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EVPN Mpls Ping Extension
draft-saum-evpn-lsp-ping-extension-01

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Document	Type	This is an older version of an Internet-Draft whose latest revision state is "Active".
	Authors	Saumya Dikshit , Gyan Mishra , Srinath Rao , Santosh Easale , Ashwini Dahiya
	Last updated	2022-05-30
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draft-saum-evpn-lsp-ping-extension-01

BESS WG S. Dikshit
Internet-Draft Aruba, HPE
Intended status: Standards Track G. Mishra
Expires: 1 December 2022 Verizon Inc.
S. Rao
S. Easale
A. Dahiya
Aruba, HPE
30 May 2022

EVPN Mpls Ping Extension
draft-saum-evpn-lsp-ping-extension-01

Abstract

In an EVPN or any other VPN deployment, there is an urgent need to
tailor the reachability checks of the client nodes via off-box tools
which can be triggered from a remote Overlay end-point or a
centralized controller. There is also a ease of operability needed
when the knowledge known is partial or incomplete. This document
aims to address the limitation in current standards for doing so and
provides solution which can be made standards in future. As an
additional requirement, in network border routers, there are liaison/
dummy VRFs created to leak routes from one network/fabric to another.
There are scenarios wherein an explicit reachability check for these
type of VRFs is not possible with existing mpls-ping mechanisms.
This draft intends to address this as well. Few of missing pieces
are equally applicable to the native lsp ping as well.

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 1 December 2022.

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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 Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.

Table of Contents

1. Important Terms . . . . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements Language . . . . . . . . . . . . . . . . . . . . 3
4. Problem Description . . . . . . . . . . . . . . . . . . . . . 3
4.1. EVPN NLRI is a Complex String . . . . . . . . . . . . . . 4
4.1.1. FEC is a Complex String too . . . . . . . . . . . . . 4
4.2. Partial Validation Support . . . . . . . . . . . . . . . 4
4.3. Reachability to Liaison VRFs . . . . . . . . . . . . . . 5
5. Solution(s) . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1. Wild Card Tlv . . . . . . . . . . . . . . . . . . . . . . 6
5.1.1. Description . . . . . . . . . . . . . . . . . . . . . 7
5.1.2. Processing . . . . . . . . . . . . . . . . . . . . . 7
5.2. Validation Scope Tlv . . . . . . . . . . . . . . . . . . 8
5.2.1. Description . . . . . . . . . . . . . . . . . . . . . 9
5.2.2. Processing . . . . . . . . . . . . . . . . . . . . . 9
5.3. EVI Sub Tlv . . . . . . . . . . . . . . . . . . . . . . . 10
5.3.1. Description . . . . . . . . . . . . . . . . . . . . . 10
6. Backward Compatibility . . . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 11
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
10.1. Normative References . . . . . . . . . . . . . . . . . . 11
10.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12

1. Important Terms

VTEP: Virtual Tunnel End Point or Vxlan Tunnel End Point

RD: Route Distinguisher

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RT: Route Target

LSP: Label Switched Path

LER: Label Edge Router

LSR: Label Switch Router

NLRI: Network Layer Reachability Information

EVPN: Etherenet Virtual Private Network

2. Introduction

In an EVPN or any other VPN deployment, there is an urgent need to
tailor the reachability checks of the client nodes via off-box tools
which can be triggered from a remote Overlay end-point or a
centralized controller and also customize check if the knowledge
known is partial or incomplete. This document aims to address the
limitation in current standards for doing so and provides solution
which can be made standards in future. As an additional requirement,
in network border routers, there are liaison/dummy VRFs created to
leak routes from one network/fabric to another. There are scenarios
wherein an explicit reachability check for these type of VRFs is not
possible with existing mpls-ping mechanisms. This draft intends to
address this as well.

3. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].

When used in lowercase, these words convey their typical use in
common language, and they are not to be interpreted as described in
[RFC2119].

4. Problem Description

This document intends to solve multiple problems, all related to ease
of serviceability, troubleshooting and provisioning. In a nut shell,
the solution eases out the network management of overlay network with
MPLS fabric for network operators and end-users. the following
subsections detail out the problems at hand.

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4.1. EVPN NLRI is a Complex String

For overlays like EVPN, where the NLRI key is complex to remember;
the OAM ping (access) to a NLRI, may be difficult to achieve by
providing the exact prefix key. For example, an EVPN NLRI index
consists of list of following parameters, which typically are
combined to be treated as long string index, comprising of, Route
Type, RD, Ethernet Segment Index (ESI), Ethernet-Tag, IP-prefix, MAC-
IP. Instead it will be easier, if the administrator remembers few or
significant of the above information and remaining can be sent as
wild-card or dont care values. For example, the OAM trigger for LSP-
ping for a host 10.10.10.1 to a remote tunnel endpoint referred by IP
address 1.1.1.1, can be initiated a combination of Route-
Distinguisher, Ethernet Segment Index and Ethernet tag as wild card
values, thus simplifying the OAM procedures.

The complex string problem is generic in nature and is applicable to
other attributes like FEC, thus making this enhancement useful for
underlay mpls ping as well.

4.1.1. FEC is a Complex String too

The complex string is similar to FEC carried in the ping packet. For
example, RSVP IPv4 FEC carries attributes to complete the traffic
engineering tuple index. While remembering the complete information
may not be trivial for the operator. Hence partial information like
Tunnel-ID and Destination IP address may be significant ones which
can achieve the same check.

4.2. Partial Validation Support

The current set of OAM standards are built around validating the co-
relation of control plane and dataplane information. For example,
set of same-prefixes which are published by more than two external
border routers, only one of them may make it to the Routing table of
other routers (receiving these routes).

* The remote OAM check may want to check all the routes published
into the routing table or may want to check all the routes in the
protocol fib.

* This selective mechanism to fetch information is not supported for
Overlays via standard OAM methods.

As mentioned above, the choice of validating control plane and
dataplane for an NLRI ping is not in place in the EVPN( or any
Overlay) OAM specifications [I-D.draft-ietf-bess-evpn-lsp-ping].
When the routing data is huge, and the control plane protocol are in

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the middle of churn, it is difficult to ascertain if the remote
network in remote site is in steady state or not. An overlay ping is
should help validate only the data plane and forgo any control plane
validation, so that the control plane churn is not adding to the CPU
cycles for the routing or OAM entities like processes and daemons
running on the remote vteps.

To extend this problem state further, when admin access to vtep (in a
non-local operator domain) is not possible, control plane information
can be obtained by leveraging the control plane options only. Thus
providing a side-view of the protocol rib on the remote device.

This problem is also generic in nature and not restricted to EVPN or
any other VPN NLRI per-se. Hence equally applicable to underlay or
transport LSPs.

4.3. Reachability to Liaison VRFs

In a typical VPN deployments between branch offices, or a Datacenter
deployment in an enterprise, be it MPLS or Vxlan fabric, the border
routers of the fabric cater to terminating or relaying of multi-
tenancy across fabric. That is, border routers are provisioned with
routing and/or bridging-domains for clients while also extending it
beyond the geography or site. The border routers are provisioned
with stitching of inter-site tunnels/Overlays.

To simplify configuration and provisioning of overlays, a dedicated
VRF is created to ensure all routes learnt from external network
(from various client VRFs) over, lets say, BGP-MPLS L3VPN peering,
can be de-multiplexed or leaked into a single VRF which is leveraged
as a dedicated VRF for learnings from external network. This VRF is
used by the intra fabric constructs as a client VRF. For example, in
a Vxlan fabric, this is vrf is one of the tenant VRFs which a
rightful mapping to EVPN constructs like EVI( for example VNI). This
client VRF does not require any interface configuration, as the
purpose of this VRF is to act as a liaison for the external routes.

Since there is no ip address( layer 3 interface) configured on this
VRF, its not possible to check the state of the VRF on the border
router via OAM methods. The state of VRF can be defined as following

* Working Configuration that is, VRF is operationally and
administratively UP and WORKING

* Network Reachability, that is, VRF is reachable via remote fabric
routers like Vteps or LSR or LER routers

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* Existing OAM tools DO NOT provide enough ammunition to address
this use case.

If there is no route leaked into the VRF, the BR will not form a
tunnel with any other Vtep in the site. Hence an OAM check to reach
out to the VRF will not work even though the VRF is up and working.

5. Solution(s)

The EVPN extension for MPLS OAM is being driven by
[I-D.draft-ietf-bess-evpn-lsp-ping], and does not resolves the
problem mentioned above.

This document proposes a three new TLVs which an Overlay OAM PDU like
mpls ping, that can carry to fill up the gap with the rightful or
optimal information to the remote tunnel end points

* dont care option

* mode of validation

* liaison vrf information.

These PDUs are described for an MPLS EVPN fabric, but can be
generalized for any EVPN fabric per se

* Wild Card List TLV

* Validation TLV

* EVI Sub Tlv

5.1. Wild Card Tlv

The Wild Card Tlv addresses the problem described in section
Section 4.1.

(1) It Carries the information regarding the fields (TLVs or sub
TLVs), which need to be ignored on processing in mpls lsp ping
PDU.

(2) For example, if an OAM ping to a prefix does not requires any RD
(Route-Distinguisher) validation, then RD value, to be carried
in IP prefix TLV; can be indicated as wild-card (dont care).

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* The control-plane validation of the lsp-ping then should
ignore the RD value in the TLV, and respond back as success
even if there is atleast one NLRI which complies with other
attributes (not set as wild card).

5.1.1. Description

The following diagram shows the wild-card list TLV and the following
table, describe the fields, followed by the receive side processing

0 1 2 3 4
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 | Sub-TLV Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bits corresponding to fields in Sub-TLV |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 1: Figure 1: WILD CARD TLV

NOTE: The bitmap for fields is very specific to the sub-tlv. The
assumption is that there are no more than 32 unique fields carried in
mpls ping packet across all sub tlvs. For example, in
[I-D.draft-ietf-bess-evpn-lsp-ping], if for a EVPN MAC Sub-TLV, the
RD is to set as wild card, then the Sub-TLV-Type carries a value 2 as
defined in [RFC7432] and bitmap has 1st bit set indicating the 1st
field of the TLV is RD.

5.1.2. Processing

(1) If the receiving BGP peer does not supports the wild-card list
TLV,

* it ignores the TLV while processing other information carried
in sub-TLVs

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(2) If the receiving BGP peer support wild-card-list TLV but does
not supports the wild-card ignorance of the field for validating
the OAM request

(a) It responds back the error defined in [RFC4379]

(b) The error code which is to be leveraged is '2' which
represent the error: 'One or more of the TLVs was not
understood'.

(3) if the receiving BPG peer supports wild-card list TLV, then,

(a) it extracts the information and maps it to the
corresponding fields in other sub-TLVs as carried in the
OAM message (MPLS LSP ping or any other fabric OAM).

(b) It Ignores the value carried in those fields for performing
Control-plane or Dataplane Validation.

(c) Then, responds back with appropriate messages with errors
or otherwise as described in
[I-D.draft-ietf-bess-evpn-lsp-ping].

5.2. Validation Scope Tlv

The validation Scope TLV addresses the problem mentioned in section
Section 4.2.

(1) It defines the type validation to be done for the OAM mpls ping
PDU at the receiving end before a response can be corroborated
and sent back to the sender

(2) The validation types are defined as follows

(a) Dataplane Validation: Validating the parameters which
matter to the FIB (forwarding information base) or
routing/switching/bridging table

(b) Control Plane Validation: Validating parameters which are
matter to the protocol(s) producing those routes. For
example, validating the carried parameters against the
protocol(s) RIB (routing information base). This operation
can be CPU intensive and can impact the control plane
processing

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(c) Both Control plane and Dataplane Validation: Typically
performed to sanitize the network in a new-installation or
post/pre upgrades when the network is in steady state and
routers/switches in contention are not experiencing
protocol churns.

5.2.1. Description

The following diagram shows the wild-card list TLV and the following
table, describe the fields

0 1 2 3 4
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 | Validation Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 2: Figure 2: Validation Scope TLV

5.2.2. Processing

(1) If the receiving BGP peer does not supports the Validation TLV,

* it ignores the TLV while processing other information carried
in sub-TLVs

* Alternatively, It responds back with the error defined in
[RFC4379],

(2) If the receiving BGP peer does supports the Validation TLV but
does not supports the non-default mode (1 and 2), it does the
validation as described in the standard document, that is the
default mode (both control plane and dataplane validation) in
[I-D.draft-ietf-bess-evpn-lsp-ping].

(3) If receiving side supports Validation TLV and all its modes, it
performs the validation only in the requested mode:

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* Both Control plane and dataplane

* Only Control Plane

* Only Dataplane

5.3. EVI Sub Tlv

The EVI Sub Tlv addresses the issues mentioned in the section
Section 4.3.

This solution proposes a new Object/TLV which carries the EVI
(Virtual Network Identifier) information, thus ensuring that
following tools and/or action-sets can be supported:

(1) Ping or path tracing to check the configuration of an EVI on a
remote Vtep

(2) Ping to check VRF configuration (mapped to an EVI) on remote
Vtep,

* even though no layer-3 configuration is enable against that
VRF

(3) Ping to check VRF configuration (mapped to an EVI) on remote
Vtep,

* For which EVPN tunnel not been provisioned yet

The EVI values carried in the EVI Sub TLV can be user-defined or
derived from underlaying fabric idenfier for the EVI.

* For mpls fabric the EVI values can be MPLS labels (mapped to the
VRFs), whereas,

* For other encapsulations like Vxlan (GUE, Geneve, GPE), the EVI
value should be the VNI (mapped to the VRFs).

5.3.1. Description

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0 1 2 3 4
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 | EVI Identifier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| EVI Identifier (continued) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Type: 1 Octet: Type field can be newly defined as a proprietary one.
Length: 1 Octet: Defines the length of the Value field.
Value: 6 Octets: EVI identifier.

Figure 3: Figure 2: Validation Scope TLV

This TLV aligns generically with any Overlay OAM-ping, agnostic to a
fabric used in the deployment (Vxlan, MPLS, GUE, Geneve, GPE). This
TLV can be integrated into OAM tools of any underlying fabric. For
example, the EVI identifier for MPLS will be 4-octets. Hence length
field will carry '4' as the length.

NOTE: Nil FEC described in [RFC8029], can also be leveraged for the
ping when the underneath fabric is MPLS.

6. Backward Compatibility

Backward Compatibility for non-support nodes is as per the following
standards already defined in [RFC7606], that, BGP speaker should
discard the unsupported TLV types

7. Security Considerations

This document inherits all the security considerations discussed in
[I-D.draft-ietf-bess-evpn-lsp-ping].

8. IANA Considerations

This document inherits all the IANA considerations discussed in
[I-D.draft-ietf-bess-evpn-lsp-ping].

9. Acknowledgements

10. References

10.1. Normative References

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

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10.2. Informative References

[I-D.draft-ietf-bess-evpn-lsp-ping]
Jain, P., "LSP-Ping Mechanisms for EVPN and PBB-EVPN",
Work in Progress, Internet-Draft, 8029, February 2022,
<https://www.ietf.org/archive/id/draft-ietf-bess-evpn-lsp-
ping-07.txt>.

[I-D.draft-tissa-nvo3-oam-fm]
Senevirathne, T., "NVO3 Fault Managemen", Work in
Progress, Internet-Draft, draft-tissa-nvo3-oam-fm-04, May
2017, <https://datatracker.ietf.org/doc/html/draft-tissa-
nvo3-oam-fm-04>.

[RFC4379] Kompella, K., "Detecting Multi-Protocol Label Switched
(MPLS) Data Plane Failures", RFC 4379, February 2006,
<https://www.rfc-editor.org/rfc/rfc4379.html>.

[RFC7348] Mahalingam, M., "Virtual eXtensible Local Area Network
(VXLAN): A Framework for Overlaying Virtualized Layer 2
Networks over Layer 3 Networks", RFC 7348, August 2014,
<http://www.rfc-editor.org/rfc/rfc7348.txt>.

[RFC7432] Sajassi, A., "BGP MPLS-Based Ethernet VPN", RFC 7432,
February 2015,
<http://www.rfc-editor.org/rfc/rfc7432.txt>.

[RFC7606] Chen, E., "Revised Error Handling for BGP UPDATE
Messages", RFC 7606, August 2015,
<https://www.rfc-editor.org/rfc/rfc7606.html>.

[RFC8029] Kompella, K., "Detecting Multi-Protocol Label Switched
(MPLS) Data Plane Failures", RFC 8029, February 2006,
<https://www.rfc-editor.org/rfc/rfc8029.html>.

[RFC9014] Rabadan, J., "Interconnect Solution for Ethernet VPN
(EVPN) Overlay Networks", RFC 9014, May 2021,
<http://www.rfc-editor.org/rfc/rfc9014.txt>.

Authors' Addresses

Saumya Dikshit
Aruba Networks, HPE
Mahadevpura
Bangalore 560 048
Karnataka
India
Email: saumya.dikshit@hpe.com

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Gyan Mishra
Verizon Inc.
Email: gyan.s.mishra@verizon.com

Srinath Rao
Aruba Networks, HPE
Email: srinath.krishnarao@hpe.com

Santosh Easale
Aruba Networks, HPE
Email: santosh.easale@hpe.com

Ashwini Dahiya
Aruba Networks, HPE
Email: ashwini.dahiya@hpe.com

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EVPN Mpls Ping Extension draft-saum-evpn-lsp-ping-extension-01

EVPN Mpls Ping Extension
draft-saum-evpn-lsp-ping-extension-01