IP DSLAM - access equipment for Triple Play. ADSL equipment for users and operators Digital subscriber line access multiplexer dslam

DSLAM (Digital Subscriber Line Access Multiplexer) - xDSL digital subscriber line access multiplexer (modem). On the network side, it has WAN ports, and on the client side, it has xDSL semi-sets (modems) to which the subscriber line is connected. At the other end of the subscriber line, the client has an xDSL subscriber half-set (modem) or IAD ( Integrated Access Device- integrated access device). The latter is used in cases where simultaneous transmission of data and voice in digital form is realized over an xDSL line, that is, VoDSL (Voice over DSL).

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Literature

Stepan Ilyin aka Step// Hacker. - 2005. - Issue. #075 .

Excerpt describing DSLAM

And, probably even more indignant that, having said this, he told an obvious lie and that Balashev stood silently in front of him in the same pose submissive to his fate, he turned sharply back, walked up to Balashev’s very face and, making energetic and quick gestures with his white hands, he almost shouted:
“Know that if you shake Prussia against me, know that I will erase it from the map of Europe,” he said with a pale face distorted with anger, striking the other with an energetic gesture of one small hand. - Yes, I will throw you beyond the Dvina, beyond the Dnieper and will restore against you that barrier that Europe was criminal and blind in allowing to be destroyed. Yes, that’s what will happen to you, that’s what you won by moving away from me,” he said and silently walked around the room several times, trembling his thick shoulders. He put a snuff box in his vest pocket, took it out again, put it to his nose several times and stopped in front of Balashev. He paused, looked mockingly straight into Balashev’s eyes and said in a quiet voice: “Et cependant quel beau regne aurait pu avoir votre maitre!”

On the network side, it has WAN ports, and on the client side, it has xDSL semi-sets (modems) to which the subscriber line is connected. At the other end of the subscriber line, the client has an xDSL subscriber half-set (modem) or IAD ( Integrated Access Device- integral access device). The latter is used in cases where simultaneous transmission of data and voice in digital form is realized over an xDSL line, that is, VoDSL (Voice over DSL).

Literature

Stepan Ilyin aka Step FAQ (Q:What is DSLAM? Why can’t I connect to ADSL if it is not installed on my PBX?) // Hacker. - 2005. - V. #075.

Links

Wikimedia Foundation. 2010.

See what "DSLAM" is in other dictionaries:

DSLAM- Saltar a navegación, búsqueda DSLAM son las siglas de Digital Subscriber Line Access Multiplexer (Multiplexor digital de acceso a la línea digital de abonado). Siemens DSLAM SURPASS hiX 5625 Es un multiplexor localizado en la central telefónica… … Wikipedia Español

DSLAM- son las siglas de Digital Subscriber Line Access Multiplexer (Multiplexor de acceso a la línea de abonado digital). Es un multiplexor localizado en la central telefónica que proporciona a los abonados acceso a los servicios DSL sobre cable de par … Enciclopedia Universal

DSLAM- Ein Digital Subscriber Line Access Multiplexer (DSLAM) (deutsch: DSL Vermittlungsstelle) ist ein Teil der für den Betrieb von DSL benötigten Infrastruktur. DSLAMs stehen an einem Ort, an dem Teilnehmeranschlussleitungen zusammenlaufen. Meist... ...Deutsch Wikipedia

DSLAM

Dslam- Digital subscriber line access multiplexer Siemens DSLAM SURPASS hiX 5625 DSLAM (prononcer /deslam/), est le sigle de la anglais “Digital Subscriber Line Access Multiplexer”, soit en français, “Multiplexeur d Accès à la Ligne d… … Wikipédia en Français

DSLAM- Digital Subscriber Line Access Multiplexer (Computing » Telecom) Digital Subscriber Line Access Multiplexer (Computing » Software) Digital Subscriber Line Access Multiplexer (Computing » Security) Digital Subscriber Line Access Multiplexer… … Abbreviations dictionary

A.V. Simonina, equipment manager at IMAG
D. Yu. Guseltsov, development manager of IMAG company

Modern DSL concentrators are a new generation of equipment that allows you to connect subscribers to a data network using the latest technologies and has network interfaces such as Ethernet, ATM, SDH. Hubs are installed in places where users are concentrated on the telecom operator's side and allow subscribers to gain high-speed access to data networks while maintaining the existing infrastructure and access to the PSTN.

Today, the number of manufacturers and suppliers of devices of this kind is several hundred, and choosing the right equipment is not so easy. The requirements that consumers place on different classes of DSL equipment vary significantly. What matters: reliability, size, port density, power consumption. For example, the reliability of carrier-grade hubs should be significantly higher than that of hubs for campus applications, where short-term disruptions in traffic transmission are not so critical; the same applies to the required set of functions. The use of copper wiring and a simple hub installation procedure make the initial investment to create an access network minimal. Thus, the use of concentrators allows subscribers to receive additional types of services, and operators - additional types of income.

Types and scope of concentrators

Based on the objectives and requirements of subscribers, as well as taking into account the features of the infrastructure, the operator selects optimal technology access. The type of hub is determined depending on the DSL technology used, for example, ADSL, SHDSL, VDSL, etc. The main criteria for selection are: the number and density of subscribers, the quality of existing wiring, the length of the subscriber line and the required bandwidth.

ADSL

The choice of ADSL technology is justified in cases where it is necessary to achieve high speeds over long distances (up to 5.5 km) from the telephone exchange to the subscriber and when it is necessary to maintain telephone communication. ADSL technology provides downstream data rates ranging from 1.5 Mbit/s to 8 Mbit/s and upstream data rates from 640 kbit/s to 1.5 Mbit/s. ADSL allows you to transfer data at a speed of 1.54 Mbit/s over a distance of up to 5.5 km over one twisted pair of wires. Transfer speeds of 6-8 Mbit/s can be achieved when transmitting data over a distance of up to 3.5 km over wires with a diameter of 0.5 mm.

Typically ADSL technology is used in the residential sector. Splitters are installed to simultaneously transmit voice traffic and data over one telephone line. They can be either built-in or external. In addition to the “classic” ADSL technology (includes a “light” version - ADSL Lite), modern concentrators support improved modifications of ADSL technology - ADSL2, ADSL2+.

They were developed to meet the increased demands of providers and end users on hubs. ADSL2 increased the speed and range of data transmission, implemented the adaptive speed change function, thanks to these changes it became possible to support a large number of new applications and additional services. ADSL2+ doubled the speed of information reception at distances of up to 1.5 km.

G.SHDSL

For the corporate sector, the most promising technology is G. SHDSL. G. SHDSL hubs allow transmission over a distance of more than 6 km at speeds of up to 2.3 Mbit/s over one copper pair in both directions. This technology is used when it is necessary to connect remote subscribers or combine several geographically dispersed offices into a single local network. The use of this technology is advisable when servicing campuses. Some DSLAMs support G. SHDSL.bis technology with a transmission speed of 5.7 Mbit/s over one copper pair with the ability to combine 4 pairs into one channel with a total speed of up to 22.8 Mbit/s.

VDSL

xDSL with support for the VDSL standard is used when building collective subscriber access systems (for example, in business centers, cottage villages, college campuses, hotel complexes, etc.) and when deploying corporate communication systems. VDSL provides the highest transmission speed of all modern DSL technologies.

Unlike other DSL technologies, VDSL can operate in two modes - symmetrical and asymmetrical. It provides data transfer speeds to the subscriber ranging from 13 to 52 Mbit/s, and data transfer speeds from the subscriber up to 2.3 Mbit/s, over one twisted pair of telephone wires. In symmetric mode, speeds up to 26 Mbps are supported. Ethernet over VDSL (EoVDSL) technology extends the Ethernet network up to 1.5 km. It is advisable to use VDSL concentrators when conducting video conferencing, providing video-on-demand services, distance learning, etc.

"Proprietary" technologies

In addition to those listed above, there are hubs that support so-called “proprietary” technologies. They allow you to expand the capabilities of standardized technologies or be additions to them. “Proprietary” technologies are the manufacturer’s own developments and are used, for example, to adapt the transmission speed over a communication channel to the speed of the terminal equipment. They can also be used when the subscriber wiring is in poor condition or when the subscriber is more than 5.5 km away. Often “proprietary” technologies are combinations of already known ones. If the technology is successfully applied on subscriber access networks, it undergoes a certification process, after which it can be used in equipment from other manufacturers.

Port density and physical dimensions of hubs

One of the main parameters when choosing a DSLAM broadband subscriber access concentrator is the number of supported DSL ports on the device. Based on their design, three main types of concentrators can be distinguished.
The most compact of them are a solution on one board and are installed in a standard 10-pair KRONE LSA-PLUS plinth. The next in size are mini-DSLAM, so-called “pizza-box” devices with a height of 1 U. The most powerful devices are modular DSLAM with a wide range of network interfaces and installation in a standard 19" rack and various port densities. An ultra-compact DSL hub is solution with a fixed configuration of 8-10 ports, and mini-DSLAM can be either fixed or modular with a capacity of 8 to 48 ports per device. Modular hubs are full-featured devices that can interface with different types transport networks (ATM, Ethernet, SDH) and contain a large number of user DSL ports (ADSL, SHDSL, VDSL).

An important criterion for choosing a particular hub is cascading devices, that is, increasing the total number of DSL ports with unified management of the entire stack of devices, which is especially important for compact hubs with low port density. On initial stage When building an access network, the operator can either expand the network gradually, using mini-hubs, or make large investments in high-capacity systems. In the second case, the payback time of the project will increase.

Reliability and security of concentrators

In order for DSLAM broadband subscriber access equipment to meet the requirements of telecom operators, that is, to be carrier-grade equipment, it is necessary to comply with industry standards in the field of security and operation. In addition, the device housing must be protected from adverse temperature influences, this must be confirmed by the appropriate safety certificate.

Another important factor for ensuring equipment reliability is component redundancy. The device architecture must provide for the possibility of redundancy of the internal switching matrix, central processor, power supplies, and transport network interfaces. For example, to prevent denial of service to subscriber traffic, the system's network interfaces can be redundantly configured with a 1+1 redundancy scheme.

Types of interfaces to the transport network

The choice of equipment for a subscriber access network largely depends on what technology is used on the backbone network: ATM, IP/Ethernet, SDH. The hub interfaces are selected accordingly.

ATM

DSL broadband subscriber access equipment was developed when data networks were built on ATM technology. This may explain the fact that until recently the main DSLAM interface to the transport network was the ATM interface (E1, E1-IMA, E3, STM-1-IMA). It can be said that the focus on ATM technology has become a serious obstacle for operators and service providers, as it requires high costs to deploy and operate expensive ATM-based systems. However, ATM technology has its undeniable advantages; it allows efficient use of channel bandwidth and ensures the required level of quality of service (QoS) for subscribers.

Ethernet

Modern trends in the transition to the IP protocol are forcing manufacturers of DSL broadband access equipment to use more promising Ethernet technologies in their solutions. First of all, this affects the cost of the solution; its price is significantly reduced.

Modern Metro Ethernet transport networks have reached speeds of 10 Gbit/s and continue to actively develop. To access such high-performance networks, DSLAM hubs are equipped with Fast or Gigabit Ethernet interfaces, depending on the device port density. However, when using the Ethernet transport interface in broadband access equipment, the problem arises of ensuring the quality of service for subscribers. To achieve this, DSLAM access equipment uses several mechanisms. First of all, it is the ability to create virtual private VLANs in accordance with the IEEE802.1Q standard. In addition, to ensure quality parameters in DSLAM equipment Ethernet traffic prioritization function must be implemented in accordance with IEEE802.1p.

SDH

One of the most common technologies on which a modern primary network can be built is SDH technology. The subscriber access concentrator is connected to the SDH transport network using the STM-1 aggregate interface. To the telephone network common use The DSL concentrator is connected using the V5.2 protocol stack, each of which allows servicing up to 16 E1 streams. SDH technology provides the ability to manage a transport network of any branch from one center.

Equipment on the subscriber side

Simultaneously with the choice of a hub, a serious question arises: which manufacturer's subscriber device should I choose? Typically, users are provided with a list of manufacturers whose equipment is compatible with the hub they are using. In most cases, providers themselves offer their subscribers one or another brand of CPE. Some manufacturers produce integrated solutions to provide subscribers not only with high-speed access to data networks, but also with additional telephone lines. In this case, an integrated access device (IAD) is installed at the subscriber's premises. Today, manufacturers are trying to produce subscriber devices that meet the most stringent requirements for compatibility with all standard DSLAMs.

Standard and custom network management tools

No matter how functional the broadband subscriber access equipment may be, without an appropriate management system it is just a useless piece of hardware. That's why Special attention When choosing a DSLAM access concentrator, you need to pay attention to management features.

In addition to standard and widely used terminal local management tools, such as the Command Line Interface (CLI), Telnet and HTTP protocols, the equipment must support a full-featured graphical element management system based on the SNMP protocol. It is important that this control system can monitor the state of communication channels, errors that occur in the access network, and allow quick setup and monitoring of parameters of both the system as a whole and the profiles of individual subscribers.

One of the main requirements for a specialized control system is the use of standard protocols (CORBA, SNMP) and open APIs. This allows you to pair this system with existing OSS systems on the operator's network, such as HP OpenView.

Another requirement for a control system is modularity and scalability. The control system must consist of separate functionally complete modules that interact with each other using standardized protocols and interfaces, and be able to increase functionality by adding additional modules. The system must also contain built-in mechanisms that ensure rapid recovery from failures, backup user settings and security of the entire system.

IEEE802.3ah standard

Separate requirements are imposed on devices that implement control mechanisms in accordance with the new IEEE802.3ah standard, better known as EFM, or “Ethernet in the first mile.” It is used for VDSL and SHDSL technologies; provides management remote devices(subscriber terminals) using a dedicated control channel. At the same time, expanded capabilities remote control devices in accordance with IEEE802.3ah allow operators to promptly respond and eliminate faults that arise in the network, ensuring high quality of services provided to subscribers.

additional characteristics

In addition to the main functional load of transmitting data traffic, the hub supports a large number of additional functions and services. To provide video on demand (VoD and NVoD) services, the DSLAM must support the IGMP-Snooping and IGMP-Proxy multicast delivery protocol stack. Thanks to them, information can be transmitted from the hub to a group of users. This protocol allows you to save network bandwidth and provide high quality of service for applications that are sensitive to time delays.

IEEE 802.1p and 802.1q standards are used to route data between multiple virtual local area networks (VLANs). VLAN allows you to separate traffic, use channel bandwidth more efficiently, guarantee reliable joint operation of network equipment from different manufacturers, and ensure a high degree of equipment security. When using the IEEE 802.1p standard, a priority level from 0 to 7 is assigned. Traffic control is carried out based on these priorities.

Market development prospects

Thanks to the support of major manufacturers, DSL family technologies are developing at a very fast pace. The number of users using existing copper lines to receive broadband services is increasing every year by approximately 50%. The production of concentrators in the fourth quarter of 2004, according to Dell’Oro Group forecasts, will reach 12.7 million units. This means that the development of multiservice networks will continue, and at the same time the cost of equipment will decrease.

Specifications

Manufacturer	Paradyne	Schmid Telekom
Product name	GrandDSLAM 4200	Pegasus
Certificate of the Ministry of Communications	OS/1-SDS-73	OS/1-SP-957
Application area	Carrier-grade equipment for providing broadband access services	Solution for providing high-speed access to data networks and telephony simultaneously
Number of access ports	24/192 (when cascading eight devices in a stack)	Up to 64 DSL lines / 256 BRI ports / 512 analog ports
Transport network interfaces	Ethernet 10/100BaseT; Ethernet 10/100/1000 BaseT; Gigabit Ethernet (optical); ATM: E1, E1-IMA, STM-1;	Ethernet 10/100BaseT; STM-1; V.5.x;
Physical and channel interfaces on the user side	50-pin AMP connector for DSL; Support ADSL, ADSL2, ADSL2+, ReachDSL;	RJ-45 for 8 subscriber lines; G.SHDSL;
Control systems	SNMP V1, V2, V3 Web interface Command line CLI, Telnet GrandVIEW element management system	Terminal port VT100, V.24 (RS-232C), DB9 connector Protocols: SSH, Telnet Ethernet port 10/100Base-T in accordance with IEEE 802.3, RJ-45 connector Protocols: SNMP, TFTP, XML/SOAP, JSP, LDAP
Price	$188 per port	$1005 per port when cart is full
additional characteristics	Support for IGMP snooping and IGMP proxy protocols Can be equipped with POTS splitters	Remote power for dedicated B-channel Duplex/half duplex modes Auto-detect baud rate Auto-detection of port type

Modern DSL hubs are new generation equipment that allows you to connect subscribers to a data network using the latest technologies and has network interfaces such as Ethernet, ATM, SDH. Hubs are installed in places where users are concentrated on the telecom operator's side and allow subscribers to gain high-speed access to data networks while maintaining the existing infrastructure and access to the PSTN.

Types and scope of concentrators

Based on the assigned tasks and subscriber requirements, as well as taking into account the characteristics of the infrastructure, the operator selects the optimal access technology. The type of hub is determined depending on the technology used, for example, ADSL, SHDSL, VDSL, etc. The main criteria for selection are: the number and density of subscribers, the quality of existing wiring, the length of the subscriber line and the required bandwidth.

ADSL

The choice of ADSL technology is justified in cases where it is necessary to achieve high speeds over long distances (up to 5.5 km) from the telephone exchange to the subscriber and when it is necessary to maintain telephone communication. ADSL technology provides downstream speeds ranging from 1.5 Mbit/s to 8 Mbit/s and upstream speeds from 640 kbit/s to 1.5 Mbit/s. ADSL allows you to transmit data at a speed of 1.54 Mbit/s over a distance of up to 5.5 km over one twisted pair of wires. Transfer speeds of 6-8 Mbit/s can be achieved when transmitting data over a distance of up to 3.5 km over wires with a diameter of 0.5 mm.

Typically ADSL technology is used in the residential sector. Splitters are installed to simultaneously transmit voice traffic and data over one telephone line. They can be either built-in or external. In addition to the “classic” ADSL technology (includes a “light” version ADSL Lite), modern concentrators support improved modifications of ADSL technology ADSL2, ADSL2+.

They were developed to meet the increased demands of providers and end users on hubs. ADSL2 has increased the speed and range of information transmission, and implemented the function of adaptive speed change. These changes make it possible to support a large number of new applications and additional services. ADSL2+ doubles the speed of information reception at distances of up to 1.5 km.

G.SHDSL

VDSL

Unlike other DSL technologies, VDSL can operate in two modes: symmetrical and asymmetrical. It provides data transfer speeds to the subscriber ranging from 13 to 52 Mbit/s, and data transfer speeds from the subscriber up to 2.3 Mbit/s, over one twisted pair of telephone wires. In symmetric mode, speeds up to 26 Mbps are supported. Ethernet over VDSL (EoVDSL) technology extends the Ethernet network up to 1.5 km. It is advisable to use VDSL concentrators when conducting video conferencing, providing video-on-demand services, distance learning, etc.

"Proprietary" technologies

In addition to those listed above, there are hubs that support so-called “proprietary” technologies. They allow you to expand the capabilities of standardized technologies or be additions to them. “Proprietary” technologies are the manufacturer’s own developments and are used, for example, to adapt the transmission speed over a communication channel to the speed of the terminal equipment. They can also be used when the subscriber wiring is in poor condition or when the subscriber is located long distances. Often “proprietary” technologies are combinations of already known ones. If the technology is successfully applied on subscriber access networks, it undergoes a certification process, after which it can be used in equipment from other manufacturers.

Port density and physical dimensions of hubs

The most compact of them are a solution on one board and are installed in a standard 10-pair KRONE LSA-PLUS plinth. The next largest ones are mini-DSLAM, so-called “pizza-box” devices with a height of 1 U. The most powerful devices are modular DSLAMs with a wide range of network interfaces and installation in a standard 19" rack and various port densities. An ultra-compact DSL hub is solution with a fixed configuration of 8-10 ports, and mini-DSLAM can be either fixed or modular with a capacity of 8 to 48 ports per device. Modular hubs are full-featured devices that can interface with different types of transport networks (ATM , Ethernet, SDH) and contain a large number of user DSL ports (ADSL, SHDSL, VDSL).

An important criterion for choosing a particular hub is cascading devices, that is, increasing the total number of DSL ports with unified control of the entire stack of devices, which is especially important for compact hubs with low port density. At the initial stage of building an access network, the operator can either expand the network gradually, using mini-hubs, or make large investments in high-capacity systems. In the second case, the payback time of the project will increase.

Reliability and security of concentrators

Types of interfaces to the transport network

The choice of equipment for a subscriber access network largely depends on what technology is used on the backbone network: ATM, IP/Ethernet, SDH. The hub interfaces are selected accordingly.

ATM

Ethernet

Modern Metro Ethernet transport networks have reached speeds of 10 Gbit/s and continue to actively develop. To access such high-performance networks, DSLAM hubs are equipped with Fast or Gigabit Ethernet interfaces, depending on the device port density. However, when using the Ethernet transport interface in broadband access equipment, the problem arises of ensuring the quality of service for subscribers. To achieve this, DSLAM access equipment uses several mechanisms. First of all, it is the ability to create virtual private VLANs in accordance with the IEEE802.1Q standard. In addition, to ensure quality parameters, DSLAM equipment must implement the Ethernet traffic prioritization function in accordance with IEEE802.1p.

SDH

One of the most common technologies on which a modern primary network can be built is SDH technology. The subscriber access concentrator is connected to the SDH transport network using the STM-1 aggregate interface. The DSL concentrator is connected to the public telephone network using the V5.2 protocol stack, each of which allows servicing up to 16 E1 streams. SDH technology provides the ability to manage a transport network of any branch from one center.

Equipment on the subscriber side

Standard and custom network management tools

No matter how functional the broadband subscriber access equipment may be, without an appropriate management system it is just a useless piece of hardware. Therefore, special attention should be paid to management tools when choosing a DSLAM access concentrator.

In addition to standard and widely used terminal local management tools, such as the Command Line Interface (CLI), Telnet and HTTP protocols, the equipment must support a full-featured graphical element management system based on the SNMP protocol. It is important that this control system can monitor the state of communication channels, errors that occur in the access network, and allow for quick configuration and monitoring of parameters of both the system as a whole and the profiles of individual subscribers.

One of the main requirements for a specialized control system is the use of standard protocols (CORBA, SNMP) and open APIs. This allows the system to be interfaced with existing OSS systems on the operator's network, such as HP OpenView.

IEEE802.3ah standard

Separate requirements are imposed on devices that implement control mechanisms in accordance with the new IEEE802.3ah standard, better known as EFM, or “Ethernet in the first mile.” It is used for VDSL and SHDSL technologies; provides control of remote devices (user terminals) using a dedicated control channel. At the same time, advanced capabilities for remote device management in accordance with IEEE802.3ah allow operators to promptly respond and eliminate faults that arise in the network, ensuring high quality of services provided to subscribers.

additional characteristics

Market development prospects

Thanks to the support of major manufacturers, DSL family technologies are developing at a very fast pace. The number of users using existing copper lines to receive broadband services is increasing every year by approximately 50%. The production of hubs in the fourth quarter of 2004, according to DellOro Group forecasts, will reach 12.7 million units. This means that the development of multiservice networks will continue, and at the same time the cost of equipment will decrease.

“Technologies and Communications”, No. 4, 2004

ABOUT Looking at the topic of Triple Play on the pages of our magazine, we are moving further and further into the depths of the network. And if in the last issue IP Set-top Box subscriber devices were presented, then in this issue we will “go through” the devices that the operator has. True, we will not consider all types of operator devices, but only one of them, namely, Internet Protocol Digital Subscriber Line Multiplexor, or, in short, IP DSLAM. Moreover, we will consider them in the context of applicability for delivering “3 in 1” services to users. There are about one and a half dozen large IP DSLAM manufacturers on the world market. We did not set ourselves the goal of “combing” the Ukrainian IP DSLAM market, as they say, “up and down” in order to find all the solutions presented here from all manufacturers. I just wanted to give a basic idea of these devices using the example of “live equipment”. Therefore, in our review only some manufacturers’ equipment will be mentioned: Alcatel, Allied Telesyn, ECI Telecom, Iskratel (“Monis”), Lucent Technologies, Keymile, Siemens and ZyXEL. We paid attention to the equipment of these particular manufacturers primarily because of the associations of the mentioned brands with solutions for Triple Play.

What is IP DSLAM?

A “regular” DSLAM (based on an ATM switching fabric) is a multiplexer that is installed on the operator’s side. In fact, it is a hub to which subscriber telephone lines are connected. At the same time, at the other end of these lines there are DSL modems. The main function of DS-LAM is to provide users with a high-quality communication channel and ensure broadcast data transmission. Structurally, these devices consist of several main elements. The largest of them is the backbone chassis, in which linear modules, control and switching modules are installed, Power supplies and cooling system ( rice. 1). Most often, DSLAM is designed in a 19½ rack version.

Rice. 1. Basic structural elements DSLAM

Linear (modem) modules are boards to which subscriber lines are connected. As a rule, up to 48 (for some manufacturers up to 64) users can be connected to each such card. The most important element of DSLAM is also control and switching module (rice. 2), the main functions of which are clear from its name. This device contains a switching matrix that provides switching of data flow between line cards, as well as a central microprocessor, chipset, RAM and flash memory. In addition, the module contains a DSLAM control controller, management ports (RS-232, Ethernet 10/100) and interfaces for connecting to the operator’s transport network. Control modules within the same backplane can be duplicated to improve the reliability of the DSLAM or to increase its performance. Digital subscriber access equipment was developed at a time when ATM was seen as the most promising technology for building multiservice networks (data, voice, video). ATM technology has a number of advantages that make it possible to efficiently use channel bandwidth and provide the required level of quality of service (QoS) to subscribers. While ATM networks were already widely developed by operators, the IP protocol was “one of many.” It was practically not used in operator networks, since it had a lot of disadvantages: lack of QoS, unacceptable time to restore the channel in the event of a connection failure (up to several minutes), etc. But time passed, the protocol developed, and shortcomings were eliminated. In addition, the cost of IP networks, per port, turned out to be much lower than ATM networks.

This situation has given rise to a new type of device - IP DSLAM, which is actually the next step in the evolution of DSLAM. Systems of this type transmit to the user the same ATM packets, on top of which IP packets are transmitted (so-called encapsulation occurs, where ATM acts as a transport). But the main distinguishing feature of IP DSLAM is the presence of Fast or Gigabit Ethernet interfaces for connecting to the core of the operator's data network, as well as a switching fabric based on Ethernet technology. This important feature is indispensable where the low subscriber density does not justify the installation of expensive communication lines. IP DSLAM can be installed closer to the end user by connecting it via Ethernet to the backbone data transmission network via single-mode (up to 100 km) or multi-mode (up to 2 km) fiber optic cable ( rice. 3).

Rice. 2. IP DSLAM control and switching module

This, in turn, allows the operator to increase the “coverage” of subscribers while maintaining the cost-effectiveness of the solution (Ethernet equipment is relatively inexpensive). As a result, it is possible to significantly reduce the connection length (“last mile”) and thereby expand the bandwidth. In addition, the ATM aggregation network is being replaced by an Ethernet routing network, which today is already capable of meeting the bandwidth and QoS requirements at the level required to provide Triple Play services. Indeed, when using Ethernet, the task of ensuring the quality of subscriber service arises. To do this, IP DSLAM uses several mechanisms - creating virtual private VLANs in accordance with the IEEE802.1Q standard, ensuring Ethernet traffic prioritization in accordance with IEEE802.1p, etc.

What to pay attention to

When choosing an IP DSLAM, the first thing people usually pay attention to is its performance, but, nevertheless, there are several other important characteristics that are also worth considering. The most important parameter of an IP DSLAM is its physical format,

which in turn determines the number of connected ports. The smallest form factor (not counting single-board devices) is a 1 U mini-DSLAM (supports up to 48 ports). The most powerful devices are modular IP DSLAMs, which can contain an extensive set of network interfaces for interaction with the operator’s transport network (ATM, Ethernet, SDH) and support hundreds of ADSL, SHDSL and VDSL subscriber ports.

Both types of devices can be installed in a standard 19½ rack. Many IP DSLAMs support stacking of multiple devices (“cascading”), allowing for common management of all IP DSLAMs that are part of it.

According to the form factor, IP DSLAM can be divided into entry-level systems (small) - from 1 to 3 U in height, medium - 4-7 U and “central office systems” (CO) - 8-19 U. Typical Representatives of the small IP DSLAM format are Iskratel SI 2000 IPBAN (5 slots), Siemens Surpass hix 5620, etc. “Medium” IP DSLAMs include Lucent Stinger MS+, Keymile Keynode, Siemens Surpass hix 5630. CO systems include Alcatel 730x, Allied Telesyn iMAP 9700, ECI Hi-FOCuS 4.

When choosing an IP DSLAM, we must not forget about the reliability of the device, because it must work 24/7, sometimes in unfavorable technical or weather conditions. Therefore, the critical components of the IP DSLAM - the central microprocessor, the internal switching matrix, as well as power supplies, network interfaces and cooling fans (if any) - must be redundant.

To be able to provide Triple Play services to subscribers (primarily this concerns video services), IP DSLAM must support IGMP (Internet Group Management Protocol) multicast delivery protocols, namely IGMP-snooping and IGMP-proxy. These protocols save bandwidth on data transmission channels and provide an appropriate level of QoS.

IP DSLAM Management Tools

When building a reliable operator access network, it is impossible to do without specialized software, allowing you to manage the entire infrastructure from a single center. This approach is necessary for operators who have an extensive IP SDLAM network (up to several hundred) and want to manage them from a single point. Each major IP DSLAM manufacturer has its own developments in this area, but most software products of this type have a number of key features. First of all, such software should have a convenient graphical interface (while maintaining the ability to control via CLI and Telnet). The main functions of the software for centralized access network management are monitoring the status of the entire network as a whole and individual devices, monitoring the status of linear interfaces and individual ports, as well as displaying various statistics (including about users) with reporting.

In addition, the operator must be able to create profiles for each individual user ( tariff plans, multicast addresses, etc.) and save them in the database. Also

the system must include mechanisms to provide disaster recovery and backup of user settings. An important function of management software is internal security control, namely authorization and control of access rights of system administrators, maintaining a “log of changes made,” etc. IP DSLAM infrastructure management software must use standard protocols (SNMP, CORBA) and open APIs.

As an illustration of the above description of the software, we can name such products as Alcatel 5523 AWS Element Manager, ZyXEL NetAtlas, Siemens APM-E, ECI EMS and a number of others.

Rice. 3. Place of IP DSLAM in the operator’s network

IP DSLAM in Ukraine and in the world

Having considered the main parameters that IP DSLAM must meet, let us now move on to consider the equipment presented in Ukraine. Obviously, each manufacturer offers its own model range and its own view on the architecture, business development and application areas of IP DSLAM.

Let's consider the most important aspects of the activities of each participant in the IP DSLAM market, as well as the main characteristics of the “flagship” models of devices of this type ( table ) .

Alcatel (France)

Alcatel is the world leader in the DSLAM market, with a market share of approximately 40%. Alcatel equipment supports more than 45 million DSL lines. Alcatel's flagship IP DSLAM device is currently the 7302 ISAM ( Fig.4). This 14 U high system went into series production last September and is based on the popular 7300 /7301 ASAM models. This multiplexer is capable of supporting up to 768 subscriber DSL lines using ADSL, ADSL2, ADSL2+, VDSL technology. In this case, the data transfer rate to the subscriber can be up to 20 Mbit/s per line, and the capacity of the second-level switching factory is 24 Gbit/s.

This year a new IP DSLAM Alcatel model appeared - 7330 ISAM FTTN. This 8U system also has a 24 Gbps switch fabric and supports up to 192 DSL subscriber lines (ADSL2+, VDSL, VDSL2). Both IP DSLAM models are initially focused on providing Triple Play services and, in particular, IPTV.

As for the method of promoting this equipment on the Ukrainian market, Alcatel sells it independently, focusing on all consumer groups - from home users (modems) to the corporate sector and large operators. In general, Alcatel is one of the few companies that produces and sells all the main components that allow operators to provide “3 in 1” services.

Rice. 4. IP DSLAM Alcatel 7302

Allied Telesyn (Japan)

When it comes to broadband access equipment, Allied Telesyn focuses on device versatility. The “senior” model of Allied Telesyn IP DSLAM - iMAP 9700 (9 U high) - allows you to support up to 408 DSL subscriber lines. Strictly speaking, this is not exactly an IP DSLAM. The fact is that in addition to cards with DSL ports (ADSL2, ADSL2+, VDSL, etc.), the iMAP 9700 has the ability to install cards with Ethernet E1, HJTS, GEPON ports within one device. Moreover, all these types of line cards can operate simultaneously ( rice. 5).

iMAP 9700 systems support link aggregation in accordance with the IEEE 802.3ad standard. Several such devices can be combined into an “access ring” using a 10 GbE interface. Moreover, in the event of a physical break in the line between ring devices, the switching time to the backup route does not exceed 50 ms.

Rice. 5. Allied Telesyn iMAP 9700 Universal Access Network Platform

Allied Telesyn access devices are specifically designed for operators wishing to provide users with Triple Play (primarily IPTV) services over both existing copper telephone lines and dedicated Ethernet channels.

The company is known for its marketing success in the Asia-Pacific region, as well as in the EMEA region. IN Lately More and more Allied Telesyn devices are being sold in Western Europe And North America. In Ukraine, the interests of Allied Telesyn are represented by ICS-Megatrade, DataLux, Iv Trading, Priocom and Sivax.

D-Link (Taiwan)

D-Link offers relatively small capacity devices on the market. The main IP DSLAM models of this company are: DAS-3224 - 24-port IP DSLAM with 2 1000Base-T ports; DAS-3248F - 48-port IP DSLAM with 1 port 1000Base-T and 1 port 1000Base-LX, as well as DAS-3248 ( rice. 6) - 48-port IP DSLAM with two 1000Base-T ports.

The interests of D-Link in Ukraine are protected by both the official representative office and the distributors of the company Versia, ICS-Megatrade and ORSI.

Rice. 6. IP DSLAM D-Link

ECI Telecom (Israel)

To implement the Triple Play concept, the company offers the Hi-FOCuS platform - a family of multi-service broadband access concentrators (Multi Service Access Gateways, MSAG).

The Hi-FOCuS line of equipment is represented by devices of various capacities: from modular chassis with a capacity of 960 lines to compact (only 1U high) MiniRAM xDSL multiplexers with a fixed configuration (16 or 32 ports).

The largest representative of the family is Hi-FOCuS-4 ( Fig.7) is a modular chassis with 15 slots for line cards (each slot supports up to 64 xDSL lines) and two slots for control cards with an up-link interface.

To increase reliability and throughput, Hi-FOCuS uses a double-star backplane architecture (Fractal-Link): each of the control cards is connected to each of the line cards with a separate high-speed (800 Mbps, full duplex) channel.

Among other features, it is worth noting the ability to connect (including simultaneously) to the backbone network both via Ethernet/IP and ATM/SDH channels, a large assortment of linear interfaces (ATM, ADSL/2/2+, SHDSL, VDSL, termination cards voice) and providing QoS at the service level.

The company’s equipment is most in demand among operators seeking to provide “Triple play” services with guaranteed quality (Hi-FOCuS services about half of all xDSL lines from companies such as Deutsche Telecom and France Telecom).

According to the analytical company Dell'Oro Group, ECI Telecom's share of the market for multiservice access concentrators (Multiservice Access Concentrators) is 36% for the European (EMEA) and 50% for the Asia-Pacific (APAC) regions.

Rice. 7.

Iskratel (Slovenia)

The Eastern European company Iskratel has a long history. But today 47.7% of its shares belong to Siemens. Its main product in the segment we are considering is the IP DSLAM SI 2000 ipBAN (Broadband Access Node). This device is a 10 U modular system with twenty expansion card bays that can support up to 912 subscriber lines. There are also modifications of this IP DSLAM in form factor heights of 6 U (up to 432 lines), 3 U (up to 195 lines) and 1U (up to 24 lines). The SI 2000 ipBAN (now renamed MSAN) is in greatest demand among operators providing IP telephony services and Internet access via DSL ( Fig.8).

Recently, Iskratel has been actively developing the Triple Play concept.

The company's activities are most noticeable in the market of equipment for building broadband access networks in Central and Eastern Europe. In Ukraine, Iskratel equipment is represented by Monis.

Rice. 8. IP DSLAM ECI Telecom Hi-FOCuS 4

Lucent Technologies (USA)

The Lucent Technologies range of broadband access multiplexers (both ATM DSLAM and IP DSLAM) is presented on the market under the general name Stinger ( rice. 9). Multiplexers are divided into FS, LS, RT (14 U each) and MC (4 U high) series. The flagship model is the IP DSLAM Stinger FS+, which supports IP ATM and Frame Relay communication protocols, as well as all the most common DSL access technologies. A year and a half to two years ago, Lucent Technologies decided to improve the Stinger systems rather than create a radically new broadband access platform. This is explained by the fact that, based on this series of multiplexers, a fairly developed access network already existed in many countries around the world. Upgrading existing Stinger systems to provide Triple Play services allows operators to seamlessly scale their access networks and improve their performance.

Thus, the Spanish company Telefonica has launched a large project to provide IPTV services, using IP DSLAM produced by Lucent Technologies. This manufacturer positions its IP DSLAMs as third-level systems.

Lucent Technologies products, thanks to a developed partner and distribution network, are represented almost all over the world, including in Ukraine (by companies such as Classica LLC, CheZara JV, Vector, Ukrainian Communications).

Rice. 9. IP DSLAM Lucent Stinger FS

Siemens (Germany)

Siemens IP DSLAM multiplexers are known on the market under the general name Surpass hiX 56xx. These systems have a lot of great features, such as support for MPLS Traffic Engineering (MPLS TE). This function allows you to control the direction of traffic in order to fulfill certain conditions (reservation of channels, distribution of network load, etc.).

Siemens' flagship model is the hiX 5635. This IP DSLAM (13U high) allows you to connect more than 1000 subscriber lines simultaneously, while the capacity of its second-level switching fabric is 24 Gbit/s. The “younger” brothers of the hiX 5635 are the hiX 5630 and hiX 5620 ( rice. 10).

Siemens IP DSLAM equipment is most often used to provide high-speed Internet access, as well as for IP telephony needs. In addition, Siemens has taken the Triple Play services market seriously and today offers a full range of hardware and software for deploying 3-in-1 solutions. Siemens also has its own comprehensive concept of organizing “triple services” on its own equipment called Surpass Home Entertainment. The company's equipment is currently represented in 160 countries around the world.

Rice. 10. IP DSLAM Siemens Surpass hix 56xx series

Keymile (Germany)

Keymile is another German company that sells its IP DSLAM in Ukraine (through its partner, INVEX Telecom). The proposed device, called KEYNode, has a height of 7 U and is capable of supporting the connection of 640 subscriber lines ( rice. eleven). The KEYNode multiplexer is positioned by the manufacturer as a second-level device, at the same time it allows you to connect to the operator’s transport network both via IP and ATM. Keymile finds its main market for its IP DSLAM in Europe.

Rice. eleven. IP DSLAM Keymile KEYNode

ZyXEL Communications (Taiwan)

Since our mini-review is organized in alphabetical order, it is completed by the Taiwanese company ZyXEL, which also has IP DSLAM multiplexers in its product line under the general name IES (1000, 1248, 2000, 2500, 3000).

Today, the “flagship” model of devices of this type is the IES-5000 ( rice. 12).

ZyXEL IES-5000 is designed for installation in a 19½ rack (height 6.5 U) and can accommodate up to 8 modem modules, allowing you to connect up to 384 subscribers using ADSL2+ or SHDSL technology) or up to 192 subscribers using VDSL2 technology.

ZyXEL was one of the first companies to design its DSL access network equipment for use in delivering triple play services. The company's equipment is widely represented in the CIS countries, where the growth rate of its sales is faster than the global one. In Ukraine, the official representative office deals with the sale of ZyXEL products. Distributors of ZyXEL equipment in Ukraine are ICS-Megatrade and MTI.

Fig.12. IP DSLAM ZyXEL IES 5000

The future is IP DSLAM

The trends in the development of the broadband access services market are very optimistic. According to analytical agencies, the increase in the number of users in the coming years will be 35-45% annually. By the beginning of summer 2005, the global number of DSL channels reached 115 million. It is expected that about 195 million DSL lines will be in operation in 2008 (twice as many as at the end of 2004).

According to forecasts, supply volumes of conventional DSLAMs will increase until 2008, while revenues from their sales will continue to decline starting next year. As for the sales structure, it is interesting that about 75% of all sales of DSLAM devices are in the EMEA region (35%) and the Asia-Pacific region (30%), about 20% are in North America. However, global analytical agencies report that revenue from the sale of traditional (ATM) DSLAM in 2005 fell by an average of 7-10%, while at the same time, during the specified period, a 20% increase in monetary terms was observed in the IP DSLAM sector . It is expected that next year the global IP DSLAM market will exceed $3.1 billion.

The editors express gratitude for their assistance in preparing the material to Mikhail Skuratovsky (Allied Telesyn), Sergei Kotlyar (Alcatel Ukraine), Stanislav Bilder (ECI Telecom Ukraine), Evgeniy Balakin (ZyXEL representative office in Ukraine), as well as specialists from the Alcatel Ukraine subsidiary Siemens Ukraine, INVEX-Telecom, Classica LLC and Monis.

Igor K irillov

A few words about access technologies

The development of digital subscriber access technologies has led to the emergence of many standards, of which the most popular in practice are ADSL, SHDSL and VDSL.

ADSL technology is most applicable in cases where it is necessary to achieve high speeds over long distances (over 5 km) from the multiplexer to the subscriber and at the same time maintain telephone communication (therefore, DSLAM with ADSL support is usually installed on PBXs). ADSL technology provides downstream and upstream data speeds of up to 8 Mbit/s and up to 1.5 Mbit/s, respectively, over a regular copper telephone pair.

IP TV, Video on Demand (VoD) services, etc. require a bandwidth of at least 4 Mbit/s. That is, the data transfer rates that can be provided to the user using ADSL technology are quite applicable for providing “3 in 1” services. In this case, the distance from the multiplexer to the subscriber should not exceed 3.5 km, because as the distance increases, the speed decreases.

Modern modifications of ADSL technology are ADSL2 and ADSL2+. In ADSL2+, the speed of information reception is doubled (compared to ADSL), but the acceptable distance between user and subscriber equipment has been reduced to 1.5 km.

SHDSL technology is most applicable to corporate clients. This technology allows you to transmit data over a copper telephone pair at a speed of more than 2 Mbit/s (both from the multiplexer to the subscriber and to reverse side) at a distance of about 6 km. SHDSL is often used where it is necessary to combine several geographically remote offices into a single local network. A further development of the technology is SHDSL.bis, which allows data transmission at speeds of up to 5.7 Mbit/s and supports the ability to combine four channels into one with a total speed of up to 22.8 Mbit/s.

VDSL technology is the optimal solution for organizing collective subscriber access systems (for example, in business centers) and corporate communication systems. VDSL provides the fastest transmission speed of all modern DSL technologies. Unlike other DSL technologies, VDSL can operate in two modes - symmetrical and asymmetrical. In asymmetric mode, the data transfer rate is up to 52 Mbit/s towards the user and up to 1.5 Mbit away from the user. The distance to DSLAM should not exceed 1.3 km. In symmetrical operating mode, VDSL technology allows you to transfer data at speeds of up to 26 Mbit/s in each direction. As the distance increases, the speed decreases, but nevertheless remains quite high. It is advisable to use multiplexers with VDSL support in areas where video conferencing services are expected, distance learning or Triple Play.

Many modern carrier-grade IP DSLAMs, as a rule, are capable of supporting all of the described (as well as some other) data transmission technologies within a single device.

There are also a number of “proprietary” data transmission technologies, which are the own developments of IP DSLAM manufacturing companies. They allow you to expand the capabilities of standardized technologies or complement them.