Using Quality Objects (QuO) Middleware for QoS Control of Video Streams

Transcription

1 Using Quality Objects (QuO) Middleware for QoS Control of Streams BBN Technologies Cambridge, MA Craig Rodrigues OMG s Third Workshop on Real-Time and Embedded Distributed Object Computing January 7-10, 2002 Burlingame, California, USA 1

2 US Navy UAV Characteristics QoS Streaming Limited Off- Board Links Constrained Shipboard Resources COTS Varying Missions Contention with other Subsystems *From the World Wide Web site for official information about Unmanned Aerial Vehicles, 2

3 UAV Basic Scenario feed from off-board source (unmanned aerial vehicle) Distributor sends video to hosts via ship s network Users hosts receive video and display it Users interact with UAV in real time 3

4 Example Dynamic Variations in UAV Mission Requirements Different mission requirements require optimizing an aspect or aspects, possibly trading off others Timeliness An out-of-the-window view of UAV imagery (e.g., piloting, targeting) Importance Receiving or collecting sufficient imagery (e.g., surveillance) Fidelity Determining relative importance of time-critical targets (e.g., commander) End-to-end latency + processing time at distributor and display, must be below threshold Highest priority frames must reach the receiver Image precision at display must approximate that at the UAV source Timeliness Invariant L(U D) + P(D) + L(D R) + P(R) < T Importance Invariant { f f Frames(U) Importance(f) > I f Frames(R) } Fidelity Invariant Fidelity(R) / Fidelity(U) > Q Trading off these properties, while maintaining invariants, under dynamic conditions is crucial to mission success 4

5 Example Variations & Adaptations in UAV Scenario Mission requirements of UAV scenario NETWORK RESERVATION Condition: excessive Network load Action: Use IntServ to reserve bandwidth X X Timeliness Maintain an outof-the-window view of UAV imagery Distributor I P BI B B I I BI B P BB I I I PP B BBBB BB B BB B BBBB B BB B IBBPBBPBBPBBPBBPBBIBBPB B B P BBBBBBBBBBBBBBBBBBBBBBBBBBBB B BP P P PB P P P PIP P B B BB B B B BB B LOAD BALANCING Condition: Excessive CPU load Action: Migrate distributor to a lightly loaded host Importance Important imagery must be received Fidelity Image fidelity must be maintained 5...PBBPBBPBBI Distributor I I I DATA FILTERING Condition: When excessive network or CPU load Action: Drop selective frames Dynamic Variations in Operating Conditions

6 UAV Application: A View of the Software Components Source Process CORBA A/V Streaming Service Frame filtering commands DIstributor Display Reservation Proxy requests Observed throughput Display QuO Contract QuO Contract UAV File UAV SIMULATION HOST VIDEO DISTRIBUTION HOST Common middleware services TAO CORBA A/V Service QuO AQoSA TAO Naming Service VIDEO DISPLAY HOST 1 VIDEO DISPLAY HOST 2 VIDEO DISPLAY HOST N Reused Off the Shelf Software DVDView video player 6

7 Functional description of UAV architecture Source Process Distributor Process Display Proxy Process Display Process Functionality Read bytes from a file Convert into frames Send out pipe Timing and sequencing of frames sent out Base Functionality Receive frames Send frames to registered receivers QuO Functionality QuO Delegate: Frame filtering (i.e., frame dropping) QuO Sysconds and Contract: Measuring frame rate Measuring resource usage and availability (CPU and network) Adapting to performance degradation (e.g., frame dropping, load balancing) Base Functionality Receive frames Display frames on the screen QuO Functionality QuO Delegate: Removing time stamp Removing sequencing Discarding frame if late or out of sequence QuO Sysconds and Contract: Measuring frame rate VIDEO DISPLAY HOST 1 UAV SIMULATION HOST VIDEO DISTRIBUTION HOST VIDEO DISPLAY HOST 2 VIDEO DISPLAY HOST N 7

8 COTS Middleware Components used in the UAV Software Quality Objects (QuO) provides higher level programming model for specifying application-level QoS CORBA Audio/ Service abstracts away network programming concerns such as connection management, can be used to specify network level QoS 8

9 Quality Objects (QuO) Provides a higher level programming model for specifying application QoS operating regions specified in QuO Contracts transitions between regions trigger adaptive behaviors Support for different middleware architectures CORBA (Java and C++) Java RMI local method call 9

10 482&25%$ '2& 02'(/ &25%$ '2& 02'(/ QuO Adds Specification, Measurement, and Adaptation to the Distributed Object Model CLIENT IDL STUBS CLIENT Delegate IDL STUBS OBJ REF in args operation() out args + return value Network OBJECT (SERVANT) IDL SKELETON ORB IIOP IIOP ORB OBJ REF SysCond Contract SysCond in args operation() out args + return value MECHANISM/PROPERTY MANAGER Network SysCond Contract SysCond OBJECT (SERVANT) IDL SKELETON Delegate ORB IIOP IIOP ORB OBJECT ADAPTER OBJECT ADAPTER Application Developer Mechanism Developer Application Developer QuO Developer Mechanism Developer 10

11 CORBA Audio/ Streaming Service Goals of OMG CORBA A/V Service Specification Define standard mechanisms for: Stream Establishment Stream Control Multiple Flows Multiple Protocols QoS Goals of TAO A/V Streaming Service Project Implement OMG CORBA A/V Service Specification using TAO 11

12 UAV Application High Level Design Source Process Distributor Stream Display Proxy Display UAV File QuO QuO VIDEO DISTRIBUTION HOST VIDEO DISPLAY HOST Source Stream Endpoint (distributor) QuO measurement and control reservation request reservation notification TAO A/V Streaming Service Sink Stream EndPoint (Display) Stream Adaptor.. flows QoS.. reservations updates request reservation ACE AQoSA API accept/ reject event notifications Stream Adaptor Stream RSVP-enabled routers 12

13 UAV Application: A View of the Software Components Source Process CORBA A/V Streaming Service Frame filtering commands DIstributor Display Reservation Proxy requests Observed throughput Display QuO Contract QuO Contract UAV File UAV SIMULATION HOST VIDEO DISTRIBUTION HOST Common middleware services TAO CORBA A/V Service QuO AQoSA TAO Naming Service VIDEO DISPLAY HOST 1 VIDEO DISPLAY HOST 2 VIDEO DISPLAY HOST N Reused Off the Shelf Software DVDView video player 13

14 Integration of QuO Components (Qoskets) in UAV Application Host A (Sender) Host B (Distributor) Host C (Receiver) distributor.{h,cpp} Distributor Code Contract SendAllFrames SendTenFrames SendTwoFrames Expected Frame Rate Sender Control POA::Sender_ Control_ Callback Sender_ Control_ Callback Object Contract Normal High Excess Actual Frame Rate sender.{h,cpp} Sender Code wrapper-> send_frame() Header Delegate Receive Frame Event Callback wrapper-> send_frame() Frame Filter Delegate TAO_AV_Protocol_ Object TAO_AV_ UDP_Object transport->send() receiver.{h,cpp} Receiver Code Receive Frame Event Callback QuO provides higher level feedback and control as video frames are transmitted from sender to receiver 14

15 RSVP fragmentation problem solved by use of QuO Qoskets Host B (Distributor) Host C (Receiver) distributor.{h,cpp} Distributor Code Receive Frame Event Callback wrapper-> send_frame() Frame Filter Delegate TAO_AV_Protocol_ Object TAO_AV_ UDP_Object transport->send() Fragment Frame Delegate Reassemble Frame Delegate receiver.{h,cpp} Receiver Code Receive Frame Event Callback MPEG in UDP packets were being fragmented by IP. Routers did not know that fragmented IP packets were part of a RSVP reservation of UDP packets. Solution: QuO delegates for fragmentation/reassembly, so UDP packets are not fragmented at IP level. 15

16 RT-CORBA and UAV application distributor.{h,cpp} Distributor Code Receive Frame Event Callback wrapper-> send_frame() 9LGHR IUDPHV Frame Filter Delegate TAO_AV_Protocol_ Object TAO_AV_ UDP_Object transport->send() 57&25%$ UHTXHVW RT-CORBA servant RT-CORBA Thread pool Distributor will need to perform real-time processing of video frames and/or sensor data which may accompany the video, or video frames Distributor invokes a method on an RT-CORBA servant which performs data processing Thread priority of task is requested in the CORBA invocation 16

17 What is Diffserv? IP Datagram Header Version (4-bits) Header Length (4-bits) Diffserv Field (8-bits) Total Length (16-bits) Identification (16-bits) Flags (3-bits) Fragment offset (13-bits) TTL (8-bits) Protocol (8-bits) Checksum (16-bits) Source Address (32-bits) Destination Address (32-bits) Diffserv field: 6 bits of Diffserv Codepoint, 2 bits ECN Each DSCP (0-63) specifies a Per-Hop-Behavior (PHB), which is a type of router-level QoS (RFC 2475) 17

18 Specifying Diffserv QoS properties using the TAO AV Service CORBA IDL for AVStreams contains a method for changng the QoS characteristics of a stream: typedef sequence<string> flowspec; struct QoS { string QoSType CosPropertyService::Properties QoSParams; }; typedef sequence<qos> streamqos; interface Basic_StreamCtrl { boolean modify_qos(inout streamqos, in flowspec) raises (nosuchflow, QoSRequestFailed) } We have modified the TAO AV service, and use modify_qos() to specify Diffserv codepoint values in video streams. AV service contributions are integrated in TAO 1.2. CORBA works well as a QoS signalling platform. 18

19 Creating RSVP and Diffserv Reusable Qoskets RSVP Qosket Diffserv Qosket Desirable to create reusable network level QoS components ( Qoskets ), to make distributed, QoS enabled applications easier to develop. Code for RSVP qosket is currently being refactored out of existing application. Diffserv qosket needs to be rewritten. Perhaps a good use for the CORBA Component Model? 19

20 Future Directions Use more RT-CORBA features to deliver end-to-end QoS Use the CORBA AV service to send multiple simultaneous data streams (video, sensor readings) Create reusable Qosket components for RSVP, Diffserv, and other QoS properties CORBA seems to work well as a signalling platform for QoS. Can we use it to request network level QoS instead of protocols like RSVP? How can we integrate with Resource Managers for requesting end-to-end QoS: network, CPU resources,.? 20

21 Distribution information Software available from our web site: Help available from: Requires latest version of TAO ORB, version 1.2, available from: 21