A

AAL (ATM adaptation layer), B-ISDN model, 319,350 AAL0, 351 AAL1, 351-353 AAL2, 353-355 AAL3 4, 355-360 AAL5, 361-363 CS, 319 SAR, 320 AAL-indicate bit, 310 ABR (available bit rate), 337-341 closed-loop flow control, 338 service category, 366 AC (access control) field DQDB slots, 380 SIP Layer 2 PDUs, 394 access classes, SMDS, 376 access signaling specifications, Frame Relay, 273 AD (Adjunct), 64 adaptation layer, 317 adaptive QAM (quadrature amplitude modulation), CAP, 416 Address Complete...

Aal1

AAL1 adapts CBR traffic, such as uncompressed voice and video, into ATM cells and is used for applications that are sensitive to cell loss, delay, and delay variation. In other words, AAL1 would be selected to transfer traffic with a constant source bit rate that must be delivered at the same rate. Because AAL1 must have timing synchronization between the source and destination, it must be implemented across a physical layer service that provides timing, such as SONET, or the timing must be...

Aal2

AAL2 provides for the bandwidth-efficient transmission of low-rate, short, and variable-length packets in delay-sensitive applications. More than one AAL2 user-information stream can be supported on a single ATM connection (multiplexing). Short-length packets can be packed into one or more ATM cells with AAL2. Used with time-sensitive rt-VBR traffic, such as compressed voice and video, AAL2 allows ATM cells to be transmitted before the payload is full to accommodate an application's timing...

Abr

The ABR service class is intended for non-real-time applications that have the capability of reducing and increasing their cell rate, based on network conditions, and that do not have strict delay requirements. ABR uses the bandwidth left over after connections using CBR and VBR service classes have registered for the bandwidth they need. Nevertheless, ABR does provide a minimum bandwidth guarantee, as the network will not establish the connection (CAC) if it cannot guarantee at least the...

ABR Service Category Definition

ABR is an ATM layer service category for which the limiting ATM layer transfer characteristics, which are provided by the network, can change subsequent to connection establishment. A flow-control mechanism is specified that supports several types of feedback to control the source rate in response to changing ATM layer transfer characteristics. This feedback is conveyed to the source through specific control cells called resource management cells (RM-cells). It is expected that an end system...

Address Subscription

Even though SMDS addresses appear as phone numbers, they behave more like MAC addresses on LANs. Recall that SMDS was derived from DQDB as a mechanism for data exchange across MANs or WANs. Also recall that SMDS had unicast and multicast routing, address screening, and source address verification as design goals. For the SMDS service to provide these features, a mechanism is needed to allow for address subscription, so that customers can build SMDS networks that are flexible, easy to...

ADSL Components

The physical ADSL infrastructure is made up of several components (see Figure 12-4). Each component plays a role in some aspect of the DSL connection. The following is a list of some of the most common components in a DSL environment DSL access multiplexer (DSLAM) DSLAM is the device that aggregates and terminates the DSL circuits. It contains multiple ADSL transmission unit central offices (COs) (ATU-Cs), and some type of network interface to uplink to the network access point (NAP). (See the...

Alarm Conditions

T1 alarm states are commonly referred to based on the colors of the lights that the original T1 equipment used to designate that particular alarm condition. Each of the three alarms discussed in this section are considered major alarms and are not usually declared for events that do not directly result in some form of failed signal state or OOF LOS condition. In fact, many manufacturers specify a set of minor alarm conditions that serve to alert administrators to the impending risk of a major...

Law Used in Europe and the rest of the world

These are known as companding algorithms because they effectively compress the PAM signal for error reduction on the transmitting end and expand the signal back to normal on the receiving end. Analog information that has been quantized by one algorithm becomes incompatible with equipment that uses the other. It is common to convert between the two standards for communication between conflicting equipment. The digital signal level 0 (DS-0) created by North American or Japanese equipment can be...

Analog Introduction

This chapter introduces terms and concepts commonly associated with analog communication. Topics covered in this chapter include a brief analog signal overview, analog signal composition, and different analog deployment methods. Although most of this book focuses on the different aspects of digital communication methods, an understanding of analog communication is essential to recognizing the fundamental differences between them and to building a strong foundation of knowledge. An analog signal...

Analog Service Deployments

Typically when you think about analog service, you imagine huge telecommunication corporations with hundreds of switches and millions of customers. This concept contains several general ideas about what the service provider or the public switched telephone network (PSTN) really is. Even if you are new to the industry, chances are you have been exposed to the infamous cloud. The cloud that encompasses anything and everything related to the service provider. These companies provide services to...

Answers to Chapter 10 Review Questions

What is the difference between UNI and NNI Answer A UNI interface connects an ATM endpoint to an ATM switch, but an NNI interface connects two ATM switches together. 2. Why are there more available VPIs in an NNI header Answer There is no GFC in the header of NNI, which leaves four more bits for the VPI field. 3. What do you call a cell that is destined for one connection but because of an error has been delivered to a different connection 4. For what technology was ATM originally designed to...

Answers to Chapter 12 Review Questions

1.What are the encoding methods used for DSL Answer Quadrature Amplitude Modulation (QAM), Carrierless Amplitude and Phase Modulation (CAP), and Discrete Multi-Tone Modulation (DMT). 2. What are the three items that characterize analog carrier signals Answer Amplitude, frequency, and phase. 3. What frequency range does voice use in POTS Answer 0-4 kHz. 4. Into how many subchannels does DMT divide the bandwidth Answer 256. Answer A bridged tap is an unterminated telephone loop. 6. What is a...

Answers to Chapter 14 Review Questions

What is the function of an add drop multiplexer Answer The ADM can crossconnect and groom traffic at the DS1 or DS3 levels without the need to completely demultiplex the signal. 2. What is one basic difference between a BLSR and a UPSR Answer A BLSR uses both fibers for bidirectional transport, and thus must reserve half of the bandwidth for failover applications. A UPSR uses one fiber for active transport, and one for protection. 3. What is the purpose of the H1 and H2 bytes in the line...

Answers to Chapter 7 Review Questions

How many T1s are found in an unchannelized T3 Answer There are no T1s in an unchannelized circuit. This is a trick question. Remember that you must have a channelized circuit to split off any of the smaller circuits. 2. True or False. T3 circuits are generally considered to be synchronous, similar to T1s. Answer False. The T3 circuits employ an asynchronous multiplexing scheme, and although T1 circuits are synchronous, their relationship to each other is asynchronous. 3. How many 0s must be...

Appendix A Answers to Review Questions 530

Answers to Chapter 1 Review Questions 530 Answers to Chapter 2 Review Questions 532 Answers to Chapter 3 Review Questions 536 Answers to Chapter 4 Review Questions 538 Answers to Chapter 5 Review Questions 541 Answers to Chapter 6 Review Questions 543 Answers to Chapter 7 Review Questions 545 Answers to Chapter 8 Review Questions 546 Answers to Chapter 9 Review Questions 548 Answers to Chapter 10 Review Questions 549 Answers to Chapter 11 Review Questions 551 Answers to Chapter 12 Review...

Associated Signaling

Associated signaling occurs when your call and signaling take the same path, but the signaling is not obtrusive to the actual bearer traffic. Figure 2-6 shows an associated signaling link between two SS7 SSPs. Several technologies use this methodology. The TDM-based E1 can use timeslot 16 (TS16) as its signaling channel for CCS signaling, such as ISDN PRI or SS7, and although the signaling is physically in-band, it's logically out-of-band because it does not directly interfere with the data...

ATM Functionality

This section details the technical foundation for ATM. In subsequent sections, you will see the five-octet header formats used with ATM. You will then see ATM as a layered model, much as any other layered approach to comprehending a protocol by classifying and ordering its core components, after which you will be presented with a discussion on topics that deal with how user information is adapted for cell production and how different traffic is classified for QoS treatment. Generally speaking,...

ATM Header Components

It is imperative to understand the functions of the fields in the ATM header to fully understand how ATM operates. Figure 10-2 shows formats of the headers for the UNI and NNI interfaces explained earlier in the ATM Functionality section. It is not uncommon to see the UNI specification used throughout a virtual circuit, but the NNI format is never seen between an endpoint and switch. The entire list of fields in both headers follows Generic flow control (GFC) (4 bits on UNI absent on NNI)...

B

B8ZS (bipolar 8-zero substitution), 133 BACP (bandwidth allocation control protocol), 243 BAP (bandwidth allocation protocol), 243 BASize field (SIP Layer 3 PDUs), 387 BE (Beginning-End) Tag fields, SIP Layer 3 PDUs, 386 Be (excess burst size), 282 bearer capability IE (Q.931 messages), 234-236 bearer channels, DSL, 427 bearer traffic, 22 Bellcore, role in SMDS development, 373-374 BERT (bit error rate test), 143-144 B-ICI (Broadband Inter-Carrier Interface), 304 billing methods, ISDN BRI,...

B3T Line Coding

International BRI circuits, commonly called ISDN-2 or ISDN Basic Access (IBA), use a different type of line coding that is called 4 Binary 3 Ternary (4B3T). This coding scheme is a bit more complicated than most and is also referred to as Modified Monitoring State Block Code 43 (MMS43). The basic premise is to take four binary digits and, using a lookup table, convert them to be used in a strict three voltage state environment of negative, zero, and positive voltage. This function creates an...

Basic E1 Controller Configuration

To access any type of controller for configuration, you have to be in global configuration mode. After you are there, select the appropriate E1 controller. Example 6-1 shows the commands required to configure an E1 controller for normal operation. Example 6-1 Configuring an E1 Controller for Normal Operation 2600-1(config) controller el 0 0 2600-1(config-controller) framing no-crc4 2600-1(config-controller) linecode hdb3 2600-1(config-controller) clock source line primary...

BRI Capabilities and Features

ISDN BRI can support up to eight devices on the S T bus, but you are limited by the number of B channels that your circuit has. Most service providers don't tell you this, but if you have two B channels with your ISDN service, you can only use two devices at any one given time. After both B channels are in use, you cannot add any other services without disconnecting something. So if your ISDN TA is using both B channels for a data call and you want to place or receive a voice call, you have to...

BRI Circuit Provisioning

Each BRI circuit is provisioned into the switch framework. The provisioning on the BRI circuits is completed through capability packages. The capability packages, also called ISDN Ordering Codes (IOCs), offer different combinations of bandwidth and service. Not only can the physical characteristics change (1B+D, 2B+D, just D), but the service types also can be modified. That means that a circuit can be provisioned for just voice, just data, or a combination of the two. These capability packages...

BRI Operation

ISDN BRI circuits are always active and use a type of heartbeat to maintain circuit status. On a standard BRI installation, if you plug an analog phone into your ISDN jack you can hear an intermittent click. That click is a good way to see if you are getting an ISDN signal. If you can hear the click, your service is turned on. That doesn't mean that there isn't a problem with the service, just that you have it. The main selling points for BRI service are that there is increased bandwidth over...

Called and Calling Party lEs

The calling and called number IEs specify the originating and destination numbers associated with the call. The numbers can be a variety of coding structures but are generally seen as ITU E.164 numbers, which mimic telephone numbers. Figure 8-19 shows the formats associated with the calling and called party IEs. Figure 8-19 Calling and Called Party IE Format Called Party Number The called party IE contains several significant fields. The type of number field describes what kind of number the...

Capability Set 1 CS1

CS-1 is the first capability set that was used with the IN architecture. It was designed to support all developing IN services and to set the framework for compatibility of future service offerings. CS-1 also takes into account that there are proprietary services that do not necessarily go through ITU-T's process for standardization. The CS-1 standard describes two different types of services Type A and Type B. Type A service is what is known as a single-ended service. In other words, if the...

Capability Set 3 CS3

CS-3 is the newest set of features to be added to the IN infrastructure. CS-3 is the next generation of IN functionality that builds upon what is already in place from CS-1 and CS-2 in the service provider network. Some of the services that are added with CS-3 are the following Feature interworking Features can now interoperate with one another, which allows for multiple simultaneous services to be deployed to the subscriber at one time or over one call. Number portability Number portability is...

Cbr

An AF term, CBR is known as the deterministic bit rate (DBR) service class in ITU-T recommendation I.371. CBR connections are requested by sources that require a static amount of bandwidth that will be unwaveringly available during the lifetime of the connection. The amount of bandwidth required is communicated through the PCR value during call setup. The network guarantees the negotiated QoS to each and every cell that conforms to the pertinent conformance tests. This commitment is applicable...

Channelized and Unchannelized T3

Asynchronous T3 circuits have two modes that they can be leased in channelized or unchannelized. The difference between the two of them is rather simple. The channelized T3 is composed of 28 T1s (672 DS0s) and has all the associated overhead and bit stuffing. Unchannelized T3 circuits are composed of a single, non-multiplexed DS3 signal. Because unchannelized T3 has no bit stuffing or overhead, all the bandwidth is available for user transmission. A T3 is clocked at 44.736 Mbps. A channelized...

ATM and BISDN 300

The Development of ATM and B-ISDN 300 Standards Bodies and the ATM Forum 301 ATM Header Components 305 GFC 306 VPI 306 VCI 306 Payload Type (PT) and OAM Cells 309 CLP 313 HEC 313 The B-ISDN Reference Model and ATM 316 Physical Layer 318 ATM Layer 319 AAL 319 QoS 320 CLR 323 maxCTD 323 Peak-to-Peak CDV 325 CER 325 SECBR 326 CMR 326 Traffic Parameters 327 Peak Cell Rate (PCR) 328 Sustained Cell Rate (SCR) 328 Maximum Burst Size (MBS) and Burst Tolerance (BT) 329 Minimum Cell Rate (MCR) 329...

Cable Modem Technology and CATV 446

The Hybrid Fiber-Coaxial (HFC) Network 449 Headends and Hubs 450 International Television Standards 451 Frequency Allocation 451 Requirements for Cable Plant Quality 453 Common Cable Plant Issues 454 DOCSIS The Cable Modem Standard 456 DOCSIS and Euro-DOCSIS 457 Modulation Types 458 Error Mitigation Through FEC 459 Error Mitigation Through Interleaving 460 Moving Picture Experts Group (MPEG) Framing 461 Throughput for DOCSIS and Euro-DOCSIS 461 DOCSIS Media Access Control (MAC) Domains 463 SID...

The Signaling System 7 Network

Signaling Introduction 22 What Is Signaling 22 SS7 Node Types 23 SSP 23 STP 27 SCP 27 Associated Signaling 29 Quasi-Associated Signaling 30 Non-Associated Signaling 31 Signaling Links and Link Sets 33 Link Categories 35 Originating, Destination, and Adjacent Point Codes 38 North American Point Code Format 39 ITU Point Code Format 40 SS7 Upper-Layer Protocols 54 DUP 54 TUP 56 ISUP 58 Intelligent Network (IN) 62 FEs 62 PEs 63 Capability Set 1 (CS-1) 65 Capability Set 2 (CS-2) 66 Expert Whiteboard...

T3 and E3 Technology 180

Evolution of the North American Digital Hierarchy 181 Synchronous or Asynchronous 182 Channelized and Unchannelized T3 182 Sorting out the Mess 184 Deployment Options 193 T3 Line Coding 194 T3 Framing Types 195 Configuration of a Channelized T3 Interface on a Cisco 10000 ESR 198 Evolution of the International Digital Hierarchy 199 Sorting out the Mess 199 Unchannelized E3 Frame Structure and Operation 202 Configuration of an E3 Interface 205

Integrated Services Digital Network 212

The ISDN Network 213 Circuit Switching 213 The Local Loop 215 Echo Cancellation 216 Network Interface Device (NID) 217 ISDN Reference Points 218 ISDN Specifications 219 ITU Q.921 220 ITU Q.931 229 SS7 and ISDN 240 Configuring a T1 and E1 PRI Connection 258 Resolving Issues with ISDN PRI 259 Q.Sig 260

Frame Relay 266

Standards Bodies and the Frame Relay Forum (FRF) 268 Frame Relay Specifications 271 Framework Specifications 271 Service Description Specifications 271 Core Aspects Specifications 272 Access Signaling Specifications 273 FRF Implementation Agreements 273 Frame Relay Functionality 275 VCs 275 Contractual Values in Frame Relay 282 Frame Discards and Recovery 284 Signaling 286 Frame Relay Configuration on Cisco Devices 292

Configuration of a Channelized T3 Interface on a Cisco 10000 ESR

This section focuses on the configuration of a channelized T3 interface for a Cisco 10000 ESR. This expansion card is normally used for channelized applications, but it can be used in an unchannelized mode, if necessary. Each CT3 card has a total of six T3 ports, each denoted by a Tx and Rx pair of 75-ohm female BNC connectors. This basic configuration gives you an idea of some of the things that you can configure on the card. For more information on the topology, refer to Figure 7-12. The T3...

Configuration of an E3 Interface

The following example is based on Cisco PA-MC-E3 Multichannel E3 port adapter, on a Cisco 7500 router. This adapter provides one channelized E3 high-speed serial interface. According to information posted on Cisco Systems' web site, the PA-MC-E3 has one channelized E3 high-speed serial interface that provides access to services at E1 (2.048 Mbps) data rates. Also from the same source the PA-MC-E3 complies with CCITT ITU G.703 physical layer standards and CCITT ITU G.751 for E3, G.742 for E2,...

Configuring a Cisco Router for DDSSW56

This section details how to configure a Cisco router with a WAN interface card (WIC)-1DSU-56K4 for DDS or SW56 operation. Just as you do with the test patterns, you must enter the proper serial interface that is associated with your WIC for DDS SW56 configuration From this interface you can begin to configure the DDS circuit. The first command to enter is whether you are using DDS or SW56. If you use switched, you also have to specify dialer in-band for the dialing method Router(config-if)...

Configuring a T1 Controller

This section gives two examples of how to configure a T1 controller on Cisco networking devices. To access the T1 controllers for configuration, you have to be in global-configuration mode and then select the appropriate T1 controller. Example 5-1 shows the simple configuration of a T1 controller for ESF framing and B8ZS line coding. Additionally, the controller is being configured to supply equalization (gain) for cables up to 133 feet. Example 5-1 Configuration of a T1 Controller router...

Configuring a T1 Hairpin

Figure 5-8 shows the use of a drop and insert function, which is also referred to as a hairpin connection. This allows you to redirect timeslots and then drop out the remaining timeslots to another device. Here, timing is important to remember because the same circuit's DS-0s travel through multiple devices. In Example 5-2, the clock source internal command at the end of the controller t1 0 1 configuration is necessary if this controller will be providing the timing to the device at the other...

Configuring Isdn Bri

The first of two types of ISDN that you will configure is ISDN BRI service. Make sure that before you go to set up your ISDN TA, you have the proper ISDN switch type, your SPIDs, and any telephone numbers that are associated with your circuit. You will be configuring a basic BRI application by using a Cisco router. Figure 8-25 shows a diagram of the network that you will configure in this example. Figure 8-25 BRI Configuration Example ISDN Switch Type NI1 Figure 8-25 BRI Configuration Example...

Configuring SMDS

Similar to other Layer-2 WAN protocols, SMDS runs over serial or HSSI interfaces. Enabling SMDS on these types of interfaces is straightforward Router(config) interface Hssi 1 0 Router(config-if) encapsulation smds Router(config-if) Z Router After enabling SMDS on an interface, you can begin configuring Layer-3 protocol families and the associated address subscription parameters required. Although the details of each of the specific protocol suites and how they work over SMDS are beyond the...

Connection Status

Connection status is only one of four extensions to the Frame Relay standards, known collectively as the LMI specification. The following list is from Cisco's Univercd web site Troubleshooting Frame Relay Connections (www.cisco.com univercd cc td doc cisintwk itg_v1 tr1918.htm) and presents these four extensions and a brief description of each. The remainder of this discussion is mainly about status messages. The term common means that a standards-based implementation of Frame Relay has this...

Contents at a Glance

Chapter 1 An Overview of Analog Communication Chapter 2 The Signaling System 7 Network Chapter 3 Analog-to-Digital Conversion Chapter 4 Digital Dataphone Service and Switched 56 Chapter 6 E1, R2, and Japanese Carrier Technology Chapter 8 Integrated Services Digital Network Chapter 11 Switched Multimegabit Data Service

Country ACountry B

A national SSP is a SSP that is located within a country which only communicates with other switches within that country. An international SSP is a SSP that is responsible for the routing of calls between different countries. There is also a hybrid SSP that functions at both national and international levels. This SSP can be considered an international gateway and has point codes associated with both networks. Each country should have at least one international gateway SSP to enable the smooth...

CRC32 and CRC32 Indication Bit Fields

The CRC-32 field was originally specified in early 802.6 drafts however, its use was later deprecated when it was decided that the 10-bit CRC carried in each DMPDU segment was sufficient for detecting errors. Today, it is required that an SMDS CPE generate a 32-bit CRC using the formula specified in 802.6 however, a receiving station need only recognize that the field is present. CRC calculations are performed by passing the bitstream through a circular shift register, which acts as a binary...

CRC4 Framing

CRC-4 framing uses a CRC to verify the integrity of the framing sequence. When you use CRC-4 framing, the frames are broken down a bit differently. CRC-4 framing splits each MF16 into two equal segments, often called submultiframes. The first submultiframe groups frames 0 through 7, and the second submultiframe groups frames 8 through 15. Within each submultiframe, the even frames (0, 2, 4, 6, and so on) place the CRC bits in the first bit position. CRC bits located in 0, 2, 4, and 6 act as a...

D

DA (Destination Address) field (SIP Layer 3 PDUs), 387 DACs (digital-to-analog converters), 10 DACS (Digital Access and Crossconnect System), 497 data-link layer functionality, Q.921 specification, 220-224 alignment process, 224-227 timers, 227-228 DB-15 connectors, 157 DBR (deterministic bit rate), 333 dBs (decibels), 7 logarithmic signal gain loss, 131 mid-span repeaters, 216 DDS (digital dataphone service). See also SW56 circuit deployment, 105 circuit testing patterns, 117-118 Cisco router...

D3 and D1D Channel Banks

While AT& T was attempting to produce a cheaper D1 channel bank, they discovered that much of the technology of the D2 channel bank also needed to be included. As a result, the D3 channel bank was suitable for long-haul connections, as was the D2. Similar to the D1, the D3 only operates on 24 channels. Unlike the D1, the D3 does so in a single stream, which precludes the need for interleaving non-consecutive channel-bytes. Nevertheless, an upgrade was made available to give D1 channel banks...

D4 Channel Banks

The SF format is also referred to as the D4 format, even though the D4 channel bank was not the first to provide SF functionality. The main impetus for the creation of the D4 channel bank was the 48-channel T1C (DS-1C) circuit that AT& T was concurrently designing. Also employing the SF format and -255 companding, the D4 channel bank standardized what we consider the channel-byte sequencing in use today, while allowing selectable backward compatibility with the previous models. The D4...

Dasa Telecommunication

Now comes the interesting part addressing. The DA and SA fields are used in the same way that a postal address is used on a letter, or that a MAC address is used on a LAN. Both the DA and SA fields are 64 bits long, with 4 bits of address type and 60 bits of address. The address type field denotes whether or not the L3_PDU is individually or group addressed. If the address type 1110, the address is a group address. If it equals 1100, it is an individual address. An L3_PDU received with any...

DB15 connector

If using twisted pair, you are using pins 1, 2, 4, and 5 of the modular plug. Pins 1 and 4 are a pair, as are pins 2 and 5. Similar to T1, to make a cross over you cross pins 1 and 4 and cross pins 2 and 5. If using balanced coax cable, you most likely have two BNC connectors one for Tx and one for Rx. DB-15 connectors are more common with T1 deployments, but you can use them with E1 circuits. A DB-15 connector has 15 pins and is similar to a monitor cable connector. DB-15s are only found...

Deployment Options

Depending on what equipment you use, several different interfaces are commonly found with T3 and E3 circuits. The most likely interface that you are to come across is 75-ohm coaxial cable. The deployment of coaxial cable for T3 generally comes in the form of two separate cables one for transmit (Tx) and one for receive (Rx). T3 and E3 circuits are high-bandwidth circuits that standard twisted copper pair cannot normally support. For example, most deployments of T3 E3 circuits today actually...

Detection of Data Errors

The frame-check sequence (FCS) field is an error detection mechanism that determines if the data in the frame in question has been compromised during its most recent leg of transmission (such as from switch to switch). The FCS is a computed value that is inserted into this position in the frame. The receiving device computes a value by using the same algorithm, the result of which should be identical to the inserted value. If there is a discrepancy, it is assumed that the frame was damaged...

Digitalto Analog Converters

DACs convert between digital and analog signals. Two common implementations of this type of equipment are modulator-demodulators (modems) and the conversion that is applied at the CO for each analog circuit. A modem converts the unipolar digital signals that are transmitted by your computer into an analog signal stream. A unipolar signal is a signal that has only a single voltage polarity. So, instead of having both positive and negative sides to a signal stream, only a positive or negative...

Docsis The Cable Modem Standard

A bi-directional cable modem technology must take into account existing CATV networks and CATV network quality and requirements for supporting IP networks. Although several proprietary cable modem network technologies exist, the internationally accepted (and by far the most popular) standard for cable IP networking is DOCSIS. Created by the MCNS to drive superior cable IP technology and to encourage competition between equipment vendors, DOCSIS and the analogous European standard Euro-DOCSIS...

Dxi

Recall from earlier in the chapter that most CPE vendors were not interested in developing the full SIP stack. This was partly because the vendors were concerned about forcing their customers to upgrade to the new hardware that would be required to implement the full SIP, which could result in stranded investment. On the other hand, the CSU DSU vendors saw this vendor disinterest as an opportunity to expand their product lines. The fact that these opposing sentiments created an opportunity for...

E12 Multiplexing

E12 multiplexing is the process of taking four international DS1 circuits (E1) and multiplexing them into a single international DS2 circuit (E2) (Figure 7-13 shows the process). This process is identical to the one described for M12. The multiplexing method is cyclic bit-interleaving with positive justification (ITU G.742), which means that the payload is built by taking one bit from the first E1, one bit from the second E1, and so on. The positive justification is what was described earlier...

Encoding

The final phase of the conversion process is one that this chapter has been alluding to for a while. This is what it's all about. After this phase, you have a stream of binary digits that is the digital traffic for transmission across the digital circuit. First, you need to understand that the term encoding, as it is used here, does not mean the same thing as encoding when it applies to transforming a bit stream into pulses of electricity. That type of encoding is discussed in chapters relating...

Error Mitigation Through FEC

Noise and interference levels fluctuate on cable networks and as a result even the most noise tolerant modulation scheme that is deployed on a cable plant with standard specifications will experience losses. FEC is one mechanism by which errors in transmission can be repaired upon receipt by the receiving device. The DOCSIS specifications include ReedSolomon (RS) FEC as a mechanism for loss mitigation. FEC works by placing binary information into a two-dimensional array and then determining...

Ethernet Aggregation Architectures

Several MSOs use an aggregated Ethernet approach to connect multiple CMTS devices, typically to a high performance switch. This is accomplished usually by either a set of multiple 100BT load sharing Fast Ethernet connections or through one or more Gigabit Ethernet connections. This simple approach to aggregating CMTSs, a switched Layer 2 approach, is popular because it is easy to understand and configure. Often the Ethernet aggregation approach is inexpensive, too. However, Ethernet media...

Evolution of Digital Communication

The idea was that analog information could be represented as distinct pulses of information, like Morse code, where only a few simple combinations are combined to represent a larger, more complex set of symbols. After conversion, analog information is stored and retrieved with more accuracy and quality than by directly recording analog information. The idea arose early on to use a bi-state mechanism as the combining element for digital communication. This was the dawn of what is now known as...

Evolution of the International Digital Hierarchy

The specifications from the International Telecommunication Union (ITU) on digital hierarchy match the NADH only in theory and the first digital signal level. From there, they deviate in data rates, management capabilities, line coding, framing, and just about everything else. The first level of the ITU digital hierarchy is the E1 circuit. Running at 2.048 Mbps, this circuit contains 32 DS0s. For more information on E1, refer to Chapter 6, E1, R2, and Japanese Carrier Technology. The second...

Expert Whiteboard LNP Operation in North America

The Telecommunications Act of 1996, which became law on February 8, 1996, was designed in large part to open local exchange markets to competition by removing existing statutory, regulatory, and operational barriers that have thwarted the ability of new entrants to provide competitive, local telecommunications services in the U.S. One of the most significant steps that Congress took to effectuate this goal was to require all local exchange carriers (LECs), both incumbents and new entrants, to...

F

FCC First Report & Order, 69 FCS (frame-check sequence) field DXI, 404 Frame Relay packets, 285 FDM (frequency-division multiplexing), 127, 450 FEBEs (far-end block errors), 161, FEC (forward error correction), 422-423, 459-460 interleaving, 423-424 FEs (functional entities), 62 FEXT (far-end crosstalk), 9, 435 F-GCRA (Frame-GCRA), 349 fiber-node combining, 482-484 fiber-optic cabling, 501, 504, 522 fields of ATM headers, 305 CLP, 313 GFC, 306 HEC, 313, 316 PT, 309-313 VCI, 306-308 VPI, 306...

Frame Discards and Recovery

There is a simple rule that makes Frame Relay so elegant in its simplicity if there is a problem, discard the data. The two main causes for data being discarded are as follows Figure 9-7 shows the Frame Relay header in the context of an entire frame. The flag field at the beginning and end of the frame is the high-level data link control (HDLC) flag (0x7E). This is 01111110 in binary. As in the case of all protocols that rely on the HDLC flag to herald the beginning and end of a frame, Frame...

Frame Relay

Frame Relay is a packet-switching service that is widely used throughout the world today. Multiple standards bodies have written specifications for Frame Relay many vendors support each of these specifications in their hardware and software. This chapter covers the history of Frame Relay and the intricacies of its design and usage. Frame Relay, unlike T1, digital dataphone service (DDS), and plain old telephone service (POTS), is a packet-switching service and not a physical circuit. Frame...

Framing Modes

Framing modes are also referred to as framing structure and framing overhead. Overhead refers to signaling and synchronization between two modems. There are two main standards-based framing modes full overhead and reduced overhead. Each of these two main modes has two subsets. The resulting four modes are usually referred to as modes 0, 1, 2, and 3. In basic terms, the four modes refer to how data is allocated to an Embedded Operations Channel (EOC), to an ADSL Overhead Control (AOC) channel,...

Frequency

Frequency is the measurement of how many cycles per second the signal waveform goes through. Typically measured in hertz (Hz) or kilohertz (kHz), this denotes how frequently the signal repeats itself. The human voice normally operates between 50 Hz and 5000 Hz, with the majority of the activity between 300 Hz and 3400 Hz (3.1 kHz). This means that most voice conversations are between 300 cycles per second and 3400 cycles per second. So, if you have ever heard someone talk about a 3.1 kHz call,...

FRF Implementation Agreements

The IAs of the FRF are listed here for completeness. The full text of these documents is available free-of-charge from various locations on the World Wide Web, including the FRF's own web site at www.frforum.com. IAs with more than one number appearing in the document number have been revised from their original draft. FRF.1.2, UNI Implementation Agreement, April 2000 FRF.2.l, Frame Relay Network-to-Network Interface (NNI) Implementation Agreement, July 1995 FRF.3.2, Multiprotocol Encapsulation...

G832 Framing

Basic E3 framing is specified by the ITU recommendation of G.832. This framing type is most commonly found in network deployments that do not require ATM interworking. The 4296-bit frames are broken down into 8-bit groups called octets, which are then separated between overhead and payload types. Of the 537 total octets, there are seven overhead octets and 530 payload octets, as shown in Figure 7-16. Frame size is 4296 bits, and repeats at 8000 times per second. The frame alignment (FA) bytes...

Gfr

The GFR service class is the last of those discussed in this chapter to support non-real-time applications, which are applications that might require a minimum rate guarantee and that can benefit from accessing leftover bandwidth in the network. It does not require adherence to a flow control protocol. Similar to EPD functions for UBR (in fact, GFR is sometimes referred to as UBR+), the GFR service guarantee is based on AAL5 PDUs (frames that can be delineated at the ATM layer) and, under...

Hardware Considerations

When deployed to your premises, they are normally installed in RJ-45 jacks using pins 4 and 5. There is no polarity with the center two pins, you just need to make sure that you have them installed properly at the jack. BRI service doesn't even have to be deployed with RJ-45 interfaces, but most service providers prefer this so as to differentiate that jack from standard analog service. If you were to plug an ISDN TA into an analog line, there is a pretty good chance that you would short out...

Header Extension HE and HE Length Fields

SMDS uses the HE and HE length fields to allow for carrier selection and to identify the SIP version number. In SMDS, the HE field is always 12 bytes, or three 32-bit words long. Thus, the HE length field is always set to 011b. If a PDU is received with any other value, the SS discards it. The format of the HE field is shown in Figure 11-15. Figure 11-15 Header Extension Field Format Figure 11-15 Header Extension Field Format 1 Byte 1 Byte Variable 1 Byte 1 Byte Variable Variable 1 Byte 1 Byte...

History of DSL

In the 1980s, Bellcore developed high-data-rate DSL (HDSL) technology. HDSL was developed to enhance the capabilities of T1 technology by replacing alternate mark inversion (AMI) encoding with 2 binary 1 quaternary (2B1Q) encoding. HDSL reduces the need for repeaters, and it causes less electromagnetic interference (EMI) in cable bundles. In the 1990s, technology vendors began to see an explosion in the use of the Internet. This Internet revolution increased the demand for pure data, as opposed...

Improvements Over Analog Communication

Recall the earlier analogy of being tasked with recognizing shades of gray, as opposed to just black and white. The point was made that dust could settle on the object, making it more difficult to correctly identify exactly which shade of gray you were looking at, especially if the shades were infinitesimally close to begin with. Quality assurance in this task would be tricky, at best. However, if you had to identify the objects only as black or white, it would take quite a bit of dust to...

Intelligent Network IN

The purpose of the IN infrastructure is to provide a suite of services to subscribers that are inherently not provided by the SS7 network. This list also includes services that are provided to the network operator. A distributed service architecture allows service providers to support a wider range of services and to deploy them to a larger subscriber base. Without this architecture, subscribers are limited to the services that their SSP was able to provide. These services can be erratic...

Introduction to DDS

This chapter provides an overview of the DDS, how it is deployed, and how it operates. Although it is fast becoming antiquated, it remains an integral part of understanding how digital services are deployed. This chapter also discusses the similarities between DDS and SW56 and details about the differences between these closely related service offerings. DDS is referred to as a digital signal customer service (DS-CS) and is deployed on a four-wire metallic interface. DDS was originally...

Introduction to SMDS

SMDS is a service more than a technology. In fact, multiple technologies are required to implement an SMDS network. An overview of the SMDS architecture is shown in Figure 11-1. Figure 11-1 shows that there are essentially two major elements to an SMDS network-CPE and carrier equipment (CE). Between the CPE and the carrier network is the Subscriber Network Interface (SNI), which is the boundary between the customer and the provider. The CPE is equipment that accesses the SMDS network in most...

Inverse ARP

Although this book is not an IP-centric work, nor does it dwell on any particular Layer 3 protocol unless it is part of the protocol stack featured by a particular chapter, we would be remiss if we did not discuss Frame Relay's interesting method of tying in with the Layer 3 address (often referred to in literature as the protocol address). Although in Ethernet environments, for example, an ARP cache table is constructed to map already-known Layer 3 addresses to learned MAC addresses for local...

ISDN Introduction

In the days of old, the service providers infrastructure was deployed as a series of analog services. Analog services are acceptable in short distances, but they simply can't provide the quality of service (QoS) and bandwidth over the long haul. Remember that when analog circuits become too attenuated, the signal is merely amplified. This amplification also increases the noise content. The analog infrastructure was never designed to provide voice, video, and data integration for customers. In...

Itu Q931

ISDN's Q.931 is the Layer 3 specification that is responsible for call control and management. These functions include call set up, tear down, and request for services from Layer 2. The purpose of this section is not to go over all of the possible state primitives, but to give you a good understanding of how Q.931 manages ISDN call control. Q.931 uses a message-based system to control the ingress and egress call functions of an ISDN circuit. Using the D channel as a vehicle for this transport,...

Jdh

Japan uses a digital hierarchy that is similar to both the NADH and ITU Digital Hierarchies. The Telecommunication Technology Commission has specified its own set of standards for use within Japan. Based off of the ITU standards, the Japanese standards preface the ITU specifications with a JT. So ITU G.701 becomes JT-G701. Within these standards, circuit speeds are specified for a 1.544-Mbps link. JDH is based on 64-kbps DS0s, as with every PCM TDM network. However, subrates at 64 kbps are...

Link Categories

In North America, links are categorized based on what SS7 node types they connect. These categorizations are not used throughout most of the world, but they are helpful in explaining what types of links can be provided. Figure 2-11 shows A-, B-, and C-links, and Figure 212 shows D-, E-, and F-links. The following are link types that are commonly associated with ANSI signaling links F-link Fully-associated link A-links provide access into a portion of the SS7 network. They connect SSPs to STPs,...

Location Portability

Location portability is basically geographic portability when a subscriber moves from one LEC's territory to another LEC's territory. With location portability comes the possibility of loss of NPA-NXX geographic recognition. Today an NPA-NXX distinguishes where a call originates. For example, area code 303 is for Denver, Colorado. If location portability was being used and a subscriber moved from Denver, Colorado to Atlanta, Georgia, when the subscriber made calls the receiving customer might...

Moving Picture Experts Group MPEG Framing

In 1994, an international body of telecommunications companies, equipment manufacturers, and other interested parties agreed upon the (MPEG) standard as the preferred method to compress and distribute digital television and other video signals. DOCSIS and Euro-DOCSIS specify the transmission of IP packets over the cable plant by using this standard MPEG framing MPEG frames 188 bytes in size with a 4-byte header. MPEG framing was chosen for the specification in part because of the prevalence of...

Multiple Access Speeds

Customers looking to access an SMDS network have many choices when selecting appropriate access speeds. As mentioned earlier, the original focus was on transparent LAN-interconnection, and the RBOCs could best realize this goal using DS3 facilities. However, DS3 speeds are far too high for connecting two 4-Mbps Token Ring LANs. To make the service both economically attractive for the customer and scalable for the provider, five access-classes were defined. Each access-class maps directly to the...

Network Congestion

Network congestion is a common occurrence within well-used networks. The only true way to avoid congestion is to over-engineer your network, which results in more expense than necessary for the preponderance of operating conditions. Different network implementations might employ equally distinct methods of dealing with congestion. For example, in the case of Ethernet, network congestion results in the expected collision of frames, thus destroying the actual information that is being transmitted...

North American Point Code Format

The ANSI point code format is formulated from three 8-bit octets for a total of 24 bits. Each octet has a range of numbers from 0 to 255, and it is broken down into three subsections (one subsection per octet) The first of these sections is the network. The network octet identifies the actual provider that is using the point code. This differentiates between Lucent, WorldCom, and Sprint. The second octet identifies the cluster within the network. Clusters are logical groupings of network nodes,...

Optical Hardware

This section discusses some of the common equipment associated with optical networks. Equipment found on optical networks is typically separated into three different types path terminating, line terminating, and section terminating. Refer to Table 14-1 for a list of the equipment to be discussed. Table 14-1 Optical Network Equipment Types Table 14-1 Optical Network Equipment Types Digital Access and Crossconnect System Path terminating equipment consists of end-user devices that directly...

Other GCRA Issues

Multiple, but generally no more than two, instances of the GCRA with independent I and L parameters can be applied to the same flow (similar CLP settings) or to multiple flows (CLP 0 and CLP 0+1) of the same connection. Technically, a cell can be considered to be conforming only if it conforms to all instances of the GCRA that apply to cells with a matching CLP state. In other words, if one instance of the GCRA tests the CLP 0 flow and another instance tests the CLP 0+1 flow, a cell with CLP 0...

Other Modulation Schemes

Besides the popular versions of ADPCM (G.721 is definitely not the only one), several other encoding methods are in use today for various applications. One of these is Delta Modulation (DM). DM works on the basis that the relative change in the direction of the amplitude from one sample to the next is adequate information to successfully reconstruct the analog waveform at the receiving end. As a result, DM requires only a single bit to represent this directional information. The next sample's...

Path Protection Switched

A dual-fed unidirectional path switched ring (UPSR), or path protection switching can also be used. The UPSR uses a path layer indicator to facilitate the failover process. Two fibers typically run in the ring, and traffic flows on each in the opposite direction (dual-fed). The basic operation premise of this topology is that traffic flows in opposite directions around the network on the working and protection fibers at the same time. The same information reaches RTP, but from different nodes....

Payload CRC Field

The CRC mechanism detects single or multiple bit errors during transmission. Because the L3_PDU 32-bit CRC is not required, the 10-bit payload CRC is the only mechanism available in SMDS to accomplish this. The payload CRC uses a 10-bit generator polynomial (x10 + x9 + x5 + x4 + x1 + 1) as the divisor and the entire L2_PDU as the dividend. The remainder is placed in the payload CRC field. SIP Level 1 is broken into two major functions physical medium dependent (PMD) functions and physical layer...

Payload Type PT and OAM Cells

The PT field is comprised of three bits that act as individual signals. This field can also be referred to as the PT identifier (PTI). Table 10-2 lists the basic aggregate meaning of the eight possible three-bit values. User cell, no explicit forward congestion information (EFCI), AAL-indicate false User cell, no EFCI, AAL-indicate true User cell, EFCI, AAL-indicate false User cell, EFCI, AAL-indicate true RM-cell Available bit rate (ABR) congestion control In English, Table 10-2 says that if...

Point Codes

Now that you are familiar with links and link sets, you are ready to begin looking at how messages are routed within the SS7 network. SS7 uses a set of addressing information and call details to route calls from one network node to another. The main addressing scheme is a logical address that identifies each SS7 node, including SSPs, STPs, and SCPs. The logical addresses are called point codes, and they operate at Layer 3 of the SS7 protocol stack. Layer 3 in the SS7 protocol model is known as...

Power Cutback and Power Boost

Power can be reduced during the train-up sequence when DSL modems calculate and exchange information regarding attenuation. This is part of Cisco's RADSL train-up process. And although you can increase power above a nominal level, this is not commonly done because of the interference imposed on other services in the same cable. This is often referred to as crosstalk between cable pairs, and results in a degraded SNR. The ability to change the default transmit power level becomes important when...

Power Levels in DSL Services

DSL power levels are much higher than those levels used in voice, fax, or analog data services. This is simply because of the much greater attenuation of signals at DSL frequencies that are caused by the electrical characteristics of telephone lines. Because the attenuation of a phone line is much greater at ADSL frequencies than at voice frequencies, the phone line is much more attenuative to DSL than to voice, fax, or analog modems. To recover a usable signal at the end of 18 kft of cable,...

Q921 Alignment

During the first message transfer in the Q.921 alignment process, a UI frame with a TEI request is sent from the user device to the network using the T202 timer. Remember that the broadcast TEI for this function is 127. Figure 8-9 shows the TEI assignment process between the subscriber equipment and the ISDN switch. Upon receipt of the UI frame, the network responds with the user device's TEI assignment. The operation of the UI frame is the same as defined for U frames in Table 8-2. After the...