Vanguard Applications Ware IP and LAN Feature Protocols. Quality Of Service

Transcription

1 Vanguard Applications Ware IP and LAN Feature Protocols Quality Of Service

2 Notice 2004 Vanguard Networks 25 Forbes Boulevard Foxboro, Massachusetts (508) All rights reserved Printed in U.S.A. Restricted Rights Notification for U.S. Government Users The software (including firmware) addressed in this manual is provided to the U.S. Government under agreement which grants the government the minimum restricted rights in the software, as defined in the Federal Acquisition Regulation (FAR) or the Defense Federal Acquisition Regulation Supplement (DFARS), whichever is applicable. If the software is procured for use by the Department of Defense, the following legend applies: Restricted Rights Legend Use, duplication, or disclosure by the Government is subject to restrictions as set forth in subparagraph (c)(1)(ii) of the Rights in Technical Data and Computer Software clause at DFARS If the software is procured for use by any U.S. Government entity other than the Department of Defense, the following notice applies: Notice Notwithstanding any other lease or license agreement that may pertain to, or accompany the delivery of, this computer software, the rights of the Government regarding its use, reproduction, and disclosure are as set forth in FAR (C). Unpublished - rights reserved under the copyright laws of the United States.

3 Notice (continued) Proprietary Material Information and software in this document are proprietary to Vanguard Managed Solutions, LLC (or its Suppliers) and without the express prior permission of an officer, may not be copied, reproduced, disclosed to others, published, or used, in whole or in part, for any purpose other than that for which it is being made available. Use of software described in this document is subject to the terms and conditions of the Software License Agreement. This document is for information purposes only and is subject to change without notice. Part No. T , Rev. J Publication Code TK First Printing June 1999 Manual is current for Release 7.3 of Vanguard Applications Ware. To comment on this manual, please send to vntechsupport@vanguardnetworks.com

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5 Contents Quality of Service... 2 QoS Features... 5 QoS Control List (QCL)... 8 IP Differentiated Services: (DiffServ) Concepts... 9 IP Differentiated Services: Configuration Area Functions Delay Bandwidth Packet Dropping VoIP QoS Applications IP Non-standard QoS (without Differentiated Services): Concepts IP Non-standard QoS: Configuration Area Functions QoS with Other IP Features Transparent Bridging QoS Using Differentiated Services Transparent Bridging QoS Without Differentiated Services IPX QoS Using Differentiated Services IPX QoS Without Differentiated Services Traffic Priority for WAN Connections Quality of Service for Parallel SVCs Parallel SVC Configuration Parameters Configuring QoS Configuring QoS General Parameters Configuring QCL Profiles Configuring the IP MF ClassifierTable Configuring IP Classifier, Traffic Conditioner & QoS Mapper Profiles. 81 Configuring IP BA Remarker Profiles Configuring IP BA PHB Mapper Profiles Configuring the IPX Classifier Table Configuring the IPX Classifier, Traffic Conditioner & QoS Mapper Table 97 Configuring TB Classifier, Traffic Conditioner & QoS Mapper Profiles 101 Configuring AT Traffic Conditioner & QoS Mapper Profiles Configuring Service Profiles Booting QoS Configuration Examples Non-standard QoS IP Network End-to-end QoS IP Network using Diff Serv Configuration Specifics Configuration Specifics: Remote Offices Configuration Specifics: Central Office (Voice only) Configuration Specifics: Branch Concentrator Offices QoS Statistics i

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7 Quality of Service Overview Introduction This document describes how to configure and use Quality of Service features with Vanguard Applications Ware products. In This Manual Topic See Page Quality of Service... 2 QoS Features... 5 QoS Control List (QCL)... 8 IP Differentiated Services: (DiffServ) Concepts... 9 IP Differentiated Services: Configuration Area Functions Delay Bandwidth Packet Dropping VoIP QoS Applications IP Non-standard QoS (without Differentiated Services): Concepts IP Non-standard QoS: Configuration Area Functions QoS with Other IP Features Transparent Bridging QoS Using Differentiated Services Transparent Bridging QoS Without Differentiated Services IPX QoS Using Differentiated Services IPX QoS Without Differentiated Services Traffic Priority for WAN Connections Quality of Service for Parallel SVCs Parallel SVC Configuration Parameters Configuring QoS Configuring QoS General Parameters Configuring QCL Profiles Configuring the IP MF ClassifierTable Configuring IP Classifier, Traffic Conditioner & QoS Mapper Profiles. 81 Configuring IP BA Remarker Profiles Configuring IP BA PHB Mapper Profiles Configuring the IPX Classifier Table Configuring the IPX Classifier, Traffic Conditioner & QoS Mapper Table 97 Configuring TB Classifier, Traffic Conditioner & QoS Mapper Profiles 101 Configuring AT Traffic Conditioner & QoS Mapper Profiles Configuring Service Profiles Booting QoS Configuration Examples Non-standard QoS IP Network End-to-end QoS IP Network using Diff Serv Configuration Specifics Configuration Specifics: Remote Offices Configuration Specifics: Central Office (Voice only) Configuration Specifics: Branch Concentrator Offices QoS Statistics Quality of Service 1

8 Quality of Service Quality of Service What Is Quality of Service? Simple Network Management Protocol functionality Quality of Service (QoS) is the performance of user application traffic through networks. QoS is intended to provide end-to-end service with respect to service availability, throughput, delay, jitter and packet loss. Quality of Service can be implemented on these protocols: Protocols and Applications within IP and IPX Appletalk Transparent Bridging Voice over IP (VoIP) Packet networks carry many different types of traffic that require better than Best Effort Service in terms of service availability, throughput, delay, jitter and packet loss. Limited network resources, bandwidth for example, makes it difficult to support varied network service demands and the increasing number of users and applications. These are a few examples service requirements for different types of traffic: Real time traffic like voice or video require tight controls on the amount of transit delay and jitter (variances in delay). Legacy protocol traffic requires shorter transit times to avoid protocol time-outs and retransmissions. Traffic from interactive web applications require small response times. Mission critical traffic must always get through to its destination. Increasing resources, or limiting the number of users or applications are not acceptable solutions since increased resources means increased costs (there is also a practical limit on how much they can be increased). Limiting users or applications means limiting growth and revenue. QoS solves these problems by segregating users and applications traffic into flows or aggregates. QoS offers differentiated services to those flows or aggregates by sharing the available resources between them. Simple Network Management Protocol (SNMP) support for Vanguard products provide SNMP functionality to Quality of Service configuration and statistics parameters. Refer to the SNMP/MIB Management Manual (Part Number T ) for information on SNMP. 2 Quality of Service

9 Quality of Service Vanguard Managed Solution s QoS Implementation Limitations Vanguard Applications Ware includes a series of QoS features that permit implementation of a QoS solution to a variety of networking applications using Vanguard products. These features classify traffic into flows, or aggregates, providing different treatments to those flows through the assigning of Per Hop Behaviors, see Per Hop Behavior (PHB) on page 10. The QoS Kit is Vanguard Managed Solutions Applications Ware QoS solution and consists of following features and functionality: QoS Control List (QCL) IP Classification, Traffic Conditioning & QoS Mapping IPX Classification, Traffic Conditioning & QoS Mapping TB Classification, Traffic Conditioning & QoS Mapping AppleTalk Traffic Conditioning & QoS Mapping Queuing and Scheduling - Active queue management with RED/WRED - Priority based forwarding - Bandwidth Allocation andsharing using CrBFQ (Credit Based Fair Queuing) - MIN, LOW and NORMAL delay services - Expedite No Drop (END) service for Network Control Traffic - Best Effort (BE) service Differentiated Services - Marking/Remarking and PHB Mapping - Expedite Forwarding (EF) PHB - Assured Forwarding (AF) PHBs - Class Selector (CS) PHBs - Custom PHBs - Default PHB End-to-end QoS for VOIP applications The current implementation of Quality of Service has these functional limitations that should be taken into consideration: QoS features are supported only for LCON, LAN & Internal IP interfaces. QoS features are not supported for Aggregate Cache. However, LCON boot (after QoS boot for the LCON) disables the Aggregate Cache, enabling the QoS features. For X.25 or Frame Relay Annex G, QoS features are per connection basis (both SVC and PVC). i.e., QoS is offered to the traffic within the connection and the connections which are not enabled for QoS features might affect the QoS offered. For Frame Relay BYPASS, QoS features are per DLCI basis. i.e., QoS is offered to the traffic within the DLCI and the DLCIs which are not enabled for QoS features might affect the QoS offered. Quality of Service 3 T , Revision J Release 7.3

10 Quality of Service Since the queue management and scheduling mechanisms are implemented in the LCONs (which control the traffic sent to WAN port(s)), any queuing in the WAN port(s) affect the QoS offered. Prioritization of the WAN port queues is controlled through the Traffic Priority features (see the Basic Protocols binder, Bandwidth Management manual, Part Number T0108, Traffic Priority chapter). PPP/MLPPP has its own queuing mechanisms and hence might affect the QoS offered. Refer to Vanguard Applications Ware Basic Protocols: Point-to-Point Protocol PPP and MLPPP (Part Number T ) for more information. The traffic conditioning is not affected by PPP/MLPPP queuing. The queue management and scheduling mechanisms are implemented for LAN IP interfaces that provisioned on Ethernet ports only. Not supported for SNA and Serial Traffic and if present on same connection or link, they might affect the QoS offered. 4 Quality of Service

11 QoS Features QoS Features Introduction This section describes the QoS features found in Applications Ware. QoS features required for a node depends on the network application. Most of the QoS features can be configured based on the application requirements. Figure 1 shows the different QoS features and where they can be used in a typical branch networking application. Packets are passed through classifiers which classify the packets using one or more fields of the packet headers. Classified packets are then conditioned using various traffic conditioners (dropping, shaping and Three Color Marking) as per the Traffic Conditioning Specifications (TCSs) associated with the classifiers. TCS mainly deals with rate and burst flow specifications for the classified packets. Classification, along with Traffic Conditioning provides policy and admission controls. For IP, classification and traffic conditioning can be done at both ingress and egress sides. At ingress, it controls the packets entering the node either from a LAN or a WAN connection, while at the egress it controls the packets sent out on a WAN connection. Packets that pass through the traffic conditioners are then mapped to their respective service levels based on the QoS mapping associated with the classifiers. Packets are then serviced (sent out on the egress WAN or LAN connection/link based) based on the Service Level Specification (SLS), using queuing and scheduling mechanisms. An SLS consists of forwarding treatment for the packets in terms of delay, bandwidth and packet drops. Quality of Service 5 T , Revision J Release 7.3

12 QoS Features. Remote Offices Branch Concentrator Offices Central Office Vanguard 320 Wide Area Network Vanguard 6450 Wide Area Network Vanguard 6560 PBX LAN Port LCON 1 only 2 o o 2 2 WAN WAN only Port Port 2 only 1 1 R u t e r 1 and 2 LCON 1 only 1 and 2 R u t e r 1 1 LAN Port Voice Port VoIP VoIP Voice Port 1 Traffic Classification, Traffic Conditioning and QoS Mapper Feature (either some or all) WAN Port LCON 1 only NOTE: The Vanguard model numbers are used as examples only, they do not imply any QoS feature restrictions. 2 Queuing and Scheduling Features 2 only Direction of packet flow to which the feature (s) can be applied. R o u t e r 1 and 2 LCON 2 only 1 only 1 and 2 WAN Port Branch Concentrator Office Node The block diagram of the Branch Concentrator Office node is only showing the WAN switching function for QoS. The node can, and probably would also be providing the same access QoS functionality as the other office nodes Figure 1. Quality of Service Functional Diagram 6 Quality of Service

13 QoS Features There are two methods of implementing QoS using Vanguards: Differentiated Services (end-to-end QoS) Non-standard QoS The details for both of these methods are discussed in later chapters. What follows are the concepts that are common to both methods. The QoS features can be grouped into five functional areas. These are: Traffic Classification Traffic Conditioning QoS Mapping Queuing Scheduling A description of each of these functional areas is given in Figure 2. Traffic Conditioner This function controls what packets will continue on and at what rate (i.e. it applies the Traffic Conditioning Specifications (TCS)). The function can be configured to specify packets of a particular classification to have no TCS applied or to be dropped or shaped based on traffic rate and burst limits. For Differential Services applications, using the same rate and burst criteria, can also be configured to mark packets using Three Color Marking. Packets entering the router from a LAN or WAN port. The packets may or may not have passed through the router function. Queuing This function provides the buffering required for implementing the forwarding requirements specified by the Service Level Specifications (SLS). This is also where Weighted Random Early Discard (WRED) can be applied to those packets that are appropriately marked. 2 Queuing Packet Traffic Classifier Traffic Conditioner QoS Mapper 2 Scheduling WAN Port Traffic Classifier This function will classify the incoming packets based on information within the packet header (e.g. addresses, protocol identifier, Differential Service Code Point, etc.). It will also provide DSCP marking if applicable. QoS Mapper This function maps the classified packets to a corresponding service level (i.e. Per Hop Behavior (PHB)). The service level that a particular packet classification receives is specified in the Service Level Specifications (SLS) and includes criteria for delay, bandwidth and packet dropping. 1 1 functions are included in the functional areas in Figure Scheduling This function is where the Service Level Specification (SLS) is applied. This is done by prioritizing the forwarding of the packets. There are three forwarding methods: MIN delay, LOW delay and NORMAL delay. MIN and LOW delays use priority based forwarding while NORMAL delay forwarding is done using Credit Based Fair Queuing (CrBFQ) algorithm. Router Function Figure 2. QoS Functional Area Description Quality of Service 7 T , Revision J Release 7.3

14 QoS Features QoS Control List (QCL) Introduction Exactly how the QoS functions and features are applied can vary depending on the method of QoS that is deployed (e.g. Differentiated Services as opposed to Non-standard QoS) and the QoS requirements for the individual router. The QCL provides a uniform and consistent way of configuring various QoS features for application to the various areas within the Vanguards - LCONs (LCON-x), IP LAN interfaces (IP-1 to IP-4) and internal IP (IP-0 for IP packets originated by node s internal applications like TELNET, SNMP, TFTP, VOIP, etc.). The required QoS features can be allocated through a QCL profile to a specific application point (e.g. Router Interface or LCON) within the Vanguard. The number of QCL profiles allowed for the node is determined by the QoS General Parameter - Maximum Number of QCL Profiles. The number of applications that can be configured for QoS features, is limited by the value of this parameter. 8 Quality of Service

15 QoS Features IP Differentiated Services: (DiffServ) Concepts Introduction Differentiated Services Code Point (DSCP) Differentiated Services (DiffServ) is a simple approach to provide scalable services in IP based networks (i.e. it requires an IP header) without the need for per-flow state and signaling at every hop (i.e. router and link). A variety of services can be built by deploying a small, well-defined set of features (building blocks) in network nodes. Services can be built by combination of: Setting bits in IP header field (marking packets) at network boundaries (autonomous system boundaries, internal administrative boundaries or hosts). Using those bits to determine how packets are forwarded by the nodes inside the network. Conditioning the marked packets at network boundaries in accordance with the requirements or rules of each service. The IP header field used for Differentiated Services is called the DS field. The DS field is the redefinition of the IPv4 TOS octet and IPv6 Traffic Class octet. The DS field structure is as shown below in Figure 3: : IPv4 TOS / IPv6 Traffic Class Octet DSCP CU DSCP: Diff Serv Code Point CU: Currently Unused Ver Header Length Type Of Service (TOS) Total Length Identification 3-Bit Flags Fragment Offset Time To Live Protocol Header Checksum Source IP Address Destination IP Address Figure 3. Differentiated Services Field within the IP Header The Differentiated Services Code Point (DSCP) is the packet marker that identifies which packet should be received by the QoS service. Once the routers receive the packet data it is translated into the appropriate action. In this way a means for end-toend QoS can be created. Quality of Service 9 T , Revision J Release 7.3

16 QoS Features The DSCP is made up of six bits given a range of 0 through 63 (RFC 2474). These 64 code points are, for practical purposes, divided into pools, the even and odd numbered codes. All of the odd number codes are designated experimental (there are actually two pools within this category) and are not often used. There are actually 32 codes (even numbered) that are commonly used to provided Differentiated Services QoS. These 32 code points are the standardized or recommended codepoints. As detailed below all but 11 of these code points have standard service levels associated with them. Each service level is identified as Per Hop Behavior (PHB). Per Hop Behavior (PHB) The implementation of the desired service is accomplished through the assignment of a Per Hop Behavior (PHB) by each of the routers through which the packet traverses. PHBs are significant only to the router that creates them. The PHB a router creates is not implicitly transmitted to the next router but if the routers are set up properly, the treatment to any specific packet should be similar at each of the routers. A router can create a PHB for any packet it receives, whether or not the packet header contains a DSCP or not. If the packet does not contain a DSCP (i.e. the DS field is equal to zero) then the router assigns a DSCP before sending the packet onto the next router. When a router receives a packet with a non-zero DSCP it is that routers responsibility to create the appropriate PHB so that the packet can receive the required QoS service. To aid in the standardization of DSCP to PHB mapping four standard PHB groups are identified: Expedite Forwarding (EF) Assured Forwarding (AF) Class Selector (CS) Best Effort (BE) Expedite Forwarding (RFC 2597): This is actually only one PHB. This PHB should be assigned to any packet requiring an assured bandwidth, low loss, low delay and low jitter (delay variation) service. It should be designed to provide what amounts to a virtual leased line connection and should be reserved for packets from real-time constant bit rate application such as voice and video. Assured Forwarding (RFC2597): This is a group of 12 PHBs. The group is divided into four different classes (AF1x - AF4x). Each class is further divided into three levels (AFx1 - AFx3). Thus the 12 different PHBs are created (e.g. the level 2 PHB in class 3 would be called AF32). This group is used to allow the implementation of up to four service classes based on the allocation of differing amounts of forwarding resources (bandwidth and buffering). Each class of service can then utilize its three levels to provide varying degrees of packet drop priority based on a received packets compliance to predetermined input rate and burst levels, giving each packet a different PHB is appropriate. This can then be utilized by the router to determine which packets should be dropped first in the event of resource overload or network/link congestion. The AF PHBs can be most effective when used in conjunction with an active queue management algorithm such as Weighted Random Early Discard (available in the Vanguards). 10 Quality of Service

17 QoS Features Class Selector: This is a group of seven (eight if the BE PHB is included with the group) PHBs. The purpose of this group of PHBs is to allow compatibility with packets that have be marked using the IP Precedence values in the IPv4 header Type of Service (ToS) octet (as specified in RFC1349). Best Effort: This is actually only one PHB. This PHB reflects the service that was provided to all IP packets before the advent of QoS. This PHB is then one used for packets that are being transported through a network using Differentiated Services but that do not require any QoS service. DSCP to PHB Mapping There are recommended DSCP values for identifying (marking) packets as requiring specific QoS service and subsequently assigning a specific PHB (i.e. DSCP to PHB mapping). The use of these recommended DSCP values help to provide end-to-end QoS services. It is important to note how any given router actually implements the PHB can vary greatly, even though there is a standard DSCP to PHB mapping. The specification only maps the even numbered (non-experimental) DSCPs. Even so there are 11 DSCPs that are not mapped to PHBs which can be used to create custom PHBs for those services that are desirable but are not covered in the standard PHB set. Recommended DSCP to PHB Mapping DSCP 0 BE - Default Best Effort Service PHB 8 CS1 - Preferential Service (higher priority/bandwidth) compared to BE 16 CS2 - Preferential Service (higher priority/bandwidth) compared to CS1 24 CS3 - Preferential Service (higher priority/bandwidth) compared to CS2 32 CS4 - Preferential Service (higher priority/bandwidth) compared to CS3 40 CS5 - Preferential Service (higher priority/bandwidth) compared to CS4 48 CS6 - Preferential Service (higher priority/bandwidth) compared to CS5 56 CS7 - Preferential Service (higher priority/bandwidth) compared to CS6 46 EF - Expedite Forwarding (Packets are forwarded at specified rate and burst with lowest possible delay) 10 AF11 - Assured Forwarding Class 1 Green (low drop probability) Service 12 AF12 - Assured Forwarding Class 1 Yellow (medium drop probability) Service Quality of Service 11 T , Revision J Release 7.3

18 QoS Features Recommended DSCP to PHB Mapping (continued) DSCP PHB 14 AF13 - Assured Forwarding Class 1 Red (high drop probability) Service 18 AF21 - Assured Forwarding Class 2 Green (low drop probability) Service 20 AF22 - Assured Forwarding Class 2 Yellow (medium drop probability) Service 22 AF23 - Assured Forwarding Class 2 Red (high drop probability) Service 26 AF31 - Assured Forwarding Class 3 Green (low drop probability) Service 28 AF32 - Assured Forwarding Class 3 Yellow (medium drop probability) Service 30 AF33 - Assured Forwarding Class 3 Red (high drop probability) Service 34 AF41 - Assured Forwarding Class 4 Green (low drop probability) Service 36 AF42 - Assured Forwarding Class 4 Yellow (medium drop probability) Service 38 AF43 - Assured Forwarding Class 4 Red (high drop probability) Service The following 11 DSCPs are not assigned PHBs: 2, 4, 6, 42, 44, 50, 52, 54, 58, 60 and 62 Classification, Behavior Aggregrates and PHBs The process of applying Differential Services (DiffServ) begins by classifying IP packets which have not had a DSCP previously assigned (i.e. the DSCP is zero) into traffic flows. In general a flow is made up of all the packets which require the same QoS service level (e.g. all packets from file transfer applications can make up a flow). All the packets that are members of a flow are assigned the same DSCP. The exception to this is if the flow is passing through Traffic Conditioning using Three Color Marking. If this is the case then any given packet in the flow can be assigned one of three different DSCPs based on the Traffic Conditioning Specifications. All packets that have the same DSCP are next grouped together into Behavior Aggregrates. This step is necessary because some packets can enter the node with a DSCP already assigned and they need to be combined with those packets that have gone through the flow process. Finally all of the packets that are members of a Behavior Aggregate are given a PHB. This is done because the DSCP is retained in the packet. DSCP is transmitted onto the WAN link, the PHB is not. Implementation of PHBs is on a node by node, link by link basis. 12 Quality of Service

19 QoS Features The DiffServ Flows and Classification process is illustrated in Figure 4. Packets entering the node Telnet Telnet TCP (VoIP signalling) VoIP Traffic Classification IP traffic is classified. The classified packets are conditioned according to the Traffic Conditioning Specification (TCS) and marked with a DSCP. Classifier 1 Classifier 2 Behavior Aggregates (BA) All packets with the same DSCP, are grouped into an Aggregate. DSCP 12 Per Hop Behaviors Aggregates are assigned PHBs based on agreements to provided specific levels of service. PHB AF12 Queuing and Scheduling FTP FTP FTP Classifier 3 DSCP 18 PHB AF21 VoIP Telnet DSCP 46 (VoIP H.323) Classifier 4 DSCP 46 PHB EF Figure 4. DiffServ Flows and Classification Three Color Marking TCM is one of the traffic conditioning options available in the Vanguard. It is implemented in the Traffic Conditioning functional area. TCM, when used is applied to packets that have passed through IP classification and are assigned a classification number or have entered the node with a DSCP already set. The purpose of TCM is to assign a DSCP to the packet (which might be different then the one they arrived with) that reflects the compliance of the packet to configured rate and burst specifications. As the traffic input increases, the packets begin to carry a different DSCP than those that preceded them. Packets that are assigned a DSCP prior to entering this node can have the DSCP changed based on the same criteria. When using TCM four rate and burst values must be determined. Listed are the four rate and burst values: Committed Rate (CR) in Kbps Committed Burst (CB) in bytes Peak Rate (PR) in Kbps Peak Burst (PB) in bytes Quality of Service 13 T , Revision J Release 7.3

20 QoS Features When a packet enters a TCM traffic conditioner, based on the previous traffic flow volumes, it is found to exist in one of three states. Each of these states is assigned a color (green, yellow and red). When the packet arrives the current traffic rate and burst levels determine which color marking (not DSCP, that marking comes later) the packet receives based on the following: Traffic rate is <= CR and CB the packet color marker is Green. Traffic rate is > CR and CB but <= PR and PB the packet color marker is Yellow. Traffic rate is > PR and PB the packet color marker is Red. Based on the packets color marker a specific DSCP is assigned. Which specific DSCPs are to be used is configurable. Typically this type of traffic conditioning is used with the Assured Forwarding PHBs. If this is the case the DSCPs are selected from those recommended for use with the AF PHBs (see Table 1). As an example there is a FTP server attached to the Vanguard. It is decided that the FTP packets should use Assured Forwarding PHBs, specifically AF class 2. Once identified as FTP packets (via traffic classification) the packets are put through TCM. When setting up the TCM the following rate and burst values were selected: CR = 48 Kbps CB = 8,000 bytes PR = 96 Kbps PB = 12,000 bytes A file transfer starts to come into the node from the LAN attached server. It is an ethernet LAN so the packets are arriving much faster then either the CR or PR. The packets that contain the first 8,000 bytes (<= CB) of the file are marked as Green. Using the recommended DSCP for an AF class 2 PHB these packets are assigned DSCP 18. Those packets that arrive containing bytes 8001 through 12,000 are marked Yellow and subsequently given DSCP 20. Finally, those packets arriving with bytes 12,001 and up are marked as Red and given DSCP 22. that TCM is only providing marking to allow other functions to identify when a source (an FTP server in this case) is inputting data above pre-determined thresholds. The traffic conditioner using TCM does not drop any of the packets, that is up to the Queuing and Scheduling functions. Quality of Service is efficient when TCM is used along with WRED in Queuing and Scheduling, see WRED with TCM on page 17. Weighted Random Early Discard (WRED) An optional part of the Queuing and Scheduling function that is available in the Vanguard QoS feature set is Weighted Random Early Discard (WRED). WRED is an active queuing management mechanism that works in conjunction with well-behaved transport protocols, such as TCP, to achieve the following: Detect and react to incipient congestion by distinguishing between transient increases in load (caused by normal bursts) that can be handled by the network and a consistent increase in load that is likely to cause congestion in the network. Ensure the network operates in the congestion avoidance regime by dropping packets when incipient congestion is detected. Responsive transport protocols decrease their rates, adverting network congestion. Prevent TCP global synchronization such as, multiple TCP sessions entering slow-start simultaneously, by dropping packets from different traffic sources randomly. 14 Quality of Service

21 QoS Features Maintain fairness among traffic sources by ensuring that reduction in sending rate of a source is in proportion to the traffic generated by that source. Control the delay and jitter experienced by a packet by controlling the average queue size. WRED accomplishes these goals by randomly dropping packets before the queues are full. The first step is to determine the point of queue occupancy that determines if something is not done the queue overflows. One of the basic concepts needed to accomplish this is the Weighted Average Queue Length (WAQL). This process results in the WAQL value increasing slowly as packets enter the queue during a burst of traffic then the actual queue occupancy. How slowly the WAQL increases is controlled by a constant called the Weight Factor. The larger the Weight Factor the slower the WAQL increases. As a packet enters the queue the WAQL is calculated and this is compared against two configured values; Minimum Queue Threshold and Maximum Queue Threshold. If the WAQL value is greater then the Maximum Queue Threshold then the packet is dropped. If the WAQL value is less then the Minimum Queue Threshold then the packet enters the queue without further processing. More packets are allowed to occupy the actual queue when the WAQL grows slowly but of course the queue does have a finite limit which when exceeded results in all arriving packets being discarded (known as tail-drop). The Weight Factor, if properly selected, allows the actual queue to grow through normal bursts but triggers packet dropping in the case of long-term congestion. This happens before the queue goes into tail-drop. This is accomplished by allowing the random discarding of packets when the WAQL value is between the Minimum and Maximum Queue Threshold values. When this is the case the packet are dropped based on a maximum probability that ranges, in the Vanguards, between 1% and 20%. The actual probability that a particular packet is dropped is somewhere between 1% and the maximum (1% - 20%) with the probability increasing relative to where the current WAQL value is between the Minimum and Maximum Queue Thresholds. As an example, given the following settings: Minimum Queue Threshold is 20, Maximum Queue Threshold is 50 and Maximum Drop Probability is 8 a packet arrives and the WAQL is calculated at 35 (halfway between Minimum and Maximum Queue Thresholds) the actual drop probability for that packet would be 4% (halfway between 1% and 8%). that with these values the drop probability is 0% until the WAQL reaches 20 and goes from 8% to 100% as soon as the WAQL reaches 50. WRED is typically implemented in the Vanguards in conjunction with Three Color Marking Traffic Conditioning but WRED can be applied without TCM. Quality of Service 15 T , Revision J Release 7.3

22 QoS Features WRED Examples WRED allows the configuration of Minimum and Maximum Queue Thresholds as described in Weighted Random Early Discard (WRED) on page 14. This causes the random probability of dropping packets to increase as the traffic volume increases. This results in a type of traffic shaping at the Queuing and Scheduling functional area. 20% Telnet traffic BA5 AF12 DSCP12 Drop Probability Min. Queue Threshold Max. Queue Threshold Max. Drop Probability % 4% Weighted Average Queue Length Figure 5. WRED Applied to a Single Assured Forwarding PHB Refer to Figure 5 above, Telnet traffic is assigned DSCP 12 which equates to the AF12 PHB. If the incoming traffic volume is such that the Weighted Average Queue Level (WAQL) does not exceed 35% then the packets are not dropped. If the volume increase so that the WAQL is between 36% and 69% then there is an increasing chance that a packet is dropped. The probability of dropping a packet is between 0% and 4%. Finally if the WAQL reaches 90% all packets not already in queue are dropped. A form of traffic prioritization can be obtained between up to three different traffic flows through this type of WRED usage. This is done by assigning multiple types of traffic (e.g. Telnet and RIP), which ultimately is transmitted over the same WAN link different AF PHBs that are in the same AF class. For example Telnet traffic could be assigned AF PHB 12 and RIP can be assigned AF PHB 11. By carefully choosing the queue thresholds the RIP traffic can be given priority over the Telnet. 16 Quality of Service

23 QoS Features 20% Telnet traffic BA5 AF12 DSCP12 RIP traffic BA4 AF11 DSCP10 Drop Probability Min. Queue Threshold Max. Queue Threshold Max. Drop Probability % 2% 4% 2% Weighted Average Queue Length Figure 6. Traffic Prioritizing with WRED Traffic Prioritizing is illustrated in Figure 6. The RIP packets always experience less chance of being dropped then the Telnet packets but, when both WAQLs are between 46% and 69% there is a possibility that both RIP and Telnet packets might be dropped. This in effect should lessen WAN congestion by decreasing the Telnet traffic first allowing the RIP traffic to continue normally. In effect the Green RIP packets have priority over the Yellow Telnet packets. WRED with TCM Often TCM and WRED are implemented together to try and keep the network/link from becoming congested and the nodes queues from going into tail-drop (i.e. dropping all incoming packets because the buffers are full). The objective is to randomly drop packets to force the source to slow down. Of course it is most effective if those sources that are sending in the most data can be slowed down first. This is where the combination of TCM and WRED come in. First TCM assigns DSCPs to the packets to indicate the rate and volume the source is inputting data (see Three Color Marking). The result is packets from the same flow can be placed into three different Behavior Aggregrates (i.e. packets are assigned one of three different DSCPs with packets having the same DSCP becoming members of the same BA). If the packets are coming in slow enough they are placed in the Green BA. Once they start coming in a bit too fast they start to be placed in the Yellow BA. Finally, if the source does not slow down the packets begin to be placed in the Red BA. Therefore, it can be seen that a source that has packets being marked as Red is putting in relatively more data then a source whose packets are being marked Green. Quality of Service 17 T , Revision J Release 7.3

24 QoS Features If all three of the BAs that are related to one source (e.g. all the FTP packets) are subsequently channeled to the same queue then WRED is applied. Typically each of the BAs are given different Minimum and Maximum Queue Threshold levels. These levels are set up so that as the Weighted Average Queue Level (WAQL) increases (often due to network congestion) it triggers the Red BA packets as being eligible for random probability dropping first. If the WAQL continues to increase then the Yellow BA packets are triggered. Finally, if the WAQL still keeps increasing the Green BA packets are at risk. Figure 7 shows an example of one sources packets (i.e. all the HTTP packets coming in from one or more hosts) being tagged with three different BAs all sharing the same queue. As an example, suppose the WAQL is 30. In this case no Green packets are dropped, Yellow packets are dropped randomly (i.e. each arriving Yellow packet has a 2.66% chance of being dropped) and all Red packets are dropped. 20% 16% BA3 BA2 BA1 HTTP traffic Red Yellow Green AF23 DSCP22 AF22 DSCP20 AF21 DSCP % % Min. Queue Threshold Max. Queue Threshold Max. Drop Probability % 8% 4% Weighted Average Queue Length Figure 7. WRED with Three Behavior Aggregates Sharing One Queue 18 Quality of Service

25 QoS Features If this use of TCM and WRED is applied to multiple sources data (e.g. HTTP and FTP) there would be up to three AF PHB classes configured (e.g. HTTP is assigned AF class 1 and FTP class 2). If each were using WRED with the same values configured then the volume of traffic from a source that results in only Green packets have a lower chance of having packets dropped then the traffic from a source whose packets are marked Red. TCM shows that the source whose packets are marked Red is sending in more traffic then the source whose packets are marked Green. For example, if the FTP traffic volume results in all Green packets and the HTTP traffic volume results in Red packets then it is more probable that HTTP packets are dropped. The greatest relief can be obtained by slowing those sources with the highest traffic levels down first. Quality of Service 19 T , Revision J Release 7.3

26 QoS Features IP Differentiated Services: Configuration Area Functions Introduction IP MF Classifier Table IP BA Remarking Profile: When setting out to implement Differentiated Services (DiffServ) QoS using Vanguard routers it is helpful to understand what the various configuration areas do. What follows is an explanation of the function each of the configuration areas as well as the input requirements and output results. Input: IP packets with or without a DSCP. Function: To place individual packets into flows. Packets are classified as being members of a specific flow based on one or more of the follow criteria: Source Address and Source Address Mask (similar to wild card to specify a sub-net or range of source addresses). Destination Address and Source Address Mask (similar to wild card to specify a sub-net or range of source addresses). Protocol Number (0 for any, 1 for ICMP, 6 for TCP or 17 for UDP) TCP/UDP Source Port Number; single or a range (0 for any, 23 for TELNET, 21 for FTP, x-y for a range where x and y are between 1 and and x<y) TCP/UDP Destination Port Number; single or a range (0 for any, 23 for TELNET, 21 for FTP, x-y for a range where x and y are between 1 and and x<y) Output: The packet is given an IP MF Classification tag. This is a marking that is internal to the Vanguard and is discarded before the packet leaves the router. If the packet entered the IP MF Classifier with a DSCP it leaves the Classifier with the same DSCP. Such a packet might also acquire an IP MF Classification tag. This combination of an IP MF Classification tag and DSCP might be used to create different flows from packets that arrive with the same DSCP but are destined for different hosts across the network. In this case the IP MF Classification would identify those packets using the destination IP address. The Vanguard software limits the number of IP flows to a maximum of 10,000 per router. Input: Any IP packet, though it is most often those packets that enter the router with a DSCP between 1 and 63. Function: To change a packet s DSCP before Traffic Conditioning and Service Level Specifications are applied. There are two reasons that this configuration might be required. The packet might have originated in a Diff Serv network which does not have the same Service Level Specifications as the network which this router is a member. In this case a comparison analysis of the two different SLS is needed to determine what appropriate DSCP mapping requirements to apply to cross network traffic. Packets with several different DSCPs need to be combined into a single DSCP. This is often a matter of simplifying the QoS at those points in the network where it makes sense to do so. Output: The packet has a different DSCP. 20 Quality of Service

27 QoS Features IP Classifier, Traffic Conditioner and QoS Mapper (IP ClTcQoSMap) Profile Input: IP packets with an IP MF Classifier tag and/or a DSCP. Functions: This configuration area performs several functions. Classification and QoS Mapping Those packets which enter the profile with an IP MF Classifier tag are assigned a DSCP, making them members of a Diff Serv Behavior Aggregrates. Traffic Conditioning All packets that enter the Profile are subject to one of four different types of traffic conditioning. Traffic conditioning is applied to all packets within a traffic flow Behavior Aggregrates (i.e. have the same IP MF Classifier tag and the same DSCP). The four types of traffic conditioning are: NONE: No traffic conditioning is applied. Drop: For each flow that is using this type of traffic conditioning two parameters are set; Committed Rate (CR) and Committed Burst (CB). This sets limits for forwarding the packets. As each packet arrives the router calculates if, by forwarding this packet, both CR and CB would be exceeded (note this is the same as SHAPE). If it is then the packet is dropped. If it cannot then the packet is forwarded. Packet IP MF Class tag or DSCP Rate and Burst? <= CR and CB > CR and CB Drop Forward to Queuing and Scheduling (with DSCP) Figure 8. DROP Traffic Conditioning SHAPE: For each flow that is using this type of traffic conditioning two parameters are set; Committed Rate (CR) and Committed Burst (CB). This sets limits for forwarding the packets. As each packet arrives the router calculates if, by forwarding this packet, both CR and CB would be exceeded (note this is the same as DROP). The packet is then placed in a shaping buffer to be forwarded and should not exceed CR and CB. If it cannot then the packet is forwarded on. that the size of each shaping buffer configurable (32 to 64,000 bytes). If a shaping buffer is overloaded the flow is put into a tail-drop (all newly arriving packets are dropped). Quality of Service 21 T , Revision J Release 7.3

28 QoS Features Packet IP MF Class tag or DSCP Rate and Burst? <= CR and CB > CR and CB Shaping Buffer Forward to Queuing and Scheduling (with DSCP) Figure 9. SHAPE Traffic Conditioning TCM (Three Color Marking): For each flow that is using this type of traffic conditioning four parameters are set: Committed Rate (CR) and Committed Burst (CB) and Peak Rate (PR) and Peak Burst (PB). Also, each TCM conditioner has three DSCPs configured. These typically match the recommended DSCPs for a particular Assured Forwarding PHB class (e.g. if the flow is to have AF PHB class 2 applied then the three DSCPs would be 18, 20 and 22). When the packet leaves the conditioner it is assigned one of the three configured DSCPs based on the current input rate relative to the rate and burst configuration. For example, when a packet arrives the router calculates, by forwarding this packet, both CR and CB would be exceeded. If it cannot (<= CR & CB) then the packet is forwarded with the Green DSCP (e.g. DSCP 18). Otherwise, the router calculates by forwarding this packet, both PR and PB would be exceeded. If it cannot (<= PR & PB) then the packet is forwarded with a Yellow DSCP (e.g. DSCP 20). If the calculation indicates that the packet exceeds both PR and PB (> PR & PB) then the packet is forwarded with a Red DSCP (e.g. DSCP 22). An exception to the above is if the packet arrives with a DSCP that matches the Yellow or Red DSCP configured in the conditioner (e.g. the packet arrives with DSCP 20). In this case the packet cannot be given a DSCP upgrade. If the packet came in marked as Yellow, no matter what the current rate calculation indicates the packet cannot be given a Green DSCP. It is possible, based on the rate calculation to down grade the packet to Red (e.g. change the DSCP from 20 to 22). Of course this means that packets which enter with a Red DSCP always leaves with the same DSCP. 22 Quality of Service

29 QoS Features Packet Any DSCP and/or IP MF Classification tag Rate and Burst? <= CR and CB > CR and CB Forward to Queuing and Scheduling (with Green DSCP) Packet Yellow DSCP (12, 20, 28, 36) Rate and Burst? > PR and PB <= PR and PB Forward to Queuing and Scheduling (with Yellow DSCP) Packet Red DSCP (14, 22, 30, 38) Forward to Queuing and Scheduling (with Red DSCP) Figure 10. TCM (Three Color Marking) Traffic Conditioning Output: All packets have a DSCP assigned. Due to traffic conditioning some packets might be dropped or they might have their DSCPs changed. The Vanguard software limits the number of Behavior Aggregrates that can have TCM traffic conditioning applied to a maximum of 1,000 per router. IP BA PHB Mapper Input: IP packets with a DSCP Function: This configuration area maps DSCPs to PHBs. Actual configuration within this area is only required if the network is using non-standard DSCPs. As long as arriving packets carry DSCPs that have recommended PHBs assigned (per RFC 2474 and RFC 2598) the appropriate PHB tag is assigned to the packet by default. This is not to say that the IP BA PHB Mapper can not be used to map a standard DSCP to a PHB other then its recommended PHB (e.g. DSCP 10 could be mapped to AF21) but it is not recommended. PHBs can be assigned to those packets that are using any of the non-standard DSCPs (2, 4, 6, 42, 44, 50, 52, 54, 58, 60 or 62). Typically these packets would be assigned one of the custom PHBs (PHB1 through PHB15). In certain circumstances it might be desirable to have packets that are carrying these DSCPs to share the same service as packets carrying standard DSCPs. This can be done in this configuration area by assigning these packets standard PHBs (BE, CS1 - CS7, EF or AF1x - AF4x (x = 1-3)). Output: IP packets with DSCPs and PHB tags. The PHB tag is a marking that is internal to the Vanguard and is discarded before the packet leaves the router. Quality of Service 23 T , Revision J Release 7.3

30 QoS Features Service Profile Input: IP packet with a PHB tag and DSCP Function: This area is responsible for queuing and scheduling and the forwarding of the packets to the WAN or LAN. This is where the Service Level Specifications are applied. Queuing is simply providing some buffer space for all of the various flows. The exception to this is flows that are assigned a MIN Delay service (described below). Packets from flows with this service are forwarded with such a high priority that they do not need buffering. Scheduling is the task of forwarding the packets in the correct order as to provide each packet with its appropriate level of QoS service. This task is divided into three functions: Delay: There are three levels; MIN, LOW and NORMAL Bandwidth: A portion of the total link bandwidth to be used by this flow. Packet Dropping: The application of WRED to AF PHBs. Each of these three functions could be applied to incoming packets depending on the PHB tag that the packet carries. Some of the functions are not available to all PHBs. First a description of the three levels of Delay and how Bandwidth affects their operation: Delay MIN Delay: Packets given this delay have the highest priority and are not queued. As soon as they arrive they are forwarded to the WAN port ahead of all other packets. Also, packets using this delay are tagged as being able to use the Link Fragmentation and Interleaving functions of the WAN port (if available and configured). This causes the WAN port to fragment large packets from other sources and allows the MIN delay packets to gain access to the link with out having to wait for the transmission of a large packet to finish. There is a maximum bandwidth assigned to flows using this service (1 to Kbps per flow). For this service if the packets coming in exceed the configured bandwidth they are dropped. MIN delay is typically reserved for real-time applications like VoIP. LOW Delay: Packets assigned to this service are forwarded after any packets with MIN Delay service but before those with NORMAL Delay service. This service uses a simple priority forwarding mechanism. The priority is set by the Priority field. This field allows the user to specify the order from 0 (lowest) to 15 (highest) in which the flows that use this service are configured in the Service Profile. In cases where services have the same Priority the order is determined by the order of entry. In other words, the higher the entry number the higher the priority (e.g. if two flows were both given LOW Delay Priority of 1, with one of the flows being configured in Entry 3 of the Service Profile and the second in Entry 7 then the packets using the service configured in Entry 7 would take priority over those in using Entry 3). There is a maximum bandwidth assigned to flows using this service (1 to 2,000 Kbps per flow). For this service if the packets coming in exceed the configured bandwidth they are buffered. There is a queue length limit that, 24 Quality of Service