Patent Application
20080232360
The present invention relates to a session admission control method with respect to a setup of a data packet stream between a source packet gateway and a destination packet gateway, a method of operating an edge router processing data packet stream exchanged between at least one source packet gateway and at least one destination packet gateway, and related apparatuses.
As Internet protocol IP technology becomes more and more widespread, the need of connecting different packet gateways, i.e. networking nodes handling many data flows in parallel through the same multiple service IP transport as intermediate devices between different network domains, e.g., a media gateway MGW, a SGSN, or a GGSN, is expressed by various operators. Here, the access network connecting the packet gateways can be basically of any kind, e.g., traditional PSTN networks, traditional PSTN networks used for dial-in access if IP services, UTRAN networks, a whole UMTS network or a corporate LAN.
In traditional IP oriented networks, there are no QoS guarantees. The need to handle different packet flows with different precedence has been addressed by the DiffServ model, S. Blake et al.: An Architecture for Differentiated Services, RFC 2475. The DiffServ architecture defines three main classes of traffic, Expedited Forwarding, Assured Forwarding, and Best Effort, to offer QoS differentiation for traffic aggregates over a router hop. Consistent treatment of the same packet stream is then prescribed over the whole DiffServ DS domain.
Further, differentiated services are extended across a DiffServ DS domain boundary by establishing a service level specification SLA between an upstream network and a downstream DS domain. The service level specification SLA may specify a packet classification and remarking rules as well as traffic profiles and actions to traffic streams, which may be in- or out-of profiles. The packet classification policy identifies the subnet of traffic that may receive a differentiated service being conditioned and/or mapped to one or more behavior aggregates through DiffServ DS code point re-marking within the DiffServ DS domain. Traffic conditioning performs metering, shaping, policing and/or re-marking to ensure that the traffic entering the DiffServ domain conforms to rules specified in the service level specification SLA.
Generally, it may be assumed that the aim for this is to offer high quality circuit switched or packet switched services, which requires a transmission service having relatively low packet loss and low packet delay.
It is further assumed that some sort of end-to-end call/session level signaling protocol is used to control the calls, e.g., H.323, SIP, DSS1, ISUP, BICC, or their appropriate combination. When a call establishment message hits the gateway, the gateway has to ensure that a high quality transmission path exists to the remote gateway, which can accommodate the new call. If the gateway is capable of ensuring the required transmission path, it accepts the call and then the call establishment proceeds. If this is not the case, the call will be rejected and the gateway returns to a negative acknowledgement.
In view of the above, different methods have been proposed for providing high quality bearer for particular session flows traveling over an IP network.
One such method is a media gateway working according to IETF Intserv framework, R. Braden et al., Resource ReSerVation Protocol (RSVP)—Version 1 Functional Specification, RFC 2205, J. Wroclawski: The Use of RSVP with IETF Integrated Services, RFC 2210, acting as follows. Upon arrival of a call/session establishment message, it uses a resource reservation message which travels through the network core. Each router along the path examines the request and reserves the necessary routing resources. If resource reservation is successful, then the related media gateway MGW will receive back an acknowledgement. Then, the call/session establishment proceeds towards the remote media gateway MGW.
However, this first method requires per-flow states to be installed in each network core router. The scalability concerns regarding these solutions are well-known. The resource reservation message travels back and forth in the network core which significantly delays the call/session establishment.
Another second method relates to a media gateway MGW applying a static admission control method being configured with static bandwidth limitations towards the transport network according to a so-called hose model or towards all destinations separately according to a so-called trunk model. The so-called trunk and hose limitations may also be applied in a combined manner. Related limitations are aligned to the provisioned transport resources, and bandwidth requirements of already admitted sessions/calls are computed by the media gateway MGW. A new call/session is then accepted if the total would-be bandwidth is below the configured limitation towards a certain direction. Otherwise, it is rejected.
Another third method is a media gateway assuming an over-dimensioned core network admitting all calls/sessions into the network without making any effort to ensure that the required high quality transmission path exists.
A first common problem of the second and third method is that the media gateways MGW do not know anything about the actual state of the transport networks, which inevitably leads to performance degradation when the call/session arrival rate exceeds the capacity of the transport network. Possible causes of this may be multiple faults or improper transport network provisioning.
Yet another problem with the second and third method is related to bandwidth efficiency and management complexity. In particular, with respect to the hose model it generally requires more transport resources than the trunk model due to the uncertainty of the traffic distribution. However, the number of parameters to be configured in the trunk model can be large in a network having many media gateways MGW. Also, as the number of simultaneous calls/sessions between two media gateway MGW pairs is relatively low, the well-known Erlang-B dimensioning formula for a certain blocking target may also result in significant over-provisioning even for the trunk model. Also, the bandwidth efficiency of the third method is low and requires management support based on continuous performance monitoring to avoid performance degradation.
Another fourth method is related to a media gateway applying an end-to-end measurement based admission control MBAC method using performance measurements to incur the availability of transport resources. Many kinds of performance measures may be used and the collection in the transport network can be provided by many methods. Basically, two important categories are distinguished.
According to a first category, the measurements are selected by using functionality in the user layer protocols, e.g., RTP. This does not require any specific functionality in the networking routers.
According to a second category, the media gateway sends probe packets into the network, e.g., upon arrival of each individual call. The networking routers in the core network maintain information about aggregated traffic load. When a networking router receives a probe packet and is congested, it will mark and drop the probe packet. The congestion information thus arrives to the remote media gateway MGW, which then rejects the new call or alternatively signals congestion back to the initiator, L. Westberg, Z. R. Turanyi: Load Control of Real-Time Traffic, Internet draft, June 1999.
A first problem with respect to the fourth method, first category, is that it detects signals of performance degradation on the transport layer. Therefore, it is not able to maintain a certain extra capacity on the transport links for redundancy purposes. I.e., single failures may cause link overload which leads to performance degradations. Further, problems of co-existence with traffic regulated by other methods arise as well.
Yet another problem with the fourth method, second category, is a potential delay of call/session establishment. The reason for this is that the probe packet travels through the core network before the call admission control decision can be made. Therefore, each networking router needs to maintain an aggregated load information, and it needs to be aware of the mechanism to act accordingly.
In view of the above, the object of the present invention is to provide session admission control which is fast and easy to implement.
According to the present invention, this object is achieved by a method of admission control with respect to a request for set-up of a data packet stream between a source packet gateway and a destination packet gateway. Operatively, the method of admission control is operated at a destination packet gateway, e.g., a media gateway receiving data from a remote media gateway, or alternatively an SGSN, a GGSN networking node, etc. Here, the destination packet gateway receives a stream of data packets forwarded thereto from a edge router of the backbone network connecting the destination packet gateway to the remote source packet gateway.
According to the present invention, it is suggested that data packets in the data packet stream for which a set-up request is received have two different service differentiation fields, a first service differentiation field indicating conformity with a predetermined traffic profile for data exchange between the destination packet gateway and the source packet gateway and a second service differentiation field indicating non-conformity with the predetermined traffic profile. Operatively, it is assumed that the change from a first service differentiation field to a second service differentiation field is an indication to the destination packet gateway for evaluation of conformity with a traffic profile.
According to the present invention, it is particularly proposed to measure the number of data packets handled by the destination packet gateway which have been remarked to the second service differentiation field. Only when the number of remarked data packets, e.g., after evaluation thereof according to a functional relationship like a threshold comparison, indicates conformity with the traffic profile, will the data traffic stream admission be given at the destination packet gateway.
Further to the above, the present invention also relates to a method of operating an edge router in support of the destination packet gateway, the edge router processing a data packet stream exchange between at least one source packet gateway and at least one destination packet gateway. Again, it is assumed that data packets carry a field classification identifying at least a related data packet stream source, a data packet stream destination, and a service differentiation code.
According to the present invention, it is suggested that at the edge router, data packets streams are filtered according to data packet stream source, data packet stream destination, and service differentiation code. There is operated a remarking step for the service differentiation code of data packet for performance indication to the destination packet gateway. In other words, through remarking at the router it is possible to indicate to a connected destination packet gateway that selected data packet streams are not conforming to a pre-configured data traffic profile without any additional signaling between the edge router and the destination packet gateway.
In particular, according to the present invention, remarking is achieved from a first service differentiation code indicating conformity with a predetermined traffic profile set for data exchange between the destination packet gateway and a source packet gateway to a second service differentiation field indicating non-conformity with the predetermined traffic profile.
Therefore, the present invention allows for a very fast call set-up. Further, the operation according to the present invention is ‘light-weight’ before it involves extra traffic functionality only at edge router without any signaling between the edge router an the destination packet gateway being executed.
Still further, the proposed edge router functionality, e.g., traffic conditioning and service field classification, may be based on existing concepts like differentiated service standards so that no extra new specification (PHB, per hob behaviour) is required. Even more important, routers in the core network do not need to be upgraded at all with invention-related functionality to implement the inventive concept.
Still further, the present invention never leads to performance degradation, as the amount of data packet stream traffic into the transport core network is controllable without data packet losses.
According to a preferred embodiment of the present invention, it is proposed to react to performance degradation at the edge router supporting the destination packet gateway to an exchange of session packet streams with a packet switched access network. In particular, it is proposed to react to an increase in a data packet dropping rate at the edge router supporting the destination packet gateway.
Therefore, this preferred embodiment of the present invention allows for the handling of unexpected core network conditions by extending the call admission control so as to react also on a measured value of data packet dropping rate besides the remarking rate.
According to a further preferred embodiment of the present invention, it is suggested to operate the edge router and the destination client according to a specific range of source addresses or destination addresses or address ranges in general.
According to these preferred embodiments, the present invention ensures a very efficient usage of transport resources by using a data packet classification based on source-destination addresses in edge routers and a call admission control according to the present invention in destination packet gateways. This is of particular benefit where the bandwidth efficiency is expected to be lower in a general case, especially for large redundant network topology implementing a large number of packet gateways.
In view of the above, the present invention requires only a low network management complexity without any additional signaling overhead. In particular, the application of the present invention is not requiring a strict alignment of network resources to packet gateway traffic. Further, it is not application specific so that it may be applied for a large range of applications and packet gateways handling applications, e.g., media gateways in fixed, mobile or VoIP telephony networks and/or media gateways handling QoS sensitive packet switched sessions like GPRS support nodes in GSM/UMTS networks.
Overall, this is achieved by a coordinated configuration of edge routes and packet gateways, wherein traffic conditioning is achieved at the edge routers in view of a call admission control processing executed at the packet gateway. It is the use of information provided by a service differentiation field of packet headers which allows for the use of traffic classification and traffic conditioning elements in edge routers supporting admission control in attached packet gateways.
According to another preferred embodiment of the present invention there is provided a computer program product directly loadable into the internal memory of a packet gateway or an edge router comprising software code portions for performing the inventive admission control or service differentiation remarking process when the product is run on a processor of the packet gateway or the edge router.
Therefore, the present invention is also provided to achieve an implementation of the inventive method steps on computer or processor systems. In conclusion, such implementation leads to the provision of computer program products for use with a computer system or more specifically a processor comprised in, e.g., a packet gateway or an edge router.
This programs defining the functions of the present invention can be delivered to a computer/processor in many forms, including, but not limited to information permanently stored on non-writable storage media, e.g., read only memory devices such as ROM or CD ROM discs readable by processors or computer I/O attachments; information stored on writable storage media, i.e. floppy discs and harddrives; or information convey to a computer/processor through communication media such as network and/or Internet and/or telephone networks via modems or other interface devices. It should be understood that such media, when carrying processor readable instructions implementing the inventive concept represent alternate embodiments of the present invention.
In the following, preferred embodiments of the present invention will be explained with reference to the drawing in which:
In the following, a best mode of the present invention and related preferred embodiments thereof will be described with reference to
Insofar as in the following reference is made to the term packet gateway, either as destination or source packet gateway, it should be noted that this term is to be understood as covering any networking node handling a plurality of packet data flows in parallel, e.g., media gateways, SGSN networking nodes, GGSN networking nodes, etc.
Also, insofar as reference is made to the term ‘service differentiation code point’, this term is to be construed as covering any type of data packet switching protocol which supports service differentiation, e.g., according to S Blake et al.: An Architecture for Differentiated Services, RFC 2475.
Further, as alternative to service differentiation, another option to differentiate between different service levels would be to use different precedence bits, e.g., according to IP protocol. Yet another alternative would be the application of ATM related standards in support of service differentiation.
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In particular, in the edge routers 14-1 to 14-m supporting the packet gateways 10-1 to 10-n data packet streams are filtered according to, e.g., certain traffic types to/from specific packet gateways or pre-set packet gateways and then remarked, should the related data packet stream not conform to a pre-configured traffic profile set at the edge router 14-1 to 14-m.
Therefore, the remarking at the edge router 14-1 to 14-m represents to the packet gateways 10-1 to 10-n a performance indicator for use within the call admission control at the packet gateway 10-1 to 10-n. In more detail, according to the present invention, it is suggested to use the grade of remarking executed at the edge routers 14-1 to 14-m for related measurement thereof at the packet gateway 10-1 to 10-n.
It should be noted that according to the present invention this performance indication is achieved without any signalling going on between edge routers and packet gateways.
Should the degree of measured remarking fulfill certain conditions, which may be specified in terms of a functional relation, e.g., at the maximum degree of remarking and a related threshold comparison, then the call admission control mechanism according to the present invention will deny set-up of a data packet stream accordingly. One option would be that in the data packet headers at least two different service differentiation codes are set for indication of a remarking at the edge router.
In other words, in the most general sense according to the present invention, it is suggested that data packets forwarded to destination packet gateways 10-1 to 10-n carry either a first service differentiation field indicating conformity with the predetermined traffic profile for data exchange between the destination packet gateway and the source packet gateway or a second service differentiation field indicating non-conformity with the predetermined traffic profile set for data exchange. Due to the change of service code points in the data packets, the packet gateway 10-1 to 10-n may then react on a detection of remarked data packets accordingly.
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In particular, the remarking unit 24 will remark the data packets in the step S12, such that remarking is achieved in a first service differentiation code indicating conformity with a predetermined traffic profile set for data exchange between a destination packet gateway and a source packet gateway to a second service differentiation field indicating non-conformity with the predetermined traffic profile.
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Generally, the admission control may be executed as any function of the measured number of data packets with remarked service differentiation code, e.g., a threshold comparison of the measured number of remarked data packets with a predetermined threshold.
Typically, without restricting the scope of the present invention, such a threshold may be expressed as percentage of the data traffic, e.g., in the range of 20%, 10%, or a couple percents of the total traffic. An alternative to a threshold comparison would be to progressively decrease the admission rate with increase of a remarking rate at the edge router 14.
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To explain one example of the application of the present invention outlined so far with respect to
Further, for this case a related traffic profile may be related to a bandwidth limit which is set according to a dimensioned transport capacity towards the attached packet gateway 10. Here, if the data packet stream traffic exceeds the configured bandwidth limit then the remarking unit 24 at the edge router remarks the service differentiation code, e.g., a DiffServ code point DSCP according to IP, of the exact data stream traffic.
Then, in the packet gateway it is checked whether the number of remarked data packets exceeds a session admission control threshold in the directly connected packet gateway 10, which would then block the admission set-up of a new data stream session. This allows to limit the total traffic towards the packet gateway 10.
In the following, more details of the present invention and related functionality will be explained with respect to
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In other words, according to the present invention the measurement of remarking grade may be executed according to specific address ranges, e.g., for source packet gateways, a group of source packet gateways, or as abstract address range as such, which may be achieved by the address range evaluation unit 32 shown in
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It should be noted that admission control according to the present invention may imply selection of an address range for which admission control is executed, further selection of a service class for which admission control is executed, and considering the remarking grade for the address range and service class in view of pre-determined admission criteria.
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Here, one option would be to change the allowability of data packet stream set-up through modification of a threshold used during a threshold comparison in view of the state of the backbone transport network. Also, to prevent performance degradation at the edge router it might be possible to consider the dropping rate at the edge router during call admission control at the packet gateway 10, such that with increase of dropping rate at the edge router 14 the barrier for admission control at the packet gateway will get higher and higher.
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The interface unit divides into a first interface unit 20-1 receiving data packet streams from the packet gateway 10, a second interface unit 20-2 forwarding data packet streams to a packet gateway 10, a third interface unit 20-3 forwarding data stream packets to the backbone network 12, and a fourth interface unit 20-4 receiving data stream packets from the backbone network 12.
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In more detail, the performance capability data determines transport capabilities towards the packet gateway 10. Further, the configuration data may indicate at least one mapping from a service differentiation code to a second service differentiation code which information is processed by the remarking set-up unit 40 shown in
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Further, it should be noted that at the packet gateway 10 one may, in addition to the filtering and remarking steps executed at the edge router 14, identify a dropping rate through analysis of sequence numbers for additional consideration of the dropping rate during session admission control. The advantage is an extension of the session admission control in reaction to a detected packet dropping rate besides consideration of remarking of data stream packets. For this reason, according to the present invention, one may incorporate the functionality of two criteria for common admission control set to have the ability to react on unexpected backbone networking conditions.
Further, for the filtering step S34 explained above one may consider a flexibility in defining the place of traffic conditioners and related filtering mechanisms in view of various types of backbone networks.
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A further case C relates to the application of the filtering process at a third interface 20-3 shown in
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In view of the above, traffic conditioning on a router-router interface, cases C and D shown in
On the other hand, if traffic is configured at a router-router interface then a more complex address filtering is needed in the edge routers because transit traffic and traffic on other classes should be filtered out from the traffic generated at a given site.
If traffic condition is configured at the ingress to the backbone, cases A and D, and the drop of the packets is above certain bandwidth limits, then the solutions also provide a protection against flooding the backbone network with traffic in case of faults. All other solutions would have to include further traffic conditioners for limiting the total traffic into the backbone network's work. I.e., the traffic conditioners supporting admission control in the packet gateways may not always take the role of the traffic conditioners specified, e.g., in the DiffServ architecture, S. Blake et al.: An Architecture for Differentiated Services, RFC 2475.
Further, it should be noted that the present invention also allows for a site aggregation of packet gateways at customer edge(s).
In particular, site aggregation is a useful practical realization of traffic conditioning supporting the admission control according to the present invention, when it is configured at customer edge routers or layer-2 switches aggregating the traffic from/to the packet gateway(s) within a site.
The site aggregation solution has advantages as follows:
It allows for a more bandwidth-efficient transport trunk provision similar to the case of conditioning on router-router interfaces, but it also reduces the complexity of filter configurations as well as the management burden for the scenarios with traffic conditioning on the packet gateway-filter interfaces.
Further, as both remarking and admission control is executed within the customer premises, the site conditioning may be regarded as a standard-compliant solution, irrespective of which standard would be actually be applied, and it is applicable with a DiffServ-compliant backbone, as long as the client notes and the aggregating router/switch at the site support this functionality.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2004/012729 | 11/10/2004 | WO | 00 | 3/17/2008 |
