QoS over IP IntServ and DiffServ

Transcription

1 QoS over IP IntServ and DiffServ 1

2 Overview Integrated services Resource Reservation Protocol: RSVP Differentiated Services QoS routing Multiprotocol Label Switching (MPLS) CoS 2

3 Multimedia on the Internet Specify source traffic requirements Protocols to create and maintain resource reservations Routing protocols that support QoS and multicast Transport protocols for error and flow control Access control Packet scheduler to provide QoS: 3

4 Multimedia on the Internet Specify source traffic requirements Flow specs from INTSERV working group Protocols to create and maintain resource reservations: RSVP Routing protocols that support QoS and multicast Mrouted, ST2+ Transport protocols for error and flow control: RTP Access control: Connection admission based on usage, packet dropping Packet scheduler to provide QoS: Weighted Fair Queueing 4

5 Multimedia Application Transport Network Datalink Physical Video Conferencing, Telephony, Fax Timing Sync, payload id, error recovery QoS, Multicast, Signaling Access Control, Multicast, signaling Multiple channels via SDM, FDM, TDM 5

6 IETF Groups Application Transport Network Datalink Physical Iptel, fax Avt (RTP), mmusic (RTSP) Qosr, MPLS, IntServ, Issll, Diff-serv, RSVP IEEE 802.1p Broadband Ethernet 10Broad36 4

7 QoS Triangle Carrier Low Capacity High Traffic Sender Receiver High QoS Senders want to send traffic any time with high load, high burstiness Receivers expect low delay and high throughput Since links are expensive, providers want to minimize the infrastructure If one of the three gives in no problem 5

8 Components of QoS Architecture 1. Services with different QoS: Service definitions 2. Ways for users to communicate what they need: Signaling or admission control 3. Ways for providers to ensure that users are following their commitment: Policing/shaping 4. Ways for providers to find the routes: QoS based routing 5. QoS based forwarding: Buffer Allocation and Drop Policy, Queueing Discipline and Service Policy, Traffic Management of elastic traffic 6

9 ATM vs IP QoS Component ATM IP Services CBR, VBR, ABR, UBR Integrated Services Signaling UNI 4.0 RSVP Policing/Shaping Leaky bucket Token bucket Forwarding Per-VC/per-class Differentiated queueing Services Elastic Traffic ABR RED, Slow-start Mgmt Routing PNNI QoS routing 7

10 Integrated Services Datagram Service Controlled-Load Service: Performance as good as in an unloaded datagram network. No quantitative assurances. Guaranteed Service: Firm bound on data throughput and delay. Every element along the path must provide delay bound. Is not always implementable, e.g., Ethernet. Delay jitter or average delay not guaranteed or minimized. 8

11 Flow Specification Flow Spec = Traffic Spec + QoS Spec = TSpec + RSpec TSpec: Peak rate (p), bucket rate (r), bucket size (b), max datagram size (M), min policed unit (m) All datagrams less than m are counted as m bytes Peak rate may be unknown or unspecified RSpec: Rate (R) and delay slack (S) S = Extra acceptable delay over that obtainable with R Zero slack Reserve exactly R. RSpec specified only for guaranteed rate service. Not for controlled load service. 9

12 Flow Specification Sender Traffic Spec Network Traffic Spec QoS Spec Available Resources Receiver TSpec: Token bucket parameters RSpec (QoS): Allocated Rate (R) and delay slack (S) S = Extra acceptable delay over that obtainable with R Zero slack Reserve exactly R. RSpec specified only for guaranteed rate service. Not for controlled load service. 10

13 IS-Capable Router Components Routing Process Reservation Process Policy Control Admission Control Packet Classifier Packet Scheduler 11

14 IS Router Components (Cont) Packet Scheduler: Manages queues and timers for different streams Classifier: Each incoming packet is examined to determine its class Packets in the same flow may have preemptable (CLP) attribute Admission Control: Determine whether a new flow can be granted without affecting existing flows Reservation Setup Protocol: RSVP 12

15 RSVP Resource ReSerVation Protocol Internet signaling protocol Carries resource reservation requests through the network Receiver initiated reservations Scales well Sets up reservations at each hop RSVP does not find routes. Multicast routing protocols do. RSVP does not do: Routing, Admission control, Packet scheduling 13

16 Path Messages S1 R1 R4 H5 H4 S2 R2 R3 H3 Sources send quasi-periodic PATH messages to multicast address Path message contain Flow spec : Sender Template: Data format, Src Address, Src Port TSpec: Traffic Characteristics 14

17 Reservation Requests S1 R1 R4 H5 H4 S2 R2 R3 H3 Receivers must join multicast address to receive path messages Receivers generate reservation (RESV) requests RESV messages contain resources to be reserved RESV messages are forwarded along the reverse path of PATH messages 15

18 Reservation (Cont) Requests are checked for resource availability (admission control) and administrative permissions (policy control) Two or more RESV messages for the same source over the same link are merged. Routers maintain a soft state. The receivers have to refresh periodically. Heterogeneous Receivers: Sources divide traffic into several flows. Each flow is a separate RSVP flow. Receivers join one or more flows. Each RSVP flow is homogeneous. 16

19 Reservation (Cont) ResV messages contain Flow Spec + Filter Spec Filter Spec: Defines the packets in the flow Used in packet classifier Flow Spec: Used in packet scheduler Contents depends upon the service. Will generally include TSpec and RSpec. 17

20 RSVP Reservation Styles Source Reservation Usage Selection Separate Shared Wildcard N/A Wildcard Filter Explicit Fixed Filter Shared-Explicit Fixed Filter: One pipe per source Wildcard Filter: One pipe for all sources on a session Shared-Explicit: Sources explicitly identified (Reserve for sources S3 or S4) 18

21 RSVP: Status A substantial internet draft (May 1997) Submitted to IESG area director. Multivendor interoperability demo at Sep'95 Interop. Product by Cisco and other vendors. Some unresolved Issues: Accounting and charging Authentication and access control Session groups 19

22 RSVP vs UNI Category IP/RSVP ATM UNI 3.0 Orientation Receiver based Sender based State Soft Hard QoS Setup time Separate from route establishment Concurrent with route establishment Directionality Unidirectional Unidirectional Heterogeneity Receiver heterogeneity UNI 4.0 adds leaf initiated join. 20 multicast Uniform QoS to all receivers

23 Problems with RSVP and Integrated Services Complexity in routers: packet classification, scheduling Per-Flow State: O(n) Not scalable. Number of flows in the backbone may be large. Suitable for small private networks Need a concept of Virtual Paths or aggregated flow groups for the backbone Need policy controls: Who can make reservations? Support for accounting and security. RSVP admission policy (rap) working group. 21

24 Problems (Cont) Receiver Based: Need sender control/notifications in some cases. Which receiver pays for shared part of the tree? Soft State: Need route/path pinning (stability). Limit number of changes during a session. Throughput and delay guarantees require support of lower layers. Shared Ethernet IP can t do GS or CLS. Need switched full-duplex LANs. Can t easily do RSVP on ATM either Most of these arguments also apply to integrated services. 22

25 Local Decision Point COPS Protocol Policy Enforcement Point COPS TCP Policy Decision Point Client Server Common Open Policy Service Protocol When the routers (clients) receive a RSVP message, they send the request the server and obtain authorization Will work with other (non-rsvp) signaling Routers can make local decisions but should keep servers informed Servers can send unsolicited responses for changes later 23

26 IP ToS Field Ver Hdr Len Precedence ToS Unused Tot Len 4b 4b 3b 4b 1b 16b IPv4: 3-bit precedence + 4-bit ToS RFC791: ToS determines packet treatment and monitory considerations RFC1349: bit 1 min delay, bit 2 max throughput, bit 3 max reliability, bit 4 min cost OSPF and integrated IS-IS can compute paths for each ToS 24

27 Differentiated Services Working Group August 97: BOF started Feb 98: Working group formed Dec 98: Final document in body: subscribe diff-serv Archive: Charter: define ds byte (IPv4 ToS or IPv6 traffic class octets) 25

28 Diff-Serv Terminology Service: Offered by the protocol layer Application: Mail, FTP, WWW, Video,... Transport: Delivery, Express Delivery,... Best effort, controlled load, guaranteed service Per-Hop Behavior (PHB): Mechanisms - Drop threshold, Queue assignment, Service priority, Service Rate Flow: Packets with specific header fields, Destination Address, Source Address, Port, Flow Label Aggregates: Stream of packets with the same DS byte pattern 26

29 Initial proposals Assured service (Jacobson): traffic profile (VBR or CLS like), in-profile and out-profile Premium Service (Clark): Peak rate (CBR or GS like), Virtual leased line Two-bit Service: A-bit (CLP) and P-bit (Priority) 2 Priority bits, 1 drop bit Bits for delay class: 2 bits 4 classes Bits for Drop preference: 3 bits 8 classes 27

30 Latest PHB Allocation ppp i 00 ppp = Precedence (Higher is generally better) i = in/out bit In profile/out Profile Drop preference. Allows in/out pkts in same Queue Compatible with current usage Precedence is used as an index to select a queue, or VC,... In IEEE-802 switches, only 1, 2, or 3 msbs used Unrecognized code points Default forwarding 28

31 PHB Allocation (Cont) Plan: 32 code points standard, 16 Experimental/local use, 16 reserved xxxxx0 Standard xxxx11 Experimental/Local Use xxxx01 Reserved for future 29

32 End-to-end QoS H R IntServ RSVP R Diff IntServ R R R R H Serv RSVP Hosts may mark DS byte or use RSVP signaling or both or none. Why hosts? 1. Encryption, 2. Hosts know the importance of info even if the header fields are same Routers may mark DS byte if necessary. Routers at the intserv diff-serv boundary accept/reject RSVP requests based on current load 30

33 Service between intserv and diff-serv regions can be statically or dynamically provisioned Current integrated services (CLS, GS) may or may not be practical DS byte may be modified at network boundary 31

34 S1 Issues R S2 Standard code points (behaviors) Receiver control over incoming low-speed link Signaling: Should users signal or network managers set resource allocations Dynamic or Static management controls? Billing: Bit for receiver billing. If receiver billing, the receiver should be able to deny/drop packets received. Congestion Check Bit: If set, network indicates highest priority for which packets are being dropped in the ToS byte. 32

35 QoS Extensions to OSPF Open shortest path first Separate metric can be specified for each ToS supported OSPF options field has a T-bit T-bit = 1 Router can compute routes for each ToS Other extensions to OSPF QoS Frequent updates Instability: Underloaded links become overloaded Also, complexity Ref: Z. Zhang, et al, QoS Extensions to OSPF, Sep. 97, 33

36 Inter-Domain QoS Routing Domains want to limit the frequency and amount of information exchanged Stability QoS based routing may cause frequent changes and instability QoS extensions to Border Gateway Protocol (BGP) also proposed Need hierarchical aggregation for scalability Crank-back 34

37 MPLS Prefix Label Out-Port Out-Label / / Multiprotocol Label Switching Current: Longest prefix match on the dest address With Labels: Search can be replaced by indexing MPLS labels contain 3-bit CoS Ethernet Header Label L3 Header Label CoS Stack Indicator Time to Live 20b 3b 1b 8b 35

38 Summary Internet protocols suite is being extended to allow QoS Integrated Services: GS = rtvbr, CLS = nrt-vbr Signaling protocol: RSVP Differentiated Services will use the DS byte QoS Routing: QOSPF Multiprotocol Label Switching has 3-bit CoS 36

39 Integrated Services Integrated Services 1. Best Effort Service: Like UBR. 2. Controlled-Load Service: Performance as good as in an unloaded datagram network. No quantitative assurances. Like nrt-vbr or UBR w MCR 3. Guaranteed Service: rt-vbr Firm bound on data throughput and delay. Like CBR or rt-vbr Need a signaling protocol: RSVP Design philosophy similar to ATM Per-flow End-to-end Signaling 6

40 Problems with IntServ+RSVP Complexity in routers: classification, scheduling Not scalable with # of flows Not suitable for backbone. Need a concept of Virtual Paths or aggregated flow groups for the backbone. Need policy controls: Who can make reservations? RSVP admission policy (rap) working group. Receiver Based: Need sender control/notifications in some cases. Soft State: Need route/path pinning (stability). No negotiation and backtracking Note: RSVP is being revised for MPLS and DiffServ 2

41 Trend: Differentiation Not Integration d/dx DiffServ to standardize IPv4 ToS byte s first six bits Packets gets marked at network ingress Marking treatment (behavior) in rest of the net Six bits 64 different per-hop behaviors (PHB) Ver Hdr Len Type of Service (ToS) Tot Len 4b 4b 8b 16b 3

42 DiffServ (Cont) Per-hop behavior = % of link bandwidth, Priority Services: End-to-end. Voice, Video,... Transport: Delivery, Express Delivery,... Best effort, controlled load, guaranteed service DS group will not develop services They will standardize Per-Hop Behaviors Marking based on static Service Level Agreements (SLAs). Avoid signaling. 4

43 Expedited Forwarding Also known as Premium Service Virtual leased line Similar to CBR Guaranteed minimum service rate Policed: Arrival rate < Minimum Service Rate Not affected by other data PHBs Highest data priority (if priority queueing) Code point:

44 Assured Forwarding PHB Group Four Classes: No particular ordering Three drop preference per class 6

45 Assured Forwarding (Cont) DS nodes SHOULD implement all 4 classes and MUST accept all 3 drop preferences. Can implement 2 drop preferences. Similar to nrt-vbr/abr/gfr Code Points: Drop Prec. Class 1 Class 2 Class 3 Class 4 Low Medium High Avoids 11x000 (used for network control) 7

46 Problems with DiffServ End-to-end Σ per-hop Designing end-to-end services with weighted guarantees at individual hops is difficult. Only Expedited Forwarding will work. Designed for static Service Level Agreements (SLAs) Both the network topology and traffic are highly dynamic. How to ensure resource availability inside the network? DiffServ is unidirectional No receiver control 8

47 DiffServ Problems (Cont) QoS is for the aggregate not micro-flows. Not intended/useful for end users. Only ISPs. Large number of short flows are better handled by aggregates. Long flows (voice and video sessions) need perflow guarantees. High-bandwidth flows (1 Mbps video) need perflow guarantees. DiffServ alone is not sufficient for backbone. Signaling via RSVP will be required. 9

48 MPLS Mechanisms for QoS Explicit Routing: Multiple label switched paths (LSPs) can be used in parallel to the same egress. Signaling, Admission Control, Routing: Each LSP can have priority, preemption, policing, overbooking Constrained based routing of LSPs Allows both Traffic constraints and Resource Constraints (Resource Attributes) Hierarchical division of the problem (Label Stacks) Danger: Too much too soon again 10

49 Bandwidth Broker Repository of policy database. Includes authentication Users request bandwidth from BB BB sends authorizations to leaf/border routers Tells what to mark. Ideally, need to account for bandwidth usage along the path BB allocates only boundary or bottleneck H H H DMZ R BB R R BR BR R 11

50 IEEE 802.1D Model Massive bandwidth. Simple priorities will do. Up to eight priorities: Strict. 1 Background 2 Spare 0 Best Effort 3 Excellent Effort 4 Control load 5 Video (Less than 100 ms latency and jitter) 6 Voice (Less than 10 ms latency and jitter) 7 Network Control 12

51 End-to-end View ATM/PPP backbone, Switched LANs/PPP in Stub IntServ/RSVP, 802.1D, MPLS in Stub networks DiffServ, ATM, MPLS in the core Switched LANs/PPP ATM/PPP Switched LANs/PPP IntServ/RSVP,802.1D, MPLS DiffServ, ATM, MPLS IntServ/RSVP,802.1D, MPLS R R COPS COPS BB BB BB R Edge R R Core R R Edge R R 13

52 Additional Mechanisms Policy based Routing Weighted Fair Queueing P(Discard) Weighted Random Early Detection Link Fragmentation and Interleaving These internal mechanisms do not require standardization Avg Q 14

53 Summary ATM: CBR, VBR, ABR, UBR, GFR Integrated Services: GS = rtvbr, CLS = nrt-vbr Signaling protocol: RSVP Differentiated Services will use the DS byte MPLS allows traffic engineering and is most promising 802.1D allows priority 15

54 References For a detailed list of references see: refs/ipqs_ref.htm P. Ferguson and G. Huston, "Quality of Service: Delivering QoS on the Internet and in Corporate Networks," Wiley RFC 2212, "Specification of Guaranteed Quality of Service", 9/97 RFC 2211 "Specification of the Controlled-Load Network Element Service", 9/97 37

55 References (Cont) RFC 2205, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", 11/97 "The COPS (Common Open Policy Service) Protocol", 03/16/1998, draft-ietf-rap-cops-01.txt "A Framework for Multiprotocol Label Switching", 11/26/1997, draft-ietf-mpls-framework-02.txt "MPLS Label Stack Encoding", 02/18/1998, draftietf-mpls-label-encaps-01.txt "A Framework for QoS-based Routing in the Internet", 04/09/1998, draft-ietf-qosr-framework- 04.txt 38

56 References (Cont) Diff-Serv Mail Thread index, "Definition of Differentiated Services Field (DS Byte) in the IPv4 and IPv6 Headers," 5/1998, draft-ietfdiffserv-header-00.txt "Differentiated Services Operational Model and Definitions", 02/11/1998, draft-nichols-dsopdef-00.txt "IP Precedence in Differentiated Services Using the Assured Service", 04/10/1998, draft-ietf-diffservprecedence-00.txt 39

57 References (Cont) "A Framework for End-to-End QoS Combining RSVP/IntServ and Differentiated Services", 03/16/1998, draft-bernet-intdiff-00.txt 40

58 IETF Working Groups IETF Working Groups Internet Fax (fax) IP Telephony (iptel) Audio/Video Transport (avt) MBONE deployment working group (mboned) Multiparty Multimedia Session Control (mmusic) Multicast Extensions to OSPF (mospf) Inter-Domain Multicast Routing (idmr) Large Scale Multicast Applications (lsma) Integrated Services (intserv) Integrated Services over Specific Link Layers (issll) Resource Reservation Setup Protocol (rsvp) QoS-based Routing (qosr) Differentiated services (diff-serv) 41

59 List of Acronyms ABR ATM BA BGP BOF CBR CDV CFI CLP CLS COPS Available Bit Rate Asynchronous Transfer Mode Behavior Aggregate Border Gateway Protocol Birds of a Feather Constant Bit Rate Cell Delay Variation Canonical Format Indicator Cell Loss Priority Controlled Load Service Common Open Policy Service Protocol 42

60 Acronyms (Cont) CoS DA DQDB DSBM DVMRP FCS FDDI FIFO FTP GS ICMP Class of Service Destination Address Distributed Queue Dual Bus Designated Subnet Bandwidth Manager Distance Vector Routing Multicast Protocol Frame Check Sequence Fiber Distributed Data Interface First in First out File Transfer Protocol Guaranteed Service Internet Control Message Protocol 43

61 IEEE IETF IGMP IP Acronyms (Cont) Institution of Electrical and Electronic Engineers Internet Engineering Task Force Internet Group Management Protocol Internet Protocol IPv4 Internet Protocol Version 4 IPv6 Internet Protocol Version 6 IS IntServ LANs LLC LU Internal System Integrated Services Local Area Networks Logical Link Control Local Use 44

62 Acronyms (Cont) MAC MBONE MBS MF MPLS MTU NHRP OOPS OSPF PASTE Media Access Control Multicast Backbone Maximum Burst Size Multi-field Multiprotocol Label Switching Maximum Transmission Unit Next Hop Resolution Protocol Open Outsourcing Policy Service Open Shortest Path First Provider Architecture for Differentiated Services and Traffic Engineering 45

63 Acronyms (Cont) PCR PHB PIM PT QOSPF QoS RED ResV RFC RIF RSVP Peak Cell Rate Per-Hop Behavior Protocol Independent Multicast Protocol Type QoS-OSPF Quality of Service Random Early Discard Reservation Request Request for Comment Routing Information Field Resource Reservation Protocol 46

64 Acronyms (Cont) RSpec RTP SBM SONET TCP TPID TR TSpec ToS UBR UDP QoS Specification Real-time Transport Protocol Subnet Bandwidth Manager Synchronous Optical Network Transmission Control Protocol Tag Protocol ID Token Ring Traffic Specification Type of Service Unspecified Bit Rate User Datagram Protocol 47

65 Acronyms (Cont) UNI VBR VC VLAN WAN WFQ User-Network Interface Variable Bit Rate Virtual Circuit Virtual Local Area Network Wide Area Network Weighted Fair Queueing 48