Multiplex communications – Data flow congestion prevention or control – Flow control of data transmission through a network
Reexamination Certificate
2000-02-16
2003-09-09
Ton, Dang (Department: 2666)
Multiplex communications
Data flow congestion prevention or control
Flow control of data transmission through a network
C370S395210, C370S433000, C370S468000
Reexamination Certificate
active
06618356
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method to be used in a telecommunication network for policing data traffic to a data traffic policer realizing such a method and to a telecommunication network including such a data traffic policer.
Such a method for policing data traffic, such a data traffic policer and such a telecommunication network are already known in the art, e.g. from the article “The Spacer-controller: an efficient UPC/NPC for ATM networks”, by P. E. Boyer et al., ISS 1992, October 1992, Vol. 2, paper A9.3, pp. 316-320. Referring to the introductory part it is described that asynchronous transfer mode ATM cells are inserted by a user on the network access multiplex, called hereafter a common data communication link, according to any arbitrary timing. Therefore, the allocation of network resources to a connection can only be based upon traffic parameters declared by the user. Call admission implies the negotiation of a Traffic Contract that describes as well as can be the traffic that will be offered at the network entry point. A policing function is used by the network in order to ascertain that the negotiated values are actually met during the connection. On the other hand, the network is bounded to meet the Quality Of Service requested in the Traffic contract by properly allocating resources to the connection. The mentioned article further addresses the integration of a policer and a shaper into the same hardware device.
It is well know to a person skilled in the art that an essential step to be executed by such a known policer is, upon reception of a data packet, determining the lower order identifier that is associated to the data packet, whereby that lower order identifier identifies a lower order data flow e.g. in an ATM network determining the predefined virtual channel identifier that is associated to the ATM cell whereby this virtual channel identifier identifies the ATM virtual connection. Indeed, within a predefined higher order data flow being identified by a higher order identifier e.g. within a predefined virtual path being identified by a predefined virtual path identifier, it is an essential step to identify the traffic contract associated to this particular received data packet. This step is executed by the policer by means of a first determining means. Furthermore the policer checks the conformance of the data packet according to predefined lower order conformance rules i.e. a traffic contract associated to the lower order identifier. This function is executed by a first control means whereto the lower order identifier is forwarded by the first determining means. The first control means provides hereby a lower order conformance result that is lower order conforming or lower order non-conforming.
A problem outstanding with this kind of policers is that the known policing units, e.g. such as described above in an ATM network, perform policing at Virtual Channel level i.e. at lower order identifier level or at Virtual Path level i.e. at higher order identifier level. This means that policing is performed only at a single identifier level. The resources that are reserved for some predetermined lower order data flow with a lower order identifier, but which are not actually used are wasted. This is not desirable, especially for quality of services QOS such as Variable Bit Rate VBR and guaranteed Frame Rate GFR, the available bandwidth could be useful to other active lower order data flows of this higher order data flow.
This will become more clear with the following example of two Local Area Networks LAN's from different companies A and B, using different Guaranteed Virtual Channels VCA1, VCA2 and VCB1, VCB2, respectively, which are multiplexed in order to share one single ATM link. Presume that VCA1 is used to transport mission critical traffic from company A, VCA2 is used to transport best-effort traffic from company A, VCB1 and VCB2 are used to transport best effort-traffic from company B with two different priorities. Different ways of sharing the available bandwidth of the common link are possible. Under the assumption that a VC is active or inactive and that an active VC is always greedy and in the event when the VCA1 is inactive, the bandwidth that is unused by this VCA1 is distributed among VCA2, VCB1 and VCB2. However, such a distribution of the available bandwidth is not appropriate from a user's point of view e.g. company A, especially as in many networks the charging is done on the basis of the amount of reserved bandwidth.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a data traffic policer such as the above know policers but with an improved and fair use of the available bandwidth.
This object is achieved by the method for policing data traffic as described in claim
1
, by the data traffic policer that is realizing such a method that is described in claim
6
, and by the telecommunication network that includes such a policer that is described in claim
7
.
Indeed, the invention is based on the insight that left-over available bandwidth of a predefined higher order data flow can be shared among all the active lower order data flows being part of this higher order data flow e.g. left-over bandwidth of a virtual path can be shared to all the active virtual channels included inside this virtual path.
The higher order identifier associated to the data packet is also determined by a second determining means of the policer. This higher order identifier is forwarded to a second control means that checks a conformance of the data packet according to predefined higher order conformance rules. The control means provides thereby a higher order conformance result that equals higher order conforming or higher order non-conforming. Furthermore the policer includes declaring means that is coupled between the first control means, the second control means and an output of the policer. The declaring means declares, in the event when the lower order conformance result provided by the first control means is lower order non-conforming, but the higher order conformance result provided by the second control means is higher order conforming, the data packet as conforming. This means that the data packet is allowed to use some leftover resources within this higher order data flow. The leftover resources includes e.g. left-over bandwidth from another lower order data flow within the same higher order data flow and buffer space previously assigned to another lower order data flow within the same higher order data flow.
According to the above mentioned example, company A would clearly prefer that the bandwidth that is not used by VCA1 would automatically be allocated to VCA2 instead of being allocated to VCA2, VCB1 and VCB2. This is realized by also defining a traffic contract with predefined higher order conformance rules for a higher order data flow that includes the lower order data flows VCA1 and VCA2 but not the lower order data flows VCB1 and VCB2. In the event when a data packet of the VCA2 connection arrives and that this data packet has a lower order non-conforming conformance result but a higher order conforming conformance result, the VCA2 data packet is declared as conforming. In this way, the VCA2 connection borrows some leftover bandwidth from the VCA1 connection.
It has to be remarked that according to the above described example in an ATM network, such a higher order data flow is not necessarily a global virtual path that includes the virtual channels VCA1 and VCA2. It should be clear that a higher order data flow might as well be a predefined set of virtual channels whereby bandwidth guarantees are associated to this set of virtual channels so that when one virtual channel is inactive the other virtual channels of the predefined set of virtual channels can benefit from the unused bandwidth. In a similar way and according to the wording of the claims, a higher order data flow can be implemented by a predefined plurality of lower order data flows or by a predefined aggregate of lower orde
Alcatel
Mehra Inder Pal
Ton Dang
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