Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks*

1. Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks* Dr. Spiros Bakiras, PhD (USC), MIEEE Dept. of Electrical & Electronic Engineering The University of Hong Kong *Joint work with Prof. Victor O.K. Li

2. Outline • Motivation • System design • Resource management • Simulation results • Conclusions Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

3. Motivation • The Differentiated Services (DiffServ) architecture has been proposed by the IETF as a scalable solution for providing end-to-end QoS guarantees. • Scalability at the data plane • Edge routers manage traffic on a per flow basis. • Core routers manage traffic on a much coarser granularity. • Only a limited number of service classes is defined, and each packet is forwarded based on Per Hop Behavior (PHB). • Examples: Expedited Forwarding (EF), and Assured Forwarding (AF) PHB. • Scalable resource management is still an open research problem. Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

4. Motivation • Initial proposal: centralized agent, called Bandwidth Broker (BB). Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

5. Motivation • Disadvantages • The signaling messages will create congestion on the links around the BB. • The BB must maintain per flow information about every flow which is active inside the domain. • The BB is a single point of failure. • We will propose a decentralized resource management scheme, where • The BB is eliminated from the admission control procedure. • All the edge routers in a domain will independently set-up and tear-down individual connections. • The BB will periodically reallocate the resources inside the domain. Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

6. System design • Intra-domain routing • Static routing tables for QoS-sensitive traffic. • A total of k paths are pre-computed for each pair of edge routers. • Each QoS flow will be assigned to one of these paths. • Inter-domain routing • All the edge routers in the domain will use the standard BGP protocol to exchange reachability information with neighbor domains. • Packet forwarding with IPv6 • The flow label (20 bits) will indicate the corresponding ingress-egress pair and path number. Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

7. Resource management • Define • SD pair: a pair of ingress-egress routers. • For each SD pair there are k pre-computed paths. • The source of each SD pair i will periodically measure the total amount of reserved bandwidth r[i]. • Every time interval T, the BB will receive the following information about every SD pair i • The current reserved bandwidth x[i][j] for each path j. • The average reserved bandwidth w[i] over the measurement window. Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

8. Resource management • The BB will then calculate the new amount of resources that should be allocated to each path. • Each path jof SD pair i will be allocated an amount of bandwidth y[i][j], where y[i][j]x[i][j]. • Rejected traffic load • Instead of the actual reserved bandwidth r[i], we will periodically measure the virtual reserved bandwidth v[i]. • This measurement will include the bandwidth of all the rejected flows. • w[i] will then represent the average virtual reserved bandwidth over the measurement window T. Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

9. Resource management • Definitions • Every SD pair i will require an additional amount of bandwidth b[i]=w[i]-r[i]. • Eligible SD pair: a pair i with b[i]>0. • Saturated SD pair: a pair for which there is at least one saturated link in each of the k paths. • Resource reallocation algorithm • In a round-robin manner, add a small amount of bandwidth dx to SD pair i, to the path j that minimizes a cost function. • Repeat until all SD pairs become either non-eligible or saturated. • Allocate the unused bandwidth to all unsaturated SD pairs. Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

10. Resource management • Admission control • The source will send a PATH message to the destination. • Admission control will be performed at the ingress router of each domain. • If the new flow is admitted, the destination will reply with a RESV message. Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

11. Resource management • Advantages • The signaling overhead is spread across multiple links. • Per flow information is distributed across the edge routers of the domain. • A failure of the BB or an edge router will not affect the functionality of the domain. • Fast response time for new connection requests. • Equal to the round-trip delay between the source and the destination. Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

12. Simulation results • We simulated our resource management scheme in the MCI internet topology. • It consists of 19 nodes and 32 links. • We assumed all links have a capacity of 2.4 Gbps. • New requests arrived at each SD pair, according to a Poisson process with average rate that was uniformly distributed in [1,rmax]. • Every new request was either for a voice or video connection with equal probability. • Voice: bandwidth 64 kbps, duration 5 min (exponential). • Video: bandwidth uniform in [0.3,2] Mbps, duration 20 min. Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

13. Simulation results Fig. 1: The simulated network topology Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

14. Simulation results Fig. 2: Bandwidth blocking rate as a function of the average arrival rate, for different values of k. Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

15. Experimental results Experimental results Fig. 3: Bandwidth blocking rate as a function of the average arrival rate, for different values of T. Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

16. Simulation results Fig. 4: Bandwidth blocking rate as a function of the average arrival rate, for different resource management schemes. Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks

17. Conclusions • We have proposed a new resource management scheme for end-to-end QoS guarantees in DiffServ-based networks. • All the edge routers of a domain actively participate in this procedure. • The BB is only responsible for periodically reallocating the resources inside the domain. • Admission control is performed instantaneously at the ingress router of each domain. • The simulation results indicate that our scheme can achieve lower bandwidth blocking rate compared to traditional shortest path routing. Efficient Resource Management for End-to-End QoS Guarantees in DiffServ Networks