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Configuration Guide - DCN and Server Management

CloudEngine 8800, 7800, 6800, and 5800 V200R003C00

This document describes the configurations of Trill, FCoE, DCB, and NLB Server Cluster Association.
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ETS

ETS

Background

A converged data center network has LAN traffic, SAN traffic, and IPC traffic. The converged network has high QoS requirements. For example, SAN traffic is sensitive to packet loss and relies on in-order deliver. IPC traffic is exchanged between servers and requires low latency. LAN traffic allows packet loss and is delivered on a best-effort (BE) basis. Traditional QoS cannot meet requirements of the converged network, whereas ETS uses a hierarchical flow control mechanism to implement QoS on the lossless Ethernet.

Principles

ETS provides two-level scheduling: scheduling based on priority groups and scheduling based on queues, as shown in Figure 3-3. An interface first schedules priority groups, and then schedules priority queues.
Figure 3-3 ETS Process

Compared with common QoS, ETS provides scheduling based on priority groups. ETS adds traffic of the same type to a priority group so that traffic of the same type obtains the same CoS.

Scheduling Based on Priority Groups

A priority group is a group of priority queues using the same scheduling mode. You can add queues with different priorities to a priority group. Scheduling based on the priority group is called level-1 scheduling.

ETS defines three priority groups by default: PG0, PG1, and PG15. PG0, PG1, and PG15 process LAN traffic, SAN traffic, and IPC traffic respectively.

Attributes of priority groups by default described as below.
Table 3-3 Scheduling based on priority groups (excluding CE6870EI and CE6875EI)

Priority Group ID

Priority Queue

Scheduling Mode

Bandwidth Usage

PG0

0, 1, 2, 4, 5

DRR

50%

PG1

3

DRR

50%

PG15

6, 7

PQ

-

Table 3-4 Scheduling based on priority groups (CE6870EI and CE6875EI)

Priority Group ID

Priority Queue

Scheduling Mode

Bandwidth Usage

PG0

0, 1, 2, 4, 5

WFQ

50%

PG1

3

WFQ

50%

PG15

6, 7

PQ

-

(excluding CE6870EI and CE6875EI) As defined by ETS, PG0 and PG1 use DRR and PG15 use PQ. PG15 uses priority queuing (PQ) to schedule delay-sensitive IPC traffic. PG0 and PG1 use Deficit Round Robin (DRR). Bandwidth can be allocated to priority groups based on actual networking.

(CE6870EI and CE6875EI) As defined by ETS, PG0 and PG1 use WFQ and PG15 use PQ. PG15 uses priority queuing (PQ) to schedule delay-sensitive IPC traffic. PG0 and PG1 use Weighted Fair Queue (WFQ). Bandwidth can be allocated to priority groups based on actual networking.

NOTE:

The scheduling mode of each priority group cannot be changed.

The queue with priority 3 carries FCoE traffic, so this queue is added to the SAN group (PG1). Queues with priorities 0, 1, 2, 4, and 5 carry LAN traffic, so these queues are added to the LAN group (PG0). The queue with priorities 6, 7 carries IPC traffic, so this queue is added to the IPC group (PG15). The total bandwidth of the interface is 10 Gbit/s. PG15 obtains 2 Gbit/s. PG1 and PG0 each obtain 50% of the total bandwidth, 4 Gbit/s.

Figure 3-4 Congestion management based on priority groups

As shown in Figure 3-4, all traffic can be forwarded because the total traffic on the interface is within the interface bandwidth at t1 and t2. At t3, the total traffic exceeds the interface bandwidth and LAN traffic exceeds given bandwidth. At this time, LAN traffic is scheduled based on ETS parameters and 1 Gbit/s LAN traffic is discarded.

ETS also provides traffic shaping based on priority groups. This traffic shaping mechanism limits traffic bursts in a priority group to ensure that traffic in this group is sent out at an even rate. For details, see Traffic Shaping in CloudEngine 8800, 7800, 6800, and 5800 Series Switches Configuration Guide - QoS Configuration.

Priority-based Scheduling

ETS also provides priority-based queue scheduling, level-2 scheduling.

In addition, ETS provides priority-based queue congestion management, queue shaping, and queue congestion avoidance. For details, see CloudEngine 8800, 7800, 6800, and 5800 Series Switches Configuration Guide - QoS Configuration.

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Updated: 2019-05-08

Document ID: EDOC1100004349

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