Abstract:
A system and method for providing Quality of Service in an Ethernet network. One or more telephony application programs are provided, along with an H.323 Recommendation stack, an IP layer, and modular Generate QoSEthernet and QoSEthernet layers. The Generate QoSEthernet layer is adapted to read Type of Service or Differentiated Service bytes and generate desired QoSEthernet commands therefrom. Either the Generate QoSEthernet layer or the QoSEthernet layer may be replaced or modified without necessarily having to modify the H.323 Recommendation stack and application program(s).

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to communications systems and, in particular, to an improved system for providing quality-of-service (QoS) in a Voice over IP (VoIP) system. 
     2. Description of the Related Art 
     The Internet Protocol (IP) is one of the most popular packet communication and networking protocols being used today. It finds use both on the Internet and in wide area networks (WANs) and local area networks (LANs), such as asynchronous transfer mode (ATM) and Ethernet networks. The promise of inexpensive voice telephony using the Internet has led to extensive interest in “Voice over IP” (VoIP) and “Telephony over LAN” (ToL) applications. In particular, several IP telephony protocols have been developed, including the H.323 Recommendation suite of protocols promulgated by the International Telecommunications Union (ITU), the Session Initiation Protocol (SIP), and Media Gateway Control Protocol (MGCP), to name a few. 
     For example,  FIG. 1A  illustrates a protocol stack  100   a  for a conventional H.323 implementation over an Ethernet IP network. One or more application programs  103   a  interface to the protocol stack  100   a . The H.323 layer  101   a  includes a control layer  106  supporting H.245 control signaling for negotiation of media channel usage, Q.931 (H.225.0) for call signaling and call setup, and H.225.0 Registration, Admission and Status (RAS). The H.323 layer  101   a  may also include a data layer  108  supporting T.120 for data conferencing. The H.323 layer  101   a  further implements audio codecs  102  and may also implement video codecs  104 . An RTP/RTCP layer  110  is provided for sequencing the audio and video packets. The H.323 layer  101   a  employs UDP and TCP  112  as its transport layer, and also employs an IP layer  114 , and then, an Ethernet layer  116 . Further details concerning the H.323 Recommendation may be obtained from the International Telecommunications Union; the H.323 Recommendation is hereby incorporated by reference in its entirety as if fully set forth herein. 
     An important key to the development of ToL and VoIP systems is the development of successful Quality of Service (QoS) IP networks. Generally, QoS refers to the ability of a network to guarantee specific performance levels, related to network bandwidth, availability, jitter, security, and data loss. High voice and/or video quality communication require high QoS levels on all network segments involved in the communication. Guaranteed QoS has been of particular concern on Ethernet LANs, both due to the bursty nature of IP traffic and the CSMA/CD contention protocol used by Ethernet. 
     Several approaches to QoS in IP networks have employed the Type of Service (TOS) byte, i.e., the second byte, in the IP header. The TOS field is an eight-bit field that signals to routers in the network a priority of handling as well as parameters related to delay, throughput, cost, and reliability. Because the TOS field itself had not been widely used, in certain implementations, it has been recast as a “differentiated service” (DS) byte, which is used to indicate to routers the per-hop behavior expected at the node. These approaches, however, do not in themselves provide a Quality of Service. Other protocols, such as the Resource Reservation Protocol (RSVP) or IEEE 802.1 p, are required to implement actual Quality of Service features. Even when the TOS/DS bits are used with such protocols, Quality of Service is not necessarily guaranteed network-wide. 
     As such, telephony vendors have been developing “Quality of Service Ethernet” (QoSEthernet), which lies between the IP layer and the Ethernet layer in the protocol stack and which provides a guaranteed QoS. Thus,  FIG. 1B  illustrates a protocol stack  100   b  including a QoSEthernet layer  115  between the IP layer  114  and the Ethernet layer  116 . An exemplary QoSEthernet system is available from Path 1 Network Technologies, Inc., San Diego, Calif., and makes use of RSVP and the intserv process, described by the Internet Engineering Task Force (IETF). 
     In practice, implementation of the QoSEthernet layer  115  requires modified application programs  103   b  in order to provide the required QoSEthernet information at call setup. That is, each application program(s)  103   b  must be modified, or replaced, to provide one or more commands in addition to standard H.323 commands in order to invoke the required QoS. Thus, to support QoSEthernet, a user must not only implement a QoSEthernet layer but also change applications programs, such as telephone, fax, and the like. Further, each application program requires setup and configuration, which can cause added costs and delays in implementation. 
     As such, there is a need for a system to be able to implement QoSEthernet without having to replace existing software systems. There is a still further need for a system to implement QoSEthernet while using TOS bits to specify the required QoSEthernet Quality of Service. 
     SUMMARY OF THE INVENTION 
     These and other drawbacks in the prior art are overcome in large part by a system and method according to the present invention. According to one implementation of the present invention, existing software sets TOS bits during IP encapsulation. A Generate QoSEthernet layer receives the TOS bits and translates them into a form compatible with the QoSEthernet requirements. In a particular implementation, the Generate QoSEthernet layer is embodied in an H.323 Recommendation telecommunication system. 
     According to one implementation of the invention, one or more telephony application programs are provided, along with an H.323 Recommendation stack, an IP layer, and modular Generate QoSEthernet and QoSEthernet layers. Either the Generate QoSEthernet layer or the QoSEthernet layer may be replaced or modified without necessarily having to modify the H.323 Recommendation stack and application program(s). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A better understanding of the invention is obtained when the following detailed description is considered in conjunction with the following drawings in which: 
         FIG. 1A  and  FIG. 1B  illustrate exemplary program stacks according to the prior art; 
         FIG. 2  is a diagram of an exemplary telecommunications system according to an implementation of the invention; 
         FIG. 3  is an exemplary program stack according to an implementation of the invention; 
         FIG. 4  is a diagram of an exemplary generate quality of service Ethernet module according to an implementation of the invention; 
         FIG. 5  illustrates exemplary mapping of type of service bits to QoS Ethernet QoS levels; 
         FIG. 6  illustrates exemplary mapping of differentiated service bits to QoS Ethernet QoS levels; and 
         FIG. 7  is a flowchart illustrating operation of an implementation of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 2–7  illustrate an improved system and method for providing QoS in an Ethernet-type local area network. Existing software is used to generate TOS (Type of Service) values or DS (Differentiated Service) values when the data packets are encapsulated in the IP. A Generate QoSEthernet layer is provided that translates the TOS or DS bits into QoSEthernet-compatible commands. The QoSEthernet commands are then provided to a QoSEthernet layer. 
     Turning now to the drawings, and with particular attention to  FIG. 2 , a diagram illustrating an exemplary IP protocol telecommunications system  300  according to an embodiment of the present invention is shown. In particular, the IP protocol communication system  300  may be embodied as an H.323 Recommendation-compatible system. It is noted that, while described herein with regard to an H.323 network, the invention is equally applicable to any network such as MGCP (Media Gateway Control Protocol), SIP+(Inter MGS Protocol), SGCP, MEGACO, and generally, any voice or multimedia over IP scheme. Further, it is noted that an exemplary generic H.323 system is the HiNet™ RC3000 system, available from Siemens. 
     The telecommunications system  300  includes a local area network (LAN) or packet network  301  and, particularly, and Ethernet LAN. Coupled to the LAN  301  may be a variety of H.323 terminals  302   a–d , a multi-point control unit (MCU)  306 , an H.323 gateway  308 , an H.323 gatekeeper  310 , a LAN server  312 , and a plurality of other devices such as personal computers (not shown). The H.323 terminals  302   a–d  are in compliance with the H.323 Recommendation. Further, the H.323 terminals  302   a–d  include Generate QoSEthernet controllers or layers  304   a–d , as will be described in greater detail below. 
     More particularly,  FIG. 3  illustrates a protocol stack according to an implementation of the invention. At the top are one or more application programs  103   a . The application programs  103   a , similar to those of  FIG. 1A , may be embodied as one or more telephony programs, such as fax, voice, video, and the like. Next is an Internet Protocol voice communication stack, such as an H.323 protocol stack  101   a , similar to that of  FIG. 1A . Thus, the H.323 stack includes video codecs  102 ; audio codecs  104 ; a control layer  106  supporting H.245 control signaling for negotiation of media channel usage, Q.931 (H.225.0) for call signaling and call setup, and H.225.0 Registration, Admission and Status (RAS); a data layer  108  supporting T.120 for data conferencing; and an RTP/RTCP layer  110 . The Internet Protocol voice communication stack  101   a  lies atop a UDP/TCP layer  112  and an IP layer  114 . The application programs  103   a  are adapted to generate commands which are encapsulated in the second byte of the IP header as type of service (TOS) or differentiated service (DS) bits. 
     Also included are a QoSEthernet layer  115  and an Ethernet layer  116 . Further, a Generate QoSEthernet layer  118  according to the present invention is provided. As will be described in greater detail below, the Generate QoSEthernet layer  118  intercepts the second byte of the IP header, derives a required QoS therefrom, and generates the appropriate QoS commands for the QoSEthernet layer  115 . 
     Turning now to  FIG. 4 , an exemplary Generate QoSEthernet module  304  is illustrated in greater detail. The Generate QoSEthernet module  304  includes a control unit  402  coupled to a memory  404 . The memory  404  includes one or more lookup tables or databases  406  for storing conversions between TOS or DS bits and QoSEthernet commands, as will be explained in greater detail below. Also included is a buffer unit  408 , including an input buffer  410  and an output buffer  412 . The input buffer  410  receives the TOS or DS bits and buffers them during access of the lookup table  406 . The TOS and DS bits are then transferred to the output buffer  412  and the appropriate QoS commands are generated. The commands are then output from the output buffer to the QoSEthernet. 
     Turning now to  FIG. 5 , a diagram illustrating the principle of mapping of the TOS bits to QoS Ethernet commands is shown.  FIG. 5  illustrates an exemplary TOS byte  502 , a Generate QoS Ethernet map module  304   a , and a QoS level mapped-to table  504 . As is known, the first six bits of the Type of Service byte are used to define levels of service, ranging from “routine” to “critical.” The Generate QoSEthernet layer  304   a  according to the present invention reads the defined TOS bits and maps them to corresponding QoS Ethernet QoS levels. 
       FIG. 6  is a similar diagram of the differentiated service byte mapping. Shown is a Differentiated Service byte  602 , an exemplary Generate QoS Ethernet layer map  304   b , and a resulting QoS level table  604 . Bits  6 – 7  are presently unused; bits  0 – 5  are presently used to define “per hop behavior,” i.e., a particular forwarding treatment at each node. The Generate QoS Ethernet layer  304   b  reads the DS byte  602  and maps the bits to a QoSEthernet quality of service level. 
     Operation of an implementation of the present invention is illustrated more clearly with reference to the flowchart of  FIG. 7 . In a step  702 , the client terminal begins a call. In a step  704 , the corresponding messages are encapsulated in IP packets. In a step  706 , the second byte of the IP header is set according to predefined QoS levels. As discussed above, the second byte may be either a Type of Service byte or a Differentiated Service byte. In a step  708 , the second byte of the IP header is read by the Generate QoS Ethernet layer. In a step  710 , the Generate QoSEthernet layer accesses the lookup table in memory for the corresponding QoSEthernet levels. Finally, in a step  712 , the Generate QoSEthernet layer generates the required QoS Ethernet commands to establish the specified quality of service. 
     The invention described in the above detailed description is not intended to be limited to the specific form set forth herein, but is intended to cover such alternatives, modifications and equivalents as can reasonably be included within the spirit and scope of the appended claims.