11.1 - 11.5 Wide Area Networks (WANs)

Packet Switching

A packet-switched network allows data to be broken up into small units called packets. Packets are transmitted along the most efficient route to the destination. Packet switching is ideal for transmitting data that can handle transmission delays, as is often the case with web pages and email.

PPP WAN Link

A point-to-point WAN link connects two endpoints on a pre-established communications path, usually through a telephone company. The Point-to-Point Protocol (PPP) moves data through the connection.

11.3 Internet Connectivity

As you study this section, answer the following questions: > What connection speeds should you expect from a PSTN internet connection? > What is multiplexing? How does it increase the bandwidth of a connection? > How does DSL enable you to talk on the phone and connect to the internet at the same time? > What are the requirements for qualifying for DSL service? > Which DSL service does not support simultaneous voice and data transmissions? > What is the difference between BRI and PRI with ISDN? > What is the difference between a B channel and a D channel? > What are the disadvantages of a satellite internet connection? In this section, you will learn to: > Connect to a DSL network. The key terms for this section include:

11.2 WAN Connections

As you study this section, answer the following questions: > What is the difference between LCP and NCP? > In which layer of the OSI model does PPP function? > Which PPP feature can detect link errors? > During PPP configuration, which authentication methods are available? In this section, you will learn to: > Configure a PPP WAN link. VThe key terms for this section include:

Public Switched Telephone Network (PSTN)

The PSTN is the network used to place local and long distance phone calls. > The PSTN is a circuit-switched network. A dedicated circuit is established when the call is placed and remains in place throughout the call. > The local loop uses analog signals over POTS (through regular telephone cable wires). The long distance network typically uses digital signaling over fiber optic. > End-to-end speeds are limited to 56 Kbps, a restriction imposed by POTS in the local loop at each end. > A modem is required to convert digital signals to analog. > Remote Access clients use the PSTN as a way to access the network or as a temporary or backup connection between sites.

Public Switched Telephone Network (PSTN)

The PSTN uses a single POTS phone line with a modem. Dial-up uses a single 64 Kbps channel. Common data transfer rates include 14.4 Kbps, 28.8 Kbps, 33.3 Kbps, and 56 Kbps. Dial-up offers a minimum level of network connectivity for a low investment. It is available virtually anywhere that regular voice grade communications are available. Computers dial an access server at the ISP. You must configure the system with the ISP server's phone number, along with a user name and password to log on. The phone line cannot be used for voice and for the internet simultaneously.

WAN Cloud

The WAN cloud is the collection of equipment that makes up the WAN network. The WAN cloud is owned and maintained by telecommunications companies.

WAN Cloud

The WAN cloud is the collection of equipment that makes up the WAN network. The WAN cloud is owned and maintained by telecommunications companies. It is represented as a cloud because the physical structure varies and different networks with common connection points may overlap. As a network administrator, you probably don't know where data goes as it is switched through the cloud. The important thing is that data goes in, travels through the line, arrives at its destination, and remains secure throughout the process.

Central Office (CO)

The central office is a switching facility connected to the WAN, and it is the nearest point of presence for the WAN provider. It provides WAN cloud entry and exit points.

11.1.6 WAN Services Facts

The following table describes common WAN services that are used to connect two networks through a WAN.

11.1.5 WAN Facts

The following table describes the components a typical wide area network uses.

Local Loop

The local loop is the cable that extends from the central office to the customer location. The local loop is owned and maintained by the WAN service provider. It typically uses UTP, but it can also be implemented using fiber optic cabling or other media. The local loop is often referred to as the last mile, because it represents the last portion of the WAN up to the customer premises.

Local Loop

The local loop is the cable that extends1 from the central office to the customer location. The local loop is owned and maintained by the WAN service provider.

Which network type establishes a dedicated physical connection between two hosts in order to transmit time-sensitive data? Frame-based Packet-switched Sliding window Multiplexed Circuit-switched

Circuit-switched A circuit-switched network establishes a dedicated physical circuit between two hosts that need to transfer time sensitive data, such as real-time audio and video. No other network host may use the medium until the communication is complete. An example of a circuit-switched network is the public switched telephone network.

Digital Subscriber Line(DSL)

Digital subscriber line (DSL) is a high-speed digital bandwidth connection from a phone wall jack on an existing telephone network. With DSL, data and voice are both sent on the same copper wire with data using one frequency and voice using another.

Distributed Switching

Distributed switching is an architecture in which multiple processor-controlled switching units are distributed. There is often a hierarchy of switching elements with a centralized host switch and remote switches located close to concentrations of users.

Distributed Switching

Distributed switching is an architecture in which multiple processor-controlled switching units are distributed. There is often a hierarchy of switching elements with a centralized host switch and remote switches located close to concentrations of users. Distributed switching: > Is often used in telephone networks, though it is often called host-remote switching. > Is used in rural areas, where population centers tend to be too small for economical deployment of a full-featured dedicated telephone exchange, and the distances between these centers make the transmission costs relatively high. > Many data-centric telecommunications platforms, such as routers and Ethernet switches, utilize distributed switching on separate cards within an equipment chassis.

Integrated Services Digital Network (ISDN)

ISDN is a WAN technology that provides increased bandwidth within the local loop. The two forms of ISDN are ISDN BRI (basic rate interface) and ISDN PRI (primary rate interface).

What connection order would two TCP/IP routers use to open a session with PPP? NCP, LCP, authentication LCP, authentication, NCP NCP, authentication, LCP LCP, NCP, authentication

LCP, authentication, NCP PPP uses the following process to open a session: Exchange LCPs to establish the link and negotiate communication parameters. Perform authentication (optional). Exchange NCPs to negotiate the Network layer protocols to use.

Which of the following are the the WAN service provider's responsibility to maintain? (Select three.) Local loop CO DTE PSE CPE

Local loop CO PSE WAN service providers are responsible for: Packet switching exchange (PSE)—equipment inside the WAN cloud. Central office (CO)—equipment that allows access to the PSE. Local loop—wiring that connects the customer to the CO. Customers are responsible for: Customer premises equipment (CPE)—any equipment at the customer site. Data terminal equipment (DTE)—devices that send local data to the WAN.

Demarcation Point (Demarc)

When you contract with a local exchange carrier (LEC) for data or telephone services, they install a physical cable and a termination jack onto your premises. The demarcation point marks the boundary between the telco equipment and your organization's network or telephone system.

Customer Premises Equipment (CPE)

Devices physically located on the subscriber's premises are referred to as the customer premises equipment. CPE includes both the wiring and devices that the subscriber owns and the equipment leased from the WAN provider. CPE can include the smart jack, demarc, local loop, copper line drivers, and repeaters.

Which of the following are benefits of LCP? (Select three.) Provides load balancing across multiple links Provides logical addressing for the data link layer Provides physical addressing for the data link layer Negotiates the use (or lack) of authentication before starting the session Monitors data dropped on the link and avoids frame looping

Provides load balancing across multiple links Negotiates the use (or lack) of authentication before starting the session Monitors data dropped on the link and avoids frame looping Benefits of LCP include the following: Negotiates the use of authentication before starting the session. Monitors data dropped on the link and avoids frame looping (error detection). Compresses data at the source and decompresses data at the destination (compression). Provides load balancing across multiple links (multilink). LCP does not encapsulate protocols; NCP handles that task. LCP is a data link layer protocol, so it does not provide support for physical interfaces. Because PPP is a point-to-point protocol, no logical or physical addressing is necessary.

POTS

56 Kbps POTS stands for plain old telephone service, and it uses analog phone technology. Existing wires use only one twisted pair. Analog signals are used through the local loop.

You are implementing internet connectivity for a new start-up company. Your client will provide online storefronts for retailers. To do this, they have calculated that their internet connection must provide a data rate of at least 20-30 Mbps. Which type of service should you implement? ISDN T3 Dial-up Integrated T1 T1 Fractional T1

T3 The T3 carrier service is similar to T1; however, it provides a throughput of 44.736 Mbps. The T1 service provides a data rate of only 1.544 Mbps. T3 is the only listed service that provides a data rate fast enough for the client in this scenario.

Public Switched Telephone Network (PSTN)

The PSTN is the network used to place local and long distance phone calls.

Packet Switching Exchange (PSE)

A packet switching exchange (PSE) is a mega switch computer capable of handling huge numbers of packets. Its job is to decide which circuit each packet will take. A PSE is typically located in the central offices just inside the cloud.

OC-12

622.08 Mbps Each OC level is a multiple of the base rate (OC-1). To get the 622.08 Mbps throughput rating of OC-12, multiply the 51.84 Mbps base rate by 12. Optical carriers use Wavelength Division Multiplexing (WDM) to increase capacity of communication over fiber optic cabling.

J1

1.544 Mbps J-carrier is a digital standard very similar to T-carrier. It is widely deployed in Japan. A J1 line is virtually identical to a T1 line. A J3 line has 480 channels that each run at 64 Kbps. J1/J3 connections require a CSU/DSU.

T1

1.544 Mbps T-carrier is a digital standard widely deployed in North America. T1 lines usually run over two pairs of shielded twisted pair (STP) cabling, but they can also run over other media like coaxial, fiber optic, or satellite. T3 lines usually run over fiber optic cable. A T1 line has 24 channels that each run at 64 Kbps. A T3 line has 672 channels that each run at 64 Kbps. A T1/T3 connection requires a channel service unit (CSU) and a data service unit (DSU). A DSU reads and writes synchronous digital signals, and a CSU manages the digital channel. To connect routers by using their CSU/DSU interfaces, you can use a T1 crossover cable. T3 is also known as a Digital Signal 3 (DS3).

OC-192

10 Gbps Each OC level is a multiple of the base rate (OC-1). To get the 622.08 Mbps throughput rating of OC-12, multiply the 51.84 Mbps base rate by 12. Optical carriers use Wavelength Division Multiplexing (WDM) to increase capacity of communication over fiber optic cabling.

OC-24

1244.16 Mbps Each OC level is a multiple of the base rate (OC-1). To get the 622.08 Mbps throughput rating of OC-12, multiply the 51.84 Mbps base rate by 12. Optical carriers use Wavelength Division Multiplexing (WDM) to increase capacity of communication over fiber optic cabling.

OC-256

13.271 Gbps Each OC level is a multiple of the base rate (OC-1). To get the 622.08 Mbps throughput rating of OC-12, multiply the 51.84 Mbps base rate by 12. Optical carriers use Wavelength Division Multiplexing (WDM) to increase capacity of communication over fiber optic cabling.

What is the speed of an OC-3 connection? 155 Mbps 622 Mbps 10 Mbps 100 Mbps

155 Mbps Optical Carrier (OC) is used to specify the speed of fiber optic networks conforming to the SONET standard. Common OC speeds are: OC-1 = 51.85 Mbps OC-3 = 155.52 Mbps OC-12 = 622.08 Mbps OC-24 = 1.244 Gbps OC-48 = 2.488 Gbps OC-192=9.952 Gbps

OC-3

155.52 Mbps Each OC level is a multiple of the base rate (OC-1). To get the 622.08 Mbps throughput rating of OC-12, multiply the 51.84 Mbps base rate by 12. Optical carriers use Wavelength Division Multiplexing (WDM) to increase capacity of communication over fiber optic cabling.

E1

2.048 Mbps E-carrier is a digital standard very similar to T-carrier. It is widely deployed in Europe. An E1 line has 32 channels that run at 64 Kbps. An E3 line transmits 16 E1 signals at the same time. E1/E3 connections require a CSU/DSU.

OC-48

2488.32 Mbps Each OC level is a multiple of the base rate (OC-1). To get the 622.08 Mbps throughput rating of OC-12, multiply the 51.84 Mbps base rate by 12. Optical carriers use Wavelength Division Multiplexing (WDM) to increase capacity of communication over fiber optic cabling.

J3

32.064 Mbps J-carrier is a digital standard very similar to T-carrier. It is widely deployed in Japan. A J1 line is virtually identical to a T1 line. A J3 line has 480 channels that each run at 64 Kbps. J1/J3 connections require a CSU/DSU.

E3

34.368 Mbps E-carrier is a digital standard very similar to T-carrier. It is widely deployed in Europe. An E1 line has 32 channels that run at 64 Kbps. An E3 line transmits 16 E1 signals at the same time. E1/E3 connections require a CSU/DSU.

OC-768

39.2 Gbps Each OC level is a multiple of the base rate (OC-1). To get the 622.08 Mbps throughput rating of OC-12, multiply the 51.84 Mbps base rate by 12. Optical carriers use Wavelength Division Multiplexing (WDM) to increase capacity of communication over fiber optic cabling.

T3

44.736 Mbps T-carrier is a digital standard widely deployed in North America. T1 lines usually run over two pairs of shielded twisted pair (STP) cabling, but they can also run over other media like coaxial, fiber optic, or satellite. T3 lines usually run over fiber optic cable. A T1 line has 24 channels that each run at 64 Kbps. A T3 line has 672 channels that each run at 64 Kbps. A T1/T3 connection requires a channel service unit (CSU) and a data service unit (DSU). A DSU reads and writes synchronous digital signals, and a CSU manages the digital channel. To connect routers by using their CSU/DSU interfaces, you can use a T1 crossover cable. T3 is also known as a Digital Signal 3 (DS3).

OC-1

51.84 Mbps Each OC level is a multiple of the base rate (OC-1). To get the 622.08 Mbps throughput rating of OC-12, multiply the 51.84 Mbps base rate by 12. Optical carriers use Wavelength Division Multiplexing (WDM) to increase capacity of communication over fiber optic cabling.

Asynchronous Transfer Mode (ATM)

> ATM is a WAN communication technology originally designed for carrying time-sensitive data like voice and video. It can also be used for regular data transport. > ATM is a packet switching technology that uses fixed-length data units called cells. Each cell is 53 bytes. > ATM establishes a virtual circuit between two locations. - A virtual channel is a data stream sent from one location to another. - A virtual path is a collection of data streams with the same destination. > The cell header includes labels that identify the virtual path information. ATM switches in the WAN cloud use the virtual path to switch cells within the WAN to their destination. > ATM is connection-oriented (compared to Frame Relay, which is connectionless).

Channel Service Unit/Data Service Unit (CSU/DSU)

A CSU/DSU converts the signal received from the WAN provider into a signal that can be used by equipment at the customer site.

Channel Service Unit/Data Service Unit (CSU/DSU)

A CSU/DSU converts the signal received from the WAN provider into a signal that can be used by equipment at the customer site. A CSU/DSU is composed of these two separate devices: > The CSU terminates the digital signal and provides error correction and line monitoring. > The DSU converts the digital data into synchronous serial data for connection to a router. *The CSU/DSU might be two separate devices, one combined device, or integrated into a router.

Circuit Switching

A circuit-switched network uses a dedicated connection between sites. Circuit switching is ideal for transmitting data that must arrive quickly in the order it is sent, as is the case with real-time audio and video.

11.2.3 PPP WAN Connection Facts

A point-to-point WAN link connects two endpoints on a pre-established communications path, usually through a telephone company. The Point-to-Point Protocol (PPP) moves data through the connection. Be aware that PPP: > Is a Data Link (Layer 2) protocol designed to facilitate communication over leased lines. > Can be used on a wide variety of physical interfaces, including asynchronous serial, synchronous serial (dial-up), and ISDN. > Defines a header and trailer that specify a protocol type field. > Contains protocols that integrate and support higher level protocols. > Supports multiple Network layer protocols over the same link. > Supports both IPv4 and IPv6. > Provides optional authentication through PAP (2-way authentication) or CHAP (3-way authentication): - PAP transmits the password in clear text over the link. - CHAP uses a hash of the password for authentication. The password itself is not transmitted on the link. > Supports multilink connections, which allows load balancing over multiple physical links. > Includes link quality monitoring (LQM), which can detect link errors and automatically terminate links with excessive errors. > Includes looped link detection, which can identify when messages sent from a router are looped back to that router. - Routers send magic numbers in communications. If a router receives a packet with its own magic number, the link is looped. *A variation of PPP called Multilink PPP (MLP) is available on some routers. MLP is used to aggregate multiple WAN links into a single logical channel.

Asynchronous Transfer Mode (ATM)

ATM is a WAN communication technology originally designed for carrying time-sensitive data like voice and video. It can also be used for regular data transport. ATM is a packet switching technology that uses fixed-length data units called cells. Each cell is 53 bytes.

Which of the following are characteristics of MPLS? (Select two.) Uses a committed information rate (CIR) Is a local loop technology Adds labels to data units Supports variable-length data units Uses fixed-length data units

Adds labels to data units Supports variable-length data units MPLS is a WAN data classification and data carrying mechanism. MPLS is a packet switching technology that supports variable-length data units. MPLS adds a label to packets between the existing Network and Data Link layer formats. Labels are added when the packet enters the MPLS network and removed when the packet exits the network. Information in the label is used to switch the packet through the MPLS network to the destination. MPLS labels can identify the route or even the network type to use. MPLS labels are often used to provide different classes of service for data streams. ATM uses labels, but uses fixed-length cells. ISDN is a local loop technology. Frame relay uses the committed information rate (CIR) to define levels of service. MPLS service levels are provided by information within the labels.

Which of the following are characteristics of ATM? (Select two.) Adds labels to data units. Connects to the WAN cloud with a CSU/DSU. Uses fixed-length cells of 53 bytes. Supports variable-length packets. Uses POTS in the local loop.

Adds labels to data units. Uses fixed-length cells of 53 bytes. ATM is a WAN communication technology originally designed for carrying time-sensitive data, such as voice and video. However, it can also be used for regular data transport. ATM is a packet switching technology that uses fixed-length data units called cells. Each cell is 53 bytes. The cell header includes labels that identify the virtual path information. ATM switches in the WAN cloud use the virtual path to switch cells within the WAN to the destination. MPLS uses labels but supports variable-length packets. ISDN is a WAN technology that uses existing telephone lines (POTS) to connect to the WAN cloud. Both frame relay and ISDN use a CSU/DSU to connect the line to the WAN link.

11.1 WAN Concepts

As you study this section, answer the following questions: > What is the optical carrier specification base rate? > Why is the base rate significant? > What are the differences between T1 and T3? E1 and E3? J1 and J3? > Concerning WAN technologies, what is a channel? Why are channels important? > What is the difference between a packet-switched network and a circuit-switched network? > What are the two parts of a CSU/DSU? Which functions does each perform? > Which WAN technology uses fixed-length cells? > Which WAN technology is a transport technology for carrying signals over fiber optic cables? > Which WAN technology can be implemented over regular telephone lines? > How does MPLS add labels to packets? What are these labels used for? The key terms for this section include:

Broadband Over Power Line (BPL)

BPL is a system that transmits two-way data over the existing electrical distribution wiring. This service could be enabled within a single building or provided throughout a metropolitan area. BPL avoids the expense of a dedicated network of wires for data communication. Multiplexing is used to divide the electrical wiring into multiple channels used for data transmissions and electrical power delivery. Another version of BPL is used within a home to interconnect home computers and networking peripherals. The electrical connections in a home serve as a LAN to home computers and other networking devices that have an Ethernet port, like home entertainment devices. Configurations for this version of BPL typically include the following: An Ethernet cable connected to the computer (or peripheral) and a powerline adapter. Powerline adapters plugged into power outlets throughout the facility. An Ethernet connection established using the existing electrical wiring as the network medium.

11.2.5 Practice Questions

CCIST 1401

11.1.7 Practice Questions

CIST 1401

Which of the following devices is used on a WAN to convert synchronous serial signals into digital signals? Modem Proxy IDS CSU/DSU

CSU/DSU A CSU/DSU is a device that converts the signal received from the WAN provider into a signal that can be used by equipment at the customer site. A CSU/DSU is composed of two separate devices. The CSU terminates the digital signal and provides error correction and line monitoring. The DSU converts the digital data into synchronous serial data for connection to a router. The CSU/DSU might be two separate devices, one combined device, or integrated into a router. A modem converts digital signals to analog signals. A proxy server is a type of firewall that can filter based on upper-layer data. An intrusion detection system (IDS) is a special network device that can detect attacks and suspicious activity.

What must you install between your network and a T1 line for your network to use the T1 line? CSU/DSU Bridge Transceiver Gateway

CSU/DSU A CSU/DSU is required for a network to send signals on a T1 line.

Cellular Networking

Cellular networking uses a digital mobile phone network for internet access.

Cellular

Cellular networking uses a digital mobile phone network for internet access. Two main communication technologies are used with mobile networks: Global System for Mobile Communications (GSM) was created in Europe and is used by the majority of the world's mobile service providers. GSM uses time-division multiple access (TDMA) technology to allow multiple connections on the same frequency. Code Division Multiple Access (CDMA) is used by the majority of mobile service providers in the United States. It enables multiple connections on the same frequency. With CDMA, each call is encoded with a unique key and then transmitted simultaneously. The unique keys are then used to extract each call from the transmission. Many mobile devices, like smart phones and tablets, can be purchased with mobile data technology integrated. A cellular adapter can be installed on a notebook computer to enable cellular internet access. Cellular networking is a truly mobile solution; the mobile device can be in motion and still have internet access. The user does not have to manually reconnect the device as it moves from cell tower to cell tower. However, the faster the device is moving, the less bandwidth is available. Cellular internet access is limited to areas with cell service coverage. Coverage is dictated by the provider's network. Some areas have weak coverage or no coverage at all. Cellular networks used for voice and data include the following types: 2G (second generation) networks were the first to offer digital data services. 2G data speeds are slow (14.4 Kbps) and are used mainly for text messaging, not internet connectivity. 2.5G supports speeds up to 144 Kbps. EDGE (also called 2.75G) networks are an intermediary, between 2G and 3G networks. EDGE is the first cellular technology to be truly internet-compatible, with speeds of 400-1,000 Kbps. 3G offers simultaneous voice and data. Minimum speeds for stationary users are quoted at 2 Mbps or higher. The following extensions enhance 3G networks: HSPA+ (also known as smart antenna) uses multiple-input and multiple-output (MIMO), and significantly increases data throughput and link range without additional bandwidth or increased transmit power. Long Term Evolution (LTE) and LTE-Advanced increase downlink/uplink speeds to 100/50 Mbps and 1Gbps/500Mbps, respectively. 4G is available with minimum speeds around 3-8 Mbps, with over 100 Mbps possible. 4G: Uses MIMO. Is not compatible with 3G; 4G requires a complete retrofit on the part of service providers and new equipment for the consumer. Utilizes Worldwide Interoperability for Microwave Access (WiMAX). WiMAX delivers high-speed internet service (up to 1 Gbps for stationary users) to large geographical areas.

Cable

Companies that provide cable television access typically offer internet access. Existing cable TV lines provide bandwidth for internet access. Cable internet uses the Data over Cable Service Interface Specification (DOCSIS) that allows data signals to be sent on existing cable TV infrastructures. DOCSIS specifies channel widths, modulation techniques, and how core components of the network communicate. A cable modem is a device that connects a computer system to the internet using a cable television network. But a cable modem doesn't function as a modem anymore because it doesn't modulate and demodulate a signal between an analog network and a digital end device. Many cable internet service providers (ISPs) are migrating to a fully digital network, including their television signals. Because of this, cable modems on digital systems are not modems. They are called media converters or cable terminal devices. Speeds are usually much faster than those provided by DSL, but the bandwidth is shared between all users within the same area (neighborhood). Actual speeds may be much less than the maximum.

Dynamic Multipoint VPN (DMVPN)

DMVPN is a Cisco IOS Software solution for building scalable IPsec Virtual Private Networks (VPNs).

Dynamic Multipoint VPN (DMVPN)

DMVPN is a Cisco IOS Software solution for building scalable IPsec Virtual Private Networks (VPNs). > Cisco DMVPN uses a centralized architecture that provides easier implementation and management for deployments that require granular access controls for diverse user communities, including: Mobile workers Telecommuters Extranet users > Cisco DMVPN also allows branch locations to communicate directly with each other over the public WAN or internet, such as when using voice over IP (VoIP) between two branch offices, but doesn't require a permanent VPN connection between sites. > DMVPN: - Reduces costs of integrating voice and video with VPN security. - Enables direct branch-to-branch connectivity for business applications like voice. - Offers a zero-touch configuration, dramatically reducing the deployment complexity in VPNs. - Prevents disruption of business-critical applications and services by incorporating routing with standards-based IPsec technology.

Digital Subscriber Line (DSL)

DSL offers digital communications over existing POTS lines. Data is sent using multiplexed channels over existing telephone wiring. Implementation requires a DSL router or a single DSL network interface connected to the phone line. DSL service is not available everywhere; the location must be within a fixed distance of network switching equipment. There are several variations of DSL (collectively referred to as xDSL): Asymmetrical DSL (ADSL) provides different download and upload speeds. ADSL allows regular analog phone calls and digital access on the same line at the same time. Splitters are required to separate the analog signals from the digital signals. ADSL works well for regular internet access (browsing), but is not the best choice if you need to host internet services (for example, to maintain your own website). Symmetrical DSL (SDSL) provides equal download and upload speeds. The entire line is used for data; simultaneous voice and data is not supported. Splitters are not required because voice traffic does not exist on the line. This is a viable option for organizations that wish to host internet services (like a web server). Very high DSL (VDSL or VHDSL) is similar to asymmetrical DSL, but has higher speeds. Both voice and digital data are supported on the same line at the same time. Splitters are required to separate voice signals from digital data signals.

Which of the following statements about the functionality of LCP are true? (Select three.) LCP is responsible for logical addressing in PPP. LCP provides remote terminal access in public data networks. LCP encapsulates multiple protocols. Data can be compressed at the source and decompressed at the destination. LCP provides multilink support. Usernames and passwords may be required during the handshake.

Data can be compressed at the source and decompressed at the destination. LCP provides multilink support. Usernames and passwords may be required during the handshake. The link control protocol (LCP) is a sublayer within the PPP protocol stack. LCP options provide authentication, compression, error detection, and multilink functionality. Multiple protocols are encapsulated in PPP by NCP. LCP is not a Layer 3 protocol, so it does not provide logical addressing. Remote terminal access is a function of the X.25 protocol.

Frame Relay

Frame Relay is a protocol used to connect to a WAN over dedicated (leased) lines. > Frame Relay is a packet switching technology that supports variable-sized data units called frames. > Frame Relay establishes a permanent virtual circuit between two locations. Because the circuit is permanent, there is no call setup or termination required. > Virtual circuits can be configured in two different ways - A point-to-point circuit is established between two locations. - A point-to-multipoint circuit is a single circuit that can be used to reach multiple locations. > Frame Relay can be implemented over a variety of connection lines (e.g., T1, T3) and achieves faster speeds by using high-quality digital lines, which require less extensive error control than X.25 networks. > Routers at the customer site connect to the T1 line through a CSU/DSU. > When congestion occurs, the Frame Relay network simply drops packets to keep up. Frame Relay networks provide error detection, but not error recovery. It is up to end devices to request a retransmission of lost packets. > When you sign up for Frame Relay service, you are assigned a level of service called a Committed Information Rate (CIR). At times, your actual bandwidth could be higher than the CIR, but the CIR represents the maximum guaranteed data transmission rate you will receive on the Frame Relay network.

Frame Relay

Frame Relay is a protocol used to connect to a WAN over dedicated (leased) lines. Frame Relay is a packet switching technology that supports variable-sized data units called frames.

Which of the following WAN technologies provides packet switching over high-quality digital lines at speeds greater than 1.544 Mbps? Frame relay ISDN X.25 POTS

Frame relay Frame relay networks are packet-switched networks that operate at T1 or T3 speeds. Frame relay achieves faster speeds by using high-quality digital lines, which require less extensive error control than X.25 networks. POTS stands for plain old telephone system. In the United States, ISDN networks can only offer speed up to 1.544 Mbps.

Integrated Services Digital Network (ISDN)

ISDN is a WAN technology that provides increased bandwidth within the local loop. These are two forms of ISDN: > SDN BRI (basic rate interface) uses digital signals over POTS. The traditional phone line is divided into separate channels, two 64 Kbps bearer (B) channels and one 16 Kbps control (D) channel. ISDN BRI is often called 2B + 1D. > ISDN PRI (primary rate interface) uses digital signals over a T1 line with 23 64 Kbps B channels and one 64 Kbps D channel in North America (up to 1.544 Mbps), or over an E1 line with 30 64 Kbps B channels and one 64 Kbps D channel in Europe (up to 2.048 Mbps). ISDN PRI is often referred to as 23B + 1D. ISDN has the following characteristics: > It is a circuit switching technology. > It is a local loop technology. When calls reach the WAN cloud, they are converted to another protocol for transmission through the WAN. > With ISDN BRI, you can use one channel for voice and one channel for data, or both channels for different voice calls. Depending on the implementation, you can also bond the B channels and use them together. > ISDN PRI requires a CSU/DSU for the T1 line.

Integrated Services Digital Network (ISDN)

ISDN offers digital communications over existing POTS lines or T1 lines. ISDN is more common in Europe than in the United States. The transmission medium is divided into channels for digital data. Subscribers must be within a certain distance of the phone company equipment, although this distance can be extended with repeaters. Phone calls use digital ISDN phones or analog phones connected to a converter. There are two main implementations of ISDN: ISDN BRI (basic rate) provides two 64 Kbps data channels and one 16 Kbps control channel. BRI uses four wires on the existing POTS installation. With ISDN BRI, you can use one channel for voice and one channel for data, or both channels for different voice calls. Depending on the implementation, you can also bond the B channels to use them together for faster data speeds. ISDN PRI (primary rate) provides twenty-three 64 Kbps data channels and one 64 Kbps control channel on a T1 line (or thirty 64 Kbps data channels and one 64 Kbps control channel on an E1 line).

Link Control Protocol (LCP)

LCP is responsible for establishing, maintaining, and tearing down the PPP link. LCP packets are exchanged periodically.

Link Control Protocol (LCP)

LCP is responsible for establishing, maintaining, and tearing down the PPP link. LCP packets are exchanged periodically. > During link establishment, LCP agrees on encapsulation, packet size, and compression settings. LCP also indicates whether authentication should be used. > Throughout the session, LCP packets are exchanged to: Detect loops. Detect and correct errors. Control the use of multiple links (multilink). > When the session is terminated, LCP tears down the link. *A single link control protocol runs for each physical connection.

Which of the following technologies uses variable-length packets, adds labels to packets as they enter the WAN cloud, and uses the labels to switch packets and prioritize traffic? Frame relay SONET MPLS ISDN ATM

MPLS MPLS is a WAN data classification and data carrying mechanism. MPLS is a packet switching technology that supports variable-length frames. MPLS adds a label to packets between the existing Network and Data Link layer formats. Labels are added when the packet enters the MPLS network and removed when the packet exits the network. Information in the label is used to switch the packet through the MPLS network to the destination. MPLS labels can identify the route or even the network type to use. MPLS labels are often used to provide different classes of service for data streams. ATM is a WAN communication technology that uses labels but has fixed-length cells of 53 bytes. Frame relay is a protocol used to connect to a WAN over dedicated (leased) lines. ISDN is a WAN technology that provides increased bandwidth within the local loop. SONET is a standard for networking over an optical medium. SONET is classified as a transport protocol, in that it can carry other types of traffic such as ATM, Ethernet, and IP. Most PSTN networks use SONET within the long-distance portion of the PSTN network.

Which networking technology creates virtual links between two remote network endpoints by prefixing packets with a header containing one or more labels? ISDN Ethernet MPLS Frame relay

MPLS Multiprotocol Label Switching (MPLS) creates virtual links between two remote network endpoints by prefixing packets with a header containing one or more labels. MPLS determines routing using the contents of each packet's label. This allows the creation of an endpoint-to-endpoint virtual circuit across a variety of network media. Ethernet, ISDN, and frame relay WAN networks do not use labels.

Multiprotocol Label Switching (MPLS)

MPLS is a WAN data classification and data carrying mechanism. > MPLS is a packet switching technology that supports variable-length frames. > MPLS adds a label to packets between the existing Network and Data Link layer formats. Labels are added when the packet enters the MPLS network and are removed when the packet exits the network. > Information in the label is used to switch the packet through the MPLS network to the destination. > MPLS labels can identify the route or even the network type to use. MPLS labels are often used to provide different classes of service for data streams. > MPLS is a connection-oriented protocol. *Cisco routers using MPLS are required to use the Cisco Express Forwarding (CEF) switching technology.

Multiprotocol Label Switching (MPLS)

MPLS is a WAN data classification and data carrying mechanism. MPLS is a packet switching technology that supports variable-length frames.

To access the internet through the PSTN, what kind of connectivity device must you use? DTE Switch Modem TDM CSU/DSU

Modem To establish a connection to the internet through the public telephone network (PSTN/POTS) you must use a modem (modulator/demodulator), which converts digital PC data into analog signals that can be transmitted through standard telephone lines.

WANs employ one of the two following methods to transfer data:

N/A

Which of the following protocols is used by PPP to enable support for multiple Network layer protocols? NCP SAP TCP HDLC LCP

NCP PPP uses the network control protocol (NCP) to support multiple upper-layer protocols. LCP is used to establish the link, negotiate compression and authentication, detect errors, and tear down the link.

Network Control Protocol (NCP)

NCP is used to agree on and configure Network layer protocols. Each Network layer protocol has a corresponding control protocol packet.

Network Control Protocol (NCP)

NCP is used to agree on and configure Network layer protocols. Each Network layer protocol has a corresponding control protocol packet. Examples of control protocols include: IP Control Protocol (IPCP) IP version 6 Control Protocol (IPv6CP) *A single PPP link can run multiple control protocols, one for each Network layer protocol supported on the link.

PPP supports authentication, compression, and multiple Network layer protocols. Which of the following correctly sequences these functions when a PPP link is established? Perform authentication, negotiate compression settings, negotiate Network layer protocols Negotiate compression settings, perform authentication, negotiate Network layer protocols Perform authentication, negotiate Network layer protocols, negotiate compression settings Negotiate Network layer protocols, perform authentication, negotiate compression settings Negotiate Network layer protocols, negotiate compression settings, perform authentication Negotiate compression settings, negotiate Network layer protocols, perform authentication

Negotiate compression settings, perform authentication, negotiate Network layer protocols PPP uses the following process to open a session: Exchange LCPs to establish the link and negotiate communication parameters (such as compression settings). Perform authentication (optional). Exchange NCPs to negotiate the Network layer protocols.

Two routers with the host names SLC and PROVO have been configured to connect using PPP with CHAP authentication through their BRI0 interfaces. Attempts to establish a session between the two routers fail. You check the running configuration on both routers and find the output shown below: What should you do to correct the problem? On SLC, change the username password to ccna. On PROVO, change the username password to cisco. On SLC, change the username password to chocolate. On SLC, change the username to SLC. On PROVO, change the username to PROVO. On PROVO, change the IP address to 172.16.55.128. On PROVO, change the enable password to cisco.

On SLC, change the username password to chocolate. The username passwords used by each router must match. In this scenario, changing the username password on SLC to chocolate would correct the problem (you could also change the password on PROVO to vanilla). The username configured on each router must match the host name of the remote router that it will be connecting to. The IP addresses assigned to the interfaces are both on the 172.16.55.128 subnet. You cannot assign that address to a host.

Which of the following describe the channels and data transfer rates used for ISDN BRI? (Select two.) One D channel operating at 16 Kbps One D channel operating at 64 Kbps 23 B channels operating at 64 Kbps each Two B channels operating at 64 Kbps each

One D channel operating at 16 Kbps Two B channels operating at 64 Kbps each ISDN BRI uses two B channels operating at 64 Kbps each and one D channel operating at 16 Kbps. It is often called 2B + 1D. ISDN PRI uses 23 B channels (at 64 Kbps) and one D channel (at 64 Kbps). It is also called 23B + 1D.

POTS Phone Line

POTS is the acronym for Plain Old Telephone Service, the standard telephone service most homes have.

Your client has acquired several small companies and would like to connect them together into one network. Not all of the routers are Cisco devices, and compatibility is a concern. Which WAN encapsulation method should you recommend your client use? PAP PPP Cisco HDLC Ethernet

PPP The point-to-point (PPP) protocol is not proprietary. For this reason, it is the best choice for connecting dissimilar vendor devices. Cisco HDLC is the default serial encapsulation method, but it is only supported on Cisco devices. PAP is a PPP authentication protocol. Ethernet is not a WAN protocol.

PPP Communication Phases

PPP establishes communication in three phases: 1. LCP phase—LCP packets are exchanged to open the link and agree on link settings. 2. Authenticate phase (optional)—Authentication-specific packets are exchanged to configure authentication parameters and authenticate the devices. LCP packets might also be exchanged during this phase to maintain the link. 3. NCP phase—NCP packets are exchanged to agree on which upper layer protocols to use. For example, routers might exchange IPCP and Cisco Discovery Protocol Control Protocol (CDPCP) packets to agree on using IP and CDP for Network layer communications. During this phase, LCP packets might continue to be exchanged.

PPP Protocols

PPP uses these two main protocols to establish and maintain the link:

You are traveling throughout North America to many metropolitan and rural areas. Which single form of internet connectivity provides the greatest potential connectivity wherever you travel? ISDN Broadband cable PSTN DSL

PSTN Network access using a modem over the telephone company network (PSTN) is not the fastest method for internet connectivity. However, it has the advantage of being available virtually anywhere that regular voice-grade communications are available. Broadband cable is dependent on service offerings from the regional cable television company, which does not have as great a presence as the telephone company. To use broadband cable, the service must be added to the cable TV lines. DSL and ISDN are offered through the telephone company; however, they are not available in all service areas. And even when available, they require that the subscriber be within a certain proximity of telephone company equipment.

Which network type divides transmitted data into smaller pieces and allows multiple communications on the network medium? Packet-switched Frame-based Multiplexed Sliding window Circuit-switched

Packet-switched A packet-switched network divides data into small units called packets. These packets are routed by their destination addresses. In a packet-switched network, multiple hosts can use the network medium at the same time. An Ethernet computer network is an example of a packet-switched network.

RouterA is connected to RouterB through Serial1. You want to configure the link to use PPP with CHAP authentication with a password of cisco. Which set of commands would you use on RouterA to complete the configuration? RouterA(config)#int s1 RouterA(config-if)#encap ppp auth chap password cisco RouterA(config)#int s1 RouterA(config-if)#encap ppp RouterA(config-if)#ppp chap username RouterA password cisco RouterA(config)#int s1 RouterA(config-if)#encap ppp RouterA(config-if)#ppp auth chap password cisco RouterA(config)#int s1 RouterA(config-if)#encap ppp RouterA(config-if)#ppp auth chap RouterA(config-if)#ppp chap username RouterB password cisco RouterA(config)#int s1 RouterA(config-if)#encap ppp RouterA(config-if)#ppp auth chap RouterA(config)#username RouterB password cisco

RouterA(config)#int s1 RouterA(config-if)#encap ppp RouterA(config-if)#ppp auth chap RouterA(config)#username RouterB password cisco To complete this configuration, you need to: Identify the interface you want to configure with the int s1 command. Set PPP encapsulation with the encapsulation command. Set the PPP authentication to CHAP with the ppp authentication command. Identify RouterB and the password with the username command.

SIP Trunk

SIP trunking is a method where business phone systems operate using an internet connection instead of a traditional phone line.

SIP Trunk

SIP trunking is a method where business phone systems operate using an internet connection instead of a traditional phone line. > SIP trunking is made available by SIP providers, which are similar to traditional phone companies, except SIP providers give access to phone lines over the internet. > SIP trunking: Saves you money on your business phone. Makes it easy to scale your operation pain-free. Offers increased phone service reliability.

Satellite

Satellite provides internet access by using signals transmitted to and received from orbiting satellites. Satellite service providers offer nearly 100% global network coverage, making local network infrastructure unnecessary. Satellite service is usually available when other internet access technologies are not. Satellite requires a local portable transmitter with an antenna (dish) and an unobstructed line of sight. Satellite reception is subject to atmospheric and weather conditions. Fog, rain, or snow can disrupt service.

11.3.3 Internet Services Facts

There are many options for connecting computers to the internet through an ISP. Each method has its advantages and disadvantages, as discussed in the following table:

Demarcation Point (Demarc)

When you contract with a local exchange carrier (LEC) for data or telephone services, they install a physical cable and a termination jack onto your premises. The demarcation point marks the boundary between the telco equipment and your organization's network or telephone system. > Normally, the LEC is responsible for all equipment on one side of the demarc, and the customer is responsible for all equipment on the other side of the demarc. > The demarc is also called the minimum point of entry (MPOE) or the end user point of termination (EU-POT). > The demarc is typically located on the bottom floor of a building, just inside the building. For residential service, the demarc is often a small box on the outside of the house.

Wireless

Wireless internet access is frequently available at local businesses, hotels, airports, libraries, and mass transit. Additionally, many city and residential areas have coverage from a wireless internet provider. Some providers offer a nationwide network of wireless access points in public locations like airports. Wireless networks in downtown areas allow limited roaming (moving) within the area of coverage. However, dead spots might limit access. Wireless networks in residential areas are best suited for stationary clients.

11.1.4 WAN Media Facts

You can use a variety of technologies to implement WANs, and each has its own unique characteristics. When you contract for WAN services, you need to analyze your bandwidth requirements and then choose the appropriate technology. The table below describes several common WAN technologies.

11.2.4 Configure a PPP WAN Link

You have two routers connected as shown in the diagram. The serial interfaces on both routers have been configured with an IP address, and the shutdown has been removed. In this lab, your task is to do the following: Configure both serial links to use PPP encapsulation. On RouterA, configure a username for RouterB using the password cisco. On RouterB, configure a username for RouterA using the password cisco. Save your changes on both routers. Use the copy running-config startup-config command to save the current running configuration to the startup configuration file. Complete this lab as follows: > Select RouterA. > Press Enter. > At the prompt, enter: RouterA>enable RouterA#config t RouterA(config)#interface s0/0/0 RouterA(config-if)#encapsulation ppp RouterA(config-if)#exit RouterA(config)#username RouterB password cisco > Press Ctrl + Z. > At the prompt, enter: RouterA#copy run start > Press Enter. > Press Enter to save your changes. > From the diagram, select RouterB. > Press Enter. > At the prompt, enter: RouterB>enable RouterB#config t RouterB(config)#interface s0/0/1 RouterB(config-if)#encapsulation ppp RouterB(config-if)#exit RouterB(config)#username RouterA password cisco > Press Ctrl + Z. > At the prompt, enter: RouterB#copy run start > Press Enter. > Press Enter to save your changes.