Towards Service Differentiation on the Internet

Transcription

1 Towards Service Differentiation on the Internet from New Internet and Networking Technologies and Their Application on Computational Sciences, invited talk given at Ho Chi Minh City, Vietnam March 3-5, 2004 and New Internet and Networking Technologies for Grids and High-Performance Computing, tutorial given at HiPC 2004, Bangalore, India December 22nd, 2004 C. Pham University of Pau, France

2 Limitations of the current Internet Bandwidth Raw bandwidth is not a problem: DWDM Provisioning bandwidth on demand is more problematic Latency Mean latencies on Internet is about ms Bounding latencies or ensuring lower latencies is a problem End-to-end performances Links are getting faster and faster! Why my FTP is still going so slow? Communication models Only unicast communications are well-defined: UDP, TCP Multi-parties communication models are slow to be deployed

3 Revisiting the same service for all paradigm N E W IP packet No delivery guarantee C H A P T E R INTERNET Regular mail Enhancing the best-effort service IP packet Introduce Service Differentiation

4 Service Differentiation The real question is to choose which packets shall be dropped. The first definition of differential service is something like "not mine. -- Christian Huitema Differentiated services provide a way to specify the relative priority of packets Some data is more important than other People who pay for better service get it! SLA Service Level Agreement

5 Divide traffic into classes Differentiated IP Services Voice Platinum Class Low Latency Application Traffic , Web Browsing E-Commerce Traffic Classification Gold Silver Guaranteed: Latency and Delivery Guaranteed Delivery Voice Borrowed from Cisco Bronze Best Effort Delivery

6 Design Goals/Challenges Ability to charge differently for different services No per flow state or per flow signaling All policy decisions made at network boundaries Boundary routers implement policy decisions by tagging packets with appropriate priority tag Traffic policing at network boundaries Deploy incrementally, then evolve Build simple system at first, expand if needed in future

7 IP implementation: DiffServ No per flow state in the core IP packet 10Gbps=2.4Mpps with 512-byte packets Flow 1 Flow 2 Flow 3 Flow 4 IP header Stateful approaches are not scalable at gigabit rates! 6 bits used for Differentiated Service Code Point (DSCP) and determine PHB that the packet will receive Ver Len Typ.Ser. TTL Ident Proto IP Data Area Source IP Address Destination IP Address Options RFC IP TOS Fl DiffServ IntServ/ RSVP Total Length Frag.Offset Header Checksum Padding

8 Traffic Conditioning User declares traffic bits profile (eg, rate and burst size); traffic b*r/(r-r) is metered and shaped if non-conforming 5Mbps bps meter time SLA 2Mbps slope R slope r Service Level Agreement Arrival curve r tokens per second time packets classifier marker Shaper/ dropper drop forward <= R bps regulator b tokens

9 Differentiated Architecture Ingress Edge Router DiffServ Domain Edge Router Interior Router r marking scheduling Marking: per-flow traffic management marks packets as in-profile and outprofile b... Per-Hop-Behavior (PHB): Ingress per class traffic management buffering and scheduling based on marking at edge preference given to in-profile packets

10 Pre-defined PHB Expedited Forwarding (EF, premium): departure rate of packets from a class equals or exceeds a specified rate (logical link with a minimum guaranteed rate) Emulates leased-line behavior Assured Forwarding (AF): 4 classes, each guaranteed a minimum amount of bandwidth and buffering; each with three drop preference partitions Emulates frame-relay behavior

11 Premium Service Example Drop always 10Mbps Fixed Bandwidth source Gordon Schaffee

12 Assured Service Example Drop if congested 10Mbps Uncongested Assured Service Congested source Gordon Schaffee

13 Border Router Functionality Premium Service Token Bucket Packet Input Data Queue Wait for token Set P-bit Packet Output Class 1 Class 2 Class 3 Class 4 Low drop probability Medium drop proba Assured Service Token Bucket High drop proba. No token Packet Input Test if token Token Set A-bit Packet Output source Gordon Schaffee, modified by C. Pham Data Queue

14 Internal Router Functionality Packets In P-bit set? Yes High Priority Queue No Low Priority Queue Packets Out If A-bit set, a_cnt++ if congested If A-bit set, a_cnt-- RED In/Out Queue Management A DSCP codes aggregates, not individual flows No state in the core Should scale to millions of flows source Gordon Schaffee, modified by C. Pham

15 Practical realization 1 Drop probalility 0 1 WRED Queue 0 WRED Queue 1 0 1/4 1/2 3/4 Queue filling 30 % Queue 0 Prec. 0 BE + AF UDP out profile Prec. 1 AF UDP in profile 30 % 30 % Queue 1 Queue 2 Classifier Prec. 2 AF TCP out profile Prec. 3 AF TCP in profile Prec. 4 Prec. 5 EF Source VTHD 10 % Queue 3 Prec. 6 Prec. 7 Control Control

16 DiffServ in action Wide-area interactive simulations display airport simulator INTERNET computer-based plane simulator (x,y,z,t) FTP scheduling Interactive applications require low latencies human in the loop flight simulator Ingress/Ingress... marking r b Assured Forwarding Premium

17 DiffServ in action (con t) airport simulator Wide-area interactive simulations display INTERNET computer-based plane simulator (x,y,z,t) FTP FTP scheduling Interactive applications require low latencies human in the loop flight simulator Ingress/Ingress... A DSCP codes aggregates, not individual flows No state in the core Should scale to millions of flows Assured Forwarding Premium

18 DiffServ in commercial products Most switch/router manufacturer (Cisco, Juniper, Procket ) have DiffServ implementations (and other advanced QoS features: WFQ, RED, WRED ) in their products for corporates, ISP, operators.