Problem Statement of RoCEv2 Congestion Management
draft-chen-nfsv4-rocev2-cm-problem-statement-00

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INTERNET-DRAFT                                                   F. Chen
Intended Status: Informational                                    W. Sun
Expires: Feb 09, 2019                                Huawei Technologies
                                                            Aug 10, 2018

           Problem Statement of RoCEv2 Congestion Management 
            draft-chen-nfsv4-rocev2-cm-problem-statement-00

Abstract

   On IP-routed datacenter networks, RDMA is deployed using RoCEv2
   protocol. RoCEv2 specification does not define the congestion
   management and load balancing methods. RoCEv2 relies on the existing
   Link-Layer Flow-Control IEEE 802.1Qbb(Priority-based Flow Control,
   PFC)to provide a lossless network. RoCEv2 Congestion Management(RCM)
   use ECN(Explicit Congestion Notification, defined in RFC3168) to
   signal the congestion to the destination and use the congestion
   notification to reduce the rate of injection and increase the
   injection rate when the extent of congestion decreases. More and more
   practice of congestion management for RoCEv2 appear in the industry,
   such as DCQCN(Data Center Quantized Congestion Notification). There
   is a demanding for the new RoCE protocol(temporary alias RoCEv3) to
   provide stronger congestion management and load balancing mechanisms
   for RDMA deployment in modern datacenter.

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Copyright and License Notice

   Copyright (c) 2018 IETF Trust and the persons identified as the
   document authors. All rights reserved.

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   document        authors.  All rights reserved.

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Table of Contents

   1  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2  Terminology . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3  Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . .  3
   4  Problem statement & requirements  . . . . . . . . . . . . . . .  4
   5  Current Congestion Management for RoCEv2  . . . . . . . . . . .  4
     5.1 PFC  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     5.2 ECN  . . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   6. Congestion Management Practice  . . . . . . . . . . . . . . . .  5
     6.1 Packet Retransmission  . . . . . . . . . . . . . . . . . . .  5
     6.2 Congestion Control Mechanisms  . . . . . . . . . . . . . . .  5
     6.4 Load Balancing . . . . . . . . . . . . . . . . . . . . . . .  6
   7  Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   8  Security Considerations . . . . . . . . . . . . . . . . . . . .  7
   9  IANA Considerations . . . . . . . . . . . . . . . . . . . . . .  7
   10  References . . . . . . . . . . . . . . . . . . . . . . . . . .  7

 

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1  Introduction

   With the emerging Distributed Storage, AI/HPC, Machine Learning,
   etc., modern datacenter applications demand high throughput(40Gbps
   and above) with ultra-low latency of < 10 microsecond per hop from
   the network, with low CPU overhead. Remote Direct Memory Access
   (RDMA) can meet these needs on Ethernet.

   On IP-routed datacenter networks, RDMA is deployed using RoCEv2
   protocol. RoCEv2 is a straightforward extension of the RoCE protocol
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