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Versions: 00 01                                                         
Network Working Group                                             C. Lin
Internet-Draft                                                   M. Chen
Intended status: Standards Track                                   H. Li
Expires: May 12, 2022                                                H3C
                                                        November 8, 2021


Distribution of Device Discovery Information in NVMe Over RoCEv2 Storage
                           Network Using BGP
                     draft-lin-idr-bgp-nof-nlri-00

Abstract

   This document proposes a method of distributing device discovery
   information in NVMe over RoCEv2 storage network using the BGP routing
   protocol.  A new BGP Network Layer Reachability Information (NLRI)
   encoding format, named NoF NLRI, is defined.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 12, 2022.

Copyright Notice

   Copyright (c) 2021 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of




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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Distribution of Device Discovery Information Using BGP  . . .   3
   3.  BGP Extentions  . . . . . . . . . . . . . . . . . . . . . . .   5
     3.1.  TLV Format  . . . . . . . . . . . . . . . . . . . . . . .   5
     3.2.  NoF NLRI  . . . . . . . . . . . . . . . . . . . . . . . .   6
     3.3.  Device Discovery NLRI . . . . . . . . . . . . . . . . . .   7
       3.3.1.  IPv4 Address TLV  . . . . . . . . . . . . . . . . . .   8
       3.3.2.  IPv6 Address TLV  . . . . . . . . . . . . . . . . . .   8
       3.3.3.  Role Type TLV . . . . . . . . . . . . . . . . . . . .   9
       3.3.4.  Online/Offline Status TLV . . . . . . . . . . . . . .   9
       3.3.5.  More Device Info TLVs . . . . . . . . . . . . . . . .  10
     3.4.  Device Zone NLRI  . . . . . . . . . . . . . . . . . . . .  10
     3.5.  Operations  . . . . . . . . . . . . . . . . . . . . . . .  11
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  11
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .  11
     6.2.  Informative References  . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   As data center networks keep growing, the performance of
   communication methods needs to accelerate.  At present, NVMe over
   RoCEv2 is becoming a popular solution of storage network based on
   Ethernet.  In such network, a host accesses to an NVMe storage
   subsystem via Ethernet Fabric with RoCEv2 protocol.

   In the traditional way, the discovery of hosts and storage subsystems
   is achieved by manual configurations.  However the manual way is
   difficult for management and maintenance.  In addition, the reaction
   speed is slow when a device goes online or offline, making it hard to
   realize hot-plug and failover.  To solve these problems, automatic
   discovery method should be deployed.

   LLDP is generally used to achieve the discovery task when a host or
   storage subsystem is directly connected to a switch.  Then, the
   device discovery information is distributed to others switches in the
   fabric.  Finally, other devices get the information from the switches
   which they directly connect with.





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   This document proposes a new method of distributing device discovery
   information among switches in NVMe over RoCEv2 storage network using
   the BGP routing protocol [RFC4271].

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Distribution of Device Discovery Information Using BGP

   In hierarchical topology, a host or storage subsystem is usually
   connected to a switch at access layer.  In Clos topology, a host or
   storage subsystem is usually connected to a "Leaf" switch.  To keep
   terminology uniform, in this document the switches which the hosts
   and storage subsystems directed connect with will be referred to as
   the access switches.

   When any host or storage subsystem is connected with an access
   switch, it periodically sends LLDP messages to the access switch.
   According to the received LLDP messages, the access switch maintains
   the states of directly connected devices.  If the state of any device
   changes, such as going online or offline, the access switch will
   announce the other devices connected with it.  However, the devices
   on the other access switches may also be concerned with the device
   discovery information, especially in a large-scale storage network.
   For example, when a storage subsystem is newly connecting to an
   access switch, a host located in another access switch needs to know
   that it gets online.  Then the host will establish connection with
   the storage subsystem, and transmit data through NVMe over RoCEv2.
   Therefore, the access switches are required to distribute device
   discovery information among them.

   In this document the distribution of device discovery information
   among access switches is achieved by using BGP.  All the access
   switches are BGP speakers, and the device discovery information is
   exchanged as BGP routes among them.

   In order to reduce the number of BGP connections, the application of
   BGP Route Reflectors [RFC4456] is recommended.  Figure 1 shows an
   example of BGP connections with route reflectors.  SW 1 and SW 2
   serve as reflectors, and SW 3, SW 4, SW 5 and SW 6 are their clients.
   When a client sends a BGP route, which contains device discovery
   information, to a reflector, the reflector will reflect the route to
   the other clients.  Therefore, all the access switches work as



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   clients, and each of them only needs to establish BGP connections to
   the reflectors, rather than establishing BGP connections between each
   other.  In this example, there are two reflectors, SW 1 and SW 2,
   which run as a hot standby for each other.  It is also fine to deploy
   only one reflector in the network.  However, to improve availability,
   deploying more than one reflectors are recommended.

         +---------+              +---------+
         |  SW 1   |              |  SW 2   |        BGP Reflector
         +---------+              +---------+
     +-----+ | | |                  | | | |
     |   +---|-|-|------------------+ | | |
     |   |   | | |    +---------------+ | |
     |   |   | | |    |                 | +-----+
     |   |   | | |    |            +----+       |
     |   |   | | +----|------------|--------+   |
     |   |   | +------|--------+   |        |   |
     |   |   +----+   |        |   |        |   |
     |   |        |   |        |   |        |   |
   +-------+    +-------+    +-------+    +-------+
   | SW 3  |    | SW 4  |    | SW 5  |    | SW 6  |  BGP Client
   +-------+    +-------+    +-------+    +-------+
     |   |        |   |        |   |        |   |
     |   |        |   |        |   |        |   |
     H3  SS3      H4  SS4      H5  SS5      H6  SS6

   SW: Switch
   H:  Host
   SS: Storage Subsystem

              Figure 1 BGP Connections with Route Reflectors

   In Figure 1, the reflector switches are not directly connected with
   hosts or storage subsystems, and they are not access switches.
   Figure 2 shows another example, in which case two of the access
   switches serve as BGP route reflectors.  The main difference with
   Figure 1 is that the reflectors, SW 1 and SW 2, also need to
   establish BGP connections between each other.  If any device directly
   connected with the reflector goes online or offline, the reflector
   not only sends the device discovery information to its clients, but
   also sends information to the other reflectors.










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            H1  SS1                  H2  SS2
            |   |                    |   |
            |   |                    |   |
         +---------+              +---------+
         |  SW 1   |--------------|  SW 2   |        BGP Reflector
         +---------+              +---------+
     +-----+ | | |                  | | | |
     |   +---|-|-|------------------+ | | |
     |   |   | | |    +---------------+ | |
     |   |   | | |    |                 | +-----+
     |   |   | | |    |            +----+       |
     |   |   | | +----|------------|--------+   |
     |   |   | +------|--------+   |        |   |
     |   |   +----+   |        |   |        |   |
     |   |        |   |        |   |        |   |
   +-------+    +-------+    +-------+    +-------+
   | SW 3  |    | SW 4  |    | SW 5  |    | SW 6  |  BGP Client
   +-------+    +-------+    +-------+    +-------+
     |   |        |   |        |   |        |   |
     |   |        |   |        |   |        |   |
     H3  SS3      H4  SS4      H5  SS5      H6  SS6

   SW: Switch
   H:  Host
   SS: Storage Subsystem

               Figure 2 Access Switches Serve as Reflectors

   This document mainly focus on the distribution method of device
   discovery information among access switches.  The interaction between
   access switch and host, or the interaction between access switch and
   storage subsystem, is beyond the scope of this document.

3.  BGP Extentions

   This document describes a mechanism by which device discovery
   information can be distributed using the BGP routing protocol.  This
   is achieved using a new BGP Network Layer Reachability Information
   (NLRI) encoding format, named NoF NLRI.

3.1.  TLV Format

   Information in the NoF NLRI is encoded in Type/Length/Value triplets.
   The TLV format is shown in Figure 3.







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    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |              Type             |             Length            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                        Value (variable)                     //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                           Figure 3: TLV Format

   The Length field defines the length of the value portion in octets
   (thus, a TLV with no value portion would have a length of zero).  The
   TLV is not padded to 4-octet alignment.  Unrecognized types MUST be
   preserved and propagated.

3.2.  NoF NLRI

   New AFI and SAFI are defined for the NoF NLRI: the NoF AFI/SAFI
   (values to be assigned by the IANA).

   In order for two BGP speakers to exchange NoF NLRI, they MUST use BGP
   Capabilities Advertisement to ensure that they are both capable of
   properly processing such NLRI.  This is done as specified in
   [RFC4760].

   The format of the NoF NLRI is shown in the following figure.

   +------------------+
   |  Type            | 2 octets
   +------------------+
   |  Length          | 2 octets
   +------------------+
   |  NoF NLRI        | variable
   +------------------+

   where:

   o  Type: the type of NoF NLRI.

   o  Length: the length of the rest of the NLRI in octets, not
      including the Type field or itself.

   o  NoF NLRI: carrying the device discovery information in NVMe over
      Fabric networks.

   BGP NoF NLRI for both IPv4 and IPv6 networks can be carried over
   either an IPv4 BGP session or an IPv6 BGP session.  If an IPv4 BGP
   session is used, then the next hop in the MP_REACH_NLRI SHOULD be an



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   IPv4 address.  Similarly, if an IPv6 BGP session is used, then the
   next hop in the MP_REACH_NLRI SHOULD be an IPv6 address.  Usually,
   the next hop will be set to the local endpoint address of the BGP
   session.  The next-hop address MUST be encoded as described in
   [RFC4760].

   The Device Discovery NLRI and Device Zone NLRI are currently defined
   in this document.  More types of NLRI will be included in the future
   version.

   +------+---------------------------+
   | Type | NoF NLRI Type             |
   +------+---------------------------+
   |  1   | Device Discovery NLRI     |
   |  2   | Device Zone NLRI          |
   +------+---------------------------+

3.3.  Device Discovery NLRI

   The Device Discovery NLRI is used to carry the discovery information
   of directly connected devices.  The format of the Device Discovery
   NLRI is shown in the following figure.

   +------------------+
   |  Router ID       | 4 octets
   +------------------+
   |  Mac Address     | 6 octets
   +------------------+
   |  Port Name Length| 2 octets
   +------------------+
   |  Port Name       | variable
   +------------------+
   |  Device Info     | variable
   +------------------+

   where:

   o  Router ID: the Router ID of the access switch which originates
      this NLRI, usually the same as the BGP Identifier.

   o  Mac Address: the Mac Address of a connected device.

   o  Port Name Length: the length of the following Port Name field in
      octets.

   o  Port Name: the name of the connecting port, to distinguishing
      different ports which share the same Mac Address.




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   o  Device Info: the specific information of the connected device and
      its connecting port, which are identified by the above Mac Address
      and Port Name fields.

   The Device Discovery NLRI carries the information of a device which
   is identified by the Router ID of the access switch and the Mac
   Address and Port Name of the connected port.

   For the purpose of BGP route key processing, only the Router ID, Mac
   Address, MAC Address, Port Name Length, and Port Name fields are
   considered to be part of the prefix in the NLRI.

   The Device Info field may contain the following TLVs.

3.3.1.  IPv4 Address TLV

   The format of the IPv4 Address TLV is shown in the following figure.

   +------------------+
   |  Type            | 2 octets
   +------------------+
   |  Length          | 2 octets
   +------------------+
   |  IPv4 Address    | 4 octets
   +------------------+

   where:

   o  Type: 1.

   o  Length: 4.

   o  IPv4 Address: the IPv4 Address of the connecting port.

3.3.2.  IPv6 Address TLV

   The format of the IPv6 Address TLV is shown in the following figure.

   +------------------+
   |  Type            | 2 octets
   +------------------+
   |  Length          | 2 octets
   +------------------+
   |  IPv6 Address    | 16 octets
   +------------------+

   where:




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   o  Type: 2.

   o  Length: 16.

   o  IPv6 Address: the IPv6 Address of the connecting port.

3.3.3.  Role Type TLV

   The format of the Role Type TLV is shown in the following figure.

   +------------------+
   |  Type            | 2 octets
   +------------------+
   |  Length          | 2 octets
   +------------------+
   |  Role Type       | 1 octets
   +------------------+

   where:

   o  Type: 3.

   o  Length: 1.

   o  Role Type: the role of the device.  The following values are
      defined.

      *  1: storage subsystem.

      *  2: host.

      *  3: the device can serve as both a host and a storage subsystem.

3.3.4.  Online/Offline Status TLV

   The format of the Online/Offline Status TLV is shown in the following
   figure.

   +------------------------+
   |  Type                  | 2 octets
   +------------------------+
   |  Length                | 2 octets
   +------------------------+
   |  Online/Offline Status | 1 octets
   +------------------------+

   where:




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   o  Type: 4.

   o  Length: 1.

   o  Online/Offline Status: indicating the device is online or offline.
      The following values are defined.

      *  0: offline.

      *  1: online.

3.3.5.  More Device Info TLVs

   More Device Info TLVs will be included in the future version of this
   document.

3.4.  Device Zone NLRI

   In storage networks, hosts and storage subsystems are generally
   divided into several zones.  Only the devices in the same zone are
   allowed to discover and communicate with each other.

   The Device Zone NLRI is used to distribute the zone configuration of
   a device.  The format of the Device Zone NLRI is shown in the
   following figure.

   +------------------+
   |  Router ID       | 4 octets
   +------------------+
   |  IP Address      | 4 or 16 octets
   +------------------+
   |  Zone Name Length| 2 octets
   +------------------+
   |  Zone Name       | variable
   +------------------+

   where:

   o  Router ID: the Router ID of the access switch which originates
      this NLRI, usually the same as the BGP Identifier.

   o  IP Address: the IPv4 or IPv6 Address of a connected device.

   o  Zone Name Length: the length of the following Zone Name field in
      octets.

   o  Zone Name: the name of the zone which the connected device belongs
      to.



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3.5.  Operations

   The source of the NoF NLRI can be a dedicated module which receive
   LLDP messages and maintain the states of directly connected devices.
   For the originator of an NoF NLRI route, BGP receives information
   from relevant module, encapsulates the information into an NoF NLRI
   route, and sends the route to other peers.  For the receiver of an
   NoF NLRI route, BGP extracts the NoF NLRI from the route and sends
   the information to relevant module.

   The NoF NLRI field may be treated as an opaque hexadecimal string,
   depending on the implementation.

4.  IANA Considerations

   TBD.

5.  Security Considerations

   TBD.

6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <https://www.rfc-editor.org/info/rfc4271>.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              DOI 10.17487/RFC4760, January 2007,
              <https://www.rfc-editor.org/info/rfc4760>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.








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6.2.  Informative References

   [RFC4456]  Bates, T., Chen, E., and R. Chandra, "BGP Route
              Reflection: An Alternative to Full Mesh Internal BGP
              (IBGP)", RFC 4456, DOI 10.17487/RFC4456, April 2006,
              <https://www.rfc-editor.org/info/rfc4456>.

Authors' Addresses

   Changwang Lin
   H3C

   Email: linchangwang.04414@h3c.com


   Mengxiao Chen
   H3C

   Email: chen.mengxiao@h3c.com


   Hao Li
   H3C

   Email: lihao@h3c.com


























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