Quality of Service in the Internet

Quality of Service in the Internet
Dr. Vasil Y. Hnatyshin 11/12/2018 Rowan University Vasil Y. Hnatyshin

Rowan University Vasil Y. Hnatyshin
Outline Introduction QoS via traffic differentiation QoS Building Blocks Integrated Services Differentiated Services Bandwidth Distribution Scheme Summary and Conclusions 11/12/2018 Rowan University Vasil Y. Hnatyshin

What is QoS? What is Quality of Service? What parameters influences perceived network QoS? Why do we need QoS in the Internet? Its user perceived degree of satisfaction related to network performance. Similar definition is applicable to other things such computer or application performance. In this talk we will discuss only network related QoS issues. Such parameters as: delay -- what is delay? loss – what is loss? jitter – what is jitter? throughput – what is throughput? The user requests a specific type of service dispatches its traffic into the network. The user expects that its traffic will be handled according his/her specifications. And its up to the network to satisfy user. 11/12/2018 Rowan University Vasil Y. Hnatyshin

Internet Architecture
APPLICATION What architectural model is being used in today’s Internet? TCP/UDP IP What are IP, TCP, and UDP and how do they work? MAC TCP/IP Internet Architecture 11/12/2018 Rowan University Vasil Y. Hnatyshin

How does Internet work? APPLICATION TCP/UDP IP MAC Widener APPLICATION TCP/UDP IP MAC Rowan APPLICATION TCP/UDP IP MAC INTERNET ISP ISP 11/12/2018 Rowan University Vasil Y. Hnatyshin

How to achieve QoS? Provisioning Traffic differentiation In ISP routers (and the end nodes) In the Internet core routers Combination of the above 11/12/2018 Rowan University Vasil Y. Hnatyshin

QoS Building Blocks Classifier Admission Control Incoming Packet Rate Controller Scheduler Classifier allows the router to determine the type of service for the incoming packet. Rate control ensures that the amount of traffic that enters the network is below a specified amount. Admission control determines if the incoming traffic can be admitted into the network without violating guarantees of existing QoS class. Scheduler determines the departing order of the packets Outgoing Packet 11/12/2018 Rowan University Vasil Y. Hnatyshin

Options (Variable Size)
Classifiers Application block Source/Destination IP addresses Source/Destination ports Transport protocol Type of Service Field (Differentiated Services) Version Header Length Type of Service Total Packet Length … Protocol Header Checksum TTL Source Address Destination Address Options (Variable Size) For each application flow in the network a block is created by a control path application that is informed of the existence of an application flow. Certain fields from the incoming packet are used to identify the correct block associated with the packet. The class of service is service to be given to the packet is maintained in the block with other info like parameters for rate control. 11/12/2018 Rowan University Vasil Y. Hnatyshin

Classifiers Class #1 Classifier Class #2 For each application flow in the network a block is created by a control path application that is informed of the existence of an application flow. Certain fields from the incoming packet are used to identify the correct block associated with the packet. The class of service is service to be given to the packet is maintained in the block with other info like parameters for rate control. 11/12/2018 Rowan University Vasil Y. Hnatyshin

Admission control Ensures that the load on a particular link is manageable by determining if the new flow can be admitted into the network. Admission Control Link utilization is 60 % Link utilization is 90 % 11/12/2018 Rowan University Vasil Y. Hnatyshin

Rate Controllers What are rate controllers and how rate control is achieved? Shapers Droppers Common rate control mechanisms Token bucket Timestamp driven Rate controllers ensure that the amount of traffic coming into a network element (node or link) is below specified amount. Packets that violate incoming rate requirements are either shaped or dropped: Shapers delay the packets and thus re-shape the packet streams sent into the network Droppers drop the packets Rate controllers are needed to limit network congestion and enforce user agreements. Token bucket – generates tokens at specific rate. If there are tokens available when the packet has arrived then packet is forwarded further, otherwise the packet is “policed” via shaping/dropping Timestamp driven approach examines the time passed between two consecutive packets to determine arrival rate of the classified flow of packets. 11/12/2018 Rowan University Vasil Y. Hnatyshin

Rate Controllers Processing Queue Rate Controller Dropper Rate controllers ensure that the amount of traffic coming into a network element (node or link) is below specified amount. Packets that violate incoming rate requirements are either shaped or dropped: Shapers delay the packets and thus re-shape the packet streams sent into the network Droppers drop the packets Rate controllers are needed to limit network congestion and enforce user agreements. Token bucket – generates tokens at specific rate. If there are tokens available when the packet has arrived then packet is forwarded further, otherwise the packet is “policed” via shaping/dropping Timestamp driven approach examines the time passed between two consecutive packets to determine arrival rate of the classified flow of packets. Delay Queue 11/12/2018 Rowan University Vasil Y. Hnatyshin

Schedulers What are schedulers? Scheduling mechanisms: FIFO Priority Queuing Potential problem? Preemptive vs. non-preemptive Weighted-Fair Queuing Schedulers determine the processing order of the packets at the node or at the outgoing link. FIFO – first in first out Strict priority queues -- multiple FIFO queues each with different priority. Packets that belong to highest priority are served first. This mechanism may cause starving of the low priority packets. Alternative solution is to modify priority of the packet based on the time waited in the queue. Scenario: a high priority packet arrives while a low low priority packet is being served: Preemptive – abort processing of the low priority packet so that the high priority packet can be transmitted Non-preemptive – let the low priority packet finish its processing and only then allow a high priority packet to proceed. Weighted-fair queuing – regulates the amount of BW used by each class of service. Each class of service has a queue. The queues are served in the round-robin fashion and the time allocated for each queue processing is determined based on the class weight. 11/12/2018 Rowan University Vasil Y. Hnatyshin

Priority Scheduler Priority Queue #1 Priority Queue #2 Priority Queue #3 Outgoing Link Schedulers determine the processing order of the packets at the node or at the outgoing link. FIFO – first in first out Strict priority queues -- multiple FIFO queues each with different priority. Packets that belong to highest priority are served first. This mechanism may cause starving of the low priority packets. Alternative solution is to modify priority of the packet based on the time waited in the queue. Scenario: a high priority packet arrives while a low low priority packet is being served: Preemptive – abort processing of the low priority packet so that the high priority packet can be transmitted Non-preemptive – let the low priority packet finish its processing and only then allow a high priority packet to proceed. Weighted-fair queuing – regulates the amount of BW used by each class of service. Each class of service has a queue. The queues are served in the round-robin fashion and the time allocated for each queue processing is determined based on the class weight. 11/12/2018 Rowan University Vasil Y. Hnatyshin

QoS Blocks Revisited Classifier Admission Control Incoming Packet SLA Rate Controller Classifier allows the router to determine the type of service for the incoming packet. Rate control ensures that the amount of traffic that enters the network is below a specified amount. Admission control determines if the incoming traffic can be admitted into the network without violating guarantees of existing QoS class. Scheduler determines the departing order of the packets. SLA – service-level agreement that contains QoS requirements of the users. Scheduler Outgoing Packet 11/12/2018 Rowan University Vasil Y. Hnatyshin

Integrated Services Simplified Idea: for each newly admitted flow reserve network resources at each node on the flow’s path from source to destination. Uses per-flow resource reservation protocol called resource reservation protocol (RSVP). IntServ: Each router on the flow’s path from source to destination reserves network resource to satisfy flow QoS requirement For example a new flow comes in the router examines user requirements and than request appropriate amount of resources in the network. 4. When a packet travels through the network the routers identify the flow the packet belongs to and process the packet according to the flow’s resource reservation. As a result, each flow received the QoS based on their individual requirements. 5. In a network there could be millions of flow simultaneously traveling through the interior routers in the network. Maintaining and processing resource reservation for each flow puts enormous overhead on the routers in terms of storage and computational power. That is why IntServ seldom deployed in real networks and considered to be not scalable 6. DiffServ tries to address the scalability problem of IntServ model by using a network architecture where only the edge nodes maintain and process per-flow information, while core routers deal with the traffic aggregates. This is achieved by combining flows that have similar QoS requirements into traffic aggregates or classes. 7. When a new flow requests to enter the network the edge nodes determine the flow’s and mark each of the flow’s packets as members of that class. The core router process arriving packet based on their marking. 8. This approach is scalable but it can provide more coarse per-aggregate QoS, where the flows receive QoS within their corresponding class specification. This often may not be adequate. 9. That is why we try to develop a scheme that combines advantages of both the DiffServ and IntServ approaches and supports scalable per-flow QoS. 11/12/2018 Rowan University Vasil Y. Hnatyshin

IntServ Example Internet ISP 2 ISP 1 Core 2 ISP 4 Core1 ISP 3 Core 3 Widener Rowan FTP connection from Rowan to CNN FTP connection from Widener to CNN Video conference call from Rowan to CNN Video conference call from Widener to CNN Allocated resources for corresponding connections 11/12/2018 Rowan University Vasil Y. Hnatyshin

IntServ Summary Main Advantage Main Disadvantage Support for fine-grained per-flow QoS Resource hogging Not Scalable Fine-grained per-flow QoS – each flow admitted into the network will receive its requested QoS. IntServ classes are omitted (e.g. Guaranteed, Control-load, and best-effort). Resource hogging – once resources are allocated for a particular flow, no other flow can benefit from those resources. This issues is addressed via policy control module that determines which flows and for how long can establish resource reservations. Scalability – in the Internet where a lot of flow travel simultaneously through the same router will require the router to maintain resources reservations for all the flows that travel through it. This will cause enormous strain on the storage and processing capabilities of the router. 11/12/2018 Rowan University Vasil Y. Hnatyshin

Differentiated Services
Goal: Provide scalable QoS. DiffServ Implementation: Establishes a few classes/aggregates Classifies arriving traffic into one of pre-defined classes. Packets are differentiated based on the DSCP marking set in the IP header. Core routers treat arriving traffic based on the packet’s class. 6. DiffServ tries to address the scalability problem of IntServ model by using a network architecture where only the edge nodes maintain and process per-flow information, while core routers deal with the traffic aggregates. This is achieved by combining flows that have similar QoS requirements into traffic aggregates or classes. 7. When a new flow requests to enter the network the edge nodes determine the flow’s and mark each of the flow’s packets as members of that class. The core router process arriving packet based on their marking. 8. This approach is scalable but it can provide more coarse per-aggregate QoS, where the flows receive QoS within their corresponding class specification. This often may not be adequate. 9. That is why we try to develop a scheme that combines advantages of both the DiffServ and IntServ approaches and supports scalable per-flow QoS. 11/12/2018 Rowan University Vasil Y. Hnatyshin

DiffServ Example Internet ISP 2 ISP 1 Core 2 ISP 4 Core1 ISP 3 Core 3 Widener Rowan FTP connection from Rowan to CNN FTP connection from Widener to CNN Video conference call from Rowan to CNN Video conference call from Widener to CNN DS Class A DS Class B 11/12/2018 Rowan University Vasil Y. Hnatyshin

DiffServ Summary Main Advantage Main Disadvantage Scalability Providing only coarse-grained per-aggregated QoS Fine-grained per-flow QoS – each flow admitted into the network will receive its requested QoS. IntServ classes are omitted (e.g. Guaranteed, Control-load, and best-effort). Resource hogging – once resources are allocated for a particular flow, no other flow can benefit from those resources. This issues is addressed via policy control module that determines which flows and for how long can establish resource reservations. Scalability – in the Internet where a lot of flow travel simultaneously through the same router will require the router to maintain resources reservations for all the flows that travel through it. This will cause enormous strain on the storage and processing capabilities of the router. 11/12/2018 Rowan University Vasil Y. Hnatyshin

Outline Introduction QoS via traffic differentiation QoS Building Blocks Integrated Services Differentiated Services Bandwidth Distribution Scheme (BDS) Summary and Conclusions 11/12/2018 Rowan University Vasil Y. Hnatyshin

Idea of the BDS Flow request certain amounts of bandwidth upon activation. Bandwidth flow requirements are aggregated and distributed in the network via Resource Distribution and Feedback Protocol (RDF Protocol). Based on the aggregate flow requirements individual edge routers control the rate of the traffic. 11/12/2018 Rowan University Vasil Y. Hnatyshin

BDS Example Internet ISP 2 ISP 1 Core 2 ISP 4 Core1 ISP 3 Core 3 Widener Rowan FTP connection from Rowan to CNN FTP connection from Widener to CNN Video conference call from Rowan to CNN Video conference call from Widener to CNN Aggregate Flow Requirements 11/12/2018 Rowan University Vasil Y. Hnatyshin

Summary and Conclusions
The BDS approach has potential to become superior to current IntServ and DiffServ approaches. BDS Advantages: Scalability Per-flow QoS Fairness Congestion control BDS Disadvantages: Not tested under real-life scenarios Overhead of the RDF protocol 11/12/2018 Rowan University Vasil Y. Hnatyshin

Ongoing BDS Research Evaluation of the BDS approach under more realistic scenarios. Dealing with the inter-domain traffic. Extending the BDS framework to mobile environment. Influence of the BDS model on TCP traffic. 11/12/2018 Rowan University Vasil Y. Hnatyshin

The BDS Publications V. Hnatyshin and A.S. Sethi, “Reducing load distribution overhead with message aggregation,” Proc of IPCCC’03, Phoenix, AZ (April 2003) V. Hnatyshin and A.S. Sethi, “Fair and Scalable Load Distribution in the Internet,” Proc. 3rd International Conference on Internet Computing, Las Vegas, NV (June 2002). V. Hnatyshin and A.S. Sethi, “Achieving Fair and Predictable Service Differentiation Through Traffic Degradation Policies,” Proc. SPIE QoS 2001, Conference on Quality of Service over Next-Generation Data Networks, Denver, CO (Aug. 2001). V. Hnatyshin and A.S. Sethi, “Avoiding Congestion Through Dynamic Load Control,” Proc. ITCom-2001, SPIE's International Symposium on The Convergence of Information Technologies and Communications, Denver, CO (Aug. 2001). 11/12/2018 Rowan University Vasil Y. Hnatyshin

The End!

Network Architecture Network Domain Edge A Edge B Edge C Edge D Core 1 Core 2 Core 3 The Internet Network Domain 11/12/2018 Rowan University Vasil Y. Hnatyshin

DiffServ Scalability Edge Routers: Maintain all per-flow information via SLA Perform traffic classification Mark arriving packets Network Domain Edge A Edge B Edge C Edge D Core 1 Core 2 Core 3 Core Routers: Maintain only class information Treat arriving traffic based on the DSCP marking 11/12/2018 Rowan University Vasil Y. Hnatyshin

BDS Edge Node Data Structures
… Flow List SLA Table … Source Destination Data Egress node … Path Table Link Table … IP Address Data Link Capacity Aggregate RBR Arrival Rate Path List … Complete Path 11/12/2018 Rowan University Vasil Y. Hnatyshin

BDS Core Node Data Structures
Interfaces Table … IP Address Data Link Capacity Aggregate RBR Arrival Rate Edge Nodes List 11/12/2018 Rowan University Vasil Y. Hnatyshin

BDS Objectives Scalability Per-flow QoS Fair distribution of bandwidth Congestion Control 11/12/2018 Rowan University Vasil Y. Hnatyshin

BDS Scalability Edge Routers: Maintain all per-flow information via SLA Perform traffic classification Adjust transmission rate of the flows based on the network feedback Network Domain Edge A Edge B Edge C Edge D Core 1 Core 2 Core 3 Core Routers: Maintain only aggregate flow requirements Provide network feedback to the edge routers BDS scalability relies on the network architecture and requirement that the core routers maintain only aggregate flow requirements 11/12/2018 Rowan University Vasil Y. Hnatyshin

BDS Per-flow QoS Admission control Resource management Control protocol Note: Fairness and congestion control achieved via same modules 11/12/2018 Rowan University Vasil Y. Hnatyshin

Admission Control Flow Requirements: Requested Bandwidth Range (RBR) [Min Rate, Max Rate] = Aggregate RBR Admission control test: -- A new flow -- A path of a flow -- A flow -- A link -- A set of flows that travel through link k -- Capacity of link k 11/12/2018 Rowan University Vasil Y. Hnatyshin

Resource Management Definitions of Fairness: Proportional Fairness Maximizing Utility Fairness Per-Flow Resource Allocation 11/12/2018 Rowan University Vasil Y. Hnatyshin

The RDF Protocol Purpose: Distribute the Aggregate RBR among the nodes in the network. Path Probing Phase: Edge routers periodically probe the network to discover the route changes (e.g. aggregate RBR, excess bandwidth). RBR Update Phase: Edge nodes notify the core routers about the change of the aggregate RBR due to flow activation or termination. Notification Phase: Core routers notify the edge nodes about congestion. 11/12/2018 Rowan University Vasil Y. Hnatyshin

The RDF Protocol Example
Flow F2 requests to enter the network at Edge 2 to travel to Edge 5 C1 Edge 2 Edge 3 Edge 1 Edge 4 Edge 5 Edge 6 C2 C3 F2 Probe Reply Probe CN F1 1. Initiates the Path Probing Phase 2. Updates Local Data Structures 3. Performs Admission Control Test Core Router C1 discovers that link C1-C2 is congested 4. Computes Allocated Rate of F2 5. Initiates the RBR Update Phase 1. C1 initiates the Notification Phase. 6. Allows F2 to enter the network 2. Edge 1 and Edge 2 adjust allocated rates of F1 and F2 to eliminate congestion. 11/12/2018 Rowan University Vasil Y. Hnatyshin

Definitions of Fairness
The BDS Architecture Excess BW Management The BDS Objectives Per-Flow QoS Congestion Control Scalability Per-Flow Admission Control Resource Allocation RBR Distribution and Feedback Protocol The BDS Framework Network Architecture Flow Requirements Definitions of Fairness Specifications and Definitions The BDS Architecture 11/12/2018 Rowan University Vasil Y. Hnatyshin

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