Version Capability for BGP
draft-abraitis-bgp-version-capability-06

Network Working Group                                        D. Abraitis
Internet-Draft                                                 Hostinger
Intended status: Informational                           August 14, 2020
Expires: February 15, 2021

                       Version Capability for BGP
                draft-abraitis-bgp-version-capability-06

Abstract

   In this document, we introduce a new BGP capability that allows the
   advertisement of a BGP speaker's routing daemon version.

   This BGP capability is an optional advertisement.  Implementations
   are not required to advertise the version nor to process received
   advertisements.

Status of This Memo

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   This Internet-Draft will expire on February 15, 2021.

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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
   2.  Specification of Requirements . . . . . . . . . . . . . . . .   2
   3.  Version Capability  . . . . . . . . . . . . . . . . . . . . .   3
     3.1.  Capabilities Length Overflow  . . . . . . . . . . . . . .   4
   4.  Operation . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.1.  Example Usage . . . . . . . . . . . . . . . . . . . . . .   5
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   In modern data center designs, we tend to have conventional routers
   participating in the routing process.  And the fleet of routers has
   different versions of routing daemon.  This means that knowing which
   versions of the routing daemons are running the various routers in
   the network can be a crucial factor in quickly identifying the root
   cause of any protocol or network problems.

   This BGP capability is an optional advertisement.  Implementations
   are not required to advertise the version nor to process received
   advertisements.

   Information about the version of the routing daemon could also be
   exchanged in protocols such as LLDP and CDP.  However, in
   containerized environments, it is very hard and not recommended to
   exchange this information between background processes.  Therefore,
   and to help minimize operational costs, it is helpful to exchange the
   routing daemon information between BGP peers directly.

2.  Specification of Requirements

   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.

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3.  Version Capability

   Capabilities advertisements with BGP are defined in [RFC5492].  They
   utilize the BGP Capabilities Optional Parameter that contains one or
   more triples <Capability Code, Capability Length, Capability Value>.
   This document defines a new BGP capability, the Version Capability,
   with Capability Code TBD and Capability Length and Capability Value
   as described below.

   The inclusion of the Version Capability is OPTIONAL.  If an
   implementation supports the inclusion of the capability, the
   implementation MUST include a configuration switch to enable or
   disable its use, and that switch MUST be off by default.

   The Version Capability is intended principally more to non-production
   environments where more visibility is needed for troubleshooting
   purposes.  It is NOT RECOMMENDED for use outside single Autonomous
   System domain or Autonomous System Confederations, except you have a
   topology with a number of routers each with a separate Autonomous
   Number.

   An implementation that does not recognize or support the Version
   Capability but which receives one MUST respond as described in
   [RFC5492] by ignoring the option.  An implementation that wishes to
   complain that its neighbor does not support the Version Capability
   MAY use the 'Unsupported Capability' Error Subcode of a Notification
   message as described in [RFC5492].

   The triple for the Version Capability is as follows:

   Capability Code

      TBD by IANA

   Capability Length

      The Capability Length for the Version Capability MUST be greater
      than zero.  A value of zero SHALL be treated as an encoding error
      and the entire triple MUST be ignored.

      The Capability Length SHOULD be no greater than 64.  This is the
      limit to allow other capabilities as much space as they require.

   Capability Value

      The Capability Value field is encoded in UTF-8 [RFC3629].  It is
      unstructured data and can be formatted in any way that the
      implementor decides.

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                   +--------------------------------+
                   |    Version Length (1 octet)    |
                   +--------------------------------+
                   |      Version (variable)        |
                   +--------------------------------+

                                 Figure 1

   Version Length:

      The number of characters in the Version

   Version:

      The Version encoded via UTF-8

3.1.  Capabilities Length Overflow

   As defined in [RFC5492] the total length of capabilities that can be
   carried by the BGP Capabilities Optional Parameter is 255 bytes.  If
   an implementation is constructing a BGP Capabilities Optional
   Parameter and its length exceeds 255 bytes, it is RECOMMENDED to
   exclude the Version Capability.  An implementation may optimally
   achieve this by making the Version Capability the last capability
   triple to add to the Parameter, and only adding it if there is
   sufficient space to do so.

4.  Operation

   The Version Capability MUST only be used for displaying the version
   of a BGP speaker's router daemon to make troubleshooting easier.

   Consider a group of routers each with a number of upstream nodes, and
   suppose that each router has a different operating system and
   different routing daemon at a different version installed.  Assuming
   that a specific feature is not working or that there is a bug which
   has not been fixed in a particular version of the code, knowledge of
   the routing daemon versions would allow an operator to quickly
   identify the pattern of which versions are affected.

   Enabling (i.e., turning on) this capability requires bouncing all
   existing BGP sessions and the feature MUST be explicitly configured
   before an implementation advertizes the Version Capability.

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4.1.  Example Usage

   Below is an example of implementation in [FRRouting] how it looks
   like with version advertised by a BGP sender:

     :~# vtysh -c 'show ip bgp summary failed'
     ...
     Neighbor EstdCnt DropCnt ResetTime Reason
     ens192         3       3  00:00:35 Waiting for peer OPEN (n/a)
     ens224         3       3  00:01:12 Waiting for NHT (FRRouting 7.2)
     eth0           3       3  00:00:14 Neighbor deleted (FRRouting 7.3)
     ...

                                 Figure 2

     :~# vtysh -c 'show ip bgp neighbors 198.51.100.1 json' \
     > | jq '."198.51.100.1".neighborCapabilities.versions'
     {
       "advertisedVersion": "FRRouting 7.2-dev-MyOwnFRRVersion",
       "receivedVersion": "FRRouting 7.2-dev-MyOwnFRRVersion-gc68bb14"
     }

                                 Figure 3

5.  IANA Considerations

   IANA maintains the "Border Gateway Protocol (BGP) Parameters"
   registry with a subregistry called "Capabilities Codes".  IANA is
   requested to assign a capability number from the First Come First
   Served range for the Version Capability in this document as follows:

                +-------+--------------------+------------+
                | Value |    Description     | Reference  |
                +-------+--------------------+------------+
                |  TBD  | Version Capability | [This.I-D] |
                +-------+--------------------+------------+

                        Table 1: Version Capability

6.  Security Considerations

   The Version Capability should be treated as sensitive information: it
   could be easier for an attacker to exploit the system if they know
   the specific version of a BGP speaker.  This information could be
   gathered by inspecting BGP OPEN messages that carry the Version
   Capability defined in this document.  Using encryption to protect the
   information exchanged in BGP sessions SHOULD, therefore, be carefully

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   considered when this feature is enabled.  Suitable encryption can be
   achieved by protecting the BGP session using TLS [RFC5246].

   Furthermore, knowledge of which versions of code is running on a
   given router and from which vendor it comes may facilitate a number
   of social-engineering attacks.  This further adds to the desire to
   protect this information through encryption.

   Modifying the information advertised by a router might lead to
   attacks including bogus software upgrades and also might mask the
   causes of faults in the network.  This can be mitigated by protecting
   the BGP session using TLS.

   Many BGP implementations leave TCP port 179 open in order to be able
   to establish sessions with new neighbors.  This could lead to an
   attack where a rogue BGP implementation attempts to open a session
   and learns the version information from the responding peer.

   The Version Capability MUST be configurable with a vendor-specific
   knob to be able to enable or disable the capability.  The vendor
   might implement to disable this capability per neighbor.

   It would be safe to enable this for iBGP or inside the same tenant
   where you have full control and the BGP speaker is behind the exit
   points.

   This capability is NOT RECOMMENDED for eBGP use.

   Sensitive information leaks can be minimized by using the [RFC5082]
   mechanism or firewalls to filter out TCP 179 port from untrusted
   networks.  This capability can be disabled per neighbor, thus the
   sensitive information can't be disclosed to untrusted neighbors.

7.  References

7.1.  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>.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
              2003, <https://www.rfc-editor.org/info/rfc3629>.

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   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

7.2.  Informative References

   [FRRouting]
              Abraitis, D., "FRRouting - BGP Version Capability", 2019,
              <https://github.com/ton31337/frr/
              commit/4c566878fd1a7df9f8c84ee03f419c0b00ae444b>.

   [RFC3552]  Rescorla, E. and B. Korver, "Guidelines for Writing RFC
              Text on Security Considerations", BCP 72, RFC 3552,
              DOI 10.17487/RFC3552, July 2003,
              <https://www.rfc-editor.org/info/rfc3552>.

Author's Address

   Donatas Abraitis
   Hostinger
   Jonavos g. 60C
   Kaunas  44192
   LT

   Phone: +370 614 18958
   Email: donatas.abraitis@hostinger.com

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