DSLAM
digitally a Subscriber LINE ACCESS multiplexer (DSLAM) is a part of the infrastructure needed for the enterprise of DSL. DSLAMs stand at a place, at which Teilnehmeranschlussleitungen gather. Usually it concerns thereby a switching center, partlyin addition, around central points of locking, z. B. in large office or residential complexes. In the specialized jargon the switching center is called cent ral Office (CO ), the DSLAM partly with the generic term cent ral Office equipment (COE).
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function of the DSLAM with its Linecards (S. and) the Teilnehmeranschlussleitungen, collects (and/or. distributed) on local level the DSL data traffic of the final customers and hands it to a regional DSL-AC further, which for the IP-Routing and the PPPoE - time limitation is responsible.
For the binding of a customer at DSL its voice grade channel in the switching center is led to the DSLAM. There - as on customer side - data and Sprachsignale become by one Fragment separately and/or. in reverse direction the Sprachsignal the data signal added (see also LINE sharing).
Customer/participant Switching center POTS Telephone -------- NTBA POTS SWITCH -- PSTN \ Teilnehmeranschlussleitung / Fragment --------------------------- Linecard haven/fragment / POTS + DSL DSLAM \ LAN-- DSL modem(CPE) --- DSL-AC -- DSL Backbone data
the DSL data traffic is transferred into in both directions into at cells. The packets of the Internet Protocols are transported in the pay load of at cells. Task of the DSLAM is, at cells, which come from the net, onto mediate correct participant haven and in reverse. In the OSI model this at switching function corresponds to a Schicht-3-Funktion. For Internet minutes against it is the DSLAM transparency. In addition, more modern products for the multi-service enterprise can schedule the IP data traffic and take over a Routing - a function.
components
of the DSLAM have two substantial components: Linecards and a network interface.
Linecards
of the DSLAM is equipped with card locations for so-called Linecards. On this Linecards those of haven for the lines become, those the participantsgo, in summary. Depending upon building method lies on a Linecard 2, 8, 12, 16, 24, 32, 48, 64 or 72 of haven. A haven essentially consists of a Transceiver unit (with ADSL ATU-C, ADSL transmission unit cent ral Office mentioned), as well as oneFragment, if the line is used at the same time for DSL data traffic and telephone calls. The ATU-C serves signal for the receipt of the Upstream of signal and sends the Downstream. The fragment can be accommodated depending upon design onto the Linecard or install externally.
network interface
the second substantial construction unit of the DSLAM is its network interface, with which it is rear tied up to a DSL-AC. Usually one uses for this AT over optical waveguide cables, for example a STM-1-Verbindung with 155 Mbit/s range.This range can divide a DSL to master with optional Slaves, which one can cascade to the master. This leads the building groups with some products to it that the DSL to master cannot be equipped fully with Linecards, there to cascading in the master(PEM in the master) and in the Slave (FEM) to be used must.LWL
outdoor DSLAM, mini DSLAM
of right: Outdoor DSLAM
within ranges, within which the connection from the switching center to the building of the customer with glass fiber lines realizesit became (OPAL) the DSL time limitation must take place, where the transition of glass fiber lines to copper cables takes place, thus z. B. in the building or in the Kabelverzweiger. This happens with Hilfte of devices, which are called outdoor DSLAM or mini DSLAM.These are substantially smaller than the DSLAMs in the switching centers, because they have substantially fewer connections.
The large advantage of this arrangement is that by the very short copper lines between DSLAM and participant very high ranges become possible and so z.B.VDSL to be used can.
see also
Web on the left of
- heise.de/.. - Article c't over outdoor DSLAMs and VDSL
