number of clients calling in), but it can also refer to the software service component of a remote access solution. You might call it a catchall phrase. Most techs call RAS “razz,” rather than using the initials, “R-A-S.” This creates a seemingly redundant phrase used to describe a system running RAS: “RAS server.” This helps distinguish servers from clients and makes geeks happier.

Figure Windows RRAS in action

RAS client setup Identical to setting up a dial-up Internet connection Obtain information from the RAS server administrator

Figure Dial-up on macOS

VPNs Connect through a tunnel to a remote network
In-depth detail is provided in Chapter 11

Dedicated Connection (1 of 2)
Always-on remote connections Dedicated private connections between two locations Usually high-speed (T-carrier, etc.) Does not use Internet

Dedicated Connection (2 of 2)
Figure Dedicated private connection

DSL and Cable (1 of 2) Used for dedicated connections to the Internet
Inexpensive and very popular The provider may supply additional software Can use OS tools or a hardware router

Figure 13.36 PPPoE connection
DSL and Cable (2 of 2) Figure PPPoE connection

Cable Issues (1 of 2) Dedicated cable connections can have issues
Splitters enable multiple connections into the home or office Split cable problem The signal degrades by half with each split Signal quality is measured in decibels (dB) Solid signal is 0dB

Cable Issues (2 of 2) dB is logarithmic
A small change in number is a very large change in percentage Signal degradation is called a dB loss Increase is called a dB gain Splitting cable with a -3 dB signal gives you two -6 dB connections—a huge loss!

Remote Terminal (1 of 6) Created using a terminal emulation program
Enables controlling a computer remotely Telnet is a text-based utility Graphical remote terminal tools WinFrame/MetaFrame from Citrix Corporation

Figure 13.37 Citrix MetaFrame
Remote Terminal (2 of 6) Figure Citrix MetaFrame

Remote Terminal (3 of 6) Remote terminal programs require a server and a client Citrix Independent Computing Architecture (ICA) Microsoft licensed and introduced Windows Terminal Services Microsoft Remote Desktop Protocol (RDP) Windows-only Note (p. 399): All RDP applications run on port 3389 by default.

Remote Terminal (4 of 6) Figure RDC in action

Remote Terminal (5 of 6) VNC third-party terminal emulation
Works with any OS Included with macOS and Linux

Remote Terminal (6 of 6) Figure VNC in action

Voice over IP (VoIP) Uses an IP network to transfer voice calls
Uses Internet connection to replace PSTN connection Needs universally adopted standards RTP SIP H.323

Real-Time Transport Protocol (RTP)
Used by a vast majority of VoIP solutions Defines the type of packets used on the Internet to move voice or data from a server to clients Tech Tip (p. 401): In-Band Management VNC and SSH enable in-band management of resources, meaning software installed on both the client and the remote system enables direct control over resources. The interaction uses the primary network connection for both devices, thus it’s in-band and sharing resources (and traffic) with the regular network. This is fast and inexpensive, but has a couple of drawbacks in a busy network. First, the remote system must be booted up with its operating system fully loaded for this to work. Second, putting management of a remote system on the main network doesn’t provide as much security or control as a dedicated, alternative connection would provide. Many servers employ lights-out-management (LOM) capabilities that enable out-of-band management to address these issues. We’ll see a lot more of these technologies when we discuss network monitoring and management in Chapter 20.

Session Initiation Protocol (SIP) and H.323
Handle initiation, setup, and delivery of VoIP sessions Both run on top of RTP SIP uses TCP ports 5060 and 5061 H.323 uses port 1720 Both have methods for handling multicasting

Skype Introduced in 2003 by Niklas Zennström
Completely different and incompatible with other VoIP solutions Uses peer-to-peer topology All calls are encrypted (nonstandard method)

Streaming Media with RTSP
Real Time Streaming Protocol Used by many media streaming servers Runs on top of RTP Features for video streaming Ability to run, pause, and stop video Runs on TCP port 554

WAN Troubleshooting Scenarios

WAN Troubleshooting Scenarios
Loss of Internet Connectivity Use utilities such as ping, ipconfig, netstat, nslookup, and others to verify connection Interface errors Local Ethernet interface LAN interface Modem interface

DNS Issues Specific DNS issue that arises in WANs
Choosing the DNS server Every ISP has their own DNS server Some ISPs use DNS helpers Servers that redirect your browser to advertising when you type an incorrect URL Get a fast public DNS IP address Examples: Google and addresses Tech Tip (p. 403): Quad9 In 2017, the Global Cyber Alliance (a group dedicated to reducing cyber crime) and IBM and other players launched Quad9, a free public DNS server that blocks the bad domains and whitelists the good domains. Phishing and scammer domains are blocked; Google and Amazon, for example, are not. Check it out by changing your DNS server to The computer you save might be your own!

Interference (1 of 2) Should not be an issue for wired connections and fiber An ongoing issue for wireless connections Every form of remote communication has very clear interference tolerances Be concerned about interference in a wired WAN during installation and when changing the connection

Figure 13.40 Demarc at my office building
Interference (2 of 2) Figure Demarc at my office building

Remote Connectivity Chapter 13.

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Remote Connectivity Chapter 13.

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