draft-ietf-6man-spring-srv6-oam-05.txt   draft-ietf-6man-spring-srv6-oam-06.txt 
6man Z. Ali 6man Z. Ali
Internet-Draft C. Filsfils Internet-Draft C. Filsfils
Intended status: Standards Track Cisco Systems Intended status: Standards Track Cisco Systems
Expires: December 14, 2020 S. Matsushima Expires: January 14, 2021 S. Matsushima
Softbank Softbank
D. Voyer D. Voyer
Bell Canada Bell Canada
M. Chen M. Chen
Huawei Huawei
June 12, 2020 July 13, 2020
Operations, Administration, and Maintenance (OAM) in Segment Routing Operations, Administration, and Maintenance (OAM) in Segment Routing
Networks with IPv6 Data plane (SRv6) Networks with IPv6 Data plane (SRv6)
draft-ietf-6man-spring-srv6-oam-05 draft-ietf-6man-spring-srv6-oam-06
Abstract Abstract
This document describes how the existing IPv6 OAM mechanisms can be This document describes how the existing IPv6 OAM mechanisms can be
used in an SRv6 network. The document also introduces enhancements used in an SRv6 network. The document also introduces enhancements
for controller-based OAM mechanisms for SRv6 networks. for OAM mechanisms for SRv6 networks.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 14, 2020. This Internet-Draft will expire on January 14, 2021.
Copyright Notice Copyright Notice
Copyright (c) 2020 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 18 skipping to change at page 2, line 18
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
1.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
1.3. Terminology and Reference Topology . . . . . . . . . . . 3 1.3. Terminology and Reference Topology . . . . . . . . . . . 3
2. OAM Mechanisms . . . . . . . . . . . . . . . . . . . . . . . 5 2. OAM Mechanisms . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. O-flag in Segment Routing Header . . . . . . . . . . . . 5 2.1. O-flag in Segment Routing Header . . . . . . . . . . . . 5
2.1.1. O-flag Processing . . . . . . . . . . . . . . . . . . 6 2.1.1. O-flag Processing . . . . . . . . . . . . . . . . . . 5
2.2. OAM Operations . . . . . . . . . . . . . . . . . . . . . 7
3. Illustrations . . . . . . . . . . . . . . . . . . . . . . . . 7 3. Illustrations . . . . . . . . . . . . . . . . . . . . . . . . 7
3.1. Ping in SRv6 Networks . . . . . . . . . . . . . . . . . . 7 3.1. Ping in SRv6 Networks . . . . . . . . . . . . . . . . . . 8
3.1.1. Classic Ping . . . . . . . . . . . . . . . . . . . . 7 3.1.1. Classic Ping . . . . . . . . . . . . . . . . . . . . 8
3.1.2. Pinging a SID . . . . . . . . . . . . . . . . . . . . 9 3.1.2. Pinging a SID . . . . . . . . . . . . . . . . . . . . 9
3.2. Traceroute . . . . . . . . . . . . . . . . . . . . . . . 10 3.2. Traceroute . . . . . . . . . . . . . . . . . . . . . . . 10
3.2.1. Classic Traceroute . . . . . . . . . . . . . . . . . 10 3.2.1. Classic Traceroute . . . . . . . . . . . . . . . . . 10
3.2.2. Traceroute to a SID . . . . . . . . . . . . . . . . . 11 3.2.2. Traceroute to a SID . . . . . . . . . . . . . . . . . 12
3.3. A Controller-Based Hybrid OAM Using O-flag . . . . . . . 13 3.3. A Hybrid OAM Using O-flag . . . . . . . . . . . . . . . . 13
3.4. Monitoring of SRv6 Paths . . . . . . . . . . . . . . . . 15 3.4. Monitoring of SRv6 Paths . . . . . . . . . . . . . . . . 16
4. Implementation Status . . . . . . . . . . . . . . . . . . . . 16 4. Implementation Status . . . . . . . . . . . . . . . . . . . . 17
5. Security Considerations . . . . . . . . . . . . . . . . . . . 16 5. Security Considerations . . . . . . . . . . . . . . . . . . . 17
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
6.1. Segment Routing Header Flags . . . . . . . . . . . . . . 17 6.1. Segment Routing Header Flags . . . . . . . . . . . . . . 17
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.1. Normative References . . . . . . . . . . . . . . . . . . 18 9.1. Normative References . . . . . . . . . . . . . . . . . . 19
9.2. Informative References . . . . . . . . . . . . . . . . . 18 9.2. Informative References . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21
1. Introduction 1. Introduction
As Segment Routing with IPv6 data plane (SRv6) simply adds a new type As Segment Routing with IPv6 data plane (SRv6) [RFC8402] simply adds
of Routing Extension Header, existing IPv6 OAM mechanisms can be used a new type of Routing Extension Header, existing IPv6 OAM mechanisms
in an SRv6 network. This document describes how the existing IPv6 can be used in an SRv6 network. This document describes how the
mechanisms for ping and trace route can be used in an SRv6 network. existing IPv6 mechanisms for ping and trace route can be used in an
SRv6 network.
The document also introduces enhancements for controller-based OAM The document also introduces enhancements for OAM mechanism for SRv6
mechanism for SRv6 networks. Specifically, the document describes an networks. Specifically, the document describes an OAM mechanism for
OAM mechanism for performing controllable and predictable flow performing controllable and predictable flow sampling from segment
sampling from segment endpoints using, e.g., IP Flow Information endpoints using, e.g., IP Flow Information Export (IPFIX) protocol
Export (IPFIX) protocol [RFC7011]. The document also outlines how
centralized OAM technique in [RFC8403] can be extended for SRv6 to [RFC7011]. The document also outlines how centralized OAM technique
perform a path continuity check between any nodes within an SRv6 in [RFC8403] can be extended for SRv6 to perform a path continuity
domain from a centralized monitoring system, with minimal or no check between any nodes within an SRv6 domain from a centralized
control plane intervene on the nodes. monitoring system.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119], [RFC8174]. document are to be interpreted as described in [RFC2119], [RFC8174].
1.2. Abbreviations 1.2. Abbreviations
The following abbreviations are used in this document: The following abbreviations are used in this document:
SID: Segment ID. SID: Segment ID.
SL: Segments Left. SL: Segments Left.
SR: Segment Routing. SR: Segment Routing.
SRH: Segment Routing Header. SRH: Segment Routing Header [RFC8754].
SRv6: Segment Routing with IPv6 Data plane. SRv6: Segment Routing with IPv6 Data plane.
TC: Traffic Class. TC: Traffic Class.
ICMPv6: ICMPv6 Specification [RFC4443]. ICMPv6: ICMPv6 Specification [RFC4443].
1.3. Terminology and Reference Topology 1.3. Terminology and Reference Topology
This document uses the terminology defined in [I-D.ietf- spring-srv6- Throughout the document, the following terminology and simple
network-programming]. The readers are expected to be familiar with topology is used for illustration.
the same.
Throughout the document, the following simple topology is used for
illustration.
+--------------------------| N100 |---------------------------------+ +--------------------------| N100 |---------------------------------+
| | | |
| ====== link1====== link3------ link5====== link9------ ====== | | ====== link1====== link3------ link5====== link9------ ====== |
||N1||------||N2||------| N3 |------||N4||------| N5 |---||N7|| ||N1||------||N2||------| N3 |------||N4||------| N5 |---||N7||
|| ||------|| ||------| |------|| ||------| |---|| || || ||------|| ||------| |------|| ||------| |---|| ||
====== link2====== link4------ link6======link10------ ====== ====== link2====== link4------ link6======link10------ ======
| | | | | | | |
---+-- | ------ | --+--- ---+-- | ------ | --+---
|CE 1| +-------| N6 |---------+ |CE 2| |CE 1| +-------| N6 |---------+ |CE 2|
------ link7 | | link8 ------ ------ link7 | | link8 ------
------ ------
Figure 1 Reference Topology Figure 1 Reference Topology
In the reference topology: In the reference topology:
Node k has a classic IPv6 loopback address 2001:DB8:A:k::/128. Node k has a classic IPv6 loopback address 2001:DB8:A:k::/128.
Nodes N1, N2, and N4 are SRv6 capable nodes. Nodes N1, N2, N4 and N7 are SRv6 capable nodes.
Nodes N3, N5 and N6 are IPv6 nodes that are not SRv6 capable. Nodes N3, N5 and N6 are IPv6 nodes that are not SRv6 capable.
Such nodes are referred as classic IPv6 nodes. Such nodes are referred as classic IPv6 nodes.
CE1 and CE2 are Customer Edge devices of any data plane capability
(e.g., IPv4, IPv6, L2, etc.).
A SID at node k with locator block 2001:DB8:B::/48 and function F A SID at node k with locator block 2001:DB8:B::/48 and function F
is represented by 2001:DB8:B:k:F::. is represented by 2001:DB8:B:k:F::.
Node N100 is a controller. Node N100 is a controller.
The IPv6 address of the nth Link between node X and Y at the X The IPv6 address of the nth Link between node X and Y at the X
side is represented as 2001:DB8:X:Y:Xn::, e.g., the IPv6 address side is represented as 2001:DB8:X:Y:Xn::, e.g., the IPv6 address
of link6 (the 2nd link) between N3 and N4 at N3 in Figure 1 is of link6 (the 2nd link) between N3 and N4 at N3 in Figure 1 is
2001:DB8:3:4:32::. Similarly, the IPv6 address of link5 (the 1st 2001:DB8:3:4:32::. Similarly, the IPv6 address of link5 (the 1st
link between N3 and N4) at node 3 is 2001:DB8:3:4:31::. link between N3 and N4) at node 3 is 2001:DB8:3:4:31::.
2001:DB8:B:k:Cij:: is explicitly allocated as the END.X function 2001:DB8:B:k:Cij:: is explicitly allocated as the END.X SID (refer
at node k towards neighbor node i via jth Link between node i and [I-D.ietf-spring-srv6-network-programming]) at node k towards
node k. e.g., 2001:DB8:B:2:C31:: represents END.X at N2 towards neighbor node i via jth Link between node i and node k. e.g.,
N3 via link3 (the 1st link between N2 and N3). Similarly, 2001:DB8:B:2:C31:: represents END.X at N2 towards N3 via link3
2001:DB8:B:4:C52:: represents the END.X at N4 towards N5 via (the 1st link between N2 and N3). Similarly, 2001:DB8:B:4:C52::
link10. represents the END.X at N4 towards N5 via link10.
A SID list is represented as <S1, S2, S3> where S1 is the first A SID list is represented as <S1, S2, S3> where S1 is the first
SID to visit, S2 is the second SID to visit and S3 is the last SID SID to visit, S2 is the second SID to visit and S3 is the last SID
to visit along the SR path. to visit along the SR path.
(SA,DA) (S3, S2, S1; SL)(payload) represents an IPv6 packet with: (SA,DA) (S3, S2, S1; SL)(payload) represents an IPv6 packet with:
* IPv6 header with source address SA, destination addresses DA * IPv6 header with source address SA, destination addresses DA
and SRH as next-header and SRH as next-header
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The document does not define any other flag in the SRH.Flags and The document does not define any other flag in the SRH.Flags and
meaning and processing of any other bit in SRH.Flags is outside of meaning and processing of any other bit in SRH.Flags is outside of
the scope of this document. the scope of this document.
2.1.1. O-flag Processing 2.1.1. O-flag Processing
The O-flag in SRH is used as a marking-bit in the user packets to The O-flag in SRH is used as a marking-bit in the user packets to
trigger the telemetry data collection and export at the segment trigger the telemetry data collection and export at the segment
endpoints. endpoints.
Without the loss of generality, this document assumes IP Flow This document does not specify the data elements that needs to be
Information Export (IPFIX) protocol [RFC7011] is used for exporting exported and the associated configurations. Similarly, this document
the traffic flow information from the network devices to a controller does not define any formats for exporting the data elements.
for monitoring and analytics. The requested information elements are Nonetheless, without the loss of generality, this document assumes IP
configured by the management plane through data set templates (e.g., Flow Information Export (IPFIX) protocol [RFC7011] is used for
as in IPFIX [RFC7012]). exporting the traffic flow information from the network devices to a
controller for monitoring and analytics. Similarly, without the loss
of generality, this document assumes requested information elements
are configured by the management plane through data set templates
(e.g., as in IPFIX [RFC7012]).
Implementation of the O-flag is OPTIONAL. If a node does not support Implementation of the O-flag is OPTIONAL. If a node does not support
the O-flag, then upon reception it simply ignores it. If a node the O-flag, then upon reception it simply ignores it. If a node
supports the O-flag, it can optionally advertise its potential via supports the O-flag, it can optionally advertise its potential via
control plan protocol(s). control plan protocol(s).
When N receives a packet whose IPv6 DA is S and S is a local SID, the When N receives a packet whose IPv6 DA is S and S is a local SID, the
line S01 of the pseudo-code associated with the SID S, as defined in line S01 of the pseudo-code associated with the SID S, as defined in
section 4.3.1.1 of [RFC8754], is modified as follows for the O-flag section 4.3.1.1 of [RFC8754], is modified as follows for the O-flag
processing. processing.
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advertised by the egress node. advertised by the egress node.
The processing node SHOULD rate-limit the number of packets punted to The processing node SHOULD rate-limit the number of packets punted to
the OAM process to avoid hitting any performance impact. the OAM process to avoid hitting any performance impact.
The OAM process MUST NOT process the copy of the packet or respond to The OAM process MUST NOT process the copy of the packet or respond to
any upper-layer header (like ICMP, UDP, etc.) payload to prevent any upper-layer header (like ICMP, UDP, etc.) payload to prevent
multiple evaluations of the datagram. multiple evaluations of the datagram.
Specification of the OAM process or the external controller Specification of the OAM process or the external controller
operations are beyond the scope of this document. section 3 operations are beyond the scope of this document. How to correlate
illustrates use of the SRH.Flags.O-flag for implementing a the data collected from different nodes at an external controller is
controller-based hybrid OAM mechanism, where the "hybrid" also outside the scope of the document. Section 3 illustrates use of
classification is based on RFC7799 [RFC7799]. The illustration is the SRH.Flags.O-flag for implementing a hybrid OAM mechanism, where
different than the In-situ OAM defined in [I.D-draft-ietf-ippm-ioam- the "hybrid" classification is based on RFC7799 [RFC7799].
data]. This is because In-situ OAM records operational and telemetry
information in the packet as the packet traverses a path between two 2.2. OAM Operations
points in the network [I.D-draft-ietf- ippm-ioam-data]. The
controller-based OAM mechanism using O-flag illustration in section 3 IPv6 OAM operations can be performed for any SRv6 SID whose behavior
does not require the recording of OAM data in the packet. allows Upper Layer Header processing for an applicable OAM payload
(e.g., ICMP, UDP).
Ping to a SID is used for SID connectivity checks and to validate the
availability of a SID. Traceroute to a SID is used for hop-by-hop
fault localization as well as path tracing to a SID. Section 3
illustrates the ICMPv6 based ping and the UDP based traceroute
mechanisms for ping and traceroute to an SRv6 SID. Although this
document only illustrates ICMP ping and UDP-based traceroute to an
SRv6 SID, the procedures are equally applicable to other IPv6 OAM
probing to an SRv6 SID (e.g., Bidirectional Forwarding Detection
(BFD) [RFC5880], Seamless BFD (SBFD) [RFC7880], Two-Way Active
Measurement Protocol (TWAMP) [RFC5357], Simple Two-Way Active
Measurement Protocol (STAMP) [RFC8762], etc.). Specifically, as long
as local configuration allows the Upper-layer Header processing of
the applicable OAM payload for SRv6 SIDs, the existing IPv6 OAM
techniques can be used to target a probe to a (remote) SID.
IPv6 OAM operations can be performed with the target SID in the IPv6
destination address without SRH or with SRH where the target SID is
the last segment. In general, OAM operations to a target SID may not
exercise all of its processing depending on its behavior definition.
For example, ping to an END.X SID (refer [I-D.ietf-spring-srv6-
network-programming]) at the target node only validates availability
of the SID and does not validate switching to the correct outgoing
interface. To exercise the behavior of a target SID, the OAM
operation SHOULD construct the probe in a manner similar to a data
packet that exercises the SID behavior, i.e. to include that SID as a
transit SID in either an SRH or IPv6 DA of an outer IPv6 header or as
appropriate based on the definition of the SID behavior.
3. Illustrations 3. Illustrations
This section shows how some of the existing IPv6 OAM mechanisms can This section shows how some of the existing IPv6 OAM mechanisms can
be used in an SRv6 network. It also illustrates an OAM mechanism for be used in an SRv6 network. It also illustrates an OAM mechanism for
performing controllable and predictable flow sampling from segment performing controllable and predictable flow sampling from segment
endpoints. How centralized OAM technique in [RFC8403] can be endpoints. How centralized OAM technique in [RFC8403] can be
extended for SRv6 is also described in this Section. extended for SRv6 is also described in this Section.
3.1. Ping in SRv6 Networks 3.1. Ping in SRv6 Networks
The following subsections outline some use cases of the ICMP ping in The following subsections outline some use cases of the ICMP ping in
the SRv6 networks. the SRv6 networks.
3.1.1. Classic Ping 3.1.1. Classic Ping
The existing mechanism to query liveliness of a remote IP address, The existing mechanism to perform the connectivity checks, along the
along the shortest path, continues to work without any modification. shortest path, continues to work without any modification. The
The initiator may be an SRv6 node or a classic IPv6 node. Similarly, initiator may be an SRv6 node or a classic IPv6 node. Similarly, the
the egress or transit may be an SRv6 capable node or a classic IPv6 egress or transit may be an SRv6 capable node or a classic IPv6 node.
node.
If an SRv6 capable ingress node wants to ping an IPv6 address via an If an SRv6 capable ingress node wants to ping an IPv6 address via an
arbitrary segment list <S1, S2, S3>, it needs to initiate ICMPv6 ping arbitrary segment list <S1, S2, S3>, it needs to initiate ICMPv6 ping
with an SR header containing the SID list <S1, S2, S3>. This is with an SR header containing the SID list <S1, S2, S3>. This is
illustrated using the topology in Figure 1. Assume all the links illustrated using the topology in Figure 1. Assume all the links
have IGP metric 10 except both links between node2 and node3, which have IGP metric 10 except both links between node2 and node3, which
have IGP metric set to 100. User issues a ping from node N1 to a have IGP metric set to 100. User issues a ping from node N1 to a
loopback of node 5, via segment list <2001:DB8:B:2:C31::, loopback of node 5, via segment list <2001:DB8:B:2:C31::,
2001:DB8:B:4:C52::>. 2001:DB8:B:4:C52::>. The SID behavior used in the example is End.X
SID (refer [I-D.ietf-spring-srv6-network-programming]) but the
procedure is equally applicable to any other (transit) SID type.
Figure 2 contains sample output for a ping request initiated at node Figure 2 contains sample output for a ping request initiated at node
N1 to the loopback address of node N5 via a segment list N1 to the loopback address of node N5 via a segment list
<2001:DB8:B:2:C31::, 2001:DB8:B:4:C52::>. <2001:DB8:B:2:C31::, 2001:DB8:B:4:C52::>.
> ping 2001:DB8:A:5:: via segment-list 2001:DB8:B:2:C31::, > ping 2001:DB8:A:5:: via segment-list 2001:DB8:B:2:C31::,
2001:DB8:B:4:C52:: 2001:DB8:B:4:C52::
Sending 5, 100-byte ICMP Echos to B5::, timeout is 2 seconds: Sending 5, 100-byte ICMP Echos to B5::, timeout is 2 seconds:
!!!!! !!!!!
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All transit nodes process the echo request message like any other All transit nodes process the echo request message like any other
data packet carrying SR header and hence do not require any change. data packet carrying SR header and hence do not require any change.
Similarly, the egress node (IPv6 classic or SRv6 capable) does not Similarly, the egress node (IPv6 classic or SRv6 capable) does not
require any change to process the ICMPv6 echo request. For example, require any change to process the ICMPv6 echo request. For example,
in the ping example of Figure 2: in the ping example of Figure 2:
o Node N1 initiates an ICMPv6 ping packet with SRH as follows o Node N1 initiates an ICMPv6 ping packet with SRH as follows
(2001:DB8:A:1::, 2001:DB8:B:2:C31::) (2001:DB8:A:5::, (2001:DB8:A:1::, 2001:DB8:B:2:C31::) (2001:DB8:A:5::,
2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::, SL=2, NH = ICMPv6)(ICMPv6 2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::, SL=2, NH = ICMPv6)(ICMPv6
Echo Request). If 2001:DB8:B:4:C52:: is a PSP SID, the OAM probes Echo Request).
encodes the PSP SID in the packet (just mimicking data packets).
No special consideration is needed to handle PSP SIDs.
o Node N2, which is an SRv6 capable node, performs the standard SRH o Node N2, which is an SRv6 capable node, performs the standard SRH
processing. Specifically, it executes the END.X function processing. Specifically, it executes the END.X behavior
(2001:DB8:B:2:C31::) and forwards the packet on link3 to N3. (2001:DB8:B:2:C31::) and forwards the packet on link3 to N3.
o Node N3, which is a classic IPv6 node, performs the standard IPv6 o Node N3, which is a classic IPv6 node, performs the standard IPv6
processing. Specifically, it forwards the echo request based on processing. Specifically, it forwards the echo request based on
the DA 2001:DB8:B:4:C52:: in the IPv6 header. the DA 2001:DB8:B:4:C52:: in the IPv6 header.
o Node N4, which is an SRv6 capable node, performs the standard SRH o Node N4, which is an SRv6 capable node, performs the standard SRH
processing. Specifically, it observes the END.X function processing. Specifically, it observes the END.X behavior
(2001:DB8:B:4:C52::) and forwards the packet on link10 towards N5. (2001:DB8:B:4:C52::) and forwards the packet on link10 towards N5.
If 2001:DB8:B:4:C52:: is a PSP SID, The penultimate node (Node N4) If 2001:DB8:B:4:C52:: is a PSP SID, The penultimate node (Node N4)
does not, should not and cannot differentiate between the data does not, should not and cannot differentiate between the data
packets and OAM probes. Specifically, if 2001:DB8:B:4:C52:: is a packets and OAM probes. Specifically, if 2001:DB8:B:4:C52:: is a
PSP SID, node N4 executes the SID like any other data packet with PSP SID, node N4 executes the SID like any other data packet with
DA = 2001:DB8:B:4:C52:: and removes the SRH. DA = 2001:DB8:B:4:C52:: and removes the SRH.
o The echo request packet at N5 arrives as an IPv6 packet with or o The echo request packet at N5 arrives as an IPv6 packet with or
without an SRH. If N5 receives the packet with SRH, it skips SRH without an SRH. If N5 receives the packet with SRH, it skips SRH
processing (SL=0). In either case, Node N5 performs the standard processing (SL=0). In either case, Node N5 performs the standard
IPv6/ ICMPv6 processing on the echo request. IPv6/ ICMPv6 processing on the echo request.
3.1.2. Pinging a SID 3.1.2. Pinging a SID
The classic ping described in the previous section applies equally to The classic ping described in the previous section applies equally to
ping a remote SID function, as explained using an example in the perform SID connectivity checks and to validate the availability of a
following. remote SID. This is explained using an example in the following.
The example uses ping to an END SID (refer [I-D.ietf-spring-srv6-
network-programming]) but the procedure is equally applicable to ping
any other SID behaviors.
Consider the example where the user wants to ping a remote SID Consider the example where the user wants to ping a remote SID
function 2001:DB8:B:4::, via 2001:DB8:B:2:C31::, from node N1. The 2001:DB8:B:4::, via 2001:DB8:B:2:C31::, from node N1. The ICMPv6
ICMPv6 echo request is processed at the individual nodes along the echo request is processed at the individual nodes along the path as
path as follows: follows:
o Node N1 initiates an ICMPv6 ping packet with SRH as follows o Node N1 initiates an ICMPv6 ping packet with SRH as follows
(2001:DB8:A:1::, 2001:DB8:B:2:C31::) (2001:DB8:B:4::, (2001:DB8:A:1::, 2001:DB8:B:2:C31::) (2001:DB8:B:4::,
2001:DB8:B:2:C31::; SL=1; NH=ICMPv6)(ICMPv6 Echo Request). If 2001:DB8:B:2:C31::; SL=1; NH=ICMPv6)(ICMPv6 Echo Request).
2001:DB8:B:2:C31:: is a PSP SID, the OAM probes encodes the PSP
SID in the packet (just mimicking data packets). No special
consideration is needed to handle PSP SIDs.
o Node N2, which is an SRv6 capable node, performs the standard SRH o Node N2, which is an SRv6 capable node, performs the standard SRH
processing. Specifically, it executes the END.X function processing. Specifically, it executes the END.X behavior
(2001:DB8:B:2:C31::) on the echo request packet. If (2001:DB8:B:2:C31::) on the echo request packet. If
2001:DB8:B:2:C31:: is a PSP SID, node N4 executes the SID like any 2001:DB8:B:2:C31:: is a PSP SID, node N4 executes the SID like any
other data packet with DA = 2001:DB8:B:2:C31:: and removes the other data packet with DA = 2001:DB8:B:2:C31:: and removes the
SRH. SRH.
o Node N3, which is a classic IPv6 node, performs the standard IPv6 o Node N3, which is a classic IPv6 node, performs the standard IPv6
processing. Specifically, it forwards the echo request based on processing. Specifically, it forwards the echo request based on
DA = 2001:DB8:B:4:: in the IPv6 header. DA = 2001:DB8:B:4:: in the IPv6 header.
o When node N4 receives the packet, it processes the 2001:DB8:B:4:: o When node N4 receives the packet, it processes the target SID
SID, as described in the pseudocode in [I-D.ietf-spring-srv6- (2001:DB8:B:4::).
network-programming].
o If the 2001:DB8:B:4:: SID is not locally programmed, the packet is o If the target SID (2001:DB8:B:4::) is not locally instantiated,
discarded the packet is discarded
o If the target SID (2001:DB8:B:4::) is locally programmed, the node o If the target SID (2001:DB8:B:4::) is locally instantiated, the
processes the upper layer header. As part of the upper layer node processes the upper layer header. As part of the upper layer
header processing node N4 respond to the ICMPv6 echo request header processing node N4 respond to the ICMPv6 echo request
message. message.
3.2. Traceroute 3.2. Traceroute
There is no hardware or software change required for traceroute There is no hardware or software change required for traceroute
operation at the classic IPv6 nodes in an SRv6 network. That operation at the classic IPv6 nodes in an SRv6 network. That
includes the classic IPv6 node with ingress, egress or transit roles. includes the classic IPv6 node with ingress, egress or transit roles.
Furthermore, no protocol changes are required to the standard Furthermore, no protocol changes are required to the standard
traceroute operations. In other words, existing traceroute traceroute operations. In other words, existing traceroute
skipping to change at page 10, line 31 skipping to change at page 10, line 48
initiator may be an SRv6 node or a classic IPv6 node. Similarly, the initiator may be an SRv6 node or a classic IPv6 node. Similarly, the
egress or transit may be an SRv6 node or a classic IPv6 node. egress or transit may be an SRv6 node or a classic IPv6 node.
If an SRv6 capable ingress node wants to traceroute to IPv6 address If an SRv6 capable ingress node wants to traceroute to IPv6 address
via an arbitrary segment list <S1, S2, S3>, it needs to initiate via an arbitrary segment list <S1, S2, S3>, it needs to initiate
traceroute probe with an SR header containing the SID list <S1, S2, traceroute probe with an SR header containing the SID list <S1, S2,
S3>. That is illustrated using the topology in Figure 1. Assume all S3>. That is illustrated using the topology in Figure 1. Assume all
the links have IGP metric 10 except both links between node2 and the links have IGP metric 10 except both links between node2 and
node3, which have IGP metric set to 100. User issues a traceroute node3, which have IGP metric set to 100. User issues a traceroute
from node N1 to a loopback of node 5, via segment list from node N1 to a loopback of node 5, via segment list
<2001:DB8:B:2:C31::, 2001:DB8:B:4:C52::>. Figure 3 contains sample <2001:DB8:B:2:C31::, 2001:DB8:B:4:C52::>. The SID behavior used in
output for the traceroute request. the example is End.X SID (refer [I-D.ietf-spring-srv6-network-
programming]) but the procedure is equally applicable to any other
(transit) SID type. Figure 3 contains sample output for the
traceroute request.
> traceroute 2001:DB8:A:5:: via segment-list 2001:DB8:B:2:C31::, > traceroute 2001:DB8:A:5:: via segment-list 2001:DB8:B:2:C31::,
2001:DB8:B:4:C52:: 2001:DB8:B:4:C52::
Tracing the route to 2001:DB8:A:5:: Tracing the route to 2001:DB8:A:5::
1 2001:DB8:1:2:21:: 0.512 msec 0.425 msec 0.374 msec 1 2001:DB8:1:2:21:: 0.512 msec 0.425 msec 0.374 msec
DA: 2001:DB8:B:2:C31::, DA: 2001:DB8:B:2:C31::,
SRH:(2001:DB8:A:5::, 2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::, SL=2) SRH:(2001:DB8:A:5::, 2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::, SL=2)
2 2001:DB8:2:3:31:: 0.721 msec 0.810 msec 0.795 msec 2 2001:DB8:2:3:31:: 0.721 msec 0.810 msec 0.795 msec
DA: 2001:DB8:B:4:C52::, DA: 2001:DB8:B:4:C52::,
skipping to change at page 11, line 34 skipping to change at page 12, line 9
on which probe was received as the source address in the ICMPv6 on which probe was received as the source address in the ICMPv6
response. ICMP extensions defined in [RFC5837] can be used to also response. ICMP extensions defined in [RFC5837] can be used to also
display information about the IP interface through which the datagram display information about the IP interface through which the datagram
would have been forwarded had it been forwardable, and the IP next would have been forwarded had it been forwardable, and the IP next
hop to which the datagram would have been forwarded, the IP interface hop to which the datagram would have been forwarded, the IP interface
upon which a datagram arrived, the sub-IP component of an IP upon which a datagram arrived, the sub-IP component of an IP
interface upon which a datagram arrived. interface upon which a datagram arrived.
The information about the IP address of the incoming interface on The information about the IP address of the incoming interface on
which the traceroute probe was received by the reporting node is very which the traceroute probe was received by the reporting node is very
useful. This information can also be used to verify if SID functions useful. This information can also be used to verify if SIDs
2001:DB8:B:2:C31:: and 2001:DB8:B:4:C52:: are executed correctly by 2001:DB8:B:2:C31:: and 2001:DB8:B:4:C52:: are executed correctly by
N2 and N4, respectively. Specifically, the information displayed for N2 and N4, respectively. Specifically, the information displayed for
hop2 contains the incoming interface address 2001:DB8:2:3:31:: at N3. hop2 contains the incoming interface address 2001:DB8:2:3:31:: at N3.
This matches with the expected interface bound to END.X function This matches with the expected interface bound to END.X behavior
2001:DB8:B:2:C31:: (link3). Similarly, the information displayed for 2001:DB8:B:2:C31:: (link3). Similarly, the information displayed for
hop5 contains the incoming interface address 2001:DB8:4:5::52:: at hop5 contains the incoming interface address 2001:DB8:4:5::52:: at
N5. This matches with the expected interface bound to the END.X N5. This matches with the expected interface bound to the END.X
function 2001:DB8:B:4:C52:: (link10). behavior 2001:DB8:B:4:C52:: (link10).
3.2.2. Traceroute to a SID 3.2.2. Traceroute to a SID
The classic traceroute described in the previous section applies The classic traceroute described in the previous section applies
equally to traceroute a remote SID function, as explained using an equally to traceroute a remote SID behavior, as explained using an
example in the following. example in the following. The example uses traceroute to an END SID
(refer [I-D.ietf-spring-srv6-network-programming]) but the procedure
is equally applicable to tracerouting any other SID behaviors.
Please note that traceroute to a SID function is exemplified using Please note that traceroute to a SID is exemplified using UDP probes.
UDP probes. However, the procedure is equally applicable to other However, the procedure is equally applicable to other implementations
implementations of traceroute mechanism. of traceroute mechanism.
Consider the example where the user wants to traceroute a remote SID Consider the example where the user wants to traceroute a remote SID
function 2001:DB8:B:4::, via 2001:DB8:B:2:C31::, from node N1. The 2001:DB8:B:4::, via 2001:DB8:B:2:C31::, from node N1. The traceroute
traceroute probe is processed at the individual nodes along the path probe is processed at the individual nodes along the path as follows:
as follows:
o Node N1 initiates a traceroute probe packet with a monotonically o Node N1 initiates a traceroute probe packet with a monotonically
increasing value of hop count and SRH as follows (2001:DB8:A:1::, increasing value of hop count and SRH as follows (2001:DB8:A:1::,
2001:DB8:B:2:C31::) (2001:DB8:B:4::, 2001:DB8:B:2:C31::; SL=1; 2001:DB8:B:2:C31::) (2001:DB8:B:4::, 2001:DB8:B:2:C31::; SL=1;
NH=UDP)(Traceroute probe). If 2001:DB8:B:2:C31:: is a PSP SID, NH=UDP)(Traceroute probe).
the OAM probes encodes the PSP SID in the packet (just mimicking
data packets). No special consideration is needed to handle PSP
SIDs.
o When node N2 receives the packet with hop-count = 1, it processes o When node N2 receives the packet with hop-count = 1, it processes
the hop count expiry. Specifically, the node N2 responses with the hop count expiry. Specifically, the node N2 responses with
the ICMPv6 message (Type: "Time Exceeded", Code: "Time to Live the ICMPv6 message (Type: "Time Exceeded", Code: "Time to Live
exceeded in Transit"). exceeded in Transit").
o When Node N2 receives the packet with hop-count > 1, it performs o When Node N2 receives the packet with hop-count > 1, it performs
the standard SRH processing. Specifically, it executes the END.X the standard SRH processing. Specifically, it executes the END.X
function (2001:DB8:B:2:C31::) on the traceroute probe. If behavior (2001:DB8:B:2:C31::) on the traceroute probe. If
2001:DB8:B:2:C31:: is a PSP SID, node N4 executes the SID like any 2001:DB8:B:2:C31:: is a PSP SID, node N4 executes the SID like any
other data packet with DA = 2001:DB8:B:2:C31:: and removes the other data packet with DA = 2001:DB8:B:2:C31:: and removes the
SRH. SRH.
o When node N3, which is a classic IPv6 node, receives the packet o When node N3, which is a classic IPv6 node, receives the packet
with hop-count = 1, it processes the hop count expiry. with hop-count = 1, it processes the hop count expiry.
Specifically, the node N3 responses with the ICMPv6 message (Type: Specifically, the node N3 responses with the ICMPv6 message (Type:
"Time Exceeded", Code: "Time to Live exceeded in Transit"). "Time Exceeded", Code: "Time to Live exceeded in Transit").
o When node N3, which is a classic IPv6 node, receives the packet o When node N3, which is a classic IPv6 node, receives the packet
with hop-count > 1, it performs the standard IPv6 processing. with hop-count > 1, it performs the standard IPv6 processing.
Specifically, it forwards the traceroute probe based on DA Specifically, it forwards the traceroute probe based on DA
2001:DB8:B:4:: in the IPv6 header. 2001:DB8:B:4:: in the IPv6 header.
o When node N4 receives the packet with DA set to the local SID o When node N4 receives the packet with DA set to the local SID
2001:DB8:B:4::, it processes the END SID, as described in the 2001:DB8:B:4::, it processes the END SID.
pseudocode in [I-D.ietf-spring-srv6-network-programming].
o If the 2001:DB8:B:4:: SID is not locally programmed, the packet is o If the target SID (2001:DB8:B:4::) is not locally instantiated,
discarded. the packet is discarded.
o If the target SID (2001:DB8:B:4::) is locally programmed, the node o If the target SID (2001:DB8:B:4::) is locally instantiated, the
processes the upper layer header. As part of the upper layer node processes the upper layer header. As part of the upper layer
header processing node N4 responses with the ICMPv6 message (Type: header processing node N4 responses with the ICMPv6 message (Type:
Destination unreachable, Code: Port Unreachable). Destination unreachable, Code: Port Unreachable).
Figure 4 displays a sample traceroute output for this example. Figure 4 displays a sample traceroute output for this example.
> traceroute 2001:DB8:B:4:C52:: via segment-list 2001:DB8:B:2:C31:: > traceroute 2001:DB8:B:4:C52:: via segment-list 2001:DB8:B:2:C31::
Tracing the route to SID function 2001:DB8:B:4:C52:: Tracing the route to SID 2001:DB8:B:4:C52::
1 2001:DB8:1:2:21:: 0.512 msec 0.425 msec 0.374 msec 1 2001:DB8:1:2:21:: 0.512 msec 0.425 msec 0.374 msec
DA: 2001:DB8:B:2:C31::, DA: 2001:DB8:B:2:C31::,
SRH:(2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::; SL=1) SRH:(2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::; SL=1)
2 2001:DB8:2:3:31:: 0.721 msec 0.810 msec 0.795 msec 2 2001:DB8:2:3:31:: 0.721 msec 0.810 msec 0.795 msec
DA: 2001:DB8:B:4:C52::, DA: 2001:DB8:B:4:C52::,
SRH:(2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::; SL=0) SRH:(2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::; SL=0)
3 2001:DB8:3:4:41:: 0.921 msec 0.816 msec 0.759 msec 3 2001:DB8:3:4:41:: 0.921 msec 0.816 msec 0.759 msec
DA: 2001:DB8:B:4:C52::, DA: 2001:DB8:B:4:C52::,
SRH:(2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::; SL=0) SRH:(2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::; SL=0)
Figure 4 A sample output for hop-by-hop traceroute to a SID Figure 4 A sample output for hop-by-hop traceroute to a SID
3.3. A Controller-Based Hybrid OAM Using O-flag 3.3. A Hybrid OAM Using O-flag
This section illustrates a hybrid OAM mechanism using the the
SRH.Flags.O-flag. Without loss of the generality, the illustration
assumes N100 is a centralized controller.
The illustration is different than the In-situ OAM defined in [I.D-
draft-ietf-ippm-ioam-data]. This is because In-situ OAM records
operational and telemetry information in the packet as the packet
traverses a path between two points in the network [I.D-draft-ietf-
ippm-ioam-data]. The illustration in section 3 does not require the
recording of OAM data in the packet.
The illustration does not assume any formats for exporting the data
elements or the data elements that needs to be exported.
Consider the example where the user wants to monitor sampled IPv4 VPN Consider the example where the user wants to monitor sampled IPv4 VPN
100 traffic going from CE1 to CE2 via a low latency SR policy P 100 traffic going from CE1 to CE2 via a low latency SR policy P
installed at Node N1. To exercise a low latency path, the SR Policy installed at Node N1. To exercise a low latency path, the SR Policy
P forces the packet via segments 2001:DB8:B:2:C31:: and P forces the packet via segments 2001:DB8:B:2:C31:: and
2001:DB8:B:4:C52::. The VPN SID at N7 associated with VPN100 is 2001:DB8:B:4:C52::. The VPN SID at N7 associated with VPN100 is
2001:DB8:B:7:DT100::. 2001:DB8:B:7:DT100:: is a USP SID. N1, N4, 2001:DB8:B:7:DT100::. 2001:DB8:B:7:DT100:: is a USP SID. N1, N4,
and N7 are capable of processing SRH.Flags.O-flag but N2 is not and N7 are capable of processing SRH.Flags.O-flag but N2 is not
capable of processing SRH.Flags.O-flag. N100 is the centralized capable of processing SRH.Flags.O-flag. N100 is the centralized
controller capable of processing and correlating the copy of the controller capable of processing and correlating the copy of the
skipping to change at page 14, line 13 skipping to change at page 15, line 4
partial copy of the packet P1 to the controller N100. The OAM partial copy of the packet P1 to the controller N100. The OAM
process includes the recorded timestamp, additional OAM process includes the recorded timestamp, additional OAM
information like incoming and outgoing interface, etc. along with information like incoming and outgoing interface, etc. along with
any applicable metadata. Node N1 forwards the original packet any applicable metadata. Node N1 forwards the original packet
towards the next segment 2001:DB8:B:2:C31::. towards the next segment 2001:DB8:B:2:C31::.
o When node N2 receives the packet with SRH.Flags.O-flag set, it o When node N2 receives the packet with SRH.Flags.O-flag set, it
ignores the SRH.Flags.O-flag. This is because node N2 is not ignores the SRH.Flags.O-flag. This is because node N2 is not
capable of processing the O-flag. Node N2 performs the standard capable of processing the O-flag. Node N2 performs the standard
SRv6 SID and SRH processing. Specifically, it executes the END.X SRv6 SID and SRH processing. Specifically, it executes the END.X
function (2001:DB8:B:2:C31::) and forwards the packet P1 (refer [I-D.ietf-spring-srv6-network-programming]) behavior
(2001:DB8:A:1::, 2001:DB8:B:4:C52::) (2001:DB8:B:7:DT100::, (2001:DB8:B:2:C31::) and forwards the packet P1 (2001:DB8:A:1::,
2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::; SL=1; O-flag=1; 2001:DB8:B:4:C52::) (2001:DB8:B:7:DT100::, 2001:DB8:B:4:C52::,
NH=IPv4)(IPv4 header)(payload) over link 3 towards Node N3. 2001:DB8:B:2:C31::; SL=1; O-flag=1; NH=IPv4)(IPv4 header)(payload)
over link 3 towards Node N3.
o When node N3, which is a classic IPv6 node, receives the packet P1 o When node N3, which is a classic IPv6 node, receives the packet P1
, it performs the standard IPv6 processing. Specifically, it , it performs the standard IPv6 processing. Specifically, it
forwards the packet P1 based on DA 2001:DB8:B:4:C52:: in the IPv6 forwards the packet P1 based on DA 2001:DB8:B:4:C52:: in the IPv6
header. header.
o When node N4 receives the packet P1 (2001:DB8:A:1::, o When node N4 receives the packet P1 (2001:DB8:A:1::,
2001:DB8:B:4:C52::) (2001:DB8:B:7:DT100::, 2001:DB8:B:4:C52::, 2001:DB8:B:4:C52::) (2001:DB8:B:7:DT100::, 2001:DB8:B:4:C52::,
2001:DB8:B:2:C31::; SL=1; O-flag=1; NH=IPv4)(IPv4 2001:DB8:B:2:C31::; SL=1; O-flag=1; NH=IPv4)(IPv4
header)(payload), it processes the SRH.Flags.O-flag. As part of header)(payload), it processes the SRH.Flags.O-flag. As part of
processing the O-flag, it sends a timestamped copy of the packet processing the O-flag, it sends a timestamped copy of the packet
to a local OAM process. The local OAM process sends a full or to a local OAM process. The local OAM process sends a full or
partial copy of the packet P1 to the controller N100. The OAM partial copy of the packet P1 to the controller N100. The OAM
process includes the recorded timestamp, additional OAM process includes the recorded timestamp, additional OAM
information like incoming and outgoing interface, etc. along with information like incoming and outgoing interface, etc. along with
any applicable metadata. Node N4 performs the standard SRv6 SID any applicable metadata. Node N4 performs the standard SRv6 SID
and SRH processing on the original packet P1. Specifically, it and SRH processing on the original packet P1. Specifically, it
executes the END.X function (2001:DB8:B:4:C52::) and forwards the executes the END.X behavior (2001:DB8:B:4:C52::) and forwards the
packet P1 (2001:DB8:A:1::, 2001:DB8:B:7:DT100::) packet P1 (2001:DB8:A:1::, 2001:DB8:B:7:DT100::)
(2001:DB8:B:7:DT100::, 2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::; (2001:DB8:B:7:DT100::, 2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::;
SL=0; O-flag=1; NH=IPv4)(IPv4 header)(payload) over link 10 SL=0; O-flag=1; NH=IPv4)(IPv4 header)(payload) over link 10
towards Node N5. towards Node N5.
o When node N5, which is a classic IPv6 node, receives the packet o When node N5, which is a classic IPv6 node, receives the packet
P1, it performs the standard IPv6 processing. Specifically, it P1, it performs the standard IPv6 processing. Specifically, it
forwards the packet based on DA 2001:DB8:B:7:DT100:: in the IPv6 forwards the packet based on DA 2001:DB8:B:7:DT100:: in the IPv6
header. header.
skipping to change at page 15, line 21 skipping to change at page 16, line 14
o The controller N100 processes and correlates the copy of the o The controller N100 processes and correlates the copy of the
packets sent from nodes N1, N4 and N7 to find segment-by-segment packets sent from nodes N1, N4 and N7 to find segment-by-segment
delays and provide other hybrid OAM information related to packet delays and provide other hybrid OAM information related to packet
P1. P1.
o The process continues for any other sampled packets. o The process continues for any other sampled packets.
3.4. Monitoring of SRv6 Paths 3.4. Monitoring of SRv6 Paths
In the recent past, network operators are interested in performing In the recent past, network operators demonstrated interest in
network OAM functions in a centralized manner. [RFC8403] describes performing network OAM functions in a centralized manner. [RFC8403]
such a centralized OAM mechanism. Specifically, the document describes such a centralized OAM mechanism. Specifically, the
describes a procedure that can be used to perform path continuity document describes a procedure that can be used to perform path
check between any nodes within an SR domain from a centralized continuity check between any nodes within an SR domain from a
monitoring system, with minimal or no control plane intervene on the centralized monitoring system. However, the document focuses on SR
nodes. However, the document focuses on SR networks with MPLS data networks with MPLS data plane. This document describes how the
plane. This document describes how the concept can be used to concept can be used to perform path monitoring in an SRv6 network
perform path monitoring in an SRv6 network from the centralized from a centralized controller.
controller.
In the reference topology in Figure 1, N100 uses an IGP protocol like In the reference topology in Figure 1, N100 uses an IGP protocol like
OSPF or ISIS to get the topology view within the IGP domain. N100 OSPF or ISIS to get the topology view within the IGP domain. N100
can also use BGP-LS to get the complete view of an inter-domain can also use BGP-LS to get the complete view of an inter-domain
topology. The controller leverages the visibility of the topology to topology. The controller leverages the visibility of the topology to
monitor the paths between the various endpoints without control plane monitor the paths between the various endpoints.
intervention required at the monitored nodes.
The controller N100 advertises an END SID 2001:DB8:B:100:1::. To The controller N100 advertises an END (refer [I-D.ietf-spring-srv6-
monitor any arbitrary SRv6 paths, the controller can create a network-programming]) SID 2001:DB8:B:100:1::. To monitor any
loopback probe that originates and terminates on Node N100. For arbitrary SRv6 paths, the controller can create a loopback probe that
example, in order to verify a segment list <2001:DB8:B:2:C31::, originates and terminates on Node N100. To distinguish between a
failure in the monitored path and loss of connectivity between the
controller and the network, Node N100 runs a suitable mechanism to
monitor its connectivity to the monitored network.
The loopback probes are exemplified using an example where controller
N100 needs to verify a segment list <2001:DB8:B:2:C31::,
2001:DB8:B:4:C52::>: 2001:DB8:B:4:C52::>:
o N100 generates an OAM packet (2001:DB8:A:100::, o N100 generates an OAM packet (2001:DB8:A:100::,
2001:DB8:B:2:C31::)(2001:DB8:B:100:1::, 2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::)(2001:DB8:B:100:1::, 2001:DB8:B:4:C52::,
2001:DB8:B:2:C31::, SL=2)(OAM Payload). The controller routes the 2001:DB8:B:2:C31::, SL=2)(OAM Payload). The controller routes the
probe packet towards the first segment, which is probe packet towards the first segment, which is
2001:DB8:B:2:C31::. 2001:DB8:B:2:C31::.
o Node N2 executes the END.X function (2001:DB8:B:2:C31::) and o Node N2 executes the END.X behavior (2001:DB8:B:2:C31::) and
forwards the packet (2001:DB8:A:100::, forwards the packet (2001:DB8:A:100::,
2001:DB8:B:4:C52::)(2001:DB8:B:100:1::, 2001:DB8:B:4:C52::, 2001:DB8:B:4:C52::)(2001:DB8:B:100:1::, 2001:DB8:B:4:C52::,
2001:DB8:B:2:C31::, SL=1)(OAM Payload) on link3 to N3. 2001:DB8:B:2:C31::, SL=1)(OAM Payload) on link3 to N3.
o Node N3, which is a classic IPv6 node, performs the standard IPv6 o Node N3, which is a classic IPv6 node, performs the standard IPv6
processing. Specifically, it forwards the packet based on the DA processing. Specifically, it forwards the packet based on the DA
2001:DB8:B:4:C52:: in the IPv6 header. 2001:DB8:B:4:C52:: in the IPv6 header.
o Node N4 executes the END.X function (2001:DB8:B:4:C52::) and o Node N4 executes the END.X behavior (2001:DB8:B:4:C52::) and
forwards the packet (2001:DB8:A:100::, forwards the packet (2001:DB8:A:100::,
2001:DB8:B:100:1::)(2001:DB8:B:100:1::, 2001:DB8:B:4:C52::, 2001:DB8:B:100:1::)(2001:DB8:B:100:1::, 2001:DB8:B:4:C52::,
2001:DB8:B:2:C31::, SL=0)(OAM Payload) on link10 to N5. 2001:DB8:B:2:C31::, SL=0)(OAM Payload) on link10 to N5.
o Node N5, which is a classic IPv6 node, performs the standard IPv6 o Node N5, which is a classic IPv6 node, performs the standard IPv6
processing. Specifically, it forwards the packet based on the DA processing. Specifically, it forwards the packet based on the DA
2001:DB8:B:100:1:: in the IPv6 header. 2001:DB8:B:100:1:: in the IPv6 header.
o Node N100 executes the standard SRv6 END function. It o Node N100 executes the standard SRv6 END behavior. It
decapsulates the header and consume the probe for OAM processing. decapsulates the header and consume the probe for OAM processing.
The information in the OAM payload is used to detect any missing The information in the OAM payload is used to detect any missing
probes, round trip delay, etc. probes, round trip delay, etc.
The OAM payload type or the information carried in the OAM probe is a The OAM payload type or the information carried in the OAM probe is a
local implementation decision at the controller and is outside the local implementation decision at the controller and is outside the
scope of this document. scope of this document.
4. Implementation Status 4. Implementation Status
skipping to change at page 17, line 4 skipping to change at page 17, line 43
5. Security Considerations 5. Security Considerations
This document does not define any new protocol extensions and relies This document does not define any new protocol extensions and relies
on existing procedures defined for ICMP. This document does not on existing procedures defined for ICMP. This document does not
impose any additional security challenges to be considered beyond impose any additional security challenges to be considered beyond
security considerations described in [RFC4884], [RFC4443], [RFC0792], security considerations described in [RFC4884], [RFC4443], [RFC0792],
and [RFC8754]. and [RFC8754].
6. IANA Considerations 6. IANA Considerations
6.1. Segment Routing Header Flags 6.1. Segment Routing Header Flags
This I-D requests to IANA to allocate bit position 2, within the This I-D requests to IANA to allocate bit position 2, within the
"Segment Routing Header Flags" registry defined in [RFC8754]. "Segment Routing Header Flags" registry defined in [RFC8754].
7. Acknowledgements 7. Acknowledgements
The authors would like to thank Joel M. Halpern, Greg Mirsky, Bob The authors would like to thank Joel M. Halpern, Greg Mirsky, Bob
Hinden, Loa Andersson and Gaurav Naik for their review comments. Hinden, Loa Andersson, Gaurav Naik, Ketan Talaulikar and Haoyu Song
for their review comments.
8. Contributors 8. Contributors
The following people have contributed to this document: The following people have contributed to this document:
Robert Raszuk Robert Raszuk
Bloomberg LP Bloomberg LP
Email: robert@raszuk.net Email: robert@raszuk.net
John Leddy John Leddy
skipping to change at page 18, line 45 skipping to change at page 19, line 40
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>. <https://www.rfc-editor.org/info/rfc8754>.
9.2. Informative References 9.2. Informative References
[I-D.ietf-spring-srv6-network-programming] [I-D.ietf-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J., Voyer, D., Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
Matsushima, S., and Z. Li, "SRv6 Network Programming", Matsushima, S., and Z. Li, "SRv6 Network Programming",
draft-ietf-spring-srv6-network-programming-15 (work in draft-ietf-spring-srv6-network-programming-16 (work in
progress), March 2020. progress), June 2020.
[I-D.matsushima-spring-srv6-deployment-status] [I-D.matsushima-spring-srv6-deployment-status]
Matsushima, S., Filsfils, C., Ali, Z., Li, Z., and K. Matsushima, S., Filsfils, C., Ali, Z., Li, Z., and K.
Rajaraman, "SRv6 Implementation and Deployment Status", Rajaraman, "SRv6 Implementation and Deployment Status",
draft-matsushima-spring-srv6-deployment-status-07 (work in draft-matsushima-spring-srv6-deployment-status-07 (work in
progress), April 2020. progress), April 2020.
[RFC0792] Postel, J., "Internet Control Message Protocol", STD 5, [RFC0792] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, DOI 10.17487/RFC0792, September 1981, RFC 792, DOI 10.17487/RFC0792, September 1981,
<https://www.rfc-editor.org/info/rfc792>. <https://www.rfc-editor.org/info/rfc792>.
skipping to change at page 19, line 26 skipping to change at page 20, line 20
Control Message Protocol (ICMPv6) for the Internet Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89, Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006, RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/info/rfc4443>. <https://www.rfc-editor.org/info/rfc4443>.
[RFC4884] Bonica, R., Gan, D., Tappan, D., and C. Pignataro, [RFC4884] Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
"Extended ICMP to Support Multi-Part Messages", RFC 4884, "Extended ICMP to Support Multi-Part Messages", RFC 4884,
DOI 10.17487/RFC4884, April 2007, DOI 10.17487/RFC4884, April 2007,
<https://www.rfc-editor.org/info/rfc4884>. <https://www.rfc-editor.org/info/rfc4884>.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, DOI 10.17487/RFC5357, October 2008,
<https://www.rfc-editor.org/info/rfc5357>.
[RFC5476] Claise, B., Ed., Johnson, A., and J. Quittek, "Packet [RFC5476] Claise, B., Ed., Johnson, A., and J. Quittek, "Packet
Sampling (PSAMP) Protocol Specifications", RFC 5476, Sampling (PSAMP) Protocol Specifications", RFC 5476,
DOI 10.17487/RFC5476, March 2009, DOI 10.17487/RFC5476, March 2009,
<https://www.rfc-editor.org/info/rfc5476>. <https://www.rfc-editor.org/info/rfc5476>.
[RFC5837] Atlas, A., Ed., Bonica, R., Ed., Pignataro, C., Ed., Shen, [RFC5837] Atlas, A., Ed., Bonica, R., Ed., Pignataro, C., Ed., Shen,
N., and JR. Rivers, "Extending ICMP for Interface and N., and JR. Rivers, "Extending ICMP for Interface and
Next-Hop Identification", RFC 5837, DOI 10.17487/RFC5837, Next-Hop Identification", RFC 5837, DOI 10.17487/RFC5837,
April 2010, <https://www.rfc-editor.org/info/rfc5837>. April 2010, <https://www.rfc-editor.org/info/rfc5837>.
[RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
(BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
<https://www.rfc-editor.org/info/rfc5880>.
[RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken, [RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
"Specification of the IP Flow Information Export (IPFIX) "Specification of the IP Flow Information Export (IPFIX)
Protocol for the Exchange of Flow Information", STD 77, Protocol for the Exchange of Flow Information", STD 77,
RFC 7011, DOI 10.17487/RFC7011, September 2013, RFC 7011, DOI 10.17487/RFC7011, September 2013,
<https://www.rfc-editor.org/info/rfc7011>. <https://www.rfc-editor.org/info/rfc7011>.
[RFC7012] Claise, B., Ed. and B. Trammell, Ed., "Information Model [RFC7012] Claise, B., Ed. and B. Trammell, Ed., "Information Model
for IP Flow Information Export (IPFIX)", RFC 7012, for IP Flow Information Export (IPFIX)", RFC 7012,
DOI 10.17487/RFC7012, September 2013, DOI 10.17487/RFC7012, September 2013,
<https://www.rfc-editor.org/info/rfc7012>. <https://www.rfc-editor.org/info/rfc7012>.
[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with [RFC7799] Morton, A., "Active and Passive Metrics and Methods (with
Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
May 2016, <https://www.rfc-editor.org/info/rfc7799>. May 2016, <https://www.rfc-editor.org/info/rfc7799>.
[RFC7880] Pignataro, C., Ward, D., Akiya, N., Bhatia, M., and S.
Pallagatti, "Seamless Bidirectional Forwarding Detection
(S-BFD)", RFC 7880, DOI 10.17487/RFC7880, July 2016,
<https://www.rfc-editor.org/info/rfc7880>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>. May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8403] Geib, R., Ed., Filsfils, C., Pignataro, C., Ed., and N. [RFC8403] Geib, R., Ed., Filsfils, C., Pignataro, C., Ed., and N.
Kumar, "A Scalable and Topology-Aware MPLS Data-Plane Kumar, "A Scalable and Topology-Aware MPLS Data-Plane
Monitoring System", RFC 8403, DOI 10.17487/RFC8403, July Monitoring System", RFC 8403, DOI 10.17487/RFC8403, July
2018, <https://www.rfc-editor.org/info/rfc8403>. 2018, <https://www.rfc-editor.org/info/rfc8403>.
[RFC8762] Mirsky, G., Jun, G., Nydell, H., and R. Foote, "Simple
Two-Way Active Measurement Protocol", RFC 8762,
DOI 10.17487/RFC8762, March 2020,
<https://www.rfc-editor.org/info/rfc8762>.
Authors' Addresses Authors' Addresses
Zafar Ali Zafar Ali
Cisco Systems Cisco Systems
Email: zali@cisco.com Email: zali@cisco.com
Clarence Filsfils Clarence Filsfils
Cisco Systems Cisco Systems
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