Patent Application
20130007285
1. Field of the Invention
This invention generally relates to multiple grants per interval (MGI) service flows.
2. Background Art
In communication systems such as Data Over Cable Service Interface Specification (DOCSIS), packets are transmitted from a source, such as an application session that generated the packet, to a destination, such as network equipment, over a DOCSIS network. In an example, the packets are transmitted on MGI service flows. However, current systems do not provide a mechanism for mapping application sessions to compatible MGI service flows.
Methods and systems are needed to overcome the above mentioned deficiency
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention. In the drawings:
The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers may indicate identical or functionally similar elements. Additionally, the left-most digit(s) of a reference number may identify the drawing in which the reference number first appears.
Quality of Service (QoS) is a critical factor that impacts real-time applications such as voice-over-IP (VoIP) and video conferencing. As the use of such applications becomes widespread, it becomes difficult to guarantee QoS for each application session. Guaranteeing QoS for each application session is especially difficult if the QoS resources available on the access network are limited. One such example of an access network is based on Data Over Cable Service Interface Specification (DOCSIS). QoS on a DOCSIS access link is realized by classifying traffic onto different Service Flows (SF) that are associated with QoS parameters required by the traffic transmitted on them. For instance, in DOCSIS systems, packets for a VoIP call session are transmitted on an Unsolicited Grant Service (UGS) service flow associated with QoS parameters that guarantee a predetermined amount of bandwidth and periodic transmission opportunities for the call session.
The maximum number of service flows supported by a DOCSIS cable modem (CM) and a DOCSIS cable modem termination system (CMTS) is usually limited by the hardware and computational resources of the CM and CMTS. If one service flow is assigned to serve one VoIP call, then the maximum number of simultaneous VoIP call sessions supported by the CM is limited by the maximum number of service flows supported by the CM and the CMTS. For example, if the CM and CMTS can support 16 service flows at a time, then up to 16 simultaneous VoIP sessions may be supported. This limitation restricts the number of simultaneous application sessions that can be supported by the CM and CMTS. In particular, when the CM is deployed in an enterprise environment where the density of simultaneous VoIP calls is relatively high (e.g. over 100), the QoS for the each VoIP call may not be guaranteed since the simultaneous VoIP call sessions may not be allocated to dedicated SFs over a DOCSIS link.
Using a Multiple Grants per Interval (MGI) service flow, a CMTS can allocate multiple grants (also know as a “transmission opportunities”) for a given grant interval (also known as a “transmission interval”). This potentially allows multiple application sessions (e.g. VoIP calls) to be carried in a single service flow, and thus allows for QoS support for a number of application sessions that is greater than the maximum number of available service flows. One of the problems associated with MGI service flows is that current systems do not provide a mechanism for mapping application sessions to MGI service flows that are compatible with a periodicity and/or packet size of the application sessions. Embodiments presented herein and described further below allow for mapping of an application session to a compatible MGI service flow.
Cable modem 110 is coupled to media sources 102 and DOCSIS network 116. Media sources may include, but are not limited to, Voice over Internet Protocol (VoIP) 102a, telemetry 102b, video 102c, audio 102d, remote surveillance 102n, etc.
Cable modem 110 includes a processor 112 coupled to a memory 114. Processor 112, based on instructions stored in memory 114, may perform the functions described herein as being performed by cable modem 110.
Each media source 102 may run one or more application sessions, each of which generate packets or frames that are transmitted by cable modem 110. Cable modem 110 maps the packets over single or multiple grants per interval service flows and transmits them over DOCSIS network 116 to CMTS 118. For example, VoIP 102a may include multiple Internet Protocol (IP) phones (not shown), with each IP phone generating a corresponding VoIP application session and each VoIP application session generating corresponding packets that are transmitted to cable modem 110. Cable modem 110 maps the packets to a single or multiple grants per interval service flow and transmits the packets to CMTS 118 over DOCSIS network 116.
In conventional systems, to guarantee quality of service (QoS), each packet 200 corresponding to a particular application session, e.g. a voice call, is transmitted by cable modem 110 in a single grant interval (T) of a unique service flow (SF) that has the DOCSIS QoS characteristics required by the application session that generated packets 200. An example of QoS characteristics may include, but are not limited to, guaranteed bandwidth and delay/jitter that allows periodic voice packets to be transmitted in corresponding periodic grants. In a single grant per interval service flow, as shown in
Multiple grants per interval service flows may be utilized when cable modem 110 receives packets from multiple simultaneous application sessions for transmission to CMTS 118. The multiple application sessions may originate from one or more of media sources 102. For example, VoIP 102a may generate multiple simultaneous VoIP call sessions. In a MGI service flow, CMTS 118 allocates multiple grants or transmit opportunities per interval. This allows cable modem 110 to transmit multiple packets from either the same or multiple application sessions during a single grant interval T. In the example shown in
In the multiple grants per interval service flow example shown in
Packets 400 from application session 1 have a periodicity P1 and a packet size S1. Packets 402 from application session 2 have a periodicity P2 and a packet size S2. Packets from application session 3 have a periodicity P3 and a packet size S3. As seen in the example in
For N application sessions, with each application session represented by “i” (i=1, 2, 3, . . . , N), a periodicity of a packet in an application session is denoted as P[i] and a maximum size of a packet in the application session is denoted as S[i]. In order for packets from an application session to be mapped to a MGI SF, the application session's periodicity must be compatible with the grant interval of the MGI SF. In other words, P[i]=k*T must be satisfied, where k is an integer and T is the grant interval of the MGI SF. For instance, if T=10 ms and P[i]=20 ms, then k=2 and the application session i is compatible with the MGI SF. On the other hand, if P[i]=25 ms, then k=2.5 and the session i would not be compatible with the SF in terms of periodicity and thus cannot be mapped to this MGI SF.
Another compatibility criterion may be a maximum packet size of an application session. A size of a packet in an application session i is compatible with a MGI SF if S[i] is smaller than or equal to the grant size of the SF. For instance, assume a grant size of an MGI SF is 500 bytes. In this case, an application session with a maximum packet size of 350 bytes is compatible with the MGI SF, since the packets can fit into the grant. However, a session with a packet size of 600 bytes is not compatible with the SF, since the packets cannot fit into the grant, and cannot be carried by this MGI SF.
In step 502, all MGI service flows provisioned by a CMTS are sorted in a descending order according to a length of the grant interval. For example, cable modem 110 sorts all provisioned MGI service flows in a descending order based on a length of their grant interval (T).
In step 504, all application sessions are sorted in descending order according to a maximum possible size of their packets S[i].
In step 506, it is determined whether all MGI service flows in the list generated in step 502 have been selected. If all service flows in the service flow list have been selected then the process proceeds to step 520. If all service flows in the list have not been selected then, the next service flow in the list is selected in step 508.
In step 510, it is determined whether all application sessions in the application session list have been mapped to a compatible MGI service flow. If all sessions have been mapped, then the process ends. If all application sessions in the session list have not been mapped, then a next session that is to be mapped to a MGI service flow is selected from the top of the session list in step 512.
In step 514, it is determined whether a periodicity P[i] and grant size S[i] of the selected application session are compatible with a grant interval and grant size of the MGI service flow selected in step 508.
If the application session and the MGI service flow are compatible, then the process proceeds to step 516. If the application session and the service flow are not compatible then the process proceeds to step 510 where a next application session is selected and it is determined whether the next application session is compatible with the MGI service flow selected in step 508.
In step 516, it is determined if there is an available grant in the service flow. If there are no more available grants in the service flow then the step proceeds to step 506 where a next MGI service flow is selected. If there is an available grant in the service flow, then the program proceeds to step 518.
In step 518, the selected session is mapped to a grant of the MGI service flow selected in step 508 and the application session is removed from the session list. The process proceeds to step 510 and is repeated until all application sessions in the session list have been mapped or all service flows in the service flow list have been selected.
In step 520, it is determined whether the application session list is empty. If the application session list is empty then the process ends.
If the application session list is not empty, then the process proceeds to step 522. In step 522, all remaining sessions in the application session list are mapped to a default service flow, for example a best effort service flow.
Embodiments presented herein, or portions thereof, can be implemented in hardware, firmware, software, and/or combinations thereof. The embodiments presented herein apply to any communication system that utilizes packets for data transmission.
The representative packet mapping functions described herein can be implemented in hardware, software, or some combination thereof. For instance, the method of flowchart 500 can be implemented using one or more of computer processors, such as processor 112, computer logic, application specific circuits (ASIC), digital signal processors, etc., or any combination thereof, as will be understood by those skilled in the arts based on the discussion given herein. Accordingly, any processor that performs the functions described herein is within the scope and spirit of the embodiments presented herein.
Further, the packet processing functions described herein could be embodied by computer program instructions that are executed by a computer processor, for example processor 112, or any one of the hardware devices listed above. The computer program instructions cause the processor to perform the instructions described herein. The computer program instructions (e.g. software) can be stored in a computer usable medium, computer program medium, or any storage medium that can be accessed by a computer or processor. Such media include a memory device, such as memory 114, a RAM or ROM, or other type of computer storage medium such as a computer disk or CD ROM, or the equivalent. Accordingly, any computer storage medium having computer program code that cause a processor to perform the functions described herein are within the scope and spirit of the embodiments presented herein.
It is to be appreciated that the Detailed Description section, and not the Abstract section, is intended to be used to interpret the claims. The Abstract section may set forth one or more but not all exemplary embodiments of the present invention as contemplated by the inventor(s), and thus, are not intended to limit the present invention and the appended claims in any way.
The present invention has been described above with the aid of functional building blocks illustrating the implementation of specified functions and relationships thereof. The boundaries of these functional building blocks have been arbitrarily defined herein for the convenience of the description. Alternate boundaries can be defined so long as the specified functions and relationships thereof are appropriately performed.
The foregoing description of the specific embodiments will so fully reveal the general nature of the invention that others can, by applying knowledge within the skill of the art, readily modify and/or adapt for various applications such specific embodiments, without undue experimentation, without departing from the general concept of the present invention. Therefore, such adaptations and modifications are intended to be within the meaning and range of equivalents of the disclosed embodiments, based on the teaching and guidance presented herein. It is to be understood that the phraseology or terminology herein is for the purpose of description and not of limitation, such that the terminology or phraseology of the present specification is to be interpreted by the skilled artisan in light of the teachings and guidance.
The breadth and scope of the present invention should not be limited by any of the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents.
