IP QOS and Traffic Management

IP QOS and Traffic Management SCUT DT&P Labs

Contents 1. What is QoS & Why QoS? 2. Integrated Services 3. Differentiated Services SCUT DT&P Labs

1. What is QoS & Why QoS？ SCUT DT&P Labs

1. What is QoS & Why QoS？ 1.1 Circuit Switching Allocate each stream a channel with the fixed bit rate Traffic characteristic: Constant Bit Rate SCUT DT&P Labs

1. What is QoS & Why QoS？ 1.2 Packet Switching (store-and-forward) All the user share a common channel Traffic characteristic: Variable & Burst Bit Rate SCUT DT&P Labs

1. What is QoS & Why QoS？ 1.3 Traditional Internet Service • Traditional Internet Applications and their features • Traditional Applications such as: • FTP (File Transfer Protocol) • Email • Telnet • WWW • ……… • These kinds of services cannot tolerate packet loss, but are less sensitive to delay and delay variation. SCUT DT&P Labs

1. What is QoS & Why QoS？ 1.4 Basic Concept of QoS A QoS is a set of parameters that describer the Quality of Service, for example, bandwidth, loss rate, delay and delay variation. …… Different QoSs may mean different network resources allocation. The resources may includes link bandwidth, buffer usage, CPU usage, priority, etc. SCUT DT&P Labs

OSI 参考模型中的QoS参数 • 吞吐量 • 传输延时 • 出错率 • 连接失败的概率 • 传输失败的概率 • 重置率（在给定的时间内服务者释放连接或重置连接的概率） • 释放延迟（从释放请求开始到释放确认为止的时间延迟） • 释放失败概率 • （其它：访问权限、优先级、成本） SCUT DT&P Labs

ITU (International Telecommunications Union )（CCITT） QOS参数 • 传输级参数： • 分组的峰值到达率、峰值持续时间、分组平均到达率、分组丢失率、分组插入率和比特出错率 • 呼叫级控制级参数： • 呼叫次数、失败率 • 连接级参数: • 连接延迟、连接失败率；释放延迟、释放失败率 SCUT DT&P Labs

ATM 网络QoS定义 • 服务类别 • 恒定位速率服务（CBR） • 实时可变位速率服务（rt－VBR） • 非实时可变位速率服务（nrt－VBR） • 可用位速率服务（ABR） • 未指定位速率服务（UBR） SCUT DT&P Labs

ATM 网络QoS定义 • QoS参数 • 峰值信元速率（PCR） • 持续信元速率（SCR） • 最小信元速率（MCR） • 信元丢失率（CLR） • 信元传输延时（CTD） • 信元传输时延方差（CDV） • 突发容许长度（BT） SCUT DT&P Labs

IETF QoS模型及定义 • 综合服务模型（Integrate Service：IntServ） • 保证型服务 • 可控负载型服务 • 区分服务模型（Differentiated Service: DiffServ） • 奖赏服务 • 确保服务 • …… SCUT DT&P Labs

用户角度 QoS 描述 • 信息流特征（用户－网络间的承诺） • 信息流的峰值速率和平均速率，突发长度等。 • 信息流性能要求（网络侧的承诺） • 网络的吞吐量、传输的延迟、抖动和丢失率等。 • 信息流的同步要求 • 多个相关信息流之间的同步关系，如会议系统同时记录的视频信号的同步播放；图像信息与声音信息的同步等。 SCUT DT&P Labs

用户角度 QoS 描述（续） • 服务层次（端到端QoS的保证程度） • 如：可控负载型服务、保证型服务、 • 区分服务和尽力而为型服务等。 • 接入控制和QoS管理策略 • 用户－网络间接入协商机制； • 带宽、延时、抖动和丢失率等状况的通知等。 • 服务成本（避免网络资源的滥用） • 不同类别与层次的服务与服务成本的关系。 SCUT DT&P Labs

1. What is QoS & Why QoS？ 1.5 Basic IP Protocol Service Function • The Basic IP Protocol stack provides only one kind of QoS: • best-effort. • With the best effort traffic model, Internet (router) handles the transmission service with first-come, first-served strategy. • All requests have the same priority and are dealt with one after the other. • No possibility of making bandwidth reservations for specific connections or raising the priority for special requests. SCUT DT&P Labs

1. What is QoS & Why QoS？ 1.6 Real-time Traffic in Internet • New Internet Applications (multimedia) and their features • Multimedia Applications such as: • Real-Audio (Audio Broadcast) • Real-Video (Video Broadcast) • Internet phone • Videoconferencing • These kinds of real-time applications show different behavior with traditional service. • Can compensate for a reasonable amount of packet • loss • Be usually very critical toward high-variable delays. SCUT DT&P Labs

1. What is QoS & Why QoS？ 1.7 The Requirement for the New Service • Without bandwidth control, the quality of real-time steams depends on the bandwidth that is just available. • Unstable bandwidth leads to poor quality real-time transmissions, such as dropout and hangs. • As a consequence of these limitations, new strategies are required to provided predictable services for the Internet. SCUT DT&P Labs

1. What is QoS & Why QoS？ 1.8 Two Classes of QoS Services • Now, there are two main rudiments for bringing QoS to the Internet: • * Integrated Services; • * Differentiated Services. • Integrated Services bring enhancements to the IP network to support real-time transmissions and guarantee bandwidth for specific flows. • Differentiated Service mechanisms do not use per-flow signaling. Different service levels can be allocated to different groups of Internet users. SCUT DT&P Labs

1.9 QoS 设计的原则 • 集成原则 • 端到端的QoS控制在网络的所有层次上都应是可以配 • 置、预测和维护的（理想情况）。 • 分离原则 • 区分控制信令和媒体数据的传输－－通常两者的传输 • 服务要求不同。 • 透明原则 • 基于友好的QoS的API函数为用户提供服务，屏蔽网络 • 底层的复杂服务细节。 SCUT DT&P Labs

1.9 QoS 设计的原则（续） • 异步资源管理原则 • 资源管理：调度、流控、路由和QoS管理－－在各种 • 资源之间定期（周期性）地交换信息。 • 异步：管理和控制的发生在时间上可能是不同的。 • 性能原则 • 既要保证QoS的实现，又要使网络的资源有高的利用 • 率。 • 资源分配的效率； • 控制信息传输的代价； • …… 。 SCUT DT&P Labs

1.10 QoS 的控制与管理 • 资源的管理的实现过程 • 静态阶段：处理信息流的建立和端到端的QoS的协商, • 使系统接受用户应用所需QoS的过程。 • 动态阶段：在接入控制之后，通过特定算法实现资源 • 调度和流控,实现用户所需QoS的过程。 SCUT DT&P Labs

1.10 QoS 的控制与管理（续） • 预留和分配机制 • 悲观方式：根据应用可能出现的最大需求来预留资源 • 例如，按应用的峰值速率来预留带宽。 • 优点：可靠性最高； • 缺点：网络的资源利用率可能收到影响。 • 乐观方式：根据平均负载预留资源。例如根据平均速 • 率预留带宽。 • 优点：资源利用率较高； • 缺点：难有高的服务质量。 • 实际方式：介于上述两种方式之间。 SCUT DT&P Labs

1.10 QoS 的控制与管理（续） • QoS 的控制机制 • 信息流整型：在网络边缘进行信息流整型，改变进入 • 网络的业务流量的特性。 • 信息流调度：根据应用的QoS要求和服务优先级别， • 采用合理的、隔离度好的调度策略。 • 信息流监控：监控用户是否按照流量的特性要求发送 • 信息；监控网络是否能够提供承诺的服 • 务。 • 对违约信息分组的处理方式。 SCUT DT&P Labs

1.10 QoS 的控制与管理（续） • QoS 的控制机制 • 信息流同步：控制事件顺序和多媒体交互行为的精确 • 同步。如所谓的“嘴唇-声音”同步。 SCUT DT&P Labs

2. Integrated Services （综合服务） SCUT DT&P Labs

2. Integrated Services 2.1 Integrated Service and RSVP (Reservation Protocol) The Integrated Service model was defined by an Internet Engineering Task Force (IETF) working group as being the keystone of the planned Integrated Service Internet. The Integrated Service are described by the ReSerVation Protocol (RSVP). To support the Integrated Service, an Internet Router must be able to provide an appropriate QoS for each flow in accordance with RSVP. SCUT DT&P Labs

IntServ QoS 概述 • 两种服务方式 • 质量保证型（guaranteed service） • 负载控制型（controlled－load service） • 同时保留“尽力而为”型的服务方式 • 实现方法 • 在路由器的控制信息路径上处理每个流的信息消息， • 维护每个流的路径和资源预留状态。 • 在路由器的数据路径上执行基于流的分类、调度和缓 • 冲区管理。 SCUT DT&P Labs

IntServ QoS 概述 • 技术方案 • 依据IETF的资源预留协议（RSVP）的QoS协商机制， • 逐点地建立或拆除每个数据流的路径状态和资源预留 • 状态。 • 依靠接纳控制来决定各节点是否有足够的资源满足用 • 户的特定请求。 • 依靠传输路径上各节点的分类、调度算法和监控机制 • 来保证用户的QoS。 SCUT DT&P Labs

2. Integrated Services 2.2 The Integrated Services (RSVP) Model Router Host RSVP Process RSVP Application RSVP Process Routing Process Policy Control Policy Control Admission Control Admission Control Classifier Packet Scheduler Packet Scheduler Data Classifier SCUT DT&P Labs

2. Integrated Services 2.3 The Components for the RSVP Traffic Control • Packet scheduler: • It manages the forwarding of the different packet streams in hosts and routers, based on their service classes, using queue management and various scheduling algorithms. • It must ensure that the packet delivery corresponds to the QoS parameters for each flow. • It can also police or shape the traffic to conform to a certain level of service. SCUT DT&P Labs

2. Integrated Services 2.3 The Components for the RSVP Traffic Control (continued) • Packet classifier: • It identifies the packets of an IP flow in hosts and routers that will receive a certain level of service. • To realize effective traffic control, each incoming packet is mapped by the classifier into a specific class. • All packets that are classified in the same class get the same treatment from the packet scheduler. • The choice of a class is based upon the source and destination IP address and source and destination port number in the existing packet header or an additional classification number（such as IP protocol number）that must be added to each packet. SCUT DT&P Labs

TCP/IP Protocol Stack Application Layer Telnet, FTP, TFTP,HTTP,SNMP,SMTP, and so on Port Number BGP RIP Transport Layer OSPF EGP TCP UDP ICMP IGMP Protocol Number Internet Layer ARP RARP IP (address) Type code Data Link Layer Ethernet, Token Ring, PPP, and so on SCUT DT&P Labs

2. Integrated Services 2.4 The Components for the RSVP Traffic Control (continued) • Admission Control: • The admission control contains the decision algorithm that a router uses to determine if there are enough routing resources to accept the requested QoS for a new flow. • Admission control is invoked at each router along a reservation path so as to make a local accept/reject decision at the time a host requests a real-time service. SCUT DT&P Labs

2. Integrated Services 2.4 The Components for the RSVP Traffic Control (continued) • Policy Control: • The policy control ensures that a host does not violate its promised traffic characteristics. • Some control policies are used to check the user authentication for a requested reservation. Unauthorized reservation requests can be rejected. • The police control makes sure that the QoS guarantees are honored. Admission control is concerned with enforcing administrative policies on resource reservations. SCUT DT&P Labs

2. Integrated Services 2.5 The Classifiers and the Scheduler Queue for Session 1 Queue for Session 2 Queue for Session 3 Classifier Queue for Session 4 Packets Queue for Session 5 Packets Queue for Session 6 Queue For Best Effort T Scheduler SCUT DT&P Labs

2. Integrated Services 2.6 Weighted Fair Queuing Scheduling （WFQ）Algorithm • WFQ is also named as General Processor Sharing (GPS). • WFQ is a service discipline designed to allocate capacity (bandwidth) equally and fairly among multiple connections sharing a link. • Suppose the capacity on a given link is C b/s; • N connections share the link; • Connection j, 1 <= j <= N, is assigned a parameter фj such that it is guaranteed service at a rate gj given by : SCUT DT&P Labs

2. Integrated Services 2.6 The Weighted Fair Queuing Scheduling Algorithm • gj is the minimum guaranteed service rate for connection j; • WFQ is defined to be work conserving: if one connection has traffic ready to be served, while another has none, capacity from the latter will be used to serve the former. • The actual connection j traffic, served in an interval (t1, t2), denoted by Sj(t2,t1), will be obey the condition: SCUT DT&P Labs

2. Integrated Services 2.6 The Weighted Fair Queuing Scheduling Algorithm • For the system being steady, it is required that: • The maximum delay of traffic on a given connection can be bounded based on its own characteristics, independent of other sessions. • Consider the special case in which each connection on a link regulated in the leaky bucket flow-constrained: • where Ai (t2,t1) is the quantity of the data transmitted in the connection i during t1~t2. • And if SCUT DT&P Labs

2. Integrated Services 2.6 The Weighted Fair Queuing Scheduling Algorithm then the worst-case backlog (data buffered) and delay bounds are established: and , respectively. Let Lmax be the maximum packet length, the end to end delay, over an m-hop path, neglecting the propagation delay: Ck is the total link capacity on link k. SCUT DT&P Labs

2. Integrated Services 2.7 Message & Data Stream The Data Stream and Message Stream (in the same data link) of The Integrated Service (IS): RSVP control message stream: The IS instances communicate via RSVP to create and maintain flow-specific states in the endpoint hosts and routers along the path of a flow. Data Stream: the data packets in a reserved flow were sent as usually, the flow is recognized with the the source and destination IP address and port number in the existing packet header. SCUT DT&P Labs

2. Integrated Services 2.8 Service Classes in the IS Model Two Service Classes in the IS Model: Controlled Load Service(defined in RFC 2211). Guaranteed Service (defined in RFC 2212). SCUT DT&P Labs

2. Integrated Services 2.8 Service Classes in the IS Model (continued) Controlled Load Service: Applications that make QoS reservation using Controlled Load Service are provided with service closely equivalent to the service uncontrolled (best-effort) traffic under lightly loaded conditions. The Controlled Load Service does not provide functions for reserving a fixed bandwidth or guaranteeing minimum packet delay. The term lightly load conditions means that a very high percentage of transmitted packets are successfully delivered to the destination. SCUT DT&P Labs

可控负载型服务的特点 • 使用户感到网络是在一种很轻的负载或具有很大容量 • 的条件下运行。 • 本质上是一种半定量半定性的服务： • 以很高的概率（百分比）将数据分组转发到接收端； • 绝大部分转发成功的分组的延时在一个可接受的范围 • 内； SCUT DT&P Labs

2. Integrated Services 2.8 Service Classes in the IS Model (continued) Guaranteed Service: Functions provided by the Guaranteed Service model assure that datagrams arrive within a guaranteed delivered time. The Guaranteed Service model represents the extreme end of delay control for networks. This control mechanism is only useful if it is provided by every router along the reservation path. SCUT DT&P Labs

质量保证型服务的特点 • 模拟某种特定速率所提供的服务，提供定量的带宽和 • 延时保证。 • 要求传输路径上的每个节点都支持质量保证型的服务。 SCUT DT&P Labs

2. Integrated Services 2.9 The Flow Descriptor Flow Descriptor: The Flow Descriptor defines the traffic and QoS characteristics for a specific flow of data packet. The information contained in the Flow Descriptor consists of Filter Specification(Filterspec), which is used in the packet classifier to identify the packets that belong to a specific flow with the send IP address and source port. Flow Specification (Flowspec), which can be assorted into two groups Traffic Specification (Tspec), Service Request Specification (Rspec). SCUT DT&P Labs

2. Integrated Services 2.9 The Flow Descriptor (continued) Filter Specification Flow Descriptor Traffic Specification Flow Specification Request Specification SCUT DT&P Labs

2. Integrated Services 2.9 The Flow Descriptor (continued) • Traffic Specification (Tspec) • The Tspec describes the traffic characteristic of the requested service. • That is represented with a token bucket filter to define a data flow control mechanism. SCUT DT&P Labs

2. Integrated Services 2.9 The Flow Descriptor (continued) The token bucket system is specified by two parameters r b Token rate r, which represents the rate at which tokens are placed into the bucket. Bucket capacity b, which is the size of the bucket. SCUT DT&P Labs

2. Integrated Services 2.9 The Flow Descriptor (continued) The parameters of the token bucket system The parameter r specifies the long-term data rate and is measured in bytes of IP datagrams per second (from 1 byte per second to 40 terabytes per second). The parameterb specifies the burst data rate allowed by the system and is also measured in bytes (from 1 byte to 250 gigabytes). Traffics that passes the token bucket filter must obey the rule that over all time periods T, the amount of data sent does not exceed rT + b. Other token bucket parameter: The minimum policed unit m: size of the min. IP datagram. The maximum packet size M: size of the max. IP datagram SCUT DT&P Labs

IP QOS and Traffic Management