Accessing the Remote Users Router

With your router and the user's router setup, you can now make a manual call to the remote user's router from your test router, which will result in a number of typical situations The circuit is not available, and the message from your test router is usually Cause 34 No Circuit Channel Available. Typically, after receiving this message, there's nothing to troubleshoot. Either the circuit is disconnected, the service is completely shut down, or you called a non-ISDN number 02 04 1995 20 54 45...

Address Field

The Address field identifies the user device and protocol, and it plays a significant role in the troubleshooting process. It is always two octets. The structure is shown in Figure 9-5. Note that the remaining 13 bits represent the data-link connection identifier (DLCI) a combination of the TEI and service access point identifier (SAPI) fields. The terminal endpoint identifier (TEI) is designed to maintain a separate logical link over the D channel with the peer process in the LE. Figure 9-5...

Address Resolution ARP Reverse ARP and Inverse ARP

The higher-layer protocol encapsulation in Frame Relay formats raises the issue of resolving the upper-layer addresses to Frame Relay addressing schemes. Especially in point-to-multipoint connections, where the hub side has many Layer-3 addresses (typically IPs) assigned, you need to resolve the Layer-2 address (regardless if it is a DLCI or Q.922 address) to the Layer-3 address (IP). The problem can be resolved by polling all subinterfaces for hardware and protocol address resolution, but this...

Adjustable Flexible CIR

If the traffic can be planned precisely (for example, trending of the production environment with different shifts and number of users), and if the service provider supports this feature (for an additional fee), it is worth it to request an adjustable CIR. This feature is also known as bandwidth on demand and it can be beneficial when you are trying to satisfy expected changes in bandwidth requirements. When requesting adjustable CIRs from the service provider, it is important to keep in mind...

Advanced Frame Relay Configurations

The represented configuration solutions in the following sections are usually referred to as advanced Frame Relay configurations. They include the following Frame switching configuration Configuring ISDN as Frame Relay backup Configuring the bridging in Frame Relay Frame Relay compression configuration Configuring IP multicast in Frame Relay Frame Relay traffic shaping configuration, including foresight adaptive shaping

Aggregate CIR

Using an aggregate CIR, also referred to as oversubscription, can be a beneficial technique when traffic bursts occur on different PVCs. For example, if a T1 is installed to a core router, and four users are each configured for four slots of 64 kbps (64 x 4 384 kbps), two basic line conditions exist in the PVC design idle and busy. If only two users use the service and the other two are idle, the first two can use the entire rate up to 1.544 Mbps, and because every user is setup for 384 kbps,...

Alternate Mark Inversion

Cisco routers support the following coding schemes ami AMI encoding b8zs B8ZS encoding One of the most widespread coding techniques for T1 carriers is alternate mark inversion (AMI). By using AMI, pulses correspond to binary 1s and 0s and alternate at 3V (+3 -3V). The presence of a signal is 1, and the absence of a signal is 0. A benefit of this encoding is a built-in method of error detection. When consecutive pulses are detected to have the same polarity, the condition is considered to be a...

Amplitude Frequency and Phase Modulations

In general, modulation and demodulation are always related to one of the three characteristics of the signal amplitude, frequency, and phase or a combination of all or some of these characteristics. Modulation, or shifting, of any of these characteristics creates a recognizable, adequate (or sometimes called constellation) state of the signal, interprets these states as 1 or 0, and digitalizes them. In amplitude-shift keying (ASK), the 1 and 0 are represented by two different amplitudes, as...

Analog Dialup Services

The analog modem dialup service gained popularity because of constant increases in speed and support from modem manufacturers. The initial offering started with speeds from 300 to 2400 bps, then to 9600 bps, 14.4 kbps, and so on. The term modem is an abbreviation for modulator-demodulator. Because the modem operates in the 4-kHz bandwidth, it requires analog to digital and digital to analog conversion on both ends. Part of this technology uses extended code correction and compression, which...

Annex D Ansi Lmi Type

The T1.617 Annex D defines a polling protocol for use between the router and the network to exchange information about the status of the interfaces and the defined PVCs. The functions of the protocol are as follows Notification of the addition of a PVC Detection of the deletion of a PVC 452 Chapter 15 Frame Relay Design Solutions Notification of the availability or unavailability of a configured PVC Verification of the integrity of the link (UNI) The router periodically polls the network,...

AS5200 Specific Commands and Debugs

There are numerous additional commands for modems in the AS5200 series. Although this product has reached the end of life (EOL), it is still in widespread use so these commands are still worth covering. Only the most useful and most commonly used commands are covered. The first of these commands is show modem, which shows a list of all modems along with the number of successful and failed incoming call attempts, outgoing call attempts, and a percentage of successful calls. In addition, it...

Authentication Options

Challenge Handshake Authentication Protocol (CHAP) to Microsoft Challenge Handshake Authentication Protocol (MSCHAP). The username and password combinations can be stored on the router, a Remote Authentication Dial-In User Service (RADIUS) server, a Terminal Access Controller Access Control System (TACACS) server, or an Extended TACACS (TACACS+) server. You can also use any combination of these. Because there are a myriad of possibilities, additional considerations are highlighted here to help...

Authentication Phase

By default, authentication is not mandatory unless the protocol number used is c023 (PAP) or c223 (CHAP). The authentication negotiation occurs during the Link Establishment phase, where only LCP, authentication protocol, and link quality monitoring packets (protocol type c025 Link Quality Report) are allowed. All other packets received during this phase are discarded. In PAP, one side supplies both a username and password in clear-text to the peer that is authenticating it. In CHAP, one peer...

Authentication Problems

Before discussing authentication problems, it's important to follow the next rule of the thumb in authentication Establish the basic IP connectivity prior to implementing any authentication. Verify that the link works, then secure it. The authentication problems are easier to resolve when used in an enterprise environment. Two basic solutions are available Local authentication is used where the username (host name) and the password are defined in the particular box to which the remote user is...

B3ZS and B6ZS for T3

Other well-known zero suppressing schemes are B3ZS and B6ZS line codes. These coding schemes are typical for T3 (digital service 3 DS3 ) circuits. In B3ZS, each pattern of 000 is replaced by 00 V or B0V. The choice depends on whether the number of bipolar pulses between violations (V) is an odd number. In this case, V is positive or negative and chosen to cause a BPV, and B is also positive or negative, and is chosen to meet the bipolar conditions. In B6ZS, each pattern of 000000 is replaced by...

B8ZS and T1

B8ZS is one of the most widespread zero-suppression coding techniques. It is implemented to prevent degradation because of long strings of 0s. B8ZS replaces a block of eight consecutive 0s with a code that contains BPVs in the fourth and seventh bits. When eight 0s appear, they are replaced with the B8ZS code before being multiplexed onto the T1 line. At the receiver, detection of the BPV is replaced with eight 0s, which allows the full 64 kbps of the DS0 to be used. This is the most common...

Basic and Advanced Frame Relay Configurations

The configuration options in Frame Relay are derived from the design and provisioning choices made in earlier phases of Frame Relay service. In the configuration phase, it is preferable to apply a Hub Spoke topology, as described in Chapter 15, Frame Relay Design Solutions, which is more suitable to the permanent nature of Frame Relay. This chapter provides detailed information about basic and advanced configurations in Cisco Frame Relay routers. The Frame Relay encapsulations (cisco, ietf),...

Beginning the Frame Relay Troubleshooting Process

The minimum information required before starting to troubleshoot includes the characteristics of the service such as point-to-point or point-to-multipoint design if routing or bridging is used what are the remote and local DLCIs and what is the access rate (link rate), CIR value, and IP addressing scheme. Regardless of the answer to these questions, some common indicators of the status allow you to start with the snapshot commands. The recommended commands are as follows 1602-frame show ip...

Benefits of Analog Dialup Services

Today, the dialup solution is the most common solution for remote users, road warriors traveling on business, and home teleworkers. Dialup technology does not require any changes to the CPE side, even if the remote user is using a 56-kbps modem. Plenty of tools exist, including web tools, which are offered by manufacturers to measure the maximum connection speed in any particular location. Another feature of the technology is that when the maximum speed cannot be achieved, the 56-kbps flex...

Benefits of Frame Relay

Enterprise remote access solutions are composed of a variety of components, including technology, hardware, software, standards, and architecture to provide Frame Relay services within the enterprise environment. Examples of these components include data, voice over Frame Relay, Frame Relay multicast, IP multicast, and compression. Frame Relay technology poses fewer issues when covering longer distances for the remote user who is far from the central office (CO). The technology is fully...

Benefits of ISDN Services

Some older Cisco routers do not have voice capable ports, such as the 1000 series routers. Also, the 770 and 800 series routers provide analog phone ports and the 1600s provide an S-bus port for ISDN phones but not analog phones. Also, video conferencing is an embedded function because ISDN is designed for voice, data, and video. The technology is defined as a viable alternative when the end user requires more bandwidth than dial-in, a variety of data and voice services, and administrative...

Benefits of VPNs

In general, VPN solutions follow two basic models service-provider dependant and service-provider independent. From a remote access perspective, both models are available, and of course, ISPs and telecommunication companies actively promote the first model. As for which model the enterprise should choose, the following considerations must be analyzed first Expected (committed) performance Network management and access control solutions Customer support and service-level agreements (SLAs) The...

Benefits of Wireless Broadband Services

From a remote access point of view, it is important to consider these technologies as a viable alternative to the existing environment. It is clear that the future belongs to wireless technologies. The current MMDS and LMDS solutions provide data rates of 40 to 54 Mbps downstream. If MMDS and LMDS are the future technologies for wireless, what future advancements should you expect The price and innovation of these technologies are expected to play a major role in defining future remote access...

Billing and Charge Backs

The decision or ability to charge back expenses to a user's organization was mentioned in the preceding section, Cost. If you decide to charge back for user services rather than funding centrally, you must ensure that the necessary processes and systems are in place to handle the financial transactions. Is there a process currently available for remote access purposes Will the vendor provide the billing information in the required format or medium Should the corporation centrally manage the...

Cable Modem Services

Cable modem technology has been in the market for a long time, but the Internet generation has imposed new features on it. The technology uses cable, which has been used by cable TV operators to deliver TV services. The cable modem converts the digital signals over the cable into analog signals, and it also carries data packets on radio frequencies (RFs), which enables it to carry video streams. When the network includes a fiber segment, the systems are called hybrid systems. When the network...

Call Reference Field

The second field is the Call Reference (CR). It identifies the relationship between the call and the message, where the number identifies the active calls. CR or the Call Reference Value (CRV) is a per-session per-connection value that is assigned at the beginning of the call, and remains the same until the call is completed. Often the only indicator of whether or not the call goes through is tracing the call and testing with the LEC. Typically, a BRI uses one octet CR length, and a PRI uses...

Carriers Service Providers and How Traffic Is Carried

In telecommunications, transferring information from one point to another is based on transferring signals that by nature can be continuous and discrete, or analog and digital. The typical Public Switched Telephone Network (PSTN) of the early 1960s is primarily an analog network. Discrete or digital signal terminology is based on the base 2 numerical system (1 and 0), where a digital signal has at least two recognizable states that can be interpreted as 1 and 0. Carriers build networks that...

Case

The remote name can be defined in the global configuration mode with the following commands 804-isdn(config) hostname 804-isdn 804-isdn(config) username gateway password ENS The parameter gateway matches the CHAP name or the host name of the remote party. Enable the multilink feature of the PPP protocol with PPP multilink. The string in the following command represents a phone number dialer-string string class DialClass In the case of Figure 11-2, the phone number is 526-5555, because the user...

Troubleshooting Scenarios for Isdn Bri 359

Recommendations for Practical Troubleshooting of ISDN Remote Services 359 Using show isdn status to View Service Layers 360 Preconfiguring the Routers on Both Ends 364 Accessing the Remote User's Router 365 Scenario 1 New Install Problems 369 Scenario 3 ISDN Performance Problems 376 Short-Term Routing Issues 377 Line Problems 377 Configuration Setting Problems 382 LEC Switch Problems 382 Scenario 4 End-to-End Communication Problems 386 The LEC's ISDN Switch Settings 387 LCP Problems and the...

Frame Relay Design Solutions 433

Frame Relay Topologies and Congestion Control 441 Partial-Mesh and Full-Mesh Frame Relay Designs 441 User and Frame Relay Switch Operations Under Congestion 441 Congestion and Windowing 443 Frame Relay Performance Criteria 444 Frame Relay and Upper-Layer Protocols 445 Encapsulating IP, Q.933, and SNAP 447 Encapsulating Other Protocols over Frame Relay 448 Frame Relay Fragmentation 448 Consortium (Cisco) LMI Type 451 Annex D (ANSI) LMI Type 451 ITU-T Q.933 Annex A LMI Type 453 Address Resolution...

Basic and Advanced Frame Relay Configurations 457

Basic Frame Relay Configurations 458 Point-to-Multipoint Configurations 458 Point-to-Point Configurations 461 Maximum Number of DLCIs Per Interface 466 Routing Protocols and Frame Relay Configurations 467 Frame Relay Broadcast Queue 468 Advanced Frame Relay Configurations 469 Configuring IP Unnumbered Frame Relay 469 Frame Switching 469 Frame Relay and ISDN Backup Configuration 471 Frame Relay and IP Multicast Configuration 482

Frame Relay Troubleshooting 491

Beginning the Frame Relay Troubleshooting Process 492 Physical Layer Troubleshooting 493 Line and Clocking Problems 493 Serial Interface 0 and Line Protocol Is Down 498 Performance Issues Related to the Physical Layer 501 Data Link Layer Troubleshooting 506 PVC Configuration Issues 507 LMI Issues 513 Performance Problems 526 Flapping Links 526 End-to-End Problems 528 Frame Relay Shaping Problems 534 Troubleshooting Compression Over Frame Relay 537

VPN Technology Background 591

Service Provider, Dedicated, and Access VPNs 591 Enterprise VPN Categories 595 Functional VPN Categories 595 Technology Category 598 Network Layer (Layer 3) VPNs 604 Layer 3 Tunneling 605 Security Associations and Security Policy for IKE and IPSec 605 Negotiations of ISAKMP and IPSec Phases and Modes 607 Mutable and Immutable Fields and the ICV 608 Fragmentation, Path MTU Discovery, and ICMP Processing 610 IPSec Modes 612 IPSec Protocols 613 Authentication in VPN 619

Remote Access VPN Troubleshooting 675

Troubleshooting Cisco Remote Access VPN Clients 676 Cisco VPN Unity SW Client 676 Cisco 3002 HW Client Troubleshooting 706 Cisco Easy VPN Client 713 Cisco PIX VPN Client 721 Internet Technologies and Remote Access VPNs 732 VPN and ADSL 732 VPN and Internet Access Through a Cable TV Infrastructure 740 VPN and Internet Access over Satellite and Wireless Systems 745 LAN and General Networking Issues Affecting Remote Access VPNs 753 Multiple VPN Clients Behind a NAT Device 753 MTU A Critical Factor...

Remote Access VPN Troubleshooting Scenarios 765

Warming Up with Preliminary Troubleshooting Steps 766 Step 1 Determine if There Is an Internet Connection 767 Step 2 Ensure that the VPN Client Is Properly Installed 771 Step 3 Check or Create Your Profiles 772 Case 1 Bad Group Name or Group Password 774 Case 2 Prompted Multiple Times for Username and Password 775 Scenario 2 Can Authenticate but Problems Passing Data 784 Case 1 Cannot Pass Traffic and Using NAT Connection Entry 785 Case 3 Connection Keeps Dropping 786 Case 4 Cannot Browse the...

Dial Design and Configuration Solutions 141

Dial Design Solutions 142 Text Dial-In Network 143 PPP Dial-In Network 143 Text Dial-Out Network 144 PPP Dial-Out Network 145 Large-Scale Dial-Out Network 146 Dial-On-Demand Backup Network 147 Dial Configuration Solutions 149 Text Dial-In Configuration 150 PPP Dial-In Configuration 151 Large-Scale Dial-In Configuration 159 Text Dial-Out Configuration 164 PPP Dial-Out Configuration 168 Large-Scale Dial-Out Configuration 171 Dial-On-Demand Backup Configuration 173

Dial Troubleshooting 181

Troubleshooting NAS WAN Links 181 Troubleshooting T1 Circuits 181 Troubleshooting PRI Circuits 188 Step One Verify that the Modem Is Ready to Accept Calls 191 Step Two Verify Type of Incoming Connection 192 Step Three Verify PPP Negotiation 194 Troubleshooting Dial-Out Service 200 AS5x00 Specific Commands and Debugs 205 AS5200 Specific Commands and Debugs 207 AS5300 Specific Commands and Debugs 209 AS5400 Specific Commands and Debugs 214

Check Bit Errors with a Bit Error Rate Tester

A bit error rate tester (BERT) alerts you of any issues on the line. Although a circuit can be operational and passing data, some data might be flawed, which can be detected by using a BERT. A BERT is not an available option on every piece of Cisco hardware. If the option is not available, the proper way to perform this test is to put a tester directly on the circuit. To use a BERT to check for bit errors, if the router supports it, use the following controller configuration command...

CIR Options

Figure 15-1 provides a general and simplistic view of CIR.1 The CIR is computed over the minimum increment of Tc. Therefore, if Tc 1.125s, a CIR of 64 kbps permits a Bc of 72 kbps (72 1.125 64). If the Bc is 144 kbps and the Tc is 1.125s, the CIR is 128 kbps (128 x 1.125 144). Figure 15-1 Committed Information Rate (CIR), Excess Information Rate (EIR), and the Service Offering Committed Information Excessive Information Figure 15-1 Committed Information Rate (CIR), Excess Information Rate...

Cisco ISDN Cost Effective Solutions

ISDN is offered by most local exchange carriers (LECs). It's used for data, voice, and video exchange. Recently, the use of ISDN for offnet video-conferencing has increased. However, ISDN became less attractive as a cost-effective solution when compared to other emerging technologies, such as digital subscriber line (DSL), cable, wireless, and satellite. The cost of ISDN service is usually composed of an initial installation charge plus usage-based charges. In some cases, a LEC might...

Cisco Systems

Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134-1706 USA http www.cisco.com Tel 408 526-4000 800 553-NETS (6387) Fax 408 526-4100 Cisco Systems Europe 11 Rue Camille Desmoulins 92782 Issy-les-Moulineaux Cedex 9 France http www-europe.cisco.com Tel 33 1 58 04 60 00 Fax 33 1 58 04 61 00 Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA 95134-1706 USA http www.cisco.com Tel 408 526-7660 Fax 408 527-0883 Level 17, 99 Walker Street North Sydney NSW 2059 Australia http www.cisco.com...

Common and Cisco Specific Tools

A variety of tools are available under different platforms. It is worthwhile to explore each of them, and to create a set of pros and cons for each one. This type of research is worth a separate book. One possible approach to classify all tools is the following Network monitoring tools such as local-area network (LAN) and wide-area network (WAN) analyzers and sniffers, such as Sniffer Pro from Network Associates or EtherPeek. Remote control software, such as pcAnywhere from www.symantec.com, or...

Common ISDN Backup Configuration for Frame Relay

The backup ISDN interface can be defined in both point-to-multipoint and point-to-point interfaces. Depending on the strategy, ISDN BRI0 can back up both the physical and per-DLCI interface. In the physical interface backup scenario, losing the PVC does not trigger the backup mechanism because it only works when there is a complete loss of connectivity (i.e., when both the interface and line protocol are down). Most probably, this is the reason that this method is called physical interface...

Configuration Setting Problems

The buffer shortage is included under interface commands and shows the number of successfully passed packets and bytes, as well as the dropped packets due to no buffer. This setting might cause performance problems. Some simple recommendations that usually work for issues caused by settings include the following If the number of drops increments after clearing the appropriate interfaces and running a ping test from the opposite site, determine what destination is incrementing input or output,...

Configuration Solutions

A wide variety of configuration solutions is available in the existing literature, comprising years of engineering experience. This chapter mainly covers the cost-effective solutions because they are the most common in the existing industry practices, and because Integrated Services Digital Network (ISDN), as a service, is under the pressure of other technologies because of its cost drawbacks in remote access solutions. Most network engineers distinguish the following configuration solutions of...

Configuring IP Unnumbered Frame Relay

One of the IP preservation schemes that is only applicable for point-to-point configurations is to use an unnumbered IP address. In Example 16-4, you can see that for the core router configuration the physical interface is configured with no ip address and the IP addresses are assigned to the subinterfaces. These IPs are all obtained from the LoopbackO interface. Given the number of configured subinterfaces, you can see how this approach maximizes the use of available IP address space. The same...

Configuring the POTS Telephone Interfaces

Plain old telephone service (POTS) functionality refers to the use of the voice capabilities of the ISDN routers. The ringer equivalent number (REN) consists of a number and a letter that indicates the frequency response of that telephone's ringer. The term telephone port refers to the physical port on the router back panel. The telephone interface refers to a logical interface that you have to configure to make an analog telephone, fax, or modem connected to the router port (phone 1 and 2)...

Congestion and Windowing

Using windowing to manage congestion is suggested in the book ISDN and SS7 Architectures for Digital Signaling Networks by Ulysses D. Black. The basic approach resembles the windowing mechanism in the TCP IP stack, but combines the FECNs and BECNs with the sliding window technique. Unlike TCP, the sliding window technique reduces and increases the size of the window by a factor of 0.125, depending on the network conditions. In Cisco routers, windowing is configurable by parameter K, where K is...

Consortium Cisco LMI Type

The Consortium designed the LMI protocol to perform the following functions Allow the network to notify the FRAD about active and present DLCIs Allow the network to notify the FRAD if DLCI is removed or fails Monitor the status of the router-to-network link in real-time through keepalive messages The Consortium LMI defines two messages status enquiry and status. The general format of this LMI type is shown in Figure 15-9. Figure 15-9 Format of Consortium LMI Messages The Message Type Can Be...

Contents

Foreword xxiii Introduction xxv Part I Remote Access Fundamentals 3 Management Considerations 6 Cost 6 Availability 7 Support 7 In-Sourcing Versus Outsourcing 7 Billing and Charge Backs 7 User-Managed Versus Corporate-Managed 8 Security 8 Applications 8 Defining the Remote Access User Population 9 Remote Access Service Options 9 Analog Dialup Services 12 ISDN Services 14 Frame Relay Services 17 VPN Services 18 VPN Service Vehicles 20 Cable Modem Services 20 xDSL Services 22 Wireless Broadband...

Contents at a Glance

Part I Remote Access Fundamentals 3 Chapter 1 Remote Access Overview 5 Chapter 2 Telecommunication Basics 37 Chapter 4 Troubleshooting Approaches, Models, and Tools 95 Chapter 5 Dial Technology Background 125 Chapter 6 Dial Design and Configuration Solutions 141 Chapter 7 Dial Troubleshooting 181 Chapter 8 Dial Troubleshooting Scenarios 219 Chapter 9 ISDN Technology Background 233 Chapter 10 ISDN Design Solutions 257 Chapter 11 Cisco ISDN Configuration Solutions 289 Chapter 12 ISDN BRI...

Control Field

The Control field of LAPD is used for frame identification. The field can be one or two octets, and provides messages that perform some of the typical functions for the Transmission Control Protocol (TCP), such as ACK and SEQ . The Control field uses three frame formats, which are indicated by the first two bits of the field Information, Supervisory and Unnumbered. Information (I) is a two-octet frame field that carries signaling or user data information from higher ISDN layers. Supervisory (S)...

Core Router Configuration

Configuring the core router for PPP callback for ISDN involves two separate configurations Defining and naming the map class Defining PPP callback for ISDN under the dialer interface Example 11-7 and Example 11-8 demonstrate these two steps. Example 11-7 PPP Callback for ISDN Core Router Configuration Defining and Naming the Map Class 7206-isdn(config) map-class dialer CALLBACK 7206-isdn(config-map-class) dialer callback-server username Example 11-8 PPP Callback for ISDN Core Router...

Cost

The budget for remote access can limit the options available. The organization must determine what base of users will be granted access, what capacity and growth estimates are required, and how the costs will be allocated internally. To form the basis for a remote access budget and funding approach, answer the following questions Who will cover the initial capital and installation costs What costs are required to deploy the solution Are there any training costs How will any monthly circuit...

Creating Dial Peers

Dial peers determine the routing of incoming calls to the telephone ports. You can create a total of six dial peers for the two telephone ports. Example 11-9 lists some of the relevant Cisco IOS Software configuration commands. Example 11-9 A Common Procedure for Dial Peers Configuration This command sets up a tag number (1 to 6) 804-isdn(config) dial-peer voice tag pots This command assigns a local directory number ldn The number of the port is defined using the following command...

Data Centers and Internet Hosting Services

Data centers usually provide physical facilities, installation and maintenance, environment management equipment (electrical mechanical temperature), power management, generators, uninterrupted power supply (UPS), electrical supply, fiber access, security, network services, monitoring, and management. The main factors that affect the enterprise in its decision to use outsourced data centers as part of its remote access plans are the following National presence of the provider with multiple data...

Data Link Layer Troubleshooting

Troubleshooting the second layer in Frame Relay includes the encapsulation types, LMI types and messages, and should be performed just after the physical layer issues are resolved. As previously mentioned show ip interface brief and show interfaces serial 1(0) are the commands that help narrow the scope of troubleshooting. Some typical reports for protocol layer issues are shown in Example 17-16 and Example 17-17. Example 17-16 The Serial 1 Interfaces Show Line Up and the Protocol Down Example...

Defining the Remote Access User Population

Several profiles of users typically require different solutions for remote connectivity. For each of these profiles, a different solution and possibly a different level of support might be required to meet their remote access needs Full-time telecommuters usually are supported with enough IP addresses to meet their requirements. For them, 32 with NAT, 30, or even 29 address space can be assigned. Day extenders use their home environment as an extension to the existing office environment. They...

Department of Defense Model

The efforts to create an interface model for internetworking started with the four-layer Department of Defense (DoD) model, which was developed by the Department of Defense in the 1970s for the Defense Advanced Research Projects Agency (DARPA) Internetwork Project (see Figure 4-1). The core Internet protocols adhere to this model, although the OSI model is preferred for new designs. Figure 4-1 The Four Layers of the Department of Defense (DoD) Model The four layers of the DoD model, from bottom...

Description

Declared when the receiver detects two or more framing-bit errors within a three millisecond period, or two or more errors out of five or less consecutive framing-bits. At this time, the framer enters the Out of Frame state, and starts searching for a correct framing pattern. The Out of Frame state ends when reframe occurs. This event is declared upon observing 175 + - 75 contiguous pulse positions with no pulses of either positive or negative polarity (also called keepalive). Code Violation...

Design Parameters

The following parameters must be considered in the Frame Relay design stage Access rate (AR) or link speed This is the data rate, which is measured at the physical interface in bits per second. The link speed determines how rapidly (maximum rate) the end user can inject data into a Frame Relay network. Committed interval (Tc) The committed interval represents a time slot over which the rates burst and the committed information rate (CIR) is measured. The measurement is in seconds usually...

Dial Configuration Solutions

A dial network can be as small as a single modem on a router or as large as millions of modems across a continent. From modest to grand, the configuration skeleton remains relatively the same. IOS lists the configurations in a standard way because of the hierarchy that is predefined in the system. By no means are you expected to write a configuration the way IOS displays it. In fact, the approach used in this chapter to create dial configurations is a logical approach where the configuration...

Dial Design and Configuration Solutions

Most commonly, modem dial access is used for dial-in network connectivity, dial-out network connectivity, and dial-on-demand routing (DDR). These specific instances are covered in the dial design solutions portion of this chapter, along with dial-out for support purposes and large-scale dial-out services. Fax server capability is another common use for dial, but is not covered here because it is more of a specialized service. The main topics covered in the design portion of this chapter are as...

Dial Design Solutions

In the design part of this chapter, some design components remain constant. Dial (in, out, or on-demand) is generally served out of an access server that is connected to the network. Usually, there is an authentication server of some kind to offload the authentication processing from the router, making it centrally manageable. Design considerations need to also include the backbone architecture. If dial is a component of a remote access solution for your company, it is a small part of the...

Dial Technology Background

Dial is an essential part of remote access infrastructures because it is one of the easiest means by which a traveling user can obtain network access. For connectivity at home, in most cases, it provides the cheapest form of Internet access. Dial also provides an inexpensive, reliable backup solution when broadband alternatives are not available because of circuit outages or maintenance windows. Dialup networking seems simplistic in terms of how it works. The steps to establish a connection...

Dial Troubleshooting

The troubleshooting approach in this chapter demonstrates the layer-by-layer and phase-by-phase approach to dial issues. It is important to be systematic and go step-by-step, starting with the physical layer from both ends. Unlike service provider-based remote access solutions, both ends of the connection are available for troubleshooting in an enterprise remote access scenario. This chapter focuses on the following main topics Detailed troubleshooting network access server (NAS) wide-area...

Dial Troubleshooting Scenarios

Many problems can occur through the train-up, authentication, and Point-to-Point Protocol (PPP) negotiation phases when making a dialup connection. In all cases, it is best to take a step-by-step approach through the connection until you find the area where the problem occurs. This book cannot cover the details of all that can occur in the case of train-up failures or slow speed connections, but it does provide many helpful hints, tips, and tricks to assist with dial troubleshooting. The...

DialOnDemand Backup Configuration

In the configuration example provided, a WAN router is used with a fractional T1 to the main office and a modem for DDR. When the fractional T1 goes down, you want the modem to place a call to the DDR server at the main office and continue to support the flow of traffic. Although it is not the easiest to configure, using dialer watch is an effective way to perform dial-on-demand backup. Dialer watch checks on a route that is supposed to be in the routing table, and if the route disappears for...

DialOnDemand Backup Network

Dial-on demand backup routing is similar to the second form of PPP dial-out covered previously. The section, PPP Dial-Out Network did not cover routing, how to bring up the line when a primary circuit fails, and how to tear it down again when the primary circuit comes back up. There are three different ways to configure DDR Using a floating static route All three options have advantages and disadvantages. Each option is explained here. A backup interface's main advantage is that it is...

Diffused IR

Diffused IR communications are described as both indirect and non-line-of-sight. The diffused IR signal, which is emitted from the transmitter, fills an enclosed area like light and does not require line-of-sight transmission. You can point the IR adapters at the ceiling or at an angle and the signal bounces off the walls and ceiling. Changing the location of the receiver does not disrupt the signal. Many diffused IR products also offer roaming capabilities, which enables you to connect several...

Digital

A telephone line connected to a remote user's minimum point of entry (MPOE) or to a telecommuter's hotel room carries a full-duplex call on a single pair of wires. This means that both send and receive signals are transmitted simultaneously, but on individual wires. When the send and receive signals are broken apart from each other, there is a leakage of audible sound from send to receive and vice versa. This leakage is heard as an echo and becomes more noticeable as the distance increases from...

Digitalization of the Signal and Pulse Code Modulation

In general, the process of digitizing the signal creates an adequate digital model for a nondigital process. The challenge is trying to represent a real-life scenario as an algorithm. In some cases, the task appears to be much easier because of the existence of repeated samples. Human voice transfer requires a 4-kHz frequency band. Based on the Nyquist sampling theorem, digital sampling must take place at least twice the highest frequency to reconstruct the analog signal accurately. As a...

Dsss

SS was first developed by the military as a secure wireless technology. It modulates (changes) a radio signal pseudo-randomly so it is difficult to decode. This modulation provides some security however, because the signal can be sent great distances, you do risk interception. To provide complete security, most SS products include encryption. DSSS works by taking a data stream of 0s and 1s and modulating it with a second pattern, the chipping sequence. The sequence is also known as the Barker...

Enable ppp multilink

300 Chapter 11 Cisco ISDN Configuration Solutions As you can see, this step differs from the legacy DDR, where only the command 804-isdn(config-if) encapsulation ppp is required under the physical interface. The reason for configuring the authentication and PPP multilink for dialer profiles DDR is because, based on the authentication information, that is how the router knows which dialer profile to switch the call to. As a result, the authentication must be set on the physical interface as...

Encapsulating IP Q933 and SNAP

ANSI T1.617a Annex F defines the standards for encapsulating IP, Q.933, and SNAP. When encapsulating IP, an optional pad can be added to align the rest of the frame on a two-octet boundary. No further control information, such as IDs or a SNAP header is required. The encapsulation format for Q.933 can be used when no specific network protocol is defined. SNAP is used for encapsulating bridged IEEE 802.3 frames for routed and bridged packets that contain LAN-to-LAN traffic. The NLPID is set to...

Encapsulating Other Protocols over Frame Relay

To indicate the usage of the ISO CLNP protocol, the NLPID field must be set to 81h. As soon as the NLPID field indicates ISO CLNP, the data packet immediately follows. NLPID is also considered part of the CLNP packet, and as such, it should not be removed before being sent to the upper layers for processing. IPX does not have a NLPID value defined. For this reason, IPX is encapsulated using the SNAP header. The frame format is in the following order Initial Q.922 Address and Control field 03h,...

End Notes

Frame Relay CIR and Billing Issues. Network VAR, 1995. 2 Stallings, W. ISDN and Broadband ISDN with Frame Relay and ATM. Prentice Hall, 1998. 3 American National Standards Institute. Integrated Services Digital Network (ISDN)-Signaling Specifications for Frame Relay Bearer Services for Digital Subscriber Signaling System Number 1 (DSS1). ANSI T1.617 Annex D, 1991.

Endto End Routing Problems

The routing problems are often related to configuration rules and errors. The first type of problem arises when no default gateway is configured, or it is misconfig-ured. The rule to follow is the default gateway must point to the local router's Ethernet interface. One example is when the local DHCP is defined and part of that definition is the default gateway, as shown in Example 13-18. Example 13-18 The Local DHCP Is Defined and Part of that Definition Is the Default Gateway network...

Enterprise and ISP Designs

From an application point of view, you can break down ISDN into the following main categories. Based on the structure of the core side, you can recognize a separate enterprise design and an ISP design in these categories ISPs, more often than enterprises, use the MMP, which is not mandatory for an enterprise solution. ISPs often use a pool of IP addresses, whereas enterprises often assign an IP subnet from their routable or private address space for remote users based on their needs. ISPs use...

FCS Field

The frame check sequence (FCS) field is two bytes and it is used for bit error detection. The next step of achieving full functionality of ISDN service, immediately after the activation of the physical link, is the logical link establishment. Here, LAPD ensures the TEI and SAPI assignments, which are the core of the logical link establishment, as shown in Figure 9-6. The figure represents another handshake link procedure. Figure 9-6 Logical Link Establishment Sequence UI (SAPI 63, TE 127) in...

Fhss

FHSS is analogous to FM radio transmission as the data signal is superimposed on, or carried by, a narrowband carrier that can change frequency. The IEEE 802.11 standard provides 22 hop patterns, or frequency shifts, to choose from in the 2.4-GHz ISM band. Each channel is 1 MHz and the signal must shift frequency, or hop, at a fixed hop rate (U.S. minimum is 2.5 hops sec). This technology modulates a radio signal by shifting it from frequency to frequency at near-random intervals. This...

First Tier Exchange Carriers

Since the Telecommunications Act of 1996 in the U.S., a service provider can be any provider of telecommunications services that is certified by individual states to become a LEC. The newly certified companies acquired the name of competitive LEC (CLEC), and the existing (former) companies are called incumbent LECs (ILECs). There are several other LECs (OLECs) and some other abbreviations, but for simplicity, only first-layer carriers are referred to as LECs. Recently, more than 1300 LECs were...

Flag Field

The Flag field is one byte that is a fixed sequence and consists of 01111110 (binary) or 0x7E (7Eh). The Flag indicates the beginning and end of the frame. If the sender needs to send 7Eh as part of the information in the middle of the transmission, but not as a Flag, the sender inspects the data stream for 011111. If found, a 0 is inserted immediately after the fifth 1, which changes the data stream (see Figure 14-5). This procedure works regardless of the value of bit 7 (0 or 1), because of...

Foreword

Cisco Systems Inc. is built on the philosophy of changing the way we work, live, play, and learn. The ability to telecommute and work remotely from any location is a large part of this change. Telecommuting is not a new concept employees have been able to work remotely for decades. Significant benefits are associated with this practice. Today, the ability to be productive while working remotely can occur only when required office applications and tools are accessed and used as if you were...

Frame Relay and Bridging

When using Frame Relay bridging, there must be a full mesh of Frame Relay virtual circuits between the bridges of a remote bridge group. If the Frame Relay network is not a full mesh, the bridge network must be divided into multiple remote bridge groups. Because LMI transforms the Frame Relay to a LAN-like architecture, this bridging model is identical to the model for remote bridging as described in IEEE P802.1g, which supports the concept of virtual ports. The Frame Relay virtual circuits...

Frame Relay and IP Multicast Configuration

To provide basic multicasting over ISDN and Frame Relay for a remote access environment, you must perform some basic tasks Enable IP multicast routing Enable Protocol Independent Multicast (PIM) on an interface Configure the router to automatically accept the rendezvous point (Auto-RP) or hardcode the RP's IP address. In a Frame Relay environment, the following steps provide basic multicast for users. On the spoke router, the lines in Example 16-16 must be configured. Example 16-16 Basic...

Frame Relay and ISDN Backup Configuration

Enterprises that require a wide-area network (WAN) service for long periods of the workday normally choose Frame Relay as a primary link. To prevent situations where this link is a single point of failure, and to meet the availability and redundancy requirements of the design, the ISDN is often used as a backup technology. In the remote access enterprise environment, remote users don't usually warrant a backup. It is up to the enterprise to determine if the additional cost of an ISDN backup is...

Frame Relay and Traffic Shaping

Traffic shaping enables the router to control the output rate and react to the congestion notification mechanisms according to the traffic shaping settings. In Cisco routers, traffic shaping uses a rate control mechanism called a token bucket filter. The token controls the following expression (Bc + Be) Access rate for the virtual circuit 484 Chapter 16 Basic and Advanced Frame Relay Configurations Traffic above the maximum speed is buffered in a traffic shaping queue, which is equal to the...

Frame Relay Backup with ISDN Dialer Profiles

This solution is based on creating dialer profiles on both the hub and spoke sides. Assume that you have a configuration with one hub and four spoke routers, as shown in Figure 16-2. If all the spoke routers have ISDN backup links available, they can be configured as shown in Example 16-9. As soon as Serial1.201 goes down, the backup ISDN interface comes up according to the configuration settings. Here, the backup delay settings are five seconds for enable-delay and ten seconds for...

Frame Relay Broadcast Queue

Remote access designs are characterized by a large number of spoke routers that terminate into one or a couple of hub routers. The routing updates can create a large amount of traffic and thus seriously affect the overall performance of the entire architecture. One of the possible solutions is the use of a Frame Relay broadcast queue per interface. For Frame Relay, the broadcast queue is separate from the regular interface queue. It has its own buffers, size, rate and is configurable with the...

Frame Relay Compression

Cisco internetworking devices use the STAC (LZS) and Predictor data compression algorithms. STAC (LZS) is based on the Lempel-Ziv compression algorithm. Cisco IOS Software uses an optimized version of LZS that provides good compression ratios but requires many CPU cycles. LZS searches the input data stream for redundant strings and replaces them with what is called a token. This token is shorter than the original data string. LZS creates dictionaries. This dictionary is built and begins...

Frame Relay Design Solutions

Frame Relay is a versatile and flexible technology where the provisioned parameters define the way that the service can be manipulated by both the service provider and the enterprise. Provider manipulation is beyond the scope of this chapter, although the enterprise will receive the type of service (ToS) and further ability to manipulate the service, based on the design parameters, topologies, and provisioned parameters. In this chapter, you learn about the following Design parameters of Frame...

Frame Relay Foresight Adaptive Shaping with ELMI

ELMI allows the router to adapt the shaping parameters dynamically. ELMI enables the automated exchange of Frame Relay quality of service (QoS) parameter information between the Cisco router and the Cisco switch. Routers can then base congestion management and prioritization decisions on known QoS values such as CIR, Bc, and Be. This enhancement operates between Cisco routers and Cisco switches (BPX MGX and IGX platforms). You can enable ELMI support on the router by using the frame-relay...

Frame Relay Multicast

The multicast provision exists in most local-area network (LAN) technologies and as part of the Internet Protocol (IP). Multicast is a feature that enables one source to send information to multiple recipients. A typical wide-area network (WAN) uses a point-to-point (unicast) connection, where the user transmits information to only one recipient. Frame Relay multicast is addressed in FRF.7, and this agreement defines one-to-many types of connection, where one sender who provides information to...

Frame Relay Protocols

The Frame Relay protocols are designed to reflect the concept of the second layer of the OSI model, based on services from the physical layer and providing services for the higher-layer protocols. At the same time these protocols are not simplistic. They provide a mechanism to maintain PVCs to establish SVCs, and to encapsulate higher-layer protocols. Frame Relay technology provides second layer functions such as framing, error control, and sequence control, and support for third layer...

Frame Relay Service Architecture

The Frame Relay service architecture is defined as two planes the C-plane (control) and U-plane (user). Both planes are governed by standards, such as shows the relationship between the two planes. The Frame Relay and frame switching concepts are shown in Figure 14-2 and Figure 14-3. Figure 14-1 C-Plane and U-Plane in Frame Relay Using the ANSI UNI Protocol ANSI I.430 I.431 Physical Layer Standards ANSI I.430 I.431 Physical Layer Standards User (TE) S T Interface Network (NT) 418 Chapter 14...

Frame Relay Services

Frame Relay technology is considered to be a derivative of ISDN. It is a connectionless service, however, which means that the frames traveling the network do not require the initial phase of establishing the connection, because the frames carry the address information. This solution is referred to as a permanent virtual circuit (PVC). Frame switching is the other alternative, where the call setup phase of the connection is necessary, and consequently the technology is based on switched virtual...

Frame Relay Standards

All written standards that govern Frame Relay implementations are American National Standards Institute (ANSI), International Telecommunication Union Telecommunication Standardization Sector (ITU-T), or Frame Relay Forum (FRF) standards. Although ANSI and ITU-T standards are based on the ISDN architecture, the FRF documents address implementation issues, ensuring the interoperability of multivendor networks. Table 14-2 summarizes some of the ANSI and ITU-T standards governing Frame Relay. Table...

Frame Relay Technology Background

Frame Relay technology includes a combination of hardware, software, standards, and architectures to provide a variety of services. They include data, Voice over Frame Relay (VoFR), Frame Relay multicast, Internet Protocol (IP) multicast over Frame Relay, Frame Relay compression, and others. It is beyond the scope of this book to include all available features of Frame Relay, so the content of Part IV, Frame Relay, only includes the technology background, common design and configuration...

Frame Relay Troubleshooting

Troubleshooting Frame Relay connections is a design-dependant process, which starts with a clear understanding of the kind of connection you are troubleshooting. You need to know if this is a point-to-point or point-to-multipoint design, if it is a routing or bridging design, if you have a partial-mesh or full-mesh design, if you are using a switched virtual circuit (SVC) or permanent virtual circuit (PVC), how the signaling is maintained, and so on. The troubleshooting has to be performed as a...