Internet DRAFT - draft-hegde-mpls-spring-epe-oam
draft-hegde-mpls-spring-epe-oam
Routing area S. Hegde
Internet-Draft K. Arora
Intended status: Standards Track M. Srivastava
Expires: December 5, 2020 Juniper Networks Inc.
S. Ninan
Individual Contributor
X. Xu
Alibaba Inc.
June 3, 2020
Label Switched Path (LSP) Ping/Traceroute for Segment Routing (SR)
Egress Peer Engineering Segment Identifiers (SIDs) with MPLS Data Planes
draft-hegde-mpls-spring-epe-oam-07
Abstract
Egress Peer Engineering (EPE) is an application of Segment Routing to
Solve the problem of egress peer selection. The Segment Routing
based BGP-EPE solution allows a centralized controller, e.g. a
Software Defined Network (SDN) controller to program any egress peer.
The EPE solution requires a node to program the PeerNode Segment
Identifier(SID) describing a session between two nodes, the PeerAdj
SID describing the link (one or more) that is used by sessions
between peer nodes, and the PeerSet SID describing an arbitrary set
of sessions or links between a local node and its peers. This
document provides new sub-TLVs for EPE Segment Identifiers (SID) that
would be used in the MPLS Target stack TLV (Type 1), in MPLS Ping and
Traceroute procedures.
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
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Internet-Drafts are draft documents valid for a maximum of six months
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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 December 5, 2020.
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Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Theory of Operation . . . . . . . . . . . . . . . . . . . . . 3
3. Requirements Language . . . . . . . . . . . . . . . . . . . . 4
4. FEC Definitions . . . . . . . . . . . . . . . . . . . . . . . 4
4.1. PeerAdj SID Sub-TLV . . . . . . . . . . . . . . . . . . . 4
4.2. PeerNode SID Sub-TLV . . . . . . . . . . . . . . . . . . 6
4.3. PeerSet SID Sub-TLV . . . . . . . . . . . . . . . . . . . 9
5. EPE-SID FEC validation . . . . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
7. Security Considerations . . . . . . . . . . . . . . . . . . . 15
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1. Normative References . . . . . . . . . . . . . . . . . . 15
9.2. Informative References . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
1. Introduction
Egress Peer Engineering (EPE) as defined in
[I-D.ietf-spring-segment-routing-central-epe] is an effective
mechanism to select the egress peer link based on different criteria.
The EPE-SIDs provide means to represent egress peer links. Many
network deployments have built their networks consisting of multiple
Autonomous Systems either for ease of operations or as a result of
network mergers and acquisitons. The inter-AS links connecting the
two Autonomous Systems could be traffic engineered using EPE-SIDs in
this case as well.It is important to be able to validate the control
plane to forwarding plane synchronization for these SIDs so that any
anomaly can be detected easily by the operator.
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+---------+ +------+
| | | |
| H B------D G
| | +---/| AS 2 |\ +------+
| |/ +------+ \ | |---L/8
A AS1 C---+ \| |
| |\\ \ +------+ /| AS 4 |---M/8
| | \\ +-E |/ +------+
| X | \\ | K
| | +===F AS 3 |
+---------+ +------+
Figure 1: Reference Diagram
In this reference diagram, EPE-SIDs are advertised from AS1 to AS2
and AS3. In certain cases the EPE-SIDs advertised by the control
plane may not be in synchronization with label programmed in data-
plane. For example, on C a PeerAdj SID could be advertised to
indicate it is for the link C->D. Due to some software anomaly the
actual data forwarding on this PeerAdj SID could be happening over
C->E link. If E had relevant data paths for further forwarding the
packet, this kind of anomalies will go unnoticed by the operator. A
FEC definition for the EPE-SIDs will define the details of the
control plane association of the SID and the data plane validation of
the SID will be done during the MPLS trace route procedure. When
there is a multi-hop EBGP session between the ASBRs, PeerNode SID is
advertised and traffic would be load-balanced between the interfaces
connecting two nodes. In the reference diagram C and F could have a
PeerNode-SID advertised. When the OAM packet is received on F, it
needs to validate if the packet came on one of the two interfaces
connected to C.
This document provides Target Forwarding Equivalence Class (FEC)
stack TLV definitions for EPE-SIDs. Other procedures for MPLS Ping
and Traceroute as defined in [RFC8287] section 7 and clarified by
[RFC8690] are applicable for EPE-SIDs as well.
2. Theory of Operation
[I-D.ietf-idr-bgpls-segment-routing-epe] provides mechanisms to
advertise the EPE-SIDs in BGP-LS. These EPE-SIDs may be used to
build Segment Routing paths as described in
[I-D.ietf-spring-segment-routing-policy] or using Path Computation
Element Protocol (PCEP) extensions as defined in [RFC8664]. Data
plane monitoring for such paths which consist of EPE-SIDs will use
extensions defined in this document to build the Taget FEC stack TLV.
The MPLS Ping and Traceroute procedures MAY be initaited by the head-
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end of the Segment Routing path or a centralized topology-aware data
plane monitoring system as described in [RFC8403]. The extensions in
[I-D.ietf-spring-segment-routing-policy] and [RFC8664] do not define
the details of the SID and such extensions are out of scope for this
document. The node initiating the data plane monitoring may acquire
the details of EPE-SIDs through BGP-LS advertisements as described in
[I-D.ietf-idr-bgpls-segment-routing-epe]. There may be other
possible mechanisms to learn the definition of the SID from
controller. Details of such mechanisms are out of scope for this
document.
The EPE-SIDs are advertised for inter-AS links which run EBGP
sessions. The procedures to operate EBGP sessions in a scenario with
unnumbered interfaces is not very well defined and hence out of scope
for this document. During AS migration scenario procedures described
in [RFC7705] may be in force. In these scenarios, if the local and
remote AS fields in the FEC as described in Section 4carries the
global AS and not the "local AS" as defined in [RFC7705], the FEC
validation procedures may fail.
3. 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.
4. FEC Definitions
Three new sub-TLVs are defined for the Target FEC Stack TLV (Type 1),
the Reverse-Path Target FEC Stack TLV (Type 16), and the Reply Path
TLV (Type 21).
Sub-Type Sub-TLV Name
-------- ---------------
TBD1 PeerAdj SID Sub-TLV
TBD2 PeerNode SID Sub-TLV
TBD3 PeerSet SID Sub-TLV
Figure 2: New sub-TLV types
4.1. PeerAdj SID Sub-TLV
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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 = TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local AS Number (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote As Number (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local BGP router ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote BGP Router ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface address (4/16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface address (4/16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: PeerAdj SID Sub-TLV
Type : TBD
Length : variable based on IPV4/IPV6 interface address. Length
excludes the length of Type and length field.For IPV4 interface
addresses length will be 24. In case of IPV6 address length will be
48
Local AS Number :
4 octet unsigned integer representing the Member ASN inside the
Confederation.[RFC5065]. The AS number corresponds to the AS to
which PeerAdj SID advertising node belongs to.
Remote AS Number :
4 octet unsigned integer representing the Member ASN inside the
Confederation.[RFC5065]. The AS number corresponds to the AS of the
remote node for which the PeerAdj SID is advertised.
Local BGP Router ID :
4 octet unsigned integer of the advertising node representing the BGP
Identifier as defined in [RFC4271] and [RFC6286].
Remote BGP Router ID :
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4 octet unsigned integer of the receiving node representing the BGP
Identifier as defined in [RFC4271] and [RFC6286].
Local Interface Address :
In case of PeerAdj SID Local interface address corresponding to the
PeerAdj SID should be apecified in this field. For IPV4,this field
is 4 octets; for IPV6, this field is 16 octets. Link Local IPV6
addresses are for further study.
Remote Interface Address :
In case of PeerAdj SID Remote interface address corresponding to the
PeerAdj SID should be apecified in this field. For IPV4,this field
is 4 octets; for IPV6, this field is 16 octets.Link Local IPv6
addresses are for further study.
[I-D.ietf-idr-bgpls-segment-routing-epe] mandates sending local
interface ID and remote interface ID in the Link Descriptors and
allows a value of 0 in the remote descriptors. It is useful to
validate the incoming interface for a OAM packet and if the remote
descriptor is 0 this validation is not possible.
[I-D.ietf-idr-bgpls-segment-routing-epe] allows optional link
descriptors of local and remote interface addresses as described in
section 4.2. This document recommends sending these optional
descriptors and use them to validate incoming interface. When these
local and remote interface addresses are not available, an ingress
node can send 0 in the local and/or remote interface address field.
The receiver SHOULD skip the validation for the incoming interface if
the address field contains 0.
4.2. PeerNode SID Sub-TLV
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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 = TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local AS Number (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote As Number (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local BGP router ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote BGP Router ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| No.of IPV4 interface pairs | No.of IPV6 interface pairs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface address1 (4/16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface address1 (4/16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface address2 (4/16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: PeerNode SID Sub-TLV
Type : TBD
Length : variable based on IPV4/IPV6 interface address. There could
be multiple pairs of local and remote interface pairs. The length
includes all the pairs. Type and Length field are not included in
the actual length carried in the packet.
Local AS Number :
4 octet unsigned integer representing the Member ASN inside the
Confederation.[RFC5065]. The AS number corresponds to the AS to
which PeerNode SID advertising node belongs to.
Remote AS Number :
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4 octet unsigned integer representing the Member ASN inside the
Confederation.[RFC5065]. The AS number corresponds to the AS of the
remote node for which the PeerNode SID is advertised.
Local BGP Router ID :
4 octet unsigned integer of the advertising node representing the BGP
Identifier as defined in [RFC4271] and [RFC6286].
Remote BGP Router ID :
4 octet unsigned integer of the receiving node representing the BGP
Identifier as defined in [RFC4271] and [RFC6286].
Number of IPV4 interface pairs:
Total number of IPV4 local and remote interface address pairs.
Number of IPV6 interface pairs:
Total number of IPV6 local and remote interface address pairs.
There can be multiple Layer 3 interfaces on which a peerNode SID
loadbalances the traffic. All such interfaces local/remote address
MUST be included in the FEC.
When a PeerNode SID load-balances over few interfaces with IPV4 only
address and few interfaces with IPV6 address then the FEC definition
should list all IPV4 address pairs together followed by IPV6 address
pairs.
Local Interface Address :
In case of PeerNode SID, the interface local address IPV4/IPV6 which
corresponds to the PeerNode SID MUST be specified. For IPV4,this
field is 4 octets; for IPV6, this field is 16 octets.Link Local IPV6
addresses are for further study.
Remote Interface Address :
In case of PeerNode SID, the interface remote address IPV4/IPV6 which
corresponds to the PeerNode SID MUST be specified. For IPV4,this
field is 4 octets; for IPV6, this field is 16 octets. Link Local
IPV6 addresses are for further study.
When there is a multi-hop EBGP session between two ASBRs, PeerNode
SID is advertised for this session and traffic can be load balanced
across these interfaces. An EPE controller that does bandiwdth
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management for these links should be aware of the links on which the
traffic will be load-balanced. [I-D.hegde-idr-bgp-ls-epe-inter-as]
provides extensions to advertise attributes that will provide details
of links that the traffic will be load-balanced for a Peer Node SID.
It is useful to validate the incoming interface for an OAM packet
received on a remote ASBR. When the interface information for a
PeerNode SID is not available an ingress node can choose to send 0
pairs of interface addresses in which case, incoming interface
validation SHOULD be skipped by the remote ASBR.
4.3. PeerSet SID Sub-TLV
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 = TBD | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local AS Number (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local BGP router ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| No.of elements in set | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote As Number (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote BGP Router ID (4 octets) |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++
| No.of IPV4 interface pairs | No.of IPV6 interface pairs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface address1 (4/16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface address1 (4/16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface address2 (4/16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
One element in set consists of below details
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote As Number (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote BGP Router ID (4 octets) |
++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++
| No.of IPV4 interface pairs | No.of IPV6 interface pairs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface address1 (4/16 octets) |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface address1 (4/16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ...... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: PeerSet SID Sub-TLV
Type : TBD
Length : variable based on IPV4/IPV6 interface address and number of
elements in the set. The length field does not include the length of
Type and Length fields.
Local AS Number :
4 octet unsigned integer representing the Member ASN inside the
Confederation.[RFC5065]. The AS number corresponds to the AS to
which PeerSet SID advertising node belongs to.
Remote AS Number :
4 octet unsigned integer representing the Member ASN inside the
Confederation.[RFC5065]. The AS number corresponds to the AS of the
remote node for which the PeerSet SID is advertised.
Advertising BGP Router ID :
4 octet unsigned integer of the advertising node representing the BGP
Identifier as defined in [RFC4271] and [RFC6286].
Receiving BGP Router ID :
4 octet unsigned integer of the receiving node representing the BGP
Identifier as defined in [RFC4271] and [RFC6286].
No.of elements in set:
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Number of remote ASes, the set SID load-balances on.
PeerSet SID may be associated with a number of PeerNode SIDs and
PeerAdj SIDs. Link address details of all these SIDs should be
included in the peerSet SID FEC so that the data-plane can be
correctly verified on the remote node.
Number of IPV4 interface pairs:
Total number of IPV4 local and remote interface address pairs.
Number of IPV6 interface pairs:
Total number of IPV6 local and remote interface address pairs.
There can be multiple Layer 3 interfaces on which a peerNode SID
loadbalances the traffic. All such interfaces local/remote address
MUST be included in the FEC.
When a PeerSet SID load-balances over few interfaces with IPV4 only
address and few interfaces with IPV6 address then the Link address
TLV should list all IPV4 address pairs together followed by IPV6
address pairs.
Local Interface Address :
In case of PeerNodeSID/PeerAdj SID, the interface local address IPV4/
IPV6 which corresponds to the PeerNode SID/PeerAdj SID MUST be
specified. For IPV4,this field is 4 octets; for IPV6, this field is
16 octets. Link Local IPV6 addresses are for further study.
Remote Interface Address :
In case of PeerNodeSID/PeerAdj SID, the interface remote address
IPV4/IPV6 which corresponds to the PeerNode SID/PeerAdj SID MUST be
specified. For IPV4,this field is 4 octets; for IPV6, this field is
16 octets. Link Local IPV6 addresses are for further study.
The details on how to obtain interface addresses in described for
PeerAdj SID and PeerNode SID in previous sections and the same is
applicable for PeerSet SID.
5. EPE-SID FEC validation
When a remote ASBR of the EPE-SID advertisement receives the MPLS OAM
packet with top FEC being the EPE-SID, it SHOULD perform validity
checks on the content of the EPE-SID FEC sub-TLV. The basic length
check should be performed on the received FEC.
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PeerAdj SID
-----------
Length = 24 or 48
Peer Node SID
-------------
Length = 20 + "No.of IPv4 interface pairs" * 8 +
"No.of IPv6 interface pairs " * 32
PeerSet SID
-----------
Length = 9 + no.of elements in the set *
(8 + "No.of IPv4 interface pairs" * 8 +
"No.of IPv6 interface pairs " * 32)
Figure 6: Length Validation
If a malformed FEC sub-TLV is received, then a return code of 1,
"Malformed echo request received" as defined in [RFC8029] SHOULD be
sent. The below section augments the section 7.4 of [RFC8287]
4a. Segment Routing EPE-SID Validation:
If the Label-stack-depth is 0 and the Target FEC Stack sub-TLV
at FEC-stack-depth is TBD1 (PeerAdj SID sub-TLV)
Set the Best-return-code to 10, "Mapping for this FEC is not
the given label at stack-depth if any below
conditions fail:
o Validate that the Receiving Node BGP Local AS matches
with the remote AS field in the received PeerAdj SID
FEC sub-TLV.
o Validate that the Receiving Node BGP Router-ID matches
with the Remote Router ID field in the received
PeerAdj SID FEC.
o Validate that there is a EBGP session with a peer
having local As number and BGP Router-ID as
specified in the Local AS number and Local Router-ID
field in the received PeerAdj SID FEC sub-TLV.
If the Remote interface address is not zero, validate the
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incoming interface.
Set the Best-return-code to 35 "Mapping for this FEC is not
associated with the incoming interface" (RFC8287) if any below
conditions fail:
o Validate the incoming interface on which the OAM packet
was receieved, matches with the remote interface
specified in the PeerAdj SID FEC sub-TLV
If all above validations have passed, set the return code to 3
"Replying router is an egress for the FEC at stack-depth"
Else, if the Target FEC sub-TLV at FEC-stack-depth is TBD2
(PeerNode SID sub-TLV),
Set the Best-return-code to 10, "Mapping for this FEC is not
the given label at stack-depth if any below
conditions fail:
o Validate that the Receiving Node BGP Local AS matches with
the remote AS field in the
received PeerNode SID FEC sub-TLV.
o Validate that the Receiving Node BGP Router-ID matches
with the Remote Router ID field in the received
PeerNode SID FEC.
o Validate that there is a EBGP session with a peer
having local As number and BGP Router-ID as
specified in the Local AS number and Local Router-ID
field in the received PeerNode SID FEC sub-TLV.
If the Remote interface address is not zero, validate the
incoming interface.
Set the Best-return-code to 35 "Mapping for this FEC is not
associated with the incoming interface" (RFC8287) if any below
conditions fail:
o Validate the incoming interface on which the OAM packet
was receieved, matches with the any of the
remote interfaces specified in the PeerNode SID FEC sub-TLV
If all above validations have passed, set the return code to 3
"Replying router is an egress for the FEC at stack-depth"
Else, if the Target FEC sub-TLV at FEC-stack-depth is TBD3
(PeerSet SID sub-TLV),
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Set the Best-return-code to 10, "Mapping for this FEC is not
the given label at stack-depth" if any below
conditions fail:
o Validate that the Receiving Node BGP Local AS matches
with one of the remote AS field in the received PeerSet
SID FEC sub-TLV.
o Validate that the Receiving Node BGP Router-ID matches
with one of the Remote Router ID field in the received
PeerSet SID FEC sub-TLV.
o Validate that there is a EBGP session with a peer having
local As number and BGP Router-ID as
specified in the Local AS number and Local Router-ID
field in the received PeerSet SID FEC sub-TLV.
If the Remote interface address is not zero, validate the
incoming interface.
Set the Best-return-code to 35 "Mapping for this FEC is not
associated with the incoming interface" (RFC8287) if any below
conditions fail:
o Validate the incoming interface on which the OAM packet
was receieved, matches with the any of the
remote interfaces specified in the PeerSet SID FEC sub-TLV
If all above validations have passed, set the return code to 3
"Replying router is an egress for the FEC at stack-depth"
Figure 7: EPE-SID FEC validiation
6. IANA Considerations
New Target FEC stack sub-TLV from the "sub-TLVs for TLV types 1,16
and 21" subregistry of the "Multi-Protocol Label switching (MPLS)
Label Switched Paths (LSPs) Ping parameters" registry
PeerAdj SID Sub-TLV : TBD1
PeerNode SID Sub-TLV: TBD2
PeerSet SID Sub-TLV : TBD3
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7. Security Considerations
The EPE-SIDs are advertised for egress links for Egress Peer
Engineering purposes or for inter-As links between co-operating ASes.
When co-operating domains are involved, they can allow the packets
arriving on trusted interfaces to reach the control plane and get
processed. When EPE-SIDs which are created for egress TE links where
the neighbor AS is an independent entity, it may not allow packets
arriving from external world to reach the control plane. In such
deployments MPLS OAM packets will be dropped by the neighboring AS
that receives the MPLS OAM packet. In MPLS traceroute applications,
when the AS boundary is crossed with the EPE-SIDs, the FEC stack is
changed. [RFC8287] does not mandate that the initiator upon
receiving an MPLS Echo Reply message that includes the FEC Stack
Change TLV with one or more of the original segments being popped
remove a corresponding FEC(s) from the Target FEC Stack TLV in the
next (TTL+1) traceroute request. If an initiator does not remove the
FECs belonging to the previous AS that has traversed, it MAY expose
the internal AS information to the following AS being traversed in
traceroute.
8. Acknowledgments
Thanks to Loa Andersson, Dhruv Dhody, Ketan Talaulikar, Italo Busi
and Alexander Vainshtein for careful review and comments.
9. References
9.1. Normative References
[I-D.hegde-idr-bgp-ls-epe-inter-as]
Hegde, S., Ramachandra, S., Srivastava, M., and X. Xu,
"BGP-LS Extensions for Inter-AS TE using EPE based
mechanisms", draft-hegde-idr-bgp-ls-epe-inter-as-03 (work
in progress), June 2020.
[I-D.ietf-idr-bgpls-segment-routing-epe]
Previdi, S., Talaulikar, K., Filsfils, C., Patel, K., Ray,
S., and J. Dong, "BGP-LS extensions for Segment Routing
BGP Egress Peer Engineering", draft-ietf-idr-bgpls-
segment-routing-epe-19 (work in progress), May 2019.
[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>.
Hegde, et al. Expires December 5, 2020 [Page 15]
Internet-Draft EPE-OAM June 2020
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017,
<https://www.rfc-editor.org/info/rfc8029>.
[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>.
[RFC8287] Kumar, N., Ed., Pignataro, C., Ed., Swallow, G., Akiya,
N., Kini, S., and M. Chen, "Label Switched Path (LSP)
Ping/Traceroute for Segment Routing (SR) IGP-Prefix and
IGP-Adjacency Segment Identifiers (SIDs) with MPLS Data
Planes", RFC 8287, DOI 10.17487/RFC8287, December 2017,
<https://www.rfc-editor.org/info/rfc8287>.
[RFC8690] Nainar, N., Pignataro, C., Iqbal, F., and A. Vainshtein,
"Clarification of Segment ID Sub-TLV Length for RFC 8287",
RFC 8690, DOI 10.17487/RFC8690, December 2019,
<https://www.rfc-editor.org/info/rfc8690>.
9.2. Informative References
[I-D.ietf-spring-segment-routing-central-epe]
Filsfils, C., Previdi, S., Dawra, G., Aries, E., and D.
Afanasiev, "Segment Routing Centralized BGP Egress Peer
Engineering", draft-ietf-spring-segment-routing-central-
epe-10 (work in progress), December 2017.
[I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture", draft-
ietf-spring-segment-routing-policy-07 (work in progress),
May 2020.
[RFC7705] George, W. and S. Amante, "Autonomous System Migration
Mechanisms and Their Effects on the BGP AS_PATH
Attribute", RFC 7705, DOI 10.17487/RFC7705, November 2015,
<https://www.rfc-editor.org/info/rfc7705>.
[RFC8403] Geib, R., Ed., Filsfils, C., Pignataro, C., Ed., and N.
Kumar, "A Scalable and Topology-Aware MPLS Data-Plane
Monitoring System", RFC 8403, DOI 10.17487/RFC8403, July
2018, <https://www.rfc-editor.org/info/rfc8403>.
Hegde, et al. Expires December 5, 2020 [Page 16]
Internet-Draft EPE-OAM June 2020
[RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "Path Computation Element Communication
Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
DOI 10.17487/RFC8664, December 2019,
<https://www.rfc-editor.org/info/rfc8664>.
Authors' Addresses
Shraddha Hegde
Juniper Networks Inc.
Exora Business Park
Bangalore, KA 560103
India
Email: shraddha@juniper.net
Kapil Arora
Juniper Networks Inc.
Email: kapilaro@juniper.net
Mukul Srivastava
Juniper Networks Inc.
Email: msri@juniper.net
Samson Ninan
Individual Contributor
Email: samson.cse@gmail.com
Xiaohu Xu
Alibaba Inc.
Beijing
China
Email: xiaohu.xxh@alibaba-inc.com
Hegde, et al. Expires December 5, 2020 [Page 17]
