CN1382362A

CN1382362A - Method and arrangement for connecting access network to switching device

Info

Publication number: CN1382362A
Application number: CN 00814617
Authority: CN
Inventors: G·梅格尔; B·达施; H·勒斯林舍菲; J·辛格
Original assignee: Siemens AG
Current assignee: Siemens AG
Priority date: 1999-10-22
Filing date: 2000-10-18
Publication date: 2002-11-27
Also published as: DE19951047A1; BR0014923A; WO2001030111A2; EP1222837A2; AR026199A1; WO2001030111A3; DE19951047B4

Abstract

The invention relates to a method and an arrangement for connecting terminals (UT) to a switching device (LE), comprising a connecting device (IAD) for connecting said terminals (UT) to an access network (AN) and an input adapter device (IAT) for linking the access network (AN) to V5-interfaces (V5IF) of the switching device (LE). The signalling information that has to be exchanged between the connecting device (IAD) and the switching device (LE) according to the VP5 protocols is at least partially conveyed between the connecting device (IAD) and the input adapter device (IAT) in a common signalling channel (CCSC).

Description

Method and apparatus for connecting access network to switching device

According to the reference model of the V5 interface provided between a switching device and its access network, the access network is regarded as a non-further-subdividable unit in which a plurality of subscribers are integrated using analog PSTN (public switched telephone network) or digital ISDN (integrated services digital network) terminals, also referred to in the specialist literature as UT (user terminal) or CTE (user telephone equipment). In this case, the V5 interface is either designed as a non-centralized V5.1 interface or as a centralized V5.2 interface. However, instead of the V5 interface, which is popular in european domains, the Telecordia GR303 interface is typically used in american domains using a similar reference model. The interfaces described are specified in the following documents:

v5.1 interface:

international ITU standard g.964, "V-INTERFACES AT THE DIGITAL LOCALEXCHANGE (LE): v5.1 INTERFACE (BASED ON 2048kbit/s) FOR THESUUPPORT OF ACCESS NETWORK (AN) [ V INTERFACE at digital local exchange: v5.1 interface (based on 2048 bits/sec) ] ", 06/94 for supporting access network

Regional ETSI standard ETN 300324-1: "V5.1 interface for the support of Access Network (AN) Part 1: v5.1 interworking [ V5.1 interface part 1 for supporting access network: v5.1 interface Specification ] ", 02/94-modified to" correction A1 ", 01/96

-international ITU standard g.965, "V-INTERFACES AT THE DIGITAL LOCALEXCHANGE (LE): v5.2 INTERFACE (BASED ON 2048kbit/s) FOR THESUUPPORT OF ACCESS NETWORK (AN) [ V INTERFACE at digital local exchange: v5.2 interface (based on 2048 bits/sec) ] ", 03/95 for supporting access network

Regional ETSI standard ETN 300347-1: "V5.2 interface for the support of Access Network (AN) Part 1: v5.2 interworking [ V5.2 interface part 1 for supporting access network: v5.2 interface Specification ] ", 09/94-modified to" amendment A1 ", 05/97

The GR303 interface:

regional Telcordia general Requirements Specification GR303-CORE, "Integrated digital Loop Carrier systems general Requirements, Objectives, and Interface [ Integrated digital Loop Carrier System general Requirements, tasks and interfaces ]", version 2, 09/98

The sum of all state information, messages and processes required to control the transmission process over the interface is referred to herein as the protocol. In order to control the transmission process via the V5 interface, multiple protocols are typically required. Herein, one refers to one protocol, a plurality of sub-protocols, or to a protocol group having a plurality of protocols according to a thinking method.

Within the scope of modern standardization, access networks which, according to the models to date, are regarded as homogeneous units are further subdivided into a connecting device IAD (integrated access device) and a transit device IAT (integrated access terminal). In the specialist literature, the connecting devices are also referred to as NT (network termination) or CP-IWF (subscriber unit interworking function), while the switching devices are referred to as CO-IWF (central office interworking function). In this case, the terminal is always connected to a usually one-piece connecting device, and the switching device is connected to a plurality of switching devices, if necessary. This reference model is for example described in the document "Baseline Text for Loop Emulation Service Using AAL2[ Baseline Text for Loop Emulation Service with AAL2 ]", ATM Forum, BTD-VTOA-LES-01.02.doc, 09/99, FIG. 1. In addition, it is known to connect a connection device and a switching device to an ATM network in an access network. For the traffic flows transmitted between the terminals and the switching devices in the associated B (bearer) channel and for the control of the transmission process, for example, the signalling flows transmitted in the D (control) channel, they are transmitted in the ATM network according to the AAL2(ATM adaptation layer type 2) protocol using ATM cells, which are normally allocated to the virtual connections VCC (ATM virtual channel connections). The protocol is in International ITU standard I.363.2, "B-ISDN ATM attachment Layer Specification; type 2 AAL [ B-ISDN ATM Adaptation layer Specification: type 2 ALL ] ", 09/97. This entire scheme is known in the professional field as "loop emulation services over ATM bearer". At the same time, it is known today to apply the V5 interface, which is standardized for uniform access networks, to such access networks that are sub-divided into models.

The invention is therefore based on the object of constructing a non-uniform access network for the use of the V5 interface. This object is achieved by the features of claim 1.

The main aspect of the invention consists in a method for connecting a terminal to at least one switching device, which makes use of at least one connection device, usually fitted to an access network, for connecting said terminal to the access network, at least one switching device, also usually fitted to an access network, for connecting said access network to said switching device, at least one V5 interface between said switching device and said switching device, and at least one, optionally virtual, common signaling channel between said connection device and said switching device, wherein signaling information that needs to be transmitted at least between said connection device and said switching device due to the use of said V5 interface is transmitted at least partially within said common signaling channel. Some of the main advantages of the present invention are as follows:

it reveals in principle how to use the signaling method based on the V5 standard in a subdivided, modeled access network,

the protocol instance for processing the signaling information according to the protocol defined in the V5 standard is kept unchanged at least within the switching device,

the existing method can be used substantially identically for controlling the common signaling channel between the transit device IAT and the connecting device IAD, since the common signaling channel is also established over said V5 interface,

the provisions of the V5 standard can be fully reused,

the adapter device and the connecting device can be produced economically optimally. This is very advantageous, for example, for the preparation phase, since the economic factors have a very important significance in this phase,

the full range of functions defined in the V5 standard can be used directly for controlling the connection between the terminal and the switching device,

even in the case of using access networks which are sub-divided modeled, the same range of functionality can be provided at the terminal UT as when using a uniformly modeled access network reliably.

According to one embodiment of the method, the signaling information for controlling the V5 interface is exchanged only between the switching device and the switching device — claim 2. A further development of the invention provides that, according to a first protocol applied to the V5 interface: signaling information established by a protection protocol, a bearer channel connection protocol or a link control protocol is transmitted only between said switching device and switching device, and according to a second protocol applied on said V5 interface: signaling information set up by the ISDN signaling protocol, the PSTN signaling protocol or the control protocol is transmitted at least between said connecting device and the switching device-claim 3. The transmission effort in the switching device, the transmission capacity required in the common signaling channel and the processing effort in the connecting device can thereby be minimized.

According to a refinement of the method according to the invention, the signaling information is transmitted in the signaling channel using a protocol element which corresponds in its structure to the elements set up in the protocol, claim 4. The transmission effort in the switching device can thereby be minimized, since the protocol elements are identical and therefore need only be passed substantially transparently to the switching device. It is thus not necessary to duplicate said signalling information between different structured protocol elements, which is very advantageous.

A variant of the method according to the invention provides that an additional protocol is used between the connection device and the switching device, with which at least the activation and deactivation of the connection between the connection device and the switching device is controlled, as claimed in claim 5. Thereby realizing the functions required for coordinating the distributed processing of the protocols. Thereby advantageously also providing all functions specified by the protocol.

According to a further development of the method according to the invention, the common control protocol part of the control protocol is at least supplemented with a continuity check function-claim 6. This makes it possible to check the interference of the common signaling channel only at the logical layer. In this case, the finite-state machine set up according to the V5 protocol is set to a specific fault state in the event of a fault, whereby undefined states in the cooperation of the distributed finite-state machines are advantageously avoided.

According to a further development of the method according to the invention, the common signaling channel is formed as a virtual channel with channel number 8, at least in the case of transmission between the connection device and the transfer device using ATM cells-claim 7. By using the channel number 8 channel reserved as a signaling channel in ATM, the existing software can be used unchanged to control the channel, and it can be used many times in the case of multiple applications. And is thus very efficient in terms of the tools required for the control software.

According to a variant of the method according to the invention, at least in the case of transmission between the connection device and the switching device using ATM cells, the signaling information set up according to the ISDN signaling protocol is transmitted in an additional, terminal-specific virtual channel — claim 8. This eliminates the need to process the signaling information in the connecting device. This reduced complexity is particularly advantageous for the connecting device, since it represents a mass-produced product, whose inexpensive production is of great interest.

Further preferred developments of the method according to the invention are given in the dependent claims, preferred devices for carrying out the method according to the invention being given in the appended claims.

The method according to the invention is described in detail below with the aid of a number of figures. Wherein:

fig. 1 shows a network configuration in a block diagram, with a unified access network according to the V5 reference model,

figure 2 shows in a block diagram a network configuration with further partitioned access networks,

fig. 3 shows in a block diagram the network configuration shown in fig. 2, with an additional ATM network between the connecting device IAD and the transit device IAT,

fig. 4 shows in a block diagram the network configuration shown in fig. 3 with an additional xDSL arrangement between the connecting device IAD and the ATM network, and

fig. 5 shows in a block diagram the network configuration shown in fig. 3 or 4 with a virtual connection VC as used in the present invention.

The network configuration according to the V5 reference model is exemplarily depicted in fig. 1. At least one terminal UT is connected to a connecting device NT (also referred to as CP-IWF, but hereinafter mostly referred to as IAD) indicated by a dotted line at a terminal interface UTIF at the terminal side of the unified access network AN. Said access network AN is connected to at least one switching device LE at a V5 interface V5IF on the switching side. Between the two units the protocol V5P used on the V5 interface V5IF is applied.

A network configuration according to a modern standardized method is shown in fig. 2. The network configuration is substantially identical to that of fig. 1. The access network AN is subdivided into a connection device IAD on the terminal side (also referred to as CP-IWF), in which the alternative name is denoted by the dotted line with NT, and a transit device IAT on the exchange side (also referred to as CO-IWF). At least one signaling channel CCSC according to the invention is set up between the connecting device IAD and the transit device IAT. A protocol V5P running over the V5 interface V5IF is additionally set up between the access network AN and the switching equipment LE. According to the invention, however, some of the protocols set up according to the V5 standard are only used between the transit device IAT and the switching device LE, which are illustrated in the figure by the first protocol V5P', while some of the protocols set up according to the V5 standard are used at least between the connecting device IAD and the switching device LE, which are illustrated in the figure by the second protocol V5P ". The last-mentioned protocol is transmitted in the common signaling channel CCSC between the connecting device IAD and the transit device IAT. In addition, an additional protocol A2CC (AAL2 channel control) can be set up between the connecting device IAD and the intermediate device IAT, as long as, for example, full V5 functionality is to be provided at the terminal UT — this option is illustrated by dotted lines in the figure. The sum of protocol V5P "and additional protocol A2CC is also referred to as a protocol suite or simply protocol A2LC (AAL2 loop control).

Another network configuration substantially in accordance with fig. 2 is shown in fig. 3. It is additionally provided that the connecting device IAD and the switching device IAT are connected to each other via an ATM network ATMN and are connected to an ATM interface ATMIF of the ATM network. Additional protocols A2LC (AAL2 loop control) are also mandatory for network configuration. It is also clear that the first protocol V5P' can be implemented, for example, as a protection protocol PP, a bearer channel connection protocol BCC or a link control protocol LP, while the second protocol V5P "can be implemented, for example, as an ISDN signaling protocol DSS, a PSTN signaling protocol PSP or a control protocol CP. Here, the control protocol CP includes at least one common control protocol part CC.

Another network configuration substantially in accordance with fig. 3 is shown in fig. 4. It is additionally provided that the connecting device IAD is not connected directly but indirectly via an access multiplexer DSLAM (digital subscriber line access multiplexer) to the ATM network ATMN. A transmission method known in the technical field as xDSL is used at the physical interface between the connection device IAD and the access multiplexer DSLAM. But here ATM cells are additionally transmitted at the higher protocol layer-this is represented by the extended name DSLAM (ATM) of the access multiplexer DSLAM. Therefore, from the viewpoint of the ATM protocol layer abstracted by the physical interface, the connecting device IAD and the transit device IAT are also connected to each other. This situation is depicted in detail in fig. 5.

A network configuration substantially in accordance with fig. 3 or 4 is shown in fig. 5. However, the ATM network ATMN or the access multiplexer DSLAM are not shown in order to illustrate the abstracted view of the ATM protocol layer. Instead, the virtual connection VCC (ATM) of the ATM protocol layer and the virtual channels VC comprised in the connection are shown. A separate common signaling channel CCSC is set up between the connecting device IAD and the transit device IAT, which preferably has a channel number CID of 8. The bearer channel B and the control channel D associated with the terminal are always transmitted in separate virtual channels, that is to say, according to the configuration of the example, the signaling information set up in the control channel D according to the ISDN signaling protocol DSS is not carried in the common signaling channel CCSC but in the virtual channel VC dedicated to the terminal. The transmission process is preferably controlled according to the AAL2 protocol. The AAL5 protocol may also be optionally employed.

For this embodiment it is assumed that the network configuration of fig. 3 has a virtual connection VCC architecture between the connecting device IAD and the transit device IAT within the ATM network ATMN as shown in fig. 5. For example, protocols such as the protection protocol PP, the bearer channel connection protocol BCC and the link control protocol LP are handled in the transit device IAT in terms of content, and protocols such as the PSTN signaling protocol PSP and the control protocol CP are handled in the connection device IAD. The ISDN signaling protocol DSS is basically processed in the terminal UT in terms of content and is only transmitted transparently within the connecting device IAD. However, if necessary, the ISDN signaling protocol DSS can also be handled in the content area within the connecting device IAD.

In principle all of the protocols described above can be transported within a common signaling channel CCS, which is configured for the ATM network ATMN as a virtual channel VC with a channel number CID 8. As an alternative, the ISDN signaling protocol DSS is transmitted at least in the terminal-specific channel VC, so that the otherwise required addressing scheme adaptation of the common signaling channel CCSC is eliminated in the connecting device IAD. This is very advantageous because otherwise a second address matching has to be performed within the access network AN in addition to the address matching within the transit device IAT for the V5 interface V5IF with the addressing scheme of the common V5 signaling channel set up on the V5 interface V5 IF.

Preferably, the protocol elements used in said common signaling channel CCSC have a structure substantially identical to that defined by the belonging V5 standard, whereby the complexity of the signaling process for the second protocol V5P "in the transit device IAT is substantially reduced to the transfer-related protocol elements. Said protocol V5P "is preferably transported within the ATM network ATMN using ATM cells complying with the ATM protocol AAL 2.

Said additional protocol A2CC is for example also added to the existing mechanism of the ATM protocol AAL2 used. The data link layer of the additional protocol A2LC corresponds here, for example, to the data link sublayer LAPV5 in accordance with ETSI standard ETN 300347, chapter 10 and ETN 300324. In case of using ATM adaptation layer 2 AAL2, the transport error detection sublayer SSTED is used by said additional protocol A2 LC. This sublayer in turn uses the segmentation and reassembly sublayer SSSAR. Said sublayers SSTED and SSSAR are assigned to the so-called service-Specific Convergence Sublayer SSCS, which was described in international ITU standard i.366.1, "Segmentation and reassembly service Specific Convergence Sublayer for the AAL type 2", 06/99. In summary, the following protocol cooperation results between the connecting device IAD and the relay device IAT:

when transmitting within the common signaling channel CCSC, protocol A2LC (AAL2 loop control), which represents the sum of protocol V5P ″ and additional protocol A2CC, requires addressing of the individual protocols for the multiple protocols in order to distinguish them and to transmit them correctly to the protocol instance for handling said protocol V5P or additional protocol A2 CC. The protocol elements described for this purpose are identified by means of an Envelope Function Address (EFA) provided in the V5 standard. The following envelope function addresses are set up:

protocol	EFA
protocol	EFA	ISDN signalling protocol DSS	＜＝8175
PSTN Signaling protocol PSP	8176	ISDN signalling protocol DSS	＜＝8175
PSTN Signaling protocol PSP	8176	Control protocol CP	8177
Bearer channel connection protocol BCC	8178	Control protocol CP	8177
Bearer channel connection protocol BCC	8178	Protection protocol PP	8179
Link control protocol LP	8180	Protection protocol PP	8179
Link control protocol LP	8180	Additional protocol A2CC	8181

The control protocol CP includes, for example, two sub-protocols: 1) user port control sub-protocol and 2) common control sub-protocol CC, both of which are described in ETSI standard ETN 300347, chapter 15 or ETSI standard ETN 300324, chapter 14. The sub-protocol CC preferably uses only the following functions for the protocol A2 LC:

variant and interface ID

Restart (PSTN)

Blocking/unblocking all relevant PSTN/ISTN subscriber ports as request, accept, reject and complete, respectively.

According to the architecture of the A2LC protocol, the common control sub-protocol CC is supplemented with a continuity check function by adding two protocol elements such as:

-A2LC continuity test

-A2LC continuity check ACK

As long as the protocol elements are exchanged, for example periodically, interference of the common signaling channel CCSC can be found. In the event of a fault, the finite state machine representing the state of the terminal UT, for example according to the V5 standard, is transitioned into the blocking state.

Said additional protocol A2CC is installed by the ATM network ATMN and is used at least for activating and deactivating said virtual channels VC used according to the AAL2 protocol-hereinafter referred to as "AAL 2 channels". It includes, for example, the following protocol elements:

-activation of

-completion of activation

-activation rejection

Deactivation of the device

-deactivation completion

Deactivation rejection

Review-optional items

Review completion-optional items

IAD Fault optional

IAD Fault confirmation-optional

Activation and deactivation of the AAL2 channel is controlled on the switch side by sending the corresponding protocol element "activate" or "deactivate". This is answered with the corresponding protocol element on the terminal side. This procedure can be carried out, for example, on the V5 interface V5IF during the time when the channel set up for the transmission of the B channel is occupied. Preferably, the protocol elements "review" and "review complete" are optional and are arranged to check the following assignments: channel number CID of AAL2 channel * AAL2 channel. Likewise, the protocol elements "IAD fault" and "IAD fault acknowledge" are also optional and are used, if necessary, to inform the transit device IAT about the fault status in the connecting device IAD.

The invention can be applied to very good advantages when applied to the network configuration shown in fig. 4. In this configuration, a higher transmission capacity is provided by means of xDSL technology over existing copper lines. This makes it possible to provide so-called multi-line telephone service, in which more channels can be provided than is generally the case for three channels 2B + D in ISDN. Due to the flexibility of statistical capacity control of the common signaling channel CCSC and the flexible number of virtual channels VC of the ATM network ATMN, the network can be further optimally adapted to the larger fluctuations of the number and capacity of transport channels required by the terminals UT for transporting useful and signaling information than the reliable PSTN and ISDN access networks AN. The transmission of information is also carried out here in the form of ATM cells over xDSL transmission links, wherein the information assigned to the plurality of terminals UT is transmitted in the virtual connection VCC used here, preferably according to the AAL2 protocol.

The same approach can also be used in a similar way if other packet-oriented networks are used, such as IP (internet protocol) based IP networks. Instead of the AAL2 protocol, an IP-specific protocol is used here, wherein the two protocols are not necessarily mutually exclusive. Thus, in the IP range of ATM bearers, it is absolutely possible to use IP and ATM protocols in combination.

This further equivalent is reflected in the field of expertise by nomenclature-like terms such as "ATM-over-ATM loop emulation service" or "IP-over-IP loop emulation service" depending on the network configuration, or in voice-over-ATM "(VoATM)," voice-over-IP "(VoIP) or" voice-over-DSL "(VoDSL) in schemes based on voice as the main useful information. Thus, the present invention may be readily applied in an equivalent manner by persons skilled in the relevant art for each technique described herein and its corresponding technique.

Claims

1. Method for connecting a terminal (UT) to at least one switching device (LE), using

-at least one connection device (IAD) for connecting said terminal (UT) to AN Access Network (AN),

-at least one transit device (IAT) for connecting said Access Network (AN) to at least one V5 interface (V5IF) of said switching device (LE),

-at least one common signalling channel (CCSC) between the connecting device (IAD) and the transit device (IAT),

wherein,

-transmitting, at least partially, within said common signalling channel (CCSC), signalling information that needs to be transmitted at least between said connecting device (IAD) and said switching device (LE) thanks to the use of said V5 interface (V5 IF).

2. The method of claim 1, wherein:

the signaling information for controlling the V5 interface (V5IF) is exchanged only between the transit device (IAT) and the exchange device (LE).

3. The method of claim 1 or 2, wherein:

according to a first protocol (V5P') applied on the V5 interface (V5 IF):

-a protection protocol (IP),

bearer channel connection protocol (BCC), or

-link control protocol (LP)

And the established signaling information is transmitted only between said transit device (IAT) and the switching device (LE), and according to a second protocol (V5P ") applied on said V5 interface (V5 IF):

-ISDN signalling protocol (DSS),

-PSTN Signaling Protocol (PSP), or

-Control Protocol (CP)

And the set-up signalling information is transmitted at least between said connecting device (IAD) and the switching device (LE).

4. A method according to any one of claims 1 to 3, wherein:

the signalling information is transmitted in the signalling channel by means of protocol elements which correspond in their structure to the elements set up in the protocol (V5P' ).

5. A method according to any of the preceding claims, characterized by:

an additional protocol (A2CC) is used between the connecting device (IAD) and the switching device (IAT), by means of which at least the activation and deactivation of the connection between the connecting device (IAD) and the switching device (IAT) is controlled.

6. A method according to any of the preceding claims, characterized by:

the common control protocol part (CC) of the Control Protocol (CP) is supplemented with at least a continuity check function.

7. A method according to any of the preceding claims, characterized by:

at least in the case of transmission between the connecting device (IAD) and the switching device (IAT) using ATM cells, the common signaling channel (CCSC) is configured as a virtual channel with a channel number (CID) of 8.

8. A method according to any of the preceding claims, characterized by:

at least in the case of transmission between the connecting device (IAD) and the switching device (IAT) by means of ATM cells, the signaling information set up according to the ISDN signaling protocol (DSS) is transmitted in an additional, terminal-specific Virtual Channel (VC).

9. Apparatus for carrying out the method according to any one of claims 1 to 8.

10. Apparatus for connecting a terminal (UT) to at least one switching device (LE), having

-at least one assembled connecting device (IAD) for connecting said terminal (UT) to AN Access Network (AN),

-at least one common signalling channel (CCSC) between said connecting device (IAD) and transit device (IAT) for the transmission of at least those signalling information which, due to the adoption of said V5 interface (V5IF), need to be transmitted at least partially between said connecting device (IAD) and switching device (LE).