EP1106029A1

EP1106029A1 - A method and apparatus to provide end-to-end quality of service guarantee

Info

Publication number: EP1106029A1
Application number: EP99931987A
Authority: EP
Inventors: Baranitharan Subbiah
Original assignee: Nokia Networks Oy; Nokia Oyj
Current assignee: Nokia Oyj
Priority date: 1998-07-30
Filing date: 1999-06-28
Publication date: 2001-06-13
Also published as: AU4838999A; WO2000007407A1

Abstract

A method and apparatus to provide end-to-end quality of service guarantee through AAL2 signaling in an AAL2 switching network is disclosed. The present invention provides a method for updating QoS parameters of ATM connections to a remote AAL2 node which includes collecting QoS parameters of a first ATM connection linking a first AAL2 node to a second AAL2 node and storing the QoS parameters of the first ATM connection for processing AAL2 connection setup requests requiring the ATM connection. Whether the QoS parameters of the first ATM connection satisfy a QoS requirement of the AAL2 connection setup request is verified and a new ATM connection is pursued when the QoS parameters of the first ATM connection do not satisfy the QoS requirement of the AAL2 connection setup request. New QoS parameters are extracted for the new ATM connection and the memory is updated with the new QoS parameters. QoS parameters of the new ATM connection are updated in an AAL2 signaling message provided to the second AAL2 node. When the QoS parameters of the first ATM connection satisfy the QoS requirement of the AAL2 connection setup request, the QoS parameters of the new ATM connection are immediately updated in an AAL2 signaling message provided to the second AAL2 node. The AAL2 signaling message is transferred to the second AAL2 node once the QoS parameters of the new ATM connection are updated in the AAL2 signaling message.

Description

A METHOD AND APPARATUS TO PROVIDE END-TO-END QUALITY OF SERVICE GUARANTEE

BACKGROUND OF THE INVENTION

1. Field of the Invention.

This invention relates in general to a network communications, and more particularly to a method and apparatus to provide end-to-end quality of service guarantee through AAL2 signaling in an AAL2 switching network.

2. Description of Related Art. ATM has been selected as a world standard for broadband ISDN in network communication systems. ATM systems have been implemented on a global basis and developed in a rapid growth. ATM technology is destined to play a major role in both public and private broadband networks. AAL2 is one of the four types of AAL (ATM Adaptive Layer) protocols which have been recommended by CCITT (now ITU-T), namely AAL 1, AAL2, AAL3/4 and AAL5. In general, the layer services provided by AAL1 are constant bit rate (CBR) services which require information to be transferred between source and destination at a constant bit rate. AAL2 offers a transfer of information with a variable bit rate. In addition, timing information is transferred between source and destination. Since the source is generating a variable bit rate, it is possible that cells are not completely filled and that filling level varies from cell to cell. AAL3/4 is used for transfer of data which is sensitive to loss, but not sensitive to delay. The AAL3/4 protocol may be used for connection oriented as well as for connectionless data communication. AAL3/4 itself does not perform all functions required by a connectionless service, since functions like routing and network addressing are performed on the network layer. AAL5 is designed to offer a service with less overhead and better error detection below the common part of the convergence sublayer (CPCS).

The AAL2 signaling protocol describes methods by which a switched AAL2 connection can be established between two AAL2 end users across a network that consists of both ATM and AAL2 switches. The important function of AAL2 signaling protocol is to establish an AAL2 connection between two AAL2 end points on a concatenation of ATM Virtual Channel Connections (VCCs) that are either on demand (SVC) or semi-permanent (PVC). Some the basic requirements of AAL2 signaling protocol include the ability to establish an AAL2 connection between AAL2 end systems that support AESA formats, the ability to support hop-by-hop routing mechanism between AAL2 end systems, the ability to indicate any failures to corresponding management entity, and the ability to setup AAL2 connections with different Quality-of-Service (QoS) requirements. In AAL2, packets (minicells) from many users are assembled into a single ATM cell and transmitted on the same ATM connection. In addition, packets are allowed to straddle across ATM cell boundary to maximize the bandwidth utilization.

The efficiency of AAL2 in transporting short packet size and delay sensitive applications in a trunking environment such as cellular and PBX has given impetus to AAL2 switching. In AAL2 switching, AAL2 packets encapsulated within an ATM cell are demultiplexed and multiplexed based on their channel identifier (CID) values within an ATM node that supports AAL2 switching capability. AAL2 network is an overlay network atop ATM network that include both ATM and AAL2 nodes in which an AAL2 node supports AAL2 level switching while an ATM node supports only ATM level switching. The AAL2 signaling protocol is being specified at the ITU-T to setup an AAL2 switched virtual connection between two AAL2 end users in an AAL2 network. The first set of requirements, capability set 1 (CS1) for such a protocol was drafted at the ITU-T Study Group 11 WP 1 Q6 meeting in January, 1998. As suggested above, an AAL2 connection over a path between an AAL2 source node and an AAL2 destination node is a concatenation of AAL2 channels within physical links along the path. The concatenated AAL2 channels may have different CIDs, VCIs, VPIs, and physical links. ATM nodes along the chosen path between two AAL2 end users are transparent to AAL2 signaling messages and AAL2 switching.

Due to the independent nature of AAL2 and ATM signaling, the values of the QoS parameters (transfer delay, delay variation, etc) of the ATM connection, through which the AAL2 connection is requested, are not included in the end-to-end QoS parameter values during the AAL2 connection setup. However, an AAL2 connection that carries speech might require end-to-end delay of 120 ms or lower, whereas an AAL2 connection for interactive video transmission might require a maximum of 300 ms end-to-end delay. This different delay requirement for different application necessitates that the AAL2 signaling protocol be capable of setting up AAL2 connections with user specific QoS requirements.

It can be seen that there is a need for a method and apparatus to provide end- to-end quality of service guarantee through AAL2 signaling in an AAL2 switching network. It can also be seen that there is a need for a method and apparatus that stores the values of the QoS parameters of the ATM connection at the AAL2 node and, during the AAL2 connection setup request, updates the values of individual QoS parameters of the ATM connection to the AAL2 signaling message. SUMMARY OF THE INVENTION To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method and apparatus to provide end-to-end quality of service guarantee through AAL2 signaling in an AAL2 switching network.

The present invention solves the above-described problems by providing a method for updating QoS parameters of ATM connections to a remote AAL2 node. A method in accordance with the principles of the present invention includes collecting QoS parameters of a first ATM connection linking a first AAL2 node to a second AAL2 node and storing the QoS parameters of the first ATM connection for processing AAL2 connection setup requests requiring the ATM connection.

Other embodiments of a system in accordance with the principles of the invention may include alternative or optional additional aspects. One such aspect of the present invention is that whether the QoS parameters of the first ATM connection satisfy a QoS requirement of the AAL2 connection setup request is verified.

Another aspect of the present invention is that a new ATM connection is pursued when the QoS parameters of the first ATM connection do not satisfy the QoS requirement of the AAL2 connection setup request.

Another aspect of the present invention is that new QoS parameters are extracted for the new ATM connection and the memory is updated with the new QoS parameters.

Another aspect of the present invention is that QoS parameters of the new ATM connection are updated in an AAL2 signaling message provided to the second AAL2 node.

Another aspect of the present invention is that when the QoS parameters of the first ATM connection satisfy the QoS requirement of the AAL2 connection setup request, the QoS parameters of the new ATM connection are immediately updated in an AAL2 signaling message provided to the second AAL2 node.

Another aspect of the present invention is that the AAL2 signaling message is transferred to the second AAL2 node once the QoS parameters of the new ATM connection are updated in the AAL2 signaling message.

These and various other advantages and features of novelty which characterize the invention are pointed out with particularity in the claims annexed hereto and form a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to accompanying descriptive matter, in which there are illustrated and described specific examples of an apparatus in accordance with the invention.

BRIEF DESCRIPTION OF THE DRAWINGS Referring now to the drawings in which like reference numbers represent corresponding parts throughout:

Fig. 1 illustrates the Open Systems Interconnection (OSI) physical layer; Fig. 2 illustrates the AAL2 packet formats;

Fig. 3 illustrates an end-to-end delay calculation during a connection setup; Fig. 4 illustrates the AAL2ME/ALCAP functional model;

Fig. 5 illustrates the problems of an AAL2 connection setup through an ATM connection;

Fig. 6 illustrates a connection setup 600 providing end-to-end QoS guarantee through AAL2 signaling according to the present invention; Fig. 7 illustrates a flow chart of the AAL2ME operation during an AAL2 connection setup; and

Fig. 8 illustrates a block diagram of a hardware implementation 800 of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In the following description of the exemplary embodiment, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration the specific embodiment in which the invention may be practiced. It is to be understood that other embodiments may be utilized as structural changes may be made without departing from the scope of the present invention.

The present invention provides a new method by which End-to-End QoS guarantee is provided for an AAL2 connection through AAL2 signaling in an AAL2 network. AAL2 signaling protocol is used in setting up a switched virtual connection between AAL2 users in an AAL2 network. An AAL2 network consists of both ATM and AAL2 nodes and AAL2 signaling is transparent to the ATM nodes along the path. Due to the independent nature of AAL2 and ATM signaling, the values of the QoS parameters (transfer delay, delay variation, etc) of the ATM connection, through which the AAL2 connection is requested, are not included in the end-to-end QoS parameter values during the AAL2 connection setup. Accordingly, the present invention provides a method, in which the values of the QoS parameters of the ATM connection are stored at the AAL2 node and, during the AAL2 connection setup request, the values of individual QoS parameters of the ATM connection is updated to the AAL2 signaling message. Thus, end-to-end values of the QoS parameters for an AAL2 connection are calculated precisely during the connection setup through AAL2 signaling.

Fig. 1 illustrates the Open Systems Interconnection (OSI) physical layer 100. Modern networks must handle multiple types of traffic such as video 110, voice 112, data files 114, and interactive data 116. The ATM Adaptation Layer 120 is a collection of standardized protocols that provide services to higher layers by adapting user traffic to a cell format. The AAL 120 is divided into the Convergence Sublayer (CS) and the Segmentation and Reassembly (SAR) sublayer (not shown). The ATM Layer 130 is the second layer of the ATM protocol stack model 100 that constructs and processes the ATM cells. The functions of the ATM layer 130 also include Usage Parameter Control (UPC) and support of Quality of Service (QoS) classes. Finally, the physical layer 140 is the bottom layer of the ATM protocol reference model 100. The physical layer 140 is subdivided into two sublayers, the Transmission Convergence (TC) and the Physical Medium (PM) (also not shown). The physical layer 140 provides the ATM cells transmitted over the physical interfaces that interconnect ATM devices.

AAL2 is the new ITU-T specification for supporting low bit rate and delay sensitive applications such as mobile telephony in an ATM environment. AAL2 allows many users to share a single ATM connection by effectively packing variable size packets into ATM cells. AAL2 is subdivided into Service Specific

Convergence Specific Layer (SSCS) and Common Parts sub-layer (CPS). The CPS layer approved by ITU-T in September 1997, enables variable size packets (0-64 bytes) from different users to be assembled in an ATM cell payload and transmitted on the same ATM Virtual Channel Connection (VCC). In addition, packets are allowed to straddle across an ATM cell boundary to maximize the bandwidth utilization.

Fig. 2 illustrates the AAL2 packet formats 200. In Fig. 2, a CPS-Packet header 201 is 3 bytes long. The CID field 202 is 8 bits long and identifies the Logical Link Control (LLC) for the packet. The Length Indicator (LI) field 203 includes 6 bits and indicates the length of the LLC packet. When the LI field 203 points beyond the end of the current ATM cell, the packet is split between cells. The five bits of the User-To-User Indication Field 204 are identifying user to user information. The Header Error Control (HEC) field 205 includes 5 bits and provides error detection over the packet header. Also shown in Fig. 2 is a typical Common Parts sublayer packet data unit

(CPS-PDU) for AAL2 206. The CPS-PDU Start Field (STF) header 208 includes a six bit Offset Field (OSF) 210, a Sequence Number (SN) 220, and a parity bit 230. The STF 202 is one byte in length and occurs at the beginning of every ATM cell payload. As Fig. 2 shows, the Offset Field (OSF) 210 is 6 bits in length. The OSF 210 indicates the remaining length of the packet that (possibly) started in the preceding cell from this ATM connection and is continuing in the current cell. Thus, the OSF 210 points to the start of the first new packet and provides immediate recovery of the packet boundary after an event causing loss of packet delineation. The 1-bit sequence number (SN) field 220 provides a modulo-2 sequence numbering of cells. The one parity (P) bit 230 provides odd parity and covers the STF. Then, the payload 240 includes 47 bytes.

Fig. 3 illustrates an end-to-end delay calculation during a connection setup 300. AAL2 connections on the same virtual channel (VC) may have different traffic and QoS requirements. For example, an AAL2 connection that carries speech might require end-to-end delay of 120 ms or lower, whereas an AAL2 connection for interactive video transmission might require a maximum of 300 ms end-to-end delay. This different delay requirement for different application necessitates that the AAL2 signaling protocol be capable of setting up AAL2 connections with user specific QoS requirements.

Finding a path that matches end-to-end QoS requirements during the connection setup phase of a signaling protocol has been implemented in existing signaling protocols such as Private Network-to-Network Interface (PNNI) signaling. The connection setup message of such signaling protocol carries QoS information Elements (IEs) that are verified and updated by the ATM nodes chosen for that connection setup. For example, End-to-end Transit Delay (ETD) IE in the setup message of the PNNI signaling is updated (cumulative) by the ATM nodes during the connection setup phase with their corresponding transfer delay. Upon receiving the connect message from the remote ATM node, which also has an ETD IE, the local ATM node verifies the value of the ETD to make sure that it is acceptable for the user (application). If the value specified in the ETD IE satisfies the user QoS (maximum transfer delay) then the connection setup is confirmed, otherwise the connection is rejected. If necessary, a new connection setup is requested on a different path to the same destination.

In Figure 3, user (Ul) 310, connected to ATM node (A) 312, requests an AAL2 connection 302 to user (U2) 320 connected to ATM node (D) 322. The path from the source to the destination also include ATM nodes B 324 and C 326. The ETD for this connection is the sum of individual transfer delay at each ATM node, i.e., the sum of D, 330, D₂ 332, D₃ 334, and D₄ 336. The individual delays 330-336 are updated by the respective nodes 312, 322, 324, 326 and added during the connection setup phase. Upon receiving the connect message 340 from the remote user (U2) 320, the local user (Ul) 310 verifies the ETD value to make sure that it is below the maximum ETD value specified by the application.

In order to reduce the complexity in modifying the existing ATM signaling and the need for a lightweight signaling protocol, AAL2 signaling is limited to setup an AAL2 connection between two AAL2 users in an AAL2 network. The traditional ATM signaling protocols such as Broadband ISDN User's Part (BISUP) and PNNI are used to setup the ATM connection between ATM nodes to transfer AAL2 packets and signaling messages transparently. This independent approach between AAL2 and ATM signaling protocols requires the AAL2 management Entity (AAL2ME) or Access Link Control Application Part (ALCAP) to perform the interface functions.

Fig. 4 illustrates the AAL2ME/ALCAP functional model 400. In Figure 4, the independent nature of AAL2 signaling and ATM signaling is evident. An AAL2 connection setup request received through AAL2 signaling 410 or directly from AAL2 user (mobile signaling) 414 is handled by the AAL2ME 420. Based on the needs, AAL2ME 420 may request a new ATM connection through the ATM signaling 422 supported at the node. Upon completion of the ATM VCC setup, AAL2ME 420 allocates resources for the AAL2 connection and transmit the AAL2 signaling message 410 to the next AAL2 node. If the next node is not an AAL2 node, then AAL2ME will request a connection through ATM nodes to the first AAL2 node on the chosen path. Even though AAL2ME is responsible for many types of functionality, represented by the other functions 430, the present invention focuses on AAL2 and ATM connection setups only. During the AAL2 connection setup, AAL2ME 420 requests certain QoS and traffic parameters for the connection to the destination AAL2 node and the values of these parameters normally reflect the requirements of all of the AAL2 connections allocated on the same ATM connection.

Accordingly, in an AAL2 network, choosing a path that satisfies the QoS requirements of an AAL2 user is more complex than in ATM networks. As can be seen, the main reason is that an AAL2 network includes both ATM and AAL2 nodes and ATM nodes are transparent to the AAL2 signaling messages. As mentioned above, the CS1 requirements necessitate the independence of AAL2 signaling protocol and are described in detail below.

AAL2 signaling should be independent of the underlying signaling bearer. For example, the signaling bearer should be able to carry the AAL2 signaling messages over both User Network Interface (UNI) and Network Node Interface (NNI) protocol stacks. Thus, the AAL2 signaling messages are transparent to ATM nodes in a path selected for an AAL2 connection. In detail, the IEs such as transfer delay and delay variation encapsulated within the AAL2 signaling messages are not processed by ATM nodes. This raises the problem of how to update the QoS parameter values of the ATM connection into the IEs in the AAL2 signaling messages. If the QoS parameters of the ATM connection are not included in the ehd-to-end QoS parameters of the AAL2 signaling message then the values that an AAL2 user receive after the connection setup is well below the actual end-to-end values. This problem will result in performance degradation for applications transmitting data through AAL2 connection and eventually will cause the termination of the connection. AAL2 packets carried by ATM cells are subjected to delay, delay variation and loss ratio inside ATM nodes. Thus, in order to calculate the end-to-end values of the QoS parameters from the source to the destination AAL2 node, any impairment (delay, loss, etc) by ATM nodes need to be included.

Fig. 5 illustrates the problems of an AAL2 connection setup through an ATM connection 500. For example, an AAL2 connection from a user 510 at the source node A 512 to a user 514 at the destination node D 516 includes AAL2 nodes B 520 and C 522, and ATM nodes X 530 and Y 532. As the connection setup message arrives at node B 520, node B 520 processes the AAL2 setup request and passes it to the next AAL2 node C 522. Since AAL2 node B 520 does not have any prior information about the values of the QoS parameters of the ATM connection that connects to the next AAL2 node C 522, via ATM nodes X 530 and Y 532, the QoS parameters contained in the AAL2 connection setup message are not updated with the QoS impairments of the ATM connection 540. For example, the transfer delay of the ATM connection D_x 550 is not updated to the ETD parameter in the AAL2 signaling message. This causes a serious problem in calculating the end-to-end values of the QoS parameters such as transfer delay for an AAL2 connection. The present invention provides for the calculation of the end-to-end values of the QoS parameters more accurately for each AAL2 connection setup request.

As described above, values of the QoS parameters for an ATM connection needs to be updated in the AAL2 signaling message to calculate the exact value of the QoS parameters for an end-to-end AAL2 connection. According to the present invention, during the initial establishment of an ATM connection between two AAL2 nodes, the AAL2 node (AAL2ME) that initiates the ATM connection collects the value of the QoS parameters of the ATM connection and stores them in the local memory. Upon receiving an AAL2 connection setup request, the corresponding AAL2ME looks for any existing ATM connection to the next AAL2 node. If it exists then the values of the QoS parameters of the ATM connection are updated in respective IEs found in the AAL2 signaling message. In case a new ATM connection is needed, AAL2ME will initiate a new request and collect the QoS parameter values and update them accordingly.

Fig. 6 illustrates a connection setup 600 providing end-to-end QoS guarantee through AAL2 signaling according to the present invention. Upon receiving an AAL2 connection setup from a user 610 through AAL2 node A 612, AAL2 node B 620 initiates an ATM connection setup to AAL2 node C 622. On successful completion of ATM connection setup, the AAL2ME at AAL2 node B 620 extracts the value of the QoS parameters of the ATM connection 640 and store the value of the QoS parameters of the ATM connection 640 in local memory. For example, transfer delay of the ATM connection D_x 650 between AAL2 nodes B 620 and C 622 is stored in AAL2 node B 620. When an AAL2 connection is to be established, the value of the QoS parameters D_x 650 is updated in the respective QoS IEs in the AAL2 signaling message. Due to the present invention, the values of QoS parameters are updated for the entire connection including both AAL2 and ATM part of the connection. After receiving a connect message, the source AAL2 node A 612 can verify whether the end-to-end values of the QoS parameters meets the requirement of the user 610. The AAL2ME operation during an AAL2 connection setup is further illustrated as a flow chart 700 shown in Figure 7.

In Fig. 7, an AAL2 connection is received 710. Whether there is a need for a new ATM connection is determined 712. If a new ATM connection is required 714, an ATM connection to the next AAL2 node through standard ATM signaling is setup 716. If the setup is unsuccessful 718, the process is repeated for a new path 720. If the setup is a success 722, the QoS parameter values are extracted and the values stored in the memory are updated 724. Then, the QoS parameter values of the ATM connection in the AAL2 signaling message are updated 730.

If there is no need for a new ATM connection 726, the QoS parameter values of the ATM connection in the AAL2 signaling message are updated 730. Thereafter, the AAL2 signaling message to the next AAL2 node is sent 740.

Fig. 8 illustrates a block diagram of a hardware implementation 800 of the present invention. Each of the AAL2 switch nodes illustrates in Fig. 6 include a processor 810 and memory 812 which may include random access memory (RAM), read-only memory (ROM), or any other memory configuration. The processor 810 operates under the control of an operating system (not shown) and is configured to executes one or more computer programs, which are represented in Fig. 8 by the "box" 830 within the block indicating the processor 810. Generally, the computer programs 830 may be tangibly embodied in a computer-readable medium or carrier 840. The computer programs 830 may be loaded from the computer-readable medium or carrier 840 into memory 812 for execution by the processor 810 as discussed above with reference to Figs. 6 and 7. The computer program 830 comprises instructions which, when read and executed by the processor 810, causes the processor 810 to perform the steps necessary to execute the steps or elements of the present invention. Although an exemplary computer system configuration is illustrated in Fig. 8, those skilled in the art will recognize that any number of different configurations performing similar functions may be used in accordance with the present invention.

Thus, the present invention provides for the precise calculation of the end-to- end values of the QoS parameters during the AAL2 connection setup phase. To meet the requirements of delay sensitive applications such as speech and interactive video, an AAL2 connection should calculate the end-to-end transfer delay of the AAL2 connection. The present invention provides a solution by which QoS impairments of the ATM connection, through which an AAL2 connection is established, are included during the AAL2 connection setup. The present invention allows the local AAL2 user to verify the values of the end-to-end QoS parameters to see if they satisfy the requirements of the application. At the same time, the present invention does not require any modification to the existing ATM signaling protocols. The procedures to obtain the end-to-end values of the QoS parameters are already supported in the existing ATM signaling. Due to the present invention, the QoS parameter values of the AAL2 signaling setup message are updated more accurately and reflect the individual parameter value for the entire connection that includes both ATM and AAL2 nodes. If the AAL2 connection cannot be guaranteed for the requested QoS, then the source AAL2 node can choose a different ATM connection that will satisfy the QoS guarantee. Overall, the present invention improves the AAL2 connection admission procedures within an AAL2 network by guaranteeing a user requested end-to-end QoS.

The foregoing description of the exemplary embodiment of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teaching. It is intended that the scope of the invention be limited not with this detailed description, but rather by the claims appended hereto.

Claims

WHAT IS CLAIMED IS:

1. A method for providing an end-to-end quality of service (QoS) guarantee through AAL2 signaling in an AAL2 switching network, comprising: collecting QoS parameters of a first ATM connection linking a first AAL2 node to a second AAL2 node; and storing the QoS parameters of the first ATM connection for processing AAL2 connection setup requests requiring the ATM connection.

2. The method of claim 1 further comprising verifying whether the QoS parameters of the first ATM connection satisfy a QoS requirement of the AAL2 connection setup request.

3. The method of claim 2 further comprising searching for a new ATM connection when the QoS parameters of the first ATM connection do not satisfy the QoS requirement of the AAL2 connection setup request.

4. The method of claim 3 further comprising extracting new QoS parameters for the new ATM connection and updating the memory with the new QoS parameters.

5. The method of claim 4 further comprising updating QoS parameters of the new ATM connection in an AAL2 signaling message provided to the second AAL2 node.

6. The method of claim 5 further comprising sending the AAL2 signaling message to the second AAL2 node.

7. The method of claim 2 further comprising updating QoS parameters of the new ATM connection in an AAL2 signaling message provided to the second AAL2 node when the QoS parameters of the first ATM connection satisfy the QoS requirement of the AAL2 connection setup request.

8. The method of claim 7 further comprising sending the AAL2 signaling message to the second AAL2 node.

9. An article of manufacture for a processor-based AAL2 switch, the article of manufacture comprising a computer readable medium having instructions for causing a processor to perform a method comprising: collecting QoS parameters of a first ATM connection linking a first AAL2 node to a second AAL2 node; and storing the QoS parameters of the first ATM connection for processing AAL2 connection setup requests requiring the ATM connection.

10. The method of claim 9 further comprising verifying whether the QoS parameters of the first ATM connection satisfy a QoS requirement of the AAL2 connection setup request.

11. The method of claim 10 further comprising searching for a new ATM connection when the QoS parameters of the first ATM connection do not satisfy the QoS requirement of the AAL2 connection setup request.

12. The method of claim 11 further comprising extracting new QoS parameters for the new ATM connection and updating the memory with the new QoS parameters.

13. The method of claim 12 further comprising updating QoS parameters of the new ATM connection in an AAL2 signaling message provided to the second

AAL2 node.

14. The method of claim 13 further comprising sending the AAL2 signaling message to the second AAL2 node.

15. The method of claim 10 further comprising updating QoS parameters of the new ATM connection in an AAL2 signaling message provided to the second

AAL2 node when the QoS parameters of the first ATM connection satisfy the QoS requirement of the AAL2 connection setup request.

16. The method of claim 15 further comprising sending the AAL2 signaling message to the second AAL2 node.

17. An AAL2 switch providing an end-to-end quality of service (QoS) guarantee through AAL2 signaling in an AAL2 switching network, comprising: an AAL2 management entity for setting-up ATM connections between AAL2 switches, the AAL2 management entity collecting QoS parameters of a first ATM connection linking to a remote AAL2 switch; and a memory, coupled to the AAL2 management entity, for storing the QoS parameters of the first ATM connection; wherein the AAL2 management entity processes AAL2 connection setup requests by comparing the QoS parameters of the first ATM connection to QoS parameters required by a AAL2 setup request requiring an AAL2 connection to the remote AAL2 switch.

18. The AAL2 switch of claim 16 wherein the AAL2 management entity searches for a new ATM connection when the QoS parameters of the first ATM connection do not satisfy the QoS requirement of the AAL2 connection setup request.

19. The AAL2 switch of claim 18 wherein the AAL2 management entity extracts new QoS parameters for the new ATM connection and updates the memory with the new QoS parameters.

20. The AAL2 switch of claim 18 wherein the AAL2 management entity updates QoS parameters of the new ATM connection in an AAL2 signaling message provided to the remote AAL2 node.

21. The AAL2 switch of claim 20 wherein the AAL2 management entity sends the AAL2 signaling message to the remote AAL2 node.

22. The AAL2 switch of claim 10 wherein the AAL2 management entity updates QoS parameters of the new ATM connection in an AAL2 signaling message provided to the remote AAL2 node when the QoS parameters of the first ATM connection satisfy the QoS requirement of the AAL2 connection setup request.

23. The AAL2 switch of claim 22 wherein the AAL2 management entity sends the AAL2 signaling message to the remote AAL2 node.