Technical Notes QoS Features on the Business Ethernet Switch 50 (BES50) Version: NN70000-004 issue 1.00 Date: February 3rd, 2009 Status: Released Copyright © 2009 Nortel Networks. All rights reserved. The information in this document is subject to change without notice. The statements, configurations, technical data, and recommendations in this document are believed to be accurate and reliable, but are presented without express or implied warranty.
Technical Notes – QoS Features on BES50 Revision History Revision (Ver.Iss) 1.00 Issue Date 2009-02-03 Document Change Description Status Released First released version. . NN70000-004 issue 1.
Technical Notes – QoS Features on BES50 About this Document This application note describes the Quality Of Service (QoS) capability of BES50 family of switches. This document also outlines the procedure to properly configure different QoS features of BES50. The document is intended for people responsible for deployment and support of the Nortel Business Ethernet Switch 50.
Technical Notes – QoS Features on BES50 Table of Contents Revision History .......................................................................................................................................... 2 About this Document .................................................................................................................................. 3 Table of Contents ............................................................................................................................
Technical Notes – QoS Features on BES50 Table of Figures Figure 1: BES50FE Priority to Traffic Class Mapping ................................................................................... 8 Figure 2: BES50GE Priority to Traffic Class Mapping .................................................................................. 8 Figure 3: Scheduler Queuing Mode ..............................................................................................................
Technical Notes – QoS Features on BES50 Overview BES50 provides a number of features to support different Quality of Service (QoS) for different types of traffic. There are multiple levels of traffic prioritization on BES50 (both BES50FE and BES50GE). Prioritization can be based on (1) (2) (3) (4) Default port priority 802.
Technical Notes – QoS Features on BES50 High-level Description of QoS Treatment in BES50 A central element for providing different QoS treatment is the concept of traffic priority and traffic classes. When an incoming Ethernet frame arrives at an ingress port, BES50 first determines the priority/CoS (value between 0 – 7) of the incoming frame based on the L2/L3 information carried in the Ethernet frame and/or the IP payload. Each priority/CoS (basically 802.
Technical Notes – QoS Features on BES50 Figure 1: BES50FE Priority to Traffic Class Mapping Figure 2: BES50GE Priority to Traffic Class Mapping These traffic classes are served by a scheduler that can run in either Weighted Round Robin (WRR) or Strict Priority. NN70000-004 issue 1.
Technical Notes – QoS Features on BES50 • • Strict Priority queuing operates in a pre-emptive fashion. Frames in the higher priority queues always take precedence over frames in lower priority queues. A low priority queue will not be serviced as long as there is a frame in one of the higher priority queues. When the highest priority queue is empty, frames from the other queues are serviced based on their precedence (i.e. from the higher priority queue to the lower priority queue).
Technical Notes – QoS Features on BES50 Figure 4: BES50FE WRR Weight Settings Figure 5: BES50GE WRR Weight Settings NN70000-004 issue 1.
Technical Notes – QoS Features on BES50 BES50 provides multiple ways to classify different types of traffic and map the traffic to one of the 8 defined priority/CoS values. There are four different methods to classify and prioritize incoming traffic, these methods are based on: 1. 2. 3. 4. Default port priority 802.
Technical Notes – QoS Features on BES50 Process Ingress Ethernet Frame Match QoS Policy? Yes Action is “Set DSCP”? Yes Set IP DSCP Get CoS from DSCP No (action is “Set CoS”) No Yes IP DSCP Enabled? Is it an IP packet? Yes Get CoS from DSCP No No Tagged Ethernet Frame? No Yes Get CoS from 802.1p value Set CoS Get default port priority Figure 6: BES50FE Traffic Prioritization Flow Chart NN70000-004 issue 1.
Technical Notes – QoS Features on BES50 Process Ingress Ethernet Frame Yes Match ACL Mapping? No Yes IP DSCP Enabled? Is it an IP packet? Yes Map DSCP to Priority Index No No Tagged Ethernet Frame? No Yes Get default port priority Get CoS from 802.1p value Map CoS to Priority Index Get IP DSCP Get Priority Index Set CoS Figure 7: BES50GE Traffic Prioritization Flow Chart The resulting priority/CoS (basically 802.
Technical Notes – QoS Features on BES50 Configure BES50 Traffic Prioritization 1. Default Port Priority A default port priority can be specified for each port on the BES50. All untagged packets entering the BES50 are tagged with the specified default port priority, and then sorted into the appropriate priority queue at the output port. The default priority applies for an untagged frame received on a port set to accept all frame types (i.e, can receive both untagged and tagged frames).
Technical Notes – QoS Features on BES50 3. Traffic prioritization based on IP DSCP This section focuses on prioritizing traffic based on the IP DSCP value in the incoming IP packets. In brief, the user first needs to enable IP DSCP prioritization (it is disabled by default). When an incoming IP packet arrives at an ingress port, BES50 first maps the DSCP value in the incoming IP packet to a traffic priority/CoS (value between 0 – 7).
Technical Notes – QoS Features on BES50 Figure 9: BES50 IP DSCP Priority Status Step (2) Configure/Check DSCP to CoS mapping BES50 has a predefined DSCP to CoS mapping. However the users can still modify the mapping if they desired. Navigate to the Applications > Priority > IP DSCP Priority panel NN70000-004 issue 1.
Technical Notes – QoS Features on BES50 Figure 10: BES50 DSCP to COS Mapping 4.
Technical Notes – QoS Features on BES50 NN70000-004 issue 1.
Technical Notes – QoS Features on BES50 Figure 11: BES50FE Extended ACL Rule Step (2) Define a class map that matches the classification of the ACL This step identifies the matching traffic as a traffic stream. All packets within the same traffic stream are subject to the same QoS policy. NN70000-004 issue 1.
Technical Notes – QoS Features on BES50 Figure 12: BES50FE Class Map NN70000-004 issue 1.
Technical Notes – QoS Features on BES50 Step (3) Define a QoS policy for the selected traffic stream A QoS policy determines the course of action applying to incoming IP packets that belong to the same traffic stream. The action can be mark/re-mark IP DSCP or mark/re-mark the CoS priority of the incoming Ethernet frames.
Technical Notes – QoS Features on BES50 Figure 13: BES50FE Policy Setting CoS Value • IP DSCP: The new DSCP value first maps into a CoS priority value based on a defined DSCP-toCoS mapping (see Figure 10: BES50 DSCP to COS Mapping). The new CoS value is then mapped into one of the traffic class based on the CoS to traffic class mapping (see Figure 1: BES50FE Priority to Traffic Class). NN70000-004 issue 1.
Technical Notes – QoS Features on BES50 NOTE: Using a QoS policy to set the new IP DSCP will modify the DSCP value of the target IP packet as well as the 802.1p value of the egress Ethernet frame (that encapsulated the target IP packet). Figure 14: BES50FE Policy Setting DSCP Value NN70000-004 issue 1.
Technical Notes – QoS Features on BES50 Step (4) Apply the QoS policy to an ingress port This step applies the QoS policy to an ingress port. Traffic classification and marking/re-marking are carried out at the ingress port where the incoming IP packets enter the BES50FE switch.
Technical Notes – QoS Features on BES50 NN70000-004 issue 1.
Technical Notes – QoS Features on BES50 Figure 16: BES50GE Extended ACL Rule Step (2) Bind ACL classification rule to an ingress port This step binds the ACL classification rule to an ingress port. Traffic classification is carried out at the ingress port where the incoming IP packets enter the BES50GE switch. All packets that match the classification rule are considered as belonging to the same traffic stream.
Technical Notes – QoS Features on BES50 Priority Index 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 CoS Value 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 Table 3: BES50GE Priority Index to CoS Mapping NN70000-004 issue 1.
Technical Notes – QoS Features on BES50 Figure 17: BES50GE ACL Priority Mapping NN70000-004 issue 1.
Technical Notes – QoS Features on BES50 BES50 Re-Marking Capability In addition to traffic prioritization, BES50 also provides the capability to re-mark the IP DSCP value of an outgoing IP packet and the 802.1p value (CoS) of an outgoing Ethernet frame. IP DSCP Re-Marking on BES50FE Figure 6: BES50FE Traffic Prioritization Flow Chart depicts the flow chart of how CoS/priority is determined by BES50FE. Re-marking in BES50FE is a simple extension to this process. BES50FE always re-marks the 802.
Technical Notes – QoS Features on BES50 BES50GE provides a default priority index to IP DSCP mapping, and this mapping is also user configurable if they desired to use a different setting. To review and/or configure the traffic index to IP DSCP mapping, navigate to the Applications > Priority > Priority to DSCP panel.
Technical Notes – QoS Features on BES50 Priority Index 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 CoS Value IP DSCP 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 10 12 14 18 20 22 26 28 30 34 36 38 46 0 0 Table 4: BES50GE Priority Index to CoS and IP DSCP Mapping A word of caution when IP DSCP based traffic prioritization is enabled. Since the DSCP value is 6 bits and there are only 8 CoS/priority value, enabling IP DSCP remarking may alter IP DSCP to an undesirable value.
Technical Notes – QoS Features on BES50 Difference Between BES50FE and BES50GE 1. Number of traffic class BES50FE has four traffic classes, while BES50GE has eight traffic classes. 2.
Technical Notes – QoS Features on BES50 Default QoS Behaviour of BES50FE and BES50GE BES50 provides a set of default (out of the box) settings that are captured in the following table: Traffic Prioritization Method Default port priority 802.1p bit (tagged Ethernet frame) IP DSCP ACL based Default Status Enabled Enabled Disabled Disabled Default CoS/Priority Value 0 Taken from 802.
Technical Notes – QoS Features on BES50 When BES50 is used in a customer premises network with BCM50/BCM450 and QoS treatment is required, it is recommended to use the IP DSCP traffic prioritization method (see “3. Traffic prioritization based on IP DSCP” on page 15) on BES50 since BCM does not tag outgoing Ethernet frames.
Technical Notes – QoS Features on BES50 Software Baseline This application note draws upon the capabilities available from the following BES50 software releases: • • BES50FE v1.0.3.0 (Release 1.1) BES50GE v1.0.5.0 (Release 1.1) NN70000-004 issue 1.
