dslam digital subscriber line access multiplexer. xDSL Hubs (DSLAMs). Standard and custom network management tools
DSLAM (Digital Subscriber Line Access Multiplexer) is a multiplexer (modem) for accessing a digital subscriber line xDSL. On the network side, it has WAN ports, and on the client side, it has xDSL half-sets (modems) to which the subscriber line is connected. At the other end of the subscriber line, the client has an xDSL subscriber set (modem) or IAD ( Integrated Access Device- integrated access device). The latter is used in cases where the simultaneous transmission of data and voice in digital form is implemented over the xDSL line, that is, VoDSL (Voice over DSL).
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Literature
- Stepan Ilyin aka Step// Hacker. - 2005. - Issue. #075 .
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An excerpt characterizing DSLAM
And, probably even more indignant at the fact that, having said this, he had told an obvious lie and that Balashev, in the same pose of his submissive fate, silently stood in front of him, he abruptly turned back, went up to Balashev's very face and, making energetic and quick gestures with his white hands, almost shouted:“Know that if you shake Prussia against me, know that I will erase her from the map of Europe,” he said with a pale face distorted by anger, striking with an energetic gesture of one small hand on the other. - Yes, I will throw you beyond the Dvina, beyond the Dnieper and restore against you that barrier that Europe was criminal and blind, which allowed it 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 several times around the room, shaking his thick shoulders. He put a snuff-box in his waistcoat 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 low voice: "Et cependant quel beau regne aurait pu avoir votre maitre!"
O Seeing the theme of Triple Play on the pages of our magazine, we are moving further and further deep into the network. And if in the last issue subscriber devices IP Set-top Box were presented, then in this one we will “walk” through the devices that the operator has. True, we will not consider all types of operator devices, but only one of them, namely, the 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 a 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 search for all the solutions presented here from all manufacturers. I just wanted to give a basic idea about these devices using the example of "live equipment". Therefore, our review will only mention equipment from some manufacturers: Alcatel, Allied Telesyn, ECI Telecom, Iskratel (Monis), Lucent Technologies, Keymile, Siemens and ZyXEL. We paid attention to the equipment of these manufacturers primarily because of the associations of the mentioned brands with Triple Play solutions.
What is IP DSLAM?
A "regular" DSLAM (based on an ATM switch 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, DSL modems are located at the other end of these lines. The main function of DS-LAM is to provide users with a high-quality communication channel and provide broadcast (broadband) data transmission. Structurally, these devices consist of several basic elements. The largest of them is the unifying chassis, in which linear modules, control and switching modules, power supplies and a cooling system are installed ( rice. one). Most often, constructively, DSLAM is performed in a 19½ rack version.
Rice. one. Basic structural elements of DSLAM
Linear (modem) modules are boards to which subscriber lines are connected. As a rule, up to 48 (some manufacturers up to 64) users can be connected to each such board. The most important element of DSLAM is also control and switching module (rice. 2), the main functions of which are already clear from its name. This device contains a switching matrix that provides data flow switching between line cards, as well as a central microprocessor, chipset, RAM and flash memory. In addition, the module contains a DSLAM control controller, control ports (RS-232, Ethernet 10/100) and interfaces for connecting to the operator's transport network. Control modules within one backplane chassis can be duplicated to increase 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 allow efficient use of channel bandwidth and provide the required level of quality of service (QoS) for subscribers. While ATM networks have already been 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 channel recovery time in case of a communication break (up to several minutes), etc. But time passed, the protocol developed, the 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 all the same ATM packets over 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 transmission network, as well as a switching factory based on Ethernet technology. This important feature is indispensable where the low density of subscribers does not justify the laying of expensive communication lines. IP DSLAM can be installed closer to the end user by connecting it via Ethernet to the backbone data network using single-mode (up to 100 km) or multi-mode (up to 2 km) fiber optic cable ( rice. 3).
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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, you can significantly reduce the length of the connection ("last mile") and thereby increase the bandwidth. In addition, the ATM aggregation network is being replaced by an Ethernet routing network, which today is already able to provide bandwidth and QoS requirements at the level required to provide Triple Play services. Indeed, when using Ethernet, the problem arises of ensuring the quality of service for subscribers. To do this, IP DSLAMs use several mechanisms - creating virtual private networks VLANs in accordance with the IEEE802.1Q standard, ensuring prioritization of Ethernet traffic in accordance with IEEE802.1p.etc.
What to pay attention to
When choosing an IP DSLAM, the first thing you 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 (outside of single board devices) is the 1 U mini-DSLAM (supports up to 48 ports). The most powerful devices are modular IP DSLAMs that 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”), which allows for the overall control of all IP DSLAMs that are part of it.
According to the IP DSLAM form factor, it can be conditionally divided into entry-level systems (small) - from 1 to 3 U, medium (medium) - 4-7 U and "head office systems" (central office, CO) - 8-19 U. Typical representatives of the small IP DSLAM format are Iskratel SI 2000 IPBAN (for 5 slots), Siemens Surpass hix 5620, etc. The "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, one should not forget about the reliability of the device, because it must work 24/7, sometimes in adverse 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 reserved.
To be able to provide triple play services to subscribers (primarily video services), IP DSLAM must support IGMP (Internet Group Management Protocol) multicast delivery protocols, namely IGMP-snooping and IGMP-proxy. These protocols allow you to save bandwidth of 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 that allows 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 retaining the ability to manage via CLI and Telnet). The main functions of the software for centralized access network management are monitoring the status of both the entire network as a whole and individual devices, monitoring the status of line 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 store them in a database. Also
the system must include mechanisms to ensure failure recovery and backup of user settings. An important function of control software is internal security control, namely, authorization and control of access rights of system administrators, keeping a "log of changes made", etc. IP DSLAM infrastructure management software should use standard protocols (SNMP, CORBA) and open APIs.
As an illustration to 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.
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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 DSLAMs must meet, let's now move on to reviewing the equipment presented in Ukraine. Obviously, each manufacturer offers its own model range and its own view on the architecture, business development and IP DSLAM applications.
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's equipment provides more than 45 million DSL lines. Alcatel's flagship IP DSLAM is currently the 7302 ISAM ( fig.4). This 14 U system was launched 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. At the same time, the data transfer rate to the subscriber can be up to 20 Mbps per line, and the capacity of the second-level switching factory can be 24 Gbps.
Alcatel's new IP DSLAM model, 7330 ISAM FTTN, has appeared this year. This 8U system also has a 24Gbps fabric and supports up to 192 DSL subscriber lines (ADSL2+, VDSL, VDSL2). Both IP DSLAM models are initially focused on the provision of 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 manufactures and sells all the main components that allow operators to provide "3 in 1" services.
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Rice. 4. IP DSLAM Alcatel 7302
Allied Telesyn (Japan)
In the field of broadband access equipment, Allied Telesyn focuses on device versatility. The "older" Allied Telesyn IP DSLAM model - iMAP 9700 (9 U high) - allows you to support up to 408 subscriber DSL lines. Strictly speaking, this is not really an IP DSLAM. The fact is that in addition to boards with DSL ports (ADSL2, ADSL2+, VDSL, etc.), iMAP 9700 has the ability to install boards with Ethernet E1, HJTS, GEPON ports within a single device. At the same time, all these types of line cards can work simultaneously ( rice. 5).
iMAP 9700 systems support data link aggregation in accordance with the IEEE 802.3ad standard. Several of these devices can be combined into an "access ring" using a 10 GbE interface. At the same time, in the event of a physical line break between the ring devices, the switching time to the backup route does not exceed 50 ms.
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Rice. 5. Allied Telesyn iMAP 9700 Universal Access Network Platform
Allied Telesyn's access devices have been specifically designed for operators who want to provide Triple Play services (primarily IPTV) to users over both existing copper telephone lines and dedicated Ethernet circuits.
The company is known for its marketing success in the Asia-Pacific region, as well as in the EMEA region. Recently, 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 1000Base-T port and 1 1000Base-LX port, plus 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 Versiya, ICS-Megatrade ORSI.
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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 multiservice broadband access concentrators (Multi Service Access Gateways, MSAG).
The Hi-FOCuS equipment line 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 member of the family is Hi-FOCuS-4 ( fig.7) is a modular chassis with 15 line card slots (each slot supports up to 64 xDSL lines) and two up-link control card slots.
To increase reliability and throughput, Hi-FOCuS uses a backplane architecture in the form of a “double star” (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 range of line interfaces (ATM, ADSL / 2/2+, SHDSL, VDSL, termination cards voices) and providing QoS at the level of services.
The company's equipment is most in demand among operators seeking to provide "Triple play" services with guaranteed quality (Hi-FOCuS serves about half of all xDSL lines of such companies as Deutsche Telecom and France Telecom).
According to the Dell "Oro Group analytical company, ECI Telecom's market share in the market for multiservice access concentrators (Multiservice Access Concentrators) is 36% for the European (EMEA) and 50% for the Asia-Pacific (APAC) regions.
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Rice. 7.
Iskratel (Slovenia)
East European company Iskratel has a long history. But to date, 47.7% of its shares are owned by Siemens. Its main product in the segment we are considering is IP DSLAM SI 2000 ipBAN (Broadband Access Node). This device is a 10 U modular system with twenty expansion card slots capable of supporting up to 912 subscriber lines. There are also modifications of this IP DSLAM in the form factor 6 U (up to 432 lines), 3 U (up to 195 lines) and 1U (up to 24 lines). The greatest demand for SI 2000 ipBAN (now renamed to MSAN) is used by 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.
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Rice. eight. 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 marketed under the general name Stinger ( rice. 9). The multiplexers are subdivided into the FS, LS, RT (14 U each) and MC (4 U) 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 made the decision to improve the Stinger systems, rather than create a radically new broadband access platform. This is explained by the fact that on the basis of this series of multiplexers there already existed a fairly developed access network in many countries of the world. Upgrading existing Stinger systems and focusing them on providing Triple Play services allows operators to painlessly scale their access networks and increase their performance.
For example, the Spanish company Telefonica launched a major project to provide IPTV services using IP DSLAM manufactured by Lucent Technologies. This manufacturer positions its IP DSLAMs as Layer 3 systems.
Thanks to a developed partner and distribution network, Lucent Technologies products are represented almost all over the world, including in Ukraine (by such companies as Classica LLC, CheZaRa JV, Vector, Ukrainian Communications).
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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 MPLS Traffic Engineering (MPLS TE) support. This function allows you to control the direction of traffic in order to fulfill certain conditions (channel reservation, network load distribution, etc.).
Siemens' flagship model is the hiX 5635. This IP DSLAM (13U high) allows more than 1000 subscriber lines to be connected simultaneously, with a 24Gbps L2 switching fabric capacity. The "younger" brothers of hiX 5635 are 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 the needs of IP telephony. In addition, Siemens has taken the Triple Play market seriously and now offers a full range of hardware and software for deploying 3-in-1 solutions. Siemens also has its end-to-end “triple services” concept on its own production equipment called Surpass Home Entertainment. The equipment of the company is presented today in 160 countries of the world.
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Rice. 10. IP DSLAM Siemens Surpass hix 56xx series
Keymile (Germany)
Keymile is another German company that sells its IP DSLAMs in Ukraine (through its partner, INVEKS 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 DSLAMs in Europe.
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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).
To date, the "flagship" model of devices of this type is the IES-5000 ( rice. 12).
The 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 with Triple Play service delivery in mind. The company's equipment is widely represented in the CIS countries, where its sales growth rates are ahead of the global ones. In Ukraine, the sale of ZyXEL products is handled by an official representative office. Distributors of ZyXEL equipment in Ukraine are ICS-Megatrade, MTI.
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Fig.12. IP DSLAM ZyXEL IES 5000
The future is IP DSLAM
The trends in the development of the market for broadband access services are very optimistic. According to analytical agencies, the increase in the number of users in the coming years will be 35-45% annually. By early summer 2005, the worldwide number of DSL channels had reached 115 million. It is expected that in 2008 there will be about 195 million DSL lines in operation (twice as many as at the end of 2004).
Conventional DSLAM shipments are forecast to grow through 2008, with revenues from their sales declining further from 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 countries of 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, on average, by 7-10%, while at the same time, a 20% growth in monetary terms was observed in the IP DSLAM sector during this period. . It is assumed that next year the turnover in the global IP DSLAM market will exceed $ 3.1 billion.
The editors would like to thank Mikhail Skuratovsky (Allied Telesyn), Sergey Kotlyar (Alcatel Ukraine), Stanislav Bilder (ECI Telecom Ukraine), Evgeniy Balakin (ZyXEL representative office in Ukraine), as well as the specialists of Alcatel Ukraine DP, DP Siemens Ukraine, INVEKS-Telecom, OOO Classica and Monis.
Igor Kirillov
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A few words about access technologies The development of digital subscriber access technologies has led to the emergence of many standards, of which ADSL, SHDSL and VDSL are the most popular in practice. ADSL technology is most applicable in cases where it is required to achieve high speeds over long distances (over 5 km) from the multiplexer to the subscriber and maintain telephone communication at the same time (therefore, ADSL-enabled DSLAMs are usually installed on PBXs). ADSL technology provides the speed of "downstream" and "upstream" data flow at the level of up to 8 Mbps and up to 1.5 Mbps, respectively, over a conventional copper telephone pair. IP TV, Video on Demand (VoD), etc. services require a bandwidth of 4 Mbps or more. That is, the data transfer rates that can be provided to the user using ADSL technology are quite applicable for the provision of "3 in 1" services. At the same time, the distance from the multiplexer to the subscriber should not exceed 3.5 km, because with increasing distance, the speed drops. Modern modifications of ADSL technology are ADSL2 and ADSL2+. In ADSL2+, the information reception speed 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 for corporate clients. This technology makes it possible to transfer data over a copper telephone pair at a speed of more than 2 Mbps (both from the multiplexer to the subscriber and in the opposite direction) over 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 you to transfer data at speeds up to 5.7 Mbps and supports the ability to combine four channels into one with a total speed of up to 22.8 Mbps. VDSL technology is the optimal solution for organizing multiple subscriber access systems (for example, in business centers) and corporate communication systems. VDSL provides the highest transmission speed among all modern DSL technologies. Unlike other DSL technologies, VDSL can operate in two modes - symmetrical and asymmetric. In asymmetric mode, the data transfer rate is up to 52 Mbps in the direction of the user and up to 1.5 Mbps in the direction away from the user. The distance to the DSLAM should not exceed 1.3 km. In symmetrical mode of operation, VDSL technology allows you to transfer data at speeds up to 26 Mbps in each direction. As the distance increases, the speed decreases, but, nevertheless, remains quite high. Multiplexers with VDSL support should be used in areas where video conferencing services, distance learning or Triple Play are expected. Many modern carrier class IP DSLAMs, as a rule, are able to support all the described data transmission technologies (as well as some others) within a single device. There are also a number of "proprietary" data transmission technologies that are proprietary developments of IP DSLAM manufacturing companies. They allow you to expand the capabilities of standardized technologies or complement them. |
A.V. Simonina, equipment manager of IMAG company
D. Yu. Guseltsov, Development Manager, IMAG
Modern DSL hubs are a new generation of equipment that allows you to connect subscribers to a data transmission network using the latest technologies and has network interfaces such as Ethernet, ATM, SDH. Concentrators are installed in places of concentration of users on the side of the telecom operator and allow subscribers to receive high-speed access to data transmission networks, while maintaining the existing infrastructure and access to the PSTN.
To date, the number of manufacturers and suppliers of devices of this kind is several hundred, and it is not so easy to choose the right equipment. The requirements that the consumer makes to different classes of DSL equipment vary significantly. Matter: reliability, size, port density, power consumption. For example, the reliability of carrier-class hubs must be significantly higher than that of hubs for campus applications, where short-term traffic outages are not as critical; the same applies to the required set of functions. The use of copper wiring and the easy installation of the hub make the initial investment for building 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 tasks and requirements of subscribers, as well as taking into account the peculiarities of the infrastructure, the operator chooses the optimal access technology. The type of concentrator is determined depending on the DSL technology used, for example, ADSL, SHDSL, VDSL, etc. The main selection criteria are: the number and density of subscribers, the quality of the existing wiring, the length of the subscriber line and the required bandwidth.
ADSL
The choice of ADSL technology is justified in those cases when it is required to achieve high speeds over long distances (up to 5.5 km) from the PBX to the subscriber and when it is necessary to maintain telephone communication. ADSL technology provides downstream data rates ranging from 1.5 Mbps to 8 Mbps and upstream data rates from 640 kbps to 1.5 Mbps. ADSL allows you to transfer data at a speed of 1.54 Mbps over a distance of up to 5.5 km over a single twisted pair of wires. Transmission rates of 6-8 Mbps can be achieved by 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. For simultaneous transmission of voice traffic and data over one telephone line, splitters are installed. They can be either built-in or external. In addition to the "classic" ADSL technology (includes a "lite" version - ADSL Lite), modern concentrators support improved modifications of ADSL technology - ADSL2, ADSL2+.
They were developed taking into account the increased requirements of providers and end users to hubs. ADSL2 has increased the speed and range of data transmission, implemented the function of adaptive speed change, thanks to these changes, it has become possible to support a large number of new applications and additional services. In ADSL2+, the speed of receiving information at distances up to 1.5 km was doubled.
G.SHDSL
For the corporate sector, the most promising technology is G.SHDSL. G. SHDSL hubs allow transmission over distances of more than 6 km at speeds up to 2.3 Mbps over a single 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 expedient when servicing campuses. Some DSLAMs support G. SHDSL.bis technology with a transmission rate of 5.7 Mbps over one copper pair with the ability to combine 4 pairs into one channel with a total speed of up to 22.8 Mbps.
VDSL
xDSL supporting the VDSL standard is used when building multiple subscriber access systems (for example, in business centers, cottage settlements, student 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 asymmetric. It provides the data transfer rate to the subscriber in the range from 13 to 52 Mbps, and the data transfer rate from the subscriber up to 2.3 Mbps, over one twisted pair of telephone wires. In symmetrical mode, speeds up to 26 Mbps are supported. Ethernet over VDSL (EoVDSL) technology extends an Ethernet network up to 1.5 km. It is advisable to use VDSL concentrators when conducting a video conference, providing video-on-demand services, distance learning, etc.
"Branded" technologies
In addition to those listed above, there are hubs that support the so-called "proprietary" technologies. They allow you to extend 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 rate over the 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 goes through the 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. According to the 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. Next in size are mini-DSLAMs, the 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 fixed configuration solution for 8-10 ports, while mini-DSLAM can be both fixed and modular with capacity from 8 to 48 ports per device. , Ethernet, SDH) and contain a large number of user DSL ports (ADSL, SHDSL, VDSL).
An important criterion for choosing one or another hub is cascading devices, that is, an increase in the total number of DSL ports with a single management 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 grow the network gradually using mini-hubs for this, or invest heavily in high-capacity systems. In the second case, the payback time of the project will increase.
Reliability and security of hubs
In order for DSLAM broadband subscriber access equipment to meet the requirements of telecom operators, that is, to be carrier-class equipment, it is necessary to comply with industry standards in the field of security and operation. In addition, the housing of the device must be protected from adverse temperature influences, this must be confirmed by the appropriate safety certificate.
Another important factor in ensuring equipment reliability is component redundancy. The architecture of the device must provide for the possibility of redundancy of the internal switching matrix, the central processor, power supplies, transport network interfaces. For example, to prevent denial of service for subscriber traffic, the network interfaces of the system may 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. In accordance with this, the interfaces of the concentrator are also selected.
ATM
DSL broadband subscriber access equipment was developed when data transmission 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, since it required high costs for the deployment and operation of expensive ATM-based systems. However, ATM technology has its undeniable advantages, it allows efficient use of the channel bandwidth and provides the required level of quality of service (QoS) for subscribers.
ethernet
Current trends in the transition to the IP protocol are forcing manufacturers of broadband equipment DSL access apply in their decisions more promising Ethernet technologies. First of all, this affects the cost of the solution, its price is significantly reduced.
Modern transport networks Metro Ethernet have reached speeds of 10 Gb / s and continue to develop rapidly. To access such high-performance networks, DSLAM hubs are equipped with Fast or Gigabit Ethernet interfaces, depending on the port density of the device. However, when using the Ethernet transport interface in broadband access equipment, the challenge is to ensure the quality of service for subscribers. To do this, DSLAM access equipment uses several mechanisms. First of all, it is the ability to create virtual private networks VLANs in accordance with the IEEE802.1Q standard. In addition, in order to ensure quality parameters, the DSLAM equipment must implement the Ethernet traffic prioritization function in accordance with IEEE802.1p.
SDH
One of the most common technologies on the basis of which a modern primary network can be built is SDH technology. The connection of the subscriber access concentrator to the SDH transport network is carried out 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 branching from one center.
Subscriber side equipment
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 hardware 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 transmission 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 broadband subscriber access equipment is, without an appropriate management system, it is just a useless piece of iron. Therefore, special attention should be paid to management tools when choosing a DSLAM access concentrator.
In addition to standard and widely used local management terminal tools such as 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 be able to monitor the status of communication channels, errors that occur in the access network, and allow for quick configuration and monitoring of the parameters of both the system as a whole and the profiles of individual subscribers.
One of the main requirements for a specialized management system is the use of standard protocols (CORBA, SNMP) and open APIs in it. This allows the system to interface with existing OSS operations and support systems on the operator's network, such as HP OpenView.
Another requirement for the control system is modularity and scalability. The control system should consist of separate functionally completed modules that interact with each other using standardized protocols and interfaces, and be able to increase functionality by adding additional modules. Also, the system should contain built-in mechanisms that provide fast recovery after failures, backup of user settings and security of the entire system.
IEEE802.3ah standard
Separate requirements apply to devices that implement control mechanisms in accordance with the new IEEE802.3ah standard, better known as EFM, or Ethernet in the First Mile. It applies to VDSL and SHDSL technologies; provides control of remote devices (user terminals) using a dedicated control channel. At the same time, the advanced capabilities of remote device management in accordance with IEEE802.3ah allow operators to respond in a timely manner and eliminate malfunctions that occur in the network, ensuring high quality of services provided to subscribers.
additional characteristics
In addition to the main functional load of data traffic transmission, 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 transferred from the hub to a group of users. This protocol allows you to save bandwidth on network channels and provide high quality of service for applications that are sensitive to time delays.
The 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 the channel bandwidth more efficiently, ensure reliable collaboration of network equipment from different manufacturers and ensure a high degree of equipment security. When using the IEEE 802.1p standard, a priority level of 0 to 7 is assigned. Based on these priorities, traffic control is performed.
Market development prospects
Thanks to the support of the largest manufacturers, the technologies of the DSL family are developing at a very fast pace. The number of users using existing copper lines to receive broadband access services is increasing every year by about 50%. The production of hubs in the IV quarter of 2004, according to the forecasts of Dell'Oro Group, 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 Telecom |
| 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 transmission networks and telephony at the same time |
| 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 |
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| Physical and channel interfaces on the user side |
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| Control systems |
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| Price | 188$ per port | $1005 per port when the cart is full |
| additional characteristics |
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On the network side, it has WAN ports, and on the client side, it has xDSL half-sets (modems) to which the subscriber line is connected. At the other end of the subscriber line, the client has an xDSL subscriber set (modem) or IAD ( Integrated Access Device- integrated access device). The latter is used in cases where the simultaneous transmission of data and voice in digital form is implemented over the 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 my PBX doesn't have it installed?) // Hacker. - 2005. - V. #075.
Links
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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 linea 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 l 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