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,...

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...

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 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 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...

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...

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

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...

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...

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 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

In Figure 14-7 and Figure 14-8, two formats of Q.922 are shown. The only difference between the core format and the control protocol format is the control field. The control field has the same format and identical functionality as the Link Access Procedure on the D channel (LAPD) field. The control protocol provides the functions of error and flow control that are missing from the LAPF core protocol. Figure 14-7 LAPF Frame Formats Frame Relay with End-to-End LAPF Control Figure 14-7 LAPF Frame...

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...

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...

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 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...

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...

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...

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.

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 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 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...

Frame Switching

When discussing Frame Relay technology options in Chapter 14, Frame switching and a set of protocols were introduced (refer to Figure 14-2 and Figure 14-3). Typically, a router is configured as data communications equipment (DCE) if it is connecting directly to another router. It can also be configured as DCE when connected to a 90i D4 channel unit, which in turn is connected to a telephone company (telco) channel bank. A variety of configuration solutions exist for frame switching, including...

Generic Traffic Shaping

The generic traffic shaping feature is a media and encapsulation-independent traffic shaping tool. It helps reduce the flow of outbound traffic when there is congestion within the cloud, on the link, or at the receiving endpoint router. You can set it on interfaces or subinterfaces within a router. See Example 16-18 for the following configuration steps. First, you need to enable traffic shaping in the main interface (interface Serial4 2 0) with the following command Then, under the...

Home Access Versus Mobility

The final criterion to be considered is the need to access the corporate network from home, and from on the road while in a hotel, convention center, airport, or a customer business partner premises. Depending on the organization's remote access requirement, a mobile solution might be a necessary part of the overall remote access service offering. The Cisco Mobile Office initiative addresses the solutions and considerations that differ based on the need to work on the road, at home, or at work...

ID Verify

The only way to change or remove the TEI assigned to the router's BRI interface is to reload the router. Then, the boot code forces the first ISDN TEI first-call flag to be reset. The first call flag affects all switch types, thus forcing incoming and outgoing calls to activate the BRI interface. To enable the router to negotiate the TEI on the first call, use the following configuration command 804-isdn(config) isdn tei-negotiation first-call NOTE Some European ISPs remove the TEI assignment...

IEEE 80211bThe Next Step

All previously mentioned, coding techniques for 802.11 provide a speed of 1 to 2 Mbps, which is lower than the widespread IEEE 802.3 standard speed of 10 Mbps. The only technique (with regards to FCC rules) that is capable of providing a higher speed is DSSS, which was selected as a standard physical layer technique that supports 1 to 2 Mbps and two new speeds of 5.5 and 11 Mbps. The original 802.11 DSSS standard specifies the 11-bit chipping, or Barker sequence, to encode all data sent over...

Info

For a Cisco 77x router, the line quality of the ISDN line can be checked with the show packets command as displayed in Example 13-7. Filtered 0 Forwarded 150 Received 201 Dropped 59 Lost 0 Corrupted 1 Misordered 0 The line quality information is shown and explained in Table 13-6. Table 13-6 Output and Description of the show packets Output From a 77x Router Table 13-6 Output and Description of the show packets Output From a 77x Router The packet diagnostic statistics for Link 2. Packets...

Information Elements Field

As previously mentioned, the data is carried in the Information Elements (IE), which are the Q.931 parameters. Unlike other protocols, Q.931 does not define a fixed length for this field that reflects the actual length of the field. Different content and different length works with different LECs. For this reason, this field might contain a length indicator, defined as Type 1 and Type 2 IE. The Type 1 IE defines a 3-bit identifier and 4 bits for the content of IE, and Type 2 contains a 7-bit IE...

Interconnection Models

The goal of every interconnection model is to provide standards to which all computer hardware and software vendors can adhere so that the present multiplicity of interconnection and interface practices is reduced, thus reducing the costs of designing and producing both hardware and software. The existing models are covered in literally hundreds of sources in great detail, but the following section provides a short description of the DoD model and the seven-layer OSI model from a standpoint of...

IP Pool Design

The purpose of the IP pool is to create and assign a group of addresses, so that when the remote user calls, after the user is authenticated, an IP address is provided from a predefined set of IP addresses. The IP pool assignment in the core router is relatively simple to configure, as shown in Example 10-6. Example 10-6 Configuration Setting for an IP Pool < output omitted> interface Dialerl description HOME_ISDN_USERS ip unnumbered Loopback0 encapsulation ppp no ip mroute-cache no...

Isdn Bri Troubleshooting

From a technology prospective, most of the ISDN fundamentals are covered in the previous chapters of this part. This chapter provides you with a systematic approach to ISDN troubleshooting and demonstrates the suggested layer-by-layer approach to ISDN problems. The approach requires you to start from the physical layer and go up, layer by layer and protocol by protocol, to identify potential issues. This chapter covers the following common issues Troubleshooting the physical layer...

ISDN Design Solutions

Typically, the hub and spoke design is the most commonly used in remote access solutions. The hub and spoke terminology can be used for ISDN design solutions however, it is more common for designers to use network access server (NAS) and remote node as typical terms that describe the design. Typically, the hub site is referred to as the core or core router, and the spoke side is referred to as the end-user router, or remote user. The objectives of this chapter are to give you more information...

ISDN Planes ISDN Layer Architecture

As with every technology, the ISDN architecture creates a framework for more informed decision making, including appropriate investments in network technologies, products, and services. The CCITT defines the ISDN architecture to consist of four planes The C-plane primarily deals with UNIs and establishing and tearing down the calls, and, the U-plane deals with User-Network data carried by the B channel. When troubleshooting ISDN, it is important to remember how the ISDN protocol architecture...

ISDN Services

ISDN is considered to be the first advancement from analog dialup service. The ISDN standard is well developed and there are a variety of solutions that make ISDN the most commonly available service offering from telecommunication companies. The T sector of the ITU-T is responsible for issuing protocols for the E-Series, I-Series, and Q-Series, and for components of the X-series that are related to ISDN, broadband ISDN (B-ISDN), and Signaling System 7 (SS7). E-Series protocols cover the...

Isdn show compressionFor IOS 121 and higher

776-isdn gateway> show packets For images 4.2 and higher Example 12-41 displays the output for a 776 router. Filtered 0 Forwarded 2081 Received 5581 Dropped 0 Lost 0 Corrupted 1 Misordered 0 Here, the router is reporting compression ratio 1.99 1 for connection 2, calculated on the base of 2081 forwarded and 5581 received packets. The last phase of PPP protocol is the teardown, or determination of the connection, which, in turn, should result in releasing the LEC's facilities.

ISDN Voice Priority

The voice priority feature of IOS handles the data and voice priority. Depending on the user preferences, voice could take precedence over data and vice versa. There are three options Always Always bumps the data call if an outgoing or incoming voice call is initiated. Conditional (by default) Voice call bumps data call only if the user has two data connections in the same direction otherwise, the calling party receives a busy signal. Never Off Voice callers always receive a busy signal. In...

ISPs and ASPs

From the standpoint of LECs, the ISP is another service that provides dedicated services through host routers with access to Internet backbone routers. LECs consider these services as point-to-point, bypassing the PSTN-switched facilities. Usually, the analog dialup ISPs require trunks in a 10 1 user to port ratio, to keep the users monthly charges ratio in the profitable range. Adding more trunks does not necessarily mean more bandwidth, but definitely means more charges. These lines are...

LAPF Core Protocol and the T1618 Q922 Annex A Frame Format

LAPF core functions are organized around five elementary procedures Frame Relay must provide services to delimit and align frames and provide transparency of the frame flags with zero-bit stuffing and unstuffing. Frame Relay must support virtual circuit multiplexing and demultiplexing through the use of the data-link connection identifier (DLCI) field in the frame. The system must inspect the frame to ensure that it aligns itself on an integer number of octets, prior to zero bit insertion and...

Large Scale Dial Out Configuration

Two types of large-scale dial-out configurations exist. The first uses static dialer maps put into a dialer interface, where they exist within the router configuration. The second type uses the AAA system for storing the dialer maps. In the first example that follows, static dialer maps dial out to each individual client. The number of configurable clients is limited by the size of the configuration. After the configuration is full, no more clients can be added. Although this limitation exists,...

Large Scale Dial Out Network

Large-scale dial-out places many calls to multiple locations, mostly for polling purposes. In this scenario, you can do one of two things include all the phone numbers and locations on the router in the form of dialer maps or place them on a Terminal Access Controller Access Control System (TACACS+) or Remote Authentication Dial-In User Service (RADIUS) server to pass to the dial-out server during the router's boot sequence. Both situations are covered later in this chapter. Figure 6-6...

Layer 2 Status

If the Layer 2 state does not show MULTIPLE_FRAME_ESTABLISHED, check the T1 circuit for incrementing errors and treat this situation as any T1 problem. More information about troubleshooting measures is covered in the section, Troubleshooting T1 Circuits. If the T1 checks out okay, verify that the ISDN switch type and PRI group time slots were set up the same as the circuit was provisioned. Then check the serial interface associated with the PRI by using the command show interface serial x 23,...

Layer 3 in the D Channel Q931 and Message Format

The term Layer 3 protocols comes from the network layer in OSI, and the Q.931 recommendations provide call routing and congestion control for calls between a user's TE and the network (between the terminal endpoint and the local ISDN switch). However, this protocol does not impose an end-to-end recommendation, and various ISDN providers and switch types use various implementations of Q.931. Also, some switch types were developed before the standards groups finalized this standard. For these...

LEC Switch Problems

LEC switch problems are related to the quality of service provided by the LEC. Also, there are different departments within a LEC's organization, and the troubleshooting engineer does not always have visibility to the LEC's internal processes. The following is an example. A user is taking an e-learning course and experiences slow performance of data and video. The user has a 30 bit (255.255.255.252) subnet assigned on one computer at home a new notebook. Here are the troubleshooting steps for...

Limitations of Cable Modem Services

On the CPE side, most home-owned splitters and drop cables need to be re-installed because of the ingress noise that can cause serious performance degradations. The 5 to 42 or 5 to 50 MHz band is susceptible to interference from appliances such as refrigerators, vacuums, or other home devices that create concentrated radiation in this bandwidth, making it unusable. To address this situation, cable providers prefer to use filters, or normal PSTN modems to provide upstream communication. In turn,...

Limitations of ISDN Services

One of the concerns of ISDN is related to standards. Besides the differences in ISDN switch type, there are interface compatibility limitations. The U-interface, which is available in the U.S. and Canada where the end terminator (NT1) is part of the CPE, is not available in other parts of the world where the S and T reference points, or S T interface, is the termination solution and the NT1 devices are governed by the local carriers. This difference requires two types of routers to be produced,...

Limitations of VPNs

From a desktop perspective, several software products can interfere with the proper functioning of a VPN client solution. Software distribution and management becomes more critical for VPN client solutions than any other remote access medium. Hardware-based and IOS-based VPN clients are less susceptible to incompatibilities with other network applications, but they pose different sets of limitations. (See Part V for more details about this topic.) 20 Chapter 1 Remote Access Overview