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 has three different formats, shown in Figure 14-6. DLCI--Data link connection identifier is a unique number that provides local identification of the connection. The default address field format is 2 bytes or 10 bits. The extended address frame format can be 3 bytes (16 or 17 bits) or 4 bytes (23 bits). C R Command Response Field provides interconnectivity with higher-layer protocols. Frame Relay does not check it and the router can use this bit for signaling and control. FECN...

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...

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 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...

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...

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...

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...

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...

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...

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...

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...

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...

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...

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.

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 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 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 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...

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 Channels

In ISDN, the local loop carries only digital signals that represent signaling information and user data. The local loop typically carries voice, data, or video. The term channel, unlike other techniques, means a unidirectional conduit that carries signaling and user information. Three basic channels are defined by the standards D channel (Delta channel, signaling channel) The D channel is a packet-switched channel that carries signaling and control information for B channels between the...

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 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,...

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 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,...

Line of the Output

Spid(1 or 2) configured, spid(1 or 2) sent, spid(1 or 2) configuration information for a working spid(1 or 2) valid , no LDN BRI. The valid combination is shown on the left column and other possible combinations are spid(1 or 2) configured, no LDN, spid1 sent, spid1 valid spid(1 or 2) NOT configured, spid1 NOT sent, spid1 NOT valid spid(1 or 2) configured, spid1 NOT sent, spid1 NOT valid spid(1 or 2) configured, spid1 sent, spid1 NOT valid The last three states indicate that either the spid was...

Line Problems

After you ensure the service is set up correctly and fully operational (the router can make calls), check the status of the BRI service by using the following set of very useful commands 804-isdn show interface bri0 804-isdn show interfaces bri0 1 2 The detailed output for these commands is explained in Table 13-5. Before you look at this output, note some of the troubleshooting steps you can take for this category of problems 1 Make sure that the user's router is configured correctly that it...

Link Establishment Phase

LCP establishes the connection through an exchange of configure packets. As soon as the Protocol field contains c021h, the phase is changed to link establishment. After a Configure-Ack packet is both sent and received, the exchange is complete and the LCP Opened state begins. The LCP codes are 1-byte long and are listed in Table 5-2. 136 Chapter 5 Dial Technology Background Table 5-2 LCP Codes, Packet Types, and Descriptions Table 5-2 LCP Codes, Packet Types, and Descriptions List of proposed...

Message Type Field

The Message Type value indicates the type of Layer 3 message that the transmission represents. Call establishment message types in Q.931 are as follows SETUP Initial call request SETUP_ACK Setup received, more information required CONNECT Call establishment phase completed CONNECT_ACK Acknowledges CONNECT CALL_PROC Shows the call is proceeding Figure 9-8 shows the process of connecting a call. The initiator of the call (the router) sends a SETUP message, and usually provides the bearer...

Mmds

MMDS includes various services and bandwidths. Deployed in a point-to-multipoint topology, MMDS generally provides a maximum of 10 Mbps speeds per customer. MMDS signals generally carry 30 to 35 miles from the transmitter with single cell coverage of 2800 to 3800 square miles. The service comprises 33 channels, which are broken down in a way to provide different types of services. Twenty out of 33 channels are used for a component, called Instructional Television Fixed Service (ITFS), where the...

MMP Sample Implementation

In the sample implementation shown in Example 10-25, you need a solution for a company with thousands of telecommuters across the U.S. who want to connect to the corporate network through an ISDN BRI from each of their homes. You are going to use two 7200 routers (7200-isdn-a and 7200-isdn-b) to terminate the ISDN calls with no offload server. Example 10-25 MMP Sample Implementation username isdnservers password cisco username user1-isdn password user1 username user2-isdn password user2 sgbp...

Modulation and Line Coding Techniques in Hybrid Networks

To prevent confusion, hybrid terminology refers to a combination of wired and wireless technologies. These technologies are available in today's market and offer some unique features. The wireless modem works as an integrated part of the Cisco uBR7200 Series Universal Broadband routers, primarily designed for the cable core router product line. The new product is a hardware adapter and it can be plugged to the existing platform. It creates a combined solution of cable and wireless technology,...

Modulation and Line Coding Techniques in Wireless LANs

The emerging wireless LAN (WLAN) technologies offer a wide range of modulations, coding schemes, and technologies.1 WLANs hold the promise of ubiquitous access to network resources without the physical limitations of the wired network. In WLANs, (otherwise popularly known as wi-fi wireless-fidelity ) users can move freely about their offices or access network resources from conference rooms, lobbies, cafeterias, and campus buildings. WLANs use radio frequency (RF) waves instead of a cable...

Network Control Protocol Phase of PPP

When the PPP phase is up, authentication has completed successfully. Then, Network Control Protocol (NCP) negotiates Layer 3 protocols, including IP Control Protocol (IPCP). In the case of dial, IPCP negotiates IP addresses for the peer IP address, the Domain Name System (DNS) servers, and the Windows Internet Naming Service (WINS) servers. The following explanations are based on the output from the command debug ppp negotiation. Remember that the output can be long and you see these lines only...

Network Layer Protocol Phase

After the link is established and optional facilities are negotiated as needed by the LCP, PPP must send NCP packets to choose and configure one or more network-layer protocols (such as IP, Internetwork Packet Exchange IPX , or AppleTalk). After it is configured, datagrams from each network layer protocol can be sent over the link. The link remains configured for communications until explicit LCP or NCP packets close the link down. Each NCP can be opened and closed at any time. After an NCP...

Network Signaling Systems and SS7

Although totally hidden from the end user, the carrier's signaling systems are similar to a central nervous system in the human body. Signaling systems provide essential information between switches to exchange link status, connection control (signaling), and routing information. Robbed bit signaling (RBS), which was typical in the early 1970s, was replaced with out-of-band signaling, which eventually became a de facto standard for the exchange of signaling information. NOTE Out-of-band...

Pointto Multipoint Configurations

The basic Frame Relay configurations for point-to-multipoint include the configuration of both the core (hub) and the remote user's (spoke) side. Figure 16-1 shows an example of this configuration. Figure 16-1 Hub and Spoke in a Point-to-Multipoint Configuration Figure 16-1 Hub and Spoke in a Point-to-Multipoint Configuration Point-to-Multipoint Configuration of the Hub Example 16-1 shows a hub side configuration, including the FastEthernet interface and the serial interface of the core router....

Pointto Point Configuration of the Spoke

Next, you configure the spoke router to ensure consistency with the hub router. The Ethernet interface is configured with a static IP address and helper address. The Serial1 interface is configured for 128 kbps (service-module t1 timeslots 1-2) with no IP address. Subinterface Serial1.201 obtains an IP address through the IP unnumbered feature of IOS, which is explained in the advanced configuration section of this chapter. The default route statement points to the Loopback0 address of the hub...

Pointto Point Configurations

Configuring a physical interface with multiple subinterfaces or multiple virtual interfaces is another example of the virtuality used in Cisco routers. This approach is commonly used in point-to-point configurations. The benefits of this configuration are realized in partially meshed Frame Relay designs. The concept of subinterfaces was originally created to better handle issues caused by split horizon over nonbroadcast multiaccess (NBMA) networks (such as Frame Relay, Asynchronous Transfer...

Ppp authentication chap

Second, use the debug command to monitor the authentication process 3640-isdn debug ppp negotiation After the LCP is open, the expected output should look like the output shown in Example 13-17. Example 13-17 Output After the LCP Is Open Jul 30 11 12 21 PDT Se2 1 5 LCP I CONFACK ACKsent id 119 len 30 AuthProto CHAP (0X0305C22305) MagicNumber 0X484CD7F7 (0X0506484CD7F7) MRRU 1524 (0X110405F4) EndpointDisc 1 Local Jul 30 11 12 21 PDT Se2 1 5 LCP State is Open The LCP opens successfully, PPP...

PPP Termination of the Connection

Consider this example After a connection is established and there is no further demand for a network connection, the end user's router sends a request for disconnect -BR0 1 LCP O TERMREQ Open , which is referred to as a termination request. After the expected acknowledgment - I TERMACK TERMsent , you can see LCP Closed, PPP down. Example 12-42 shows the PPP termination sequence if the debug ppp negotiation command is turned on. Example 12-42 PPP Termination Sequence ISDN-6-CONNECT Interface...

PRI1544Mbps Interface

The ITU-T recommendation I.431 defines the physical layer protocol of PRI for both 1.544 and 2.048 Mbps. The electrical characteristics are defined in G.703 and G.704. The primary use of PRIs are as the trunk and trunk groups, and not as the TEs. Usually, LECs have separate service groups for BRIs and PRIs, which is based on the nature of their usage (see Figure 2-11). Figure 2-11 ITU-T I.431 Recommendation Primary Rate Interface (PRI) 1.544 Mpbs Interface Primary Rate Interface (PRI) 1.544...

Provisioning of Enterprise Remote Access Services

A key function of IT planning and design includes provisioning of remote access services for employees. Remote work is defined as work conducted away from corporate facilities. The provisioning activities described in this section support remote workers in a home office (telecommuting), as opposed to another type of virtual office (for example, a satellite or hotel office), instead of commuting to a corporate facility. Cisco's internal remote access offering has changed over the last couple of...

Pseudo Ternary Line Coding and the ST Interface

ISDN and the first layer of Frame Relay use a coding scheme called pseudo-ternary signaling, which is used by the S T interface. This technique provides DC balance and non-voltage drifting procedures for signaling by using positive and negative 0s. In pseudo-signaling, 0 is represented as a line signal of approximately 750 millivolts that alternates between positive and negative polarity, and the 1 represents the absence of voltage. As you can see from Figure 2-6, synchronization is important...

PVC Configuration Issues

Configuration issues for a PVC include problems with configuration, encapsulation, and bandwidth definitions. In the case of a 56-kbps configuration shown in Example 17-18, the configuration line is shaded and defines the type of PVC encapsulation. Example 17-18 First Step Is to Make Sure the Configuration Is Correct The frame relay encapsulation and its type (IETF) are your primary focus here encapsulation frame-relay IETF no fair-queue service-module 56k clock source line service-module 56k...

Remote Access Service Options

Building remote access networks is not only related to management, but also to some fundamental technical choices that include last mile decisions, WAN technologies, and subscribed services. These choices can be made based on capacity planning analysis, expected functionality, baselines, and simulative models. The viable service options offered by practically all service providers include dial-in, ISDN, and Frame Relay. During the last several years in the U.S. market, new technologies, such as...

Review Questions

Answers to the review questions can be found in Appendix A, Answers to Review Questions. 1 What is the command to see the status of the D channel of the IOS-based ISDN router In which mode of the IOS router can you type the command 2 If you want to see what IP address has triggered the last call in Cisco 77x router, what command should you type 3 What do you look for in the output of the IOS command Router sh isdn status to be sure if the physical layer in BRI is functional 4 What IOS command...

Routing Protocols and Frame Relay Configurations

It is well known that every routing protocol adds overhead, which in some cases, can be considerable, and reduces the overall bandwidth. Distance vector protocols, such as RIP and the Interior Gateway Routing Protocol (IGRP), use periodic updates to exchange routing information. RIP updates are exchanged every 30 seconds. RIP IPX updates are exchanged every 60 seconds, which results in the bandwidth consumption reaching 18.7 percent of the access rate of a T1. Some size estimates of the various...

Satellite Services

Direct Broadband Satellite (DBS) is a typical service for satellite communications. The system is capable of delivering downstream data at a rate of 23 Mbps by using one-way communication. All solutions are based on MPEG I Layer II audio encoding and use extensive compression methods. The upstream directions in early deployment for data were based on PSTN-wired modems, which was not a successful solution, especially combined with VPN technology. The most common speed offering is 400 kbps to 1...

Scenario 1 Authentication Time Outs Part I

A user calls in to report that his modem won't authenticate successfully. It seems to be stuck at the verifying username and password stage. First, you use the command debug ppp negotiation to debug the problem. 220 Chapter 8 Dial Troubleshooting Scenarios After debugging the problem, the output in Example 8-1 is produced. Example 8-1 Output from debug ppp negotiation for Authentication Time Outs Part I MagicNumber 0XBC6B9F91 (0X0506BC6B9F91) MagicNumber 0XBC6B9F91 (0X0506BC6B9F91) MagicNumber...

Scenario 2 Authentication Time Outs Part II

An end user calls up and states that the connection hangs during the verifying username and password stage of the connection. This time, the problem seems to be widespread. Again, the command debug ppp negotiation is used to log the connection while the client tries to dial in. After debugging, you see the LCP information in Example 8-3 repeat itself. Example 8-3 Output from debug ppp negotiation for Authentication Time Outs Part II Example 8-3 Output from debug ppp negotiation for...

Scenario 2 Dial Out Problems

The very first thing the router should be able to do is make outgoing calls and accept incoming ones. A variety of complexities are related to dial functions, but keep in mind that, regardless of first layer functions, a call requires all three layers to be set up correctly. Begin dial issue troubleshooting with the show isdn active command. This command shows the active outgoing calls, called party number, and called remote site name, as displayed in Example 13-5. Example 13-5 show isdn active...

Scenario 3 Frequent Retrains and Disconnects

To the client, frequent retrains or speedshifts are reported as a bad connection, where data flow is interrupted often. In most cases, a client does not hear the modem retrain because the speaker is turned off after the first train-up is successful. If you encounter a problem such as this, you can easily determine if the modem is retraining frequently. Just look at the output of the show modem operational-status command for the modem that this client last connected to or is currently connected...

Scenario 3 ISDN Performance Problems

Usually, a user has bandwidth expectations and uses software or a tester to measure the network speed. If the service is provisioned for 2 x 56+D, you can expect a maximum bandwidth of 112 kbps. If the service is provisioned for 2 x 64+D, you can expect a maximum of 128 kbps. The user must be educated about the overall bandwidth, which needs to be distinguished from the user's expectations, based on the size of his test files. Don't forget that, in ISDN, a significant part of the frame (1 4) is...

Scenario 4 Dirty Phone Line

A dirty phone line usually does not have the same symptoms as frequent retrains and disconnects however, they do occur. In this case, the primary issue that the client reports is that the speed of the connection is unacceptable. The same outputs as Scenario 3 Frequent Retrains and Disconnects are provided here, except that these outputs show a modem that is connected to a dirty phone line. Again, the command to use is show modem operational-status while having the client attempt a connection....

Scenario 5 Bad Modem

A bad modem is not something generally reported by your clients. A modem that is experiencing problems usually does not mark itself as defective unless there is an obvious hardware problem. Instead, you must analyze the modem with the show modem command. An output from show modem is provided in Example 8-7, where a group of six modems are obviously bad. In the AS5300 access server, modems generally become faulty in groups of six or 12, depending on the types of modems in the device. Example 8-7...

Service Assurance Agent

A sophisticated Cisco IOS-based tool is available in IOS versions 12.2 or higher. The Service Assurance Agent (SAA) feature replaces the Response Time Reporter (RTR) in earlier IOS versions and provides extra capabilities such as VoIP metrics, response time, availability of HTTP (port 80) applications, and QoS based on the precedence field of the IP packet. The feature allows you to monitor network performance between a Cisco router and a remote device, which can be another Cisco router, an IP...

Service Offering

One of the main directions in the service offering for remote access is Multiprotocol Label Switching VPN (RA to MPLS VPN). This service enables users to connect to the corporate network and handles remote access connectivity for mobile users, telecommuters, and small offices through dial, ISDN, DSL, cable, and wireless technologies (see more in Chapter 19). The increase of IP-based transport changes the focus of the transport from TDM to packet-based services. The connection-oriented...

Shannons Capacity Theorem

Error-correcting codes can alleviate some errors, but cannot alleviate all the errors introduced by the channel in a digital communications system. Shannon's Capacity Theorem states that error-free transmission is possible as long as the transmitter does not exceed the channel's capacity. N bits constitute a block of information bits that have K bits of error correction tacked on. In terms of the bit error probability (p), the probability of an error can reach 0 as N becomes larger if the...

Snapshot Routing and OSPF Demand Circuits

Another innovative cost-effective ISDN configuration technique is called snapshot routing. Before snapshot routing became available in Cisco IOS Software Release 10.2, ISDN interfaces were configured using static routes, which prevent bandwidth from being consumed by routing updates. But, they are difficult to maintain as the network grows. Snapshot routing supports dynamic routes by allowing routing updates to occur during an active period. It also reduces connection cost by suppressing...

Step 1 Implement the Manufacturers Recommendations and Determine if They Are Effective

The information provided by Microsoft about the problem and possible remedies can be found at Generally speaking, this problem is a legacy issue carried over from Windows NT. It is based on certain periodic exchanges between the workstation and the server. At the URL just given, you can find that Microsoft recognizes the significance of the problem and points to four major factors contributing in the issue Keeping the ISDN line up to ensure interoperability of Windows OS. The directory service...

Step 1Configuring the Dialer Interface

As previously mentioned, the dialer interface is a non-physical interface. It defines the call destination. As is usual for every interface configuration, you have to first configure the interface, its type, and its number. Figure 11-2 shows the network setup and configuration information. Figure 11-2 Configuring the Dialer Interface for Cisco IOS-Based ISDN Router on the Remote User's Side and on the Core Router's Side Host name - 804-isdn ISDN switch-type NI ISDN SPID1 40857647400101 5764740...

Step 2 Monitor and Sniff All Traffic and Try to Find Patterns and Characteristics of the Traffic

It can sometimes take days or months, and hundreds of pages of sniffer information, logs, and analysis. Some examples follow. When analyzing the service and processes of Windows 2000, you can establish that a service automatically runs as soon as you start the computer. It is called remote procedure call (RPC) and provides the endpoint mapper and other miscellaneous RPC services. Sniffing the traffic shows the role of RPC in keeping the ISDN line up. The...

Step 3 Use a Cisco Knowledge Base to Remedy any Identified Problems

It's time to implement the existing Cisco knowledge base. Based on the available information on Cisco.com for an ACL, you can create the following solution. For IOS routers, the ACL might include the following The 77x version would include the following pattern 00 6f pattern 00 89 pattern 00 8a pattern 00 7b set set set set set set set set set set set set tcp139 tcp445 ip filte ip filte ip filte ip filte ip filte offset 2 offset 2 r icmp out out udp111 out udp137 out udp138 out udp123 from...

Step 3Specifying the Interesting Traffic

As you already know, the dialer-list command and its definition distinguish the interesting from the non-interesting traffic. The dialer list can use ACLs and the associated security mechanisms and techniques for this purposes as well. ACLs can be referred to as standard, extended, named, and temporary. You can find a multitude of resources about ACLs at Cisco.com. Example 11-5 shows a sample ACL for the remote user's side of the connection, based on Cisco IOS ISDN 804 router, where dialer-list...

Step 4Defining the Static Route

The static route can be configured using the following command syntax 804-isdn(config) ip route prefix mask address interface distance permanent The following is an example for setting the default route 804-isdn(config) ip route 0.0.0.0 0.0.0.0 161.68.26.1 If the router needs to redistribute IP addresses in the defined range, on the hub side, they need to be redistributed with the appropriate set of commands. You can find additional discussions related to routing protocols at Cisco.com.

Step Three Verify PPP Negotiation

After the call connects, PPP negotiation starts. The following output is from debug PPP negotiation. It is split into the major steps, which are explained Mar 2 13 32 45.354 LINK-3-UPDOWN Interface Asyncl, changed state to up Mar 2 13 32 45.354 As1 PPP Treating connection as a dedicated line Mar 2 13 32 45.354 As1 PPP Phase is ESTABLISHING, Active Open NOTE The Link Dead (physical layer not ready) transition state changes to the Link Establishment phase only if an external event, such as a...

Step Two Verify Type of Incoming Connection

After step one, where the connection is a fact, perform the second step from the core router (NAS). The Cisco IOS features give you much more insight about the type of the connection than any other approach. Start the incoming type verification by using the debug modem command. The first debug reflects the configuration from a basic PPP dial-in service in Chapter 6, Dial Design and Configuration Solutions. When dialing into an external modem, one that does not have out-of-band signaling, the...

Supplementary Phone Services

Cisco supports some supplementary phone services that are available in Cisco IOS Software. Use of these services is possible, but not mandatory it depends on the way the line is provisioned. Some of the phone services might include the following, depending on the LEC settings Call holding and retrieving By default, this option is set to **number,number , but it depends on the LEC settings. Call waiting By default, it is enabled with no call-waiting. To disable it, enter Three-way call...

Switches and Tandems

From the carrier's point of view, every carrier system can be broken down into switching systems, transmission facilities and CPE. The CPE (or station equipment) includes all available equipment on the customer side. The dividing line between provider access services and the CPE is called the network point of termination (POT), network interface (NI), Demarcation Point (D-mark), or minimum point of entry (MPOE). The transmission facilities include loop and interoffice. Loop transmission...

T1E1 and Primary Rate Interfaces T1s and DS

Usage of T1s is still a growing LEC and inter-exchange carrier (IXC) service. The T1 signal can be transmitted one mile before requiring a repeater, which regenerates the signals, recovers the timing, and sends the regenerated version of the coding sequence. A T1 signal is referred to as a DSX-1 interface (digital signal crossconnection point for DS-1 signals), which is capable of sending receiving the T1 signal up to 655 feet. The maximum distance between the CSU and the last network repeater...