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DSL Limitations

DSL is a relatively distance-sensitive technology. As the distance between the subscriber and their local CO increases, the signal quality and connection speeds decrease. ADSL service is limited to a maximum distance of 18,000 feet (5460 m) between the DSL CPE and the DSLAM, although many ADSL providers place an even lower limit on the distance to ensure quality. The 18,000-foot distance limitation for ADSL is not a limitation for voice telephone calls, but for data transmission. Telephone...

Step 1 Specify Interesting Traffic

Interesting traffic is better thought of as traffic that must be protected by the IPsec VPN. When an IPsec VPN tunnel exists between two sites, traffic that is considered interesting is sent securely through the VPN to the remote location. Once inside the VPN, the data is safe until it reaches the other end of the tunnel. The traffic cannot be modified without detection, nor can it be read by anyone in the middle (if ESP is employed). In fact, such traffic can only travel to the other end of...

Step 1 Create the GRE Tunnel

The first part of the GRE over IPsec tunnel is the GRE tunnel. Figure 14-3 showed the various layers within the GRE over IPsec tunnel. The original IP packet is the innermost portion. Next comes the GRE layer. Figure 14-6 shows the GRE Tunnel Information window. The GRE Tunnel Information window is the first configuration window of the Secure GRE Wizard. There are two sets of IP addresses that are applied to the GRE tunnel interface the tunnel source and destination (at the top of the window)...

Internet Key Exchange IKE

A secure IPsec connection between two devices can initially be established by configuring encryption keys in both devices. However, the failure to periodically change these keys makes the network susceptible to brute-force password attacks. The need to manually change the IPsec keys every hour or every day can prove troublesome. If dozens or hundreds of IPsec connections are in use, manual key maintenance can be a nightmare. The IKE protocol, as described earlier, is a means of dynamically...

The Overall CPE Router Configuration

Overall, the configuration of the CPE router is relatively uncomplicated, although the preceding sections have discussed the interface-specific and routing-specific dependencies. Example 5-7 assembles the configuration options detailed in this chapter to render the basic CPE router configuration. Example 5-7 CPE Router Configuration service timestamps debug datetime msec localtime show-timezone service timestamps log datetime msec localtime show-timezone service password-encryption memory-size...

Configure Port Address Translation

Port Address Translation (PAT) is an extension of Network Address Translation (NAT). PAT adds a unique identifier to the outside translation entry of each inside host. Using PAT allows many inside IP addresses to use a single outside IP address because the outside address has a unique port number mapped to each inside host. NAT allows IP addresses to be changed as they pass through a router in order to be properly routed on another network. For NAT to work properly, some additional information...

Launch the GRE over IPsec Wizard

The GRE over IPsec wizard is accessed from the same window that started the Site-to-Site VPN wizard as seen in Chapter 13. Figure 14-5 shows how to access the GRE over IPsec wizard. Similar to how the Site-to-Site VPN Wizard was initiated in Chapter 13, the GRE over IPsec wizard is accessed as follows Step 1 Click the Configure button at the top of the window. Step 2 Click the VPN button in the Tasks bar on the left. Step 3 Click the Site-to-Site VPN option at the top of the menu. Step 4 Click...

Secure GRE Tunnels

GRE over IPsec implies that the GRE packet sits higher in the stack than the IPsec portion. Similar to how TCP IP is represented, TCP is at Layer 4, while IP is at Layer 3. When laid out in a graphical packet, the TCP portion is inside of the IP part. The same is true with GRE over IPsec. The original packet is the innermost layer. Then the GRE wrapper appears. Finally, the IPsec portion is added for security. Figure 14-3 shows the GRE over IPsec packet format. Figure 14-3 GRE over IPsec Packet...

Psec Stateless Failover

There are three primary stateless means to detect and react to a fault. The ideal reaction to a detected fault is to automatically send traffic a different way. The three failure detection methods are as follows An IGP within GRE over IPsec Hot Standby Routing Protocol (HSRP) (or one of the related protocols) The sections that follow discuss each of these methods in greater detail. Dead peer detection is a configuration option during the IPsec VPN setup. DPD also offers a stateless failover...

Configure a Cisco Router as a PPPoA Client

To clear up a rather widespread misconception, PPPoA is defined in RFC 2364 as PPP over AAL5. However, it is commonly referred to simply as PPP over ATM. Chapter 5, Configuring DSL Access with PPPoE, covered the configuration of PPPoE on a home router for DSL connectivity in some detail. The relative technology behind PPPoA is identical in nature to PPPoE. However, there are some significant differences that exist on the provider-facing side of the configuration, primarily The handling of the...

Step 2 Create a Backup GRE Tunnel

The Secure GRE Wizard offers the option to create a second GRE tunnel for survivability. If the GRE tunnel fails for any reason, then the IPsec tunnel that is carried within it fails also. A backup GRE tunnel provides stateless failover in the event of the loss of the primary GRE tunnel. Figure 14-7 shows the Backup GRE Tunnel Information window. Because a backup GRE tunnel is an optional feature, you must check the Create a backup secure GRE tunnel for resilience box to activate this window....

Provisioning Cable Modems

Cable modem provisioning can seem a bit daunting when compared with other technologies. There are several steps involved in the process. The headend CMTS must have operational provisioning servers such as DHCP and TFTP in order for IP addressing and configuration files to be provided. The steps defined by DOCSIS are as follows Step 1 Downstream setup At power-on, the cable modem scans and locks the downstream path for the allocated RF data channel in order for physical and data link layers to...

Step 5 Apply the Crypto Map to the Interface

After the crypto map is successfully configured, it must be applied to an interface to be operational. Remember that the crypto map is a collection of the IP address of the remote peer, the interesting traffic that will flow through the IPsec tunnel, and the IPsec security parameters (transform set) that will be used to protect the data. Figure 13-8 shows the application of the crypto map to an interface. Figure 13-8 IPsec Interface Configuration S2 1 172.16.1.2 , S3 2 10.1.3.2 Figure 13-8...

Configuring a Siteto Site VPN in SDM

To configure site-to-site VPNs in SDM, start by clicking the Configure button at the top of the screen to display the Configure page, shown in Figure 13-11. On the left side of this window is the Tasks bar, which lists all the configuration options, described next Interfaces and Connections Used to create and edit interfaces on the router. Firewall and ACL Used to create and edit basic (inside and outside) and advanced (inside, outside, and DMZ) firewall configurations in the router. VPN Used...

Configuring MPLS on a Frame Mode Interface

The second step of MPLS configuration entails the setting of interface parameters. This means that a label distribution protocol needs to be configured so that label information exchange can being. In some environments, the Cisco proprietary Tag Distribution Protocol (TDP) is used. TDP was used prior to the existence of a standardized label exchange mechanism. TDP is not typically used at this time. Instead, the Label Distribution Protocol (LDP) is used in most deployments. To enable MPLS...

Configuring MTU Size

As mentioned previously in this chapter, the addition of one or more labels to a packet traversing an MPLS network might cause the violation of the MTU size parameter. This is one of the most common issues experienced in MPLS deployments and should not be taken lightly by any means. The introduction of jumbo frames, giants, or baby giants, however one might wish to name them, into a LAN environment can have far-reaching effects. This is typically only an issue on LAN interfaces where the MTU...

Do I Know This Already Quiz Abe

The purpose of the Do I Know This Already quiz is to help you decide whether you really need to read the entire chapter. If you already intend to read the entire chapter, you do not necessarily need to answer these questions now. The 12-question quiz, derived from the major sections in the Foundation Topics portion of the chapter, helps you to determine how to spend your limited study time. Table 5-1 outlines the major topics discussed in this chapter and the Do I Know This Already quiz...

Lib Lfib and FIB

The LIB, LFIB, and FIB are designations that have nothing to do with political beliefs or untruths, large or small. Neither are they evolutionary results of each other. Well, not in the Darwinian sense, anyway. They are somewhat interconnected and interdependent, however. This is mentioned simply because these are among the most common responses to the introduction of the concepts of all three. Proper configuration of an advanced routing protocol can limit the effects of convergence on the...

Label Distribution

By now, it is clear that the processes of label switching and distribution are shockingly similar to routing in a traditional sense. This is true with the significant exception that label switching and distribution do not have any need to analyze network layer information. When the edge LSR adds the label, the packet is predestined to arrive at its appropriate end. This greatly increases the efficiency of the routing process overall. MPLS does add overhead in the form of additional...

Mpls Wan Connectivity

With the history lesson done, the conversation now moves to MPLS. Simply put, MPLS extends Layer 3 natively across the distance between central, branch, and SOHO sites. The MPLS network, though owned by the service provider, is an extension of the enterprise network. Picture the entire WAN, which was previously a Layer 2 obstacle, as a single router with multiple interfaces. It contains a routing table with all of the route entries of the enterprise network. The WAN provides any-to-any...

Step 2 Configure the IPsec Transform Sets

The configuration of the IPsec transform sets actually covers three of the IPsec configuration steps mentioned earlier. The IPsec transform set, crypto ACL, and crypto map are tightly woven together. It is difficult to talk about one of them without mentioning the other two. Thus, this section covers all three together. The following list is a reminder of the IPsec security parameters that are negotiated between peers IPsec encryption type (DES, 3DES, or AES) IPsec authentication (MD5 or SHA-1)...

CEF Switching

CEF is a topology-driven technology and makes use of a FIB. The FIB is basically a mirror image of the IP routing table. When topological changes occur, the FIB is updated based on the updates in the IP routing table. The FIB maintains next-hop address information based on information provided by the protocol routing table. Because CEF maintains a one-to-one listing of routes in the IP routing table, the need for constant maintenance of FIB entries is eliminated because that function is...

Intelligent Information Network

The Intelligent Information Network (IIN) offers companies an understanding of how the role of the network is evolving to meet business needs. The IIN vision is essentially the concept of network simplification through the alignment of technology and business priorities. Beyond evolution, the role of the network is expanding as more and more services become available network offerings. Cisco has established four technological roadmaps specific to the individual business needs of its customers....

Configuring CEF

A Cisco proprietary switching mechanism, CEF is extremely fast and efficient. CEF is an advanced Layer 3 switching technology that optimizes the performance and stability of networks with large, dynamic traffic patterns. CEF switching is less CPU intensive than process switching or fast switching, allowing more CPU time to be allocated to services and applications. CEF can be run in central mode or distributed mode. In central mode, only one instance of CEF is running on the router. Distributed...

PPP over Ethernet

Point-to-Point Protocol over Ethernet (PPPoE) is, obviously, a twist on traditional PPP implementations. It is essentially a bridging architecture. Typical bridging implementations include wide-ranging security holes. Adding PPP architecture (using PAP or CHAP authentication) on top of this Ethernet bridging function alleviates the security holes and provides a well-known, robust platform. PPPoE, as defined in RFC 2516, provides the ability to connect a network of hosts over a simple bridging...

Configure an ATM Interface for PPPoA

In a PPPoA configuration, there is typically a single Ethernet interface and an ATM interface on the CPE router. The Ethernet interface is the subscriber-facing component of the CPE router. Example 6-1 shows how to configure an Ethernet interface. Example 6-1 Subscriber-Facing Ethernet Interface Configuration interface Ethernet0 0 description ****Inside Private Network**** ip address 172.16.0.1 255.255.0.0 Once the Layer 1 connection is established, the router's PPP subsystem will initialize...

Siteto Site VPN Wizard

The Site-to-Site VPN Wizard is launched by clicking the Site-to-Site VPN option at the top of the list to the right of the Tasks bar on the SDM Configure page. This option is available only if you previously clicked the Configure button at the top of the SDM screen and selected the VPN option from the Tasks bar. Figure 13-12 shows the initial screen of the Site-to-Site VPN Wizard. This wizard has two tabs at the top of the window Create Site to Site VPN Used to create either a new site-to-site...

Step 3 IKE Phase

The actual IPsec tunnels are established in IKE phase 2. IKE phase 1 creates a very secure communications channel (its own SAs) so that the IPsec tunnels (SAs) can be created for data encryption and transport. IPsec parameters are negotiated via the IKE SAs. The following functions are performed in IKE phase 2 Negotiation of IPsec security parameters via IPsec transform sets Establishment of IPsec SAs (unidirectional IPsec tunnels) Periodic renegotiation of IPsec SAs to ensure security An...

Step 1 Configure the Isakmp Policy

Configuration of the ISAKMP policy basically maps to IKE phase 1, described earlier. Remember that IKE phase 1 establishes a secure bidirectional tunnel that is used to exchange IPsec keys for the SAs. The following list is a reminder of the IKE phase 1 parameters IKE encryption algorithm (DES, 3DES, or AES) IKE authentication algorithm (MD5 or SHA-1) IKE key (preshared, RSA signatures, nonces) Diffie-Hellman version (1, 2, or 5) IKE tunnel lifetime (time and or byte count) Figure 13-6 shows...

Mpls Vpn Architecture

To properly understand MPLS VPNs as a solution, it is important to understand the problem. MPLS VPNs are a Layer 3 WAN solution to an age-old Layer 2 WAN problem that is, the quest to provide any-to-any connectivity among sites in a cost-efficient manner. In the past, WAN architects struggled with topological design principals that amounted to choosing the least of all evils. A full mesh topology was too expensive but most robust. A hub-and-spoke topology was least expensive but least robust. A...

Do I Know This Already Quiz Uvu

The purpose of the Do I Know This Already quiz is to help you decide whether you really need to read the entire chapter. If you already intend to read the entire chapter, you do not necessarily need to answer these questions now. The 12-question quiz, derived from the major sections in the Foundation Topics portion of the chapter, helps you to determine how to spend your limited study time. Table 16-1 outlines the major topics discussed in this chapter and the Do I Know This Already quiz...

Branch Network Architecture

Branch network architecture provides an integrated, multiservice environment that provides connectivity to its users who are working in remote or satellite offices rather than in the primary corporate headquarters or campus. This provision requires both hardware- and software-specific integration considerations to provide the applications and services required for the users to properly perform their job functions. The SONA branch architecture allows an enterprise to extend campus-like services...

Campus Network Architecture

Campus network architecture has evolved rapidly over the last decade or more. The number of services supported in a campus environment has evolved just as quickly, if not more so. The basic infrastructure has traditionally been summed up under the Cisco Hierarchical Network Model mentioned in the previous section. This remains the case because that model scales very well. The role has expanded somewhat on its own to include technologies such as quality of service (QoS), Multiprotocol Label...

GRE Characteristics

The initial power of GRE was that anything could be encapsulated into it. The primary use of GRE was to carry non-IP packets through an IP network however, GRE was also used to carry IP packets through an IP cloud. Used this way, the original IP header is buried inside of the GRE header and hidden from prying eyes. The generic characteristics of a GRE tunnel are as follows A GRE tunnel is similar to an IPsec tunnel because the original packet is wrapped inside of an outer shell. GRE is...

PPP over ATM

PPPoA is similar in operation to PPPoE. In fact, both implementations use RFC 1483 2684 functions. Unlike RFC 1483 2684 bridging, PPPoA is a routed solution. PPPoA uses ATM adaptation layer 5 (AAL5) framing along with Logical Link Control Subnetwork Access Protocol (LLC SNAP) encapsulation on virtual circuits. Both permanent virtual circuits (PVC) and switched virtual circuits (SVC) are possible in PPPoA installations however, only PVC implementations are addressed at this time. An overall...

POTS Coexistence

Plain old telephone service (POTS) has evolved greatly over the years. When Bell invented the telephone in 1876, he had no idea of the profound effect it would have on the world. In fact, few people initially thought of the invention as having any commercial value. Even the media was more than a little skeptical, stating that well-informed people know that it is impossible to transmit voice over wires. Obviously, they were not so well informed. The telephone has undergone countless changes in...

Configure DHCP for DSL Router Users

The CPE router can function as a Cisco IOS-based DHCP server for subscriber network hosts. Address pools are configured for each subnet to be serviced. The address of the Ethernet interface should be excluded from the address range defined for the DHCP server. This is also the case for any other statically assigned host addresses on the subscriber's network such as print servers. The Cisco IOS DHCP functionality has been enhanced to support centralized DHCP services and administration. The pool...

Where to Begin

The easiest way to determine which layer you should begin to troubleshoot is to issue the command show ip interface brief, as demonstrated in Example 7-1. Example 7-1 show ip interface brief Command Output Helps You Discern at Which OSI Layer the Problem Originate The output of this command differs slightly depending on your configuration. However, the essential information provided is all there. The interface Status and Protocol columns provide excellent information. If the status of ATM0 and...

Configure the PPPoA DSL Dialer and Virtual Template Interfaces

The dialer interface is the DSL provider-facing component of the CPE router. Example 6-4 shows how to configure the basic elements of the dialer interface. Example 6-4 Dialer Interface Configuration interface ATM0 0 no ip address dsl operating-mode auto pvc 8 35 interface Dialer0 ip address negotiated ip mtu 1492 encapsulation ppp dialer pool 1 This configuration specifies that the dialer interface should get its IP address from the provider's DHCP server while specifying the upstream MTU and...

Easy VPN Server Configuration

To configure the Easy VPN Server, some amount of information gathering is necessary. The information necessary includes the user's account information, any required enable secret passwords, AAA configuration (if not already done), and the configuration of the Easy VPN Server itself. The configuration can be done through the traditional command-line interface (CLI) or through the Security Device Manager (SDM) interface of the router itself. SDM provides a graphical, web-based interface for...

Symmetric DSL Types

Although SDSL methodologies are not as widespread as those in the ADSL offerings, they are just as viable as broadband technologies. SDSL is available in the following forms SDSL (symmetric DSL) Provides identical transfer rates, both downstream and upstream, ranging from as slow as 128 kbps to as fast as 2.32 Mbps. The most typical implementation is 768 kbps. SDSL is a rather general term that encompasses a number of varying vendor implementations providing variable rates of service over a...

DSL Operating Mode

If the DSL modulation is set incorrectly, the connection cannot train up. The service provider should be consulted to determine whether or not the chipset (Alcatel, for example) contained in the DSL router or modem is supported. The modulation type should be configured according to that used by the provider. Table 7-2 shows the supported types. Table 7-2 Supported DSL Operating Modes Table 7-2 Supported DSL Operating Modes Automatic negotiation of the modulation type with the DSLAM On Cisco DSL...

PPP Session Phase

Once the PPPoE Session phase begins, PPP data is sent as in any other PPP encapsulation. That is to say that the LCP negotiation takes place and NCPs are opened as needed. All Ethernet frames are unicast between the aggregation router and PPPoE client at this point. RFC 2516 specifies a Maximum Receivable Unit (MRU) for PPPoE negotiated payload size at 1492 bytes. The PPPoE header is 6 bytes in length with a Protocol-ID field of 2 bytes. This keeps PPPoE in line with Ethernet's 1500-byte...

Configuring DSL Access with PPPoA

With the discussion of PPPoE covered in Chapter 5, some of the information presented here is redundant. This is to be expected with two fairly similar technologies. However, in the interest of reducing the amount of page turning, some of the covered information is offered once again as review. PPPoA is a technology based on the ability of the customer premises equipment (CPE) to offer a native Asynchronous Transfer Mode (ATM)-capable interface as the provider-facing interface. As with PPPoE,...

Digital Signals over RF Channels

Cable specifications are defined by a document known as Data-over-Cable Service Interface Specifications (DOCSIS). DOCSIS is an international standard developed by CableLabs, a nonprofit organization and development consortium dedicated to cable-related technologies. Founded in 1988, CableLabs is essentially charged with the testing and certification of cable technology access equipment such as cable modems and CMTS. The organization makes decisions on standardization and grants for DOCSIS...

Optimizing PPPoE MTU

This brief discussion is meant to add a bit of additional value to the overall picture. Perhaps some additional comprehension will result as well because many of the pieces of the PPPoE puzzle must be considered. However, this information does not fall under the category of Exam Objective. Discussions of payload sizing typically end in the assumption that bigger is better. If the MTU is as large as it can be, then the throughput must be optimal as well. Unfortunately, that is not the case. To...

Playing with Colors

Another logical starting point is with the most useful troubleshooting tool ever created, the trusty old light emitting diode (LED). Look at the front of the DSL modem or router and check the LED states. Many hours of troubleshooting have been avoided by the mantra of the network technician, Green is good That is to say that on the front of the DSL router or modem, there should be a Carrier Detect (CD) LED. When training, it may flash, but when connected properly, it will be solid and green. If...

Tangled Wires

If the DSL connection will not train up, there are some items to be checked prior to placing the call to the provider's help desk. A high percentage of DSL customers maintain multiple phone lines. There is one in place to provide traditional phone services (long distance calling, international calling, call waiting, and so on). The other line is typically dedicated to DSL and inbound outbound fax. Of course, this varies, and the splitting of the call capabilities in this manner is unnecessary...

Easy VPN Server Requirements

To implement Easy VPN Remote capabilities, a number of prerequisite guidelines must be met. The Cisco Easy VPN Remote feature requires that the destination peer be a Cisco Easy VPN Server or VPN Concentrator that supports the Cisco Easy VPN Server feature. Essentially, the hardware and software feature sets must be those capable of performing the roles and functions of the Easy VPN solution. To that end, a minimum Cisco IOS version is required as follows Cisco 831, 836, 837, 851, 857, 871, 876,...

PPP Negotiation

The Point-to-Point Protocol (PPP) is key to the success of the connectivity for DSL. If the ATM configuration and encapsulation have been found to be properly configured and trained, the PPP connectivity is the next item on the troubleshooting list. PPP connections go through three distinct phases during negotiation Link Control Protocol (LCP) phase Parameters related to establishing, configuring, and testing the connection are negotiated. This phase is mandatory. Authentication phase User...

Psec Stateful Failover

IPsec stateful failover typically requires a set of identical equipment so that failover can occur, and requires some continuous exchange of data between the devices to track the state of the IPsec VPNs (SA information). This also implies that there are multiple active IPsec VPN tunnels. Thus, the failure of one path can immediately switch the traffic to an alternate and operational IPsec VPN. As described in the previous section on IPsec stateless failover, failover typically involves the...

Configuring DSL Access with PPPoE

DSL access has become an overwhelmingly popular access methodology for homes and home offices. Along with this surge in popularity comes a host of additional possible application and service offerings. These applications and services may be provided by a service provider or offered by a corporation deploying a teleworker architecture. This chapter builds upon the topics discussed in Chapter 4, Using DSL to Connect to a Central Site. Configuring a Cisco router for PPPoE access, like other...

Reverse Route Injection

Reverse Route Injection (RRI) is the process of injecting a static route into the Interior Gateway Protocol (IGP) routing table. This static route points to the client's destination network. This is useful when per-client static IP addressing is used with VPN Clients rather than per-VPN address pools. RRI should be enabled on the dynamic crypto map when per-user IP addresses are used in environments where multiple VPN Servers are used. The redistribution of the RRI ensures reachability to the...

Cable Technology Terminology

In any discussion of relatively new or different technologies, a definition of terminology associated with that technology is necessary. This allows a more rapid familiarization with the technology. With cable access, the new terms are quite numerous compared with other networking technologies. The following are terms that will be referenced throughout this chapter Broadband Data transmission using a multiplexing methodology to provide more efficient use of available bandwidth. In cable, the...

Basic GRE Configuration

A GRE tunnel carries some Layer 3 protocol between two IP endpoints. During the initial use of GRE tunnels, the tunnel contents were typically any protocol except IP. Today, GRE tunnels are used to carry IP data over an IP network. But the GRE tunnel itself can be sent through an IPsec tunnel for security. Figure 14-2 shows a basic GRE tunnel setup. Figure 14-2 GRE Tunnel Configuration Figure 14-2 GRE Tunnel Configuration interface serial 3 2 ip address 10.1.3.2 255.255.255.0 interface tunnel 2...

IIN and the Teleworker

The idea of the Intelligent Information Network (IIN) brings into focus the idea that a network should be dynamic, flexible, and, above all, consistent in the experience offered to its user community. The IIN will provide service integration and allow the shared resource pools to maximize the business productivity. Intelligent networks make it possible to merge dissimilar networks (that is, traditional data, voice, and video networks) into a single, converged network. By building in the...

WAN Backed Up by an IPsec VPN

This chapter has focused on how to ensure that the loss of one IPsec VPN can be easily recovered by a second. Both stateful and stateless methods were examined. IPsec VPN tunnels can also be used to back up normal WAN connections. Most of Part III, IPsec VPNs, of this book deals with IPsec VPNs, which offer confidentiality to data as it passes from one site to another. A normal WAN connection is simply a PVC, such as a Frame Relay or ATM link between sites. No confidentiality or integrity is...

Data Transmission over ADSL

The discussion up to this point has dealt with Layer 1 of the OSI reference model entirely. The technologies surrounding the actual transmission of bit patterns through manipulation of voltage, frequency, amplitude, phase, and so on tend to have the ability to numb the sharpest mind. The migraine-inducing mathematical equations that make it all work are necessary to understanding, at very least in concept. To simply state, Trust me, it works. Please don't put both wires in your mouth at once....

Cable Access Technologies

Cable access is among the fastest growing technologies for home access to multiple services via a common connection. One connection to the cable company carries the television signal and Internet traffic. Most cable carriers are now getting into the voice market as well by providing voice services with unlimited long distance and other traditional services over the cable connection. The addition of teleworker functionality is a natural extension of this already multiservice connection...

Asymmetric DSL Types

ADSL is most commonly deployed in the current broadband market where DSL is offered. The following are the different flavors of DSL currently available ADSL The full-rate offering of ADSL, which can be configured to deliver from 1.5 to 8 Mbps downstream and 16 kbps to 1 Mbps upstream over a local loop up to 18,000 feet in length. ADSL enables voice and high-speed data to be sent simultaneously over the existing telephone line. ITU-T Recommendation G.992.1 and ANSI Standard T1.413-1998 specify...

Acknowledgments

First and foremost, we would like to acknowledge the sacrifices made by our families in allowing us to make the time to write this book. Without their support, it would not have been possible. Thanks to our friends who were not shy about stepping in for a bit of motivational correction when timelines were slipping. As always, a huge thank you goes to the production team. Mary Beth, Chris, and Tonya suffered no end of frustration throughout this writing. They never fully gave up on it, and for...