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Integrated Services RSVP Differentiated Services 전산과학과 정보통신 연구실 최 선 웅 9월 23일 2017-05-25 SNU INC Lab History IP-based Internet provide a simple best-effort delivery service to all applications New real-time, multimedia, and multicasting applications are not well supported, in IP-based Internet. construct a second networking infrastructure for real-time traffic replace the existing IP-based configuration with ATM 2017-05-25 SNU INC Lab Integrated Services Architecture(ISA) Strong need to support a variety of traffic with a variety of QoS requirements, within the TCP/IP architecture Fundamental requirement add new functionality to routers and a means for requesting QoS-based service from Internet IETF is developing a suite of standards under the general umbrella of the Integrated Services Architecture(ISA) 2017-05-25 SNU INC Lab Integrated Services(intserv) Integrated Services Purpose of this working group The transport of audio, video, real-time, and classical data traffic within a single network infrastructure Define the enhanced Internet service model Defining the application service, router scheduling and (general) subnet interfaces Developing router validation requirements which can ensure that the proper service is provided RFC’s Specification of the Controlled-Load Network Element Service (RFC 2211) Specification of Guaranteed Quality of Service (RFC 2212) 2017-05-25 SNU INC Lab Internet Traffic Elastic Traffic can adjust to change in delay and throughput across Internet and still meet the needs of its applications non-real-time application FTP, SMTP, TELNET, SNMP, HTTP Inelastic Traffic does not easily adapt to changes in delay and throughput across Internet real-time application 2017-05-25 SNU INC Lab Inelastic traffic Inelastic traffic Tolerant / Intolerant depending on whether they can tolerate occasional loss Adaptive / Non-adaptive depending on their adaptability Delay-adaptive / Rate-adaptive Requirement for inelastic traffic need of means to give preferential treatment to applications with more demanding requirements elastic traffic must still be supported 2017-05-25 SNU INC Lab ISA Service Class Guaranteed(RFC 2212) Controlled load(RFC 2211) provide assured capacity level, or data rate specified upper bound on the queuing delay no queuing losses approximation no specified upper bound on the queuing delay, but ensure that a very high percentage of the packets do not experience delays that greatly exceed the minimum transit delay almost no queuing loss Best effort 2017-05-25 SNU INC Lab Flow Flow distinguishable stream of related IP packets that results from a single user activity and requires the same QoS Flow vs. TCP connection A flow is unidirectional There can be more than one recipient of a flow(multicast) 2017-05-25 SNU INC Lab Internet Traffic Control Conventional Traffic Control Routing algorithm Most routing protocols in use in Internet allow routes to be selected to minimize delay Packet discard When overflows, discard packets Typically, the most recent packet is discarded These tools have worked reasonably well 2017-05-25 SNU INC Lab Requirements ISA Approach Flowspec Admission Control Routing algorithm may be based on a variety of QoS parameters, not just minimum delay Queuing discipline Discard policy Resource reservation Reservation Protocol(RSVP) 2017-05-25 SNU INC Lab IS Router Components Classifier Incoming packet must be mapped into some class Choice of a class is based on fields in the packet header Packet scheduler Manage queues for each output port Determine the order of packet transmission and discard Based on a packet’s class, the contents of the traffic control database, and current and past activity on this outgoing port Determine whether the packet traffic in given flow exceeds the required capacity and if so, decide how to treat the excess packets policing 2017-05-25 SNU INC Lab IS Router Components(Cont’d) Admission Control Implement the decision algorithm Enforce administrative policy Accounting and administrative reporting Reservation Setup Protocol Create and maintain flow-specific state Carry flowspec to admission control 2017-05-25 SNU INC Lab IS Host/Router Components HOST ROUTER RSVP Application RSVP Process RSVP Process Policy Control Policy Control Routing Process Admission Control Classifier 2017-05-25 Packet Scheduler Admission Control DATA Classifier SNU INC Lab Packet Scheduler Resource Reservation: RSVP Design goals Heterogeneous receivers Dynamic multicast group membership Enable receivers to select one source from among multiple sources transmitting to a multicast group Deal gracefully with changes in routes, automatically reestablishing tree the resource reservation along the new paths Minimize protocol overhead Be independent of routing protocol RFC’s Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification(RFC 2205) 2017-05-25 SNU INC Lab RSVP Characteristics Characteristics Unicast and multicast Soft state Receiver-initiated reservation Simplex Different reservation styles Transparent operation through non-RSVP routers Support for IPv4 and IPv6 2017-05-25 SNU INC Lab Receiver-initiated Reservation In ATM, the source of a data flow requests resources Why? In unicast, this approach is reasonable Inadequate for multicasting Some members of a multicasting group may not require delivery from a particular source over some period of time Some members of a group may only be able to a portion of the source transmissions Sender provide the routers with the traffic characteristics of the transmission Receiver specify the desired QoS 2017-05-25 SNU INC Lab Soft State Reservation state is cached information in the router Periodically refreshed by end system If a state is not refreshed within a required time limit, the router discards the state If a new route becomes preferred for a given flow, the end systems provide the reservation to the new routers on the route 2017-05-25 SNU INC Lab RSVP Admission Control RSVP process communicates with two local decision modules admission control determines the node has sufficient available resources to supply the requested QoS policy control determines whether the user has administrative permission to make the reservation 2017-05-25 SNU INC Lab RSVP Admission Control(Cont’d) If either check fails, RSVP returns an error notification to the application process that originated the request If both check succeed, RSVP sets parameters in a packet classifier and packet scheduler to obtain the desired QoS The packet classifier determines the QoS class for each packet The packet scheduler orders packet transmission to achieve the promised QoS for each stream 2017-05-25 SNU INC Lab RSVP Admission Policy(rap) Network Node PEP Policy Server COPS LDP 2017-05-25 SNU INC Lab PDP Scalability Scalability Receiver-oriented reservation requests that merge as they progress up the multicast tree While RSVP protocol is designed specifically for multicast applications, it may also make unicast reservations 2017-05-25 SNU INC Lab Robustness RSVP is designed to utilize the robustness of current Internet routing algorithms RSVP does not perform its own routing Use underlying routing protocols to determine where it should carry reservation requests As routing changes paths to adapt to topology changes, RSVP adapts its reservation to the new paths wherever reservations are in place RSVP runs over IP, both IPv4 and IPv6 2017-05-25 SNU INC Lab Data Flows Session Flow spec Destination IP address IP protocol id Destination port Service class RSpec TSpec Filter spec Source address UDP/TCP source port 2017-05-25 SNU INC Lab Relationship Packet Scheduler Packets that pass filter Packets Flowspec Filterspec Best-effort delivery Other packets 2017-05-25 QoS delivery SNU INC Lab RSVP Operation: Filtering An example of filtering Fig. Filtering a substream 2017-05-25 SNU INC Lab Reservation Styles Reservation attribute shared/ distinct Sender selection explicit/ wildcard Reservation Attribute Sender Selection 2017-05-25 Distinct Shared Explicit Fixed-filter (FF) style Shared-explicit (SE) style Wildcard - Wildcard-filter (WF) style SNU INC Lab Reservation Style Notation Notation Wildcard Filter(WF) style WF(*{Q}) Shared Explicit style Filterspec{Flowspec} SE(S1, S2, … {Q}) Fixed Filter(FF) style FF(S1{Q1}, S2{Q2}, …) 2017-05-25 SNU INC Lab 2017-05-25 SNU INC Lab Basic RSVP Message Two basic message type Path message Resv / Path Provide upstream routing information Each host that wishes to participate as a sender in a multicast group issues a Path message Transmitted throughout the distribution tree to all multicast destination Resv message Originate at a receiver and propagate upstream, being merged Must be repeated periodically to maintain the soft states 2017-05-25 SNU INC Lab RSVP Mechanism Overview Procedure a. A receiver joins a multicast group by sending an IGMP join message to a neighboring router b. A potential sender issues a Path message to the multicast group address c. A receiver receives a Path message identifying a sender d. The receiver sends Resv messages, specifying the desired flow descriptors e. The Resv message propagates through the internet and is delivered to the sender f. The sender starts sending data packets g. The receiver starts receiving data packets 2017-05-25 SNU INC Lab Reservation Example R1 Path(N2, S2) Path(N2, S1) Path(N1, S2) S1 N1 Path(S1, S1) N2 N1 N2 2017-05-25 Path(N2, S1) Path(N2, S2) S2 Phop S1 N1 R2 Path(N1, S1) Path(N2, S2) Filterspec S1 S1 Path(N2, S2) Path(N2, S1) R3 Reserved 0 0 Filterspec Phop Reserved S1 S1 0 N1 S2 S2 0 S1 N1 0 N2 S2 N1 0 SNU INC Lab Reservation Example : WF R1 Resv(WF(*{3B})) S1 N1 Resv(WF(*{5B}) N2 Resv(WF(*{5B})) Resv(WF(*{5B})) S2 Resv(WF(*{5B})) Resv(WF(*{2B})) R3 Filterspec Phop Reserved S1 S1 5B N1 S2 S2 5B S1 N1 5B N2 S2 N1 5B 2017-05-25 SNU INC Lab R2 Reservation Example : FF R1 Resv(FF(S1{4B}, S2{2B})) S1 N1 Resv(FF(S1{5B})) N2 Resv(FF(S1{5B})) Resv(FF(S1{5B}, S2{3B})) Resv(FF(S2{3B})) S2 Resv(FF(S1{B}, S2{3B})) R3 Filterspec Phop Reserved S1 S1 5B N1 S2 S2 3B S1 N1 5B N2 S2 N1 3B 2017-05-25 SNU INC Lab R2 Reservation Example : SE R1 Resv(SE(S1, S2{2B})) S1 N1 Resv(SE(S1{5B})) N2 Resv(SE(S1, S2{5B})) Resv(SE(S2{5B})) S2 Resv(SE(S2{5B})) Resv(SE(S1, S2{3B})) R3 Filterspec Phop Reserved S1 S1 5B N1 S2 S2 5B S1 N1 5B N2 S2 N1 5B 2017-05-25 SNU INC Lab R2 Flow Specification Flowspec = Traffic Spec + QoS Spec = TSpec + RSpec TSpec : Peak rate(p), bucket rate(r), bucket size(b), max datagram size(M), min policed unit(m) RSpec : Rate(R) and delay slack(S) All datagrams less than m are counted as m bytes Peak rate may be unknown or unspecified 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. 2017-05-25 SNU INC Lab Guaranteed Service Firm end-to-end delay bound ( b M )( p R ) M Ctot Qdelayend2end Dtot( p R r ) R( p r ) R M Ctot Qdelayend2end Dtot( R p r ) R Error terms : C, D 2017-05-25 SNU INC Lab Path Message Phop Sender Template last node address Filter specification Sender TSpec Optional ADSPEC One Path With Advertising(OPWA) information 2017-05-25 SNU INC Lab Processing Path Message Update the path state Store Phop If no path state exists, create it In order to route Resv message Set cleanup timer Expiration of the cleanup timer triggers deletion of the path state Soft-state 2017-05-25 SNU INC Lab ADSPEC Optional object to advertise to receivers the characteristics of the end-to-end communication path ADSPEC format Message header Default General Parameters fragment minimum path latency, Global break bit, Path bandwidth, Integrated Service Hop Count, PathMTU Guaranteed Service fragment Ctot, Dtot, Csum, Dsum, Guaranteed Service Break bit, Guaranteed Service General Parameters Header/Values Controlled-Load Service fragment Controlled-Load Service Break Bit, Controlled-Load Service General Parameters Headers/Values 2017-05-25 SNU INC Lab Reservation using OPWA Qdelreq : the required bound on end-to-end queuing delay Initial check (R = p) End-to-end delay required by the receiver’s application – the minimum path latency Choose an equation Find R 2017-05-25 SNU INC Lab Slack Term S : slack term End-to-end delay required by the application – End-to-end delay bound b Ctot i b Ctot i Sout Sin ( r Rout Rin ) Rout Rout Rin Rin Ctot i : the cumulative sum of the error terms, C for all the routers that are upstream of, and including, the current element i 2017-05-25 SNU INC Lab 2017-05-25 SNU INC Lab Problems of Intserv Resource reservations for flow-based traffic High overheads of setting-up a reservation Difficult determination of required resources Overhead of authentication, authorization, and accounting per flow Scalability problem 2017-05-25 SNU INC Lab Differentiated Services(diffserv) Objective Provide scalable service discrimination in the Internet without the need for per-flow state and signaling at every hop Simple and coarse methods of providing differentiated classes of service for Internet traffic How-to-do Setting bits in the TOS octet at network edges and administrative boundaries Using those bits to determine how packets are treated by the routers inside the network Conditioning the marked packets at network boundaries in accordance with the requirements of each service 2017-05-25 SNU INC Lab Related Proposals Premium Service(V. Jacobson) Assured Service(D. Clark) Scheduling priority Strict admission control Virtual leases line Drop priority A better best-effort User-Share Differentiation(Z. Wang) User Who are granted some bandwidth Share How much bandwidth is allocated to a user 2017-05-25 SNU INC Lab Diffserv Working Group Feb 98 Working group formed Goals Standardize the 'DS byte’ Assign specific per-hop behaviors to the DS byte Define the framework of the differentiated services architecture Experiment with other per-hop behaviors that can be used to produce additional services 2017-05-25 SNU INC Lab Terminology Behavior aggregate DS byte A collection of packets with the same code point crossing a boundary in a particular direction IPv4 TOS octet or IPv6 Traffic Class octet Per-hop Behavior(PHB) Forwarding treatment applied at a differentiated servicesenabled node to a behavior aggregate 2017-05-25 SNU INC Lab DS byte 0 1 2 3 PHB 4 5 6 7 CU PHB: per-hop behavior CU: currently unused 2017-05-25 SNU INC Lab Per-Hop Behaviors Differentiated services model Router has a set of parameters that can be used to control how packets are scheduled onto an output interface N separate queues with settable priorities, queue lengths, round-robin weights, drop algorithm, drop preference weights and thresholds, etc Two per-hop behaviors Default(DE: 000000) common, best-effort forwarding Expedited Forwarding(EF: 000010) high priority behavior typically used for network control traffic such as routing updates 2017-05-25 SNU INC Lab Traffic Classification and Conditioning Packet classification Identify the subset of traffic which may receive a differentiated service within the DS domain Traffic conditioning Metering, shaping, policing and remarking 2017-05-25 SNU INC Lab Classifier and Conditioner Conditioner Meter Packets Classifier 2017-05-25 Marker SNU INC Lab Shaper/ Dropper Traffic Management Traffic conditioner Meter Measures traffic against profile Passes state information to other conditioning functions Marker Sets codepoint(possibly based on metering) Shaper/dropper Delays or drops packets 2017-05-25 SNU INC Lab Summary Support QoS in the Internet Intserv/RSVP Diffserv 2017-05-25 SNU INC Lab