draft-ietf-6man-spring-srv6-oam-04.txt   draft-ietf-6man-spring-srv6-oam-05.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: October 1, 2020 S. Matsushima Expires: December 14, 2020 S. Matsushima
Softbank Softbank
D. Voyer D. Voyer
Bell Canada Bell Canada
M. Chen M. Chen
Huawei Huawei
March 30, 2020 June 12, 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-04 draft-ietf-6man-spring-srv6-oam-05
Abstract Abstract
This document defines building blocks for Operations, Administration, This document describes how the existing IPv6 OAM mechanisms can be
and Maintenance (OAM) in Segment Routing Networks with IPv6 Dataplane used in an SRv6 network. The document also introduces enhancements
(SRv6). The document also describes some SRv6 OAM mechanisms. for controller-based 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.
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This Internet-Draft will expire on October 1, 2020. This Internet-Draft will expire on December 14, 2020.
Copyright Notice Copyright Notice
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. Abbreviations . . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
4. Terminology and Reference Topology . . . . . . . . . . . . . 3 1.3. Terminology and Reference Topology . . . . . . . . . . . 3
5. OAM Mechanisms . . . . . . . . . . . . . . . . . . . . . . . 5 2. OAM Mechanisms . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. O-flag in Segment Routing Header . . . . . . . . . . . . 5 2.1. O-flag in Segment Routing Header . . . . . . . . . . . . 5
5.1.1. O-flag Processing . . . . . . . . . . . . . . . . . . 5 2.1.1. O-flag Processing . . . . . . . . . . . . . . . . . . 6
5.2. OAM Segments . . . . . . . . . . . . . . . . . . . . . . 6 3. Illustrations . . . . . . . . . . . . . . . . . . . . . . . . 7
5.3. End.OP: OAM Endpoint with Punt . . . . . . . . . . . . . 6 3.1. Ping in SRv6 Networks . . . . . . . . . . . . . . . . . . 7
6. Illustrations . . . . . . . . . . . . . . . . . . . . . . . . 7 3.1.1. Classic Ping . . . . . . . . . . . . . . . . . . . . 7
6.1. Ping in SRv6 Networks . . . . . . . . . . . . . . . . . . 7 3.1.2. Pinging a SID . . . . . . . . . . . . . . . . . . . . 9
6.1.1. Classic Ping . . . . . . . . . . . . . . . . . . . . 7 3.2. Traceroute . . . . . . . . . . . . . . . . . . . . . . . 10
6.1.2. Pinging a SID . . . . . . . . . . . . . . . . . . . . 9 3.2.1. Classic Traceroute . . . . . . . . . . . . . . . . . 10
6.2. Traceroute . . . . . . . . . . . . . . . . . . . . . . . 9 3.2.2. Traceroute to a SID . . . . . . . . . . . . . . . . . 11
6.2.1. Classic Traceroute . . . . . . . . . . . . . . . . . 10 3.3. A Controller-Based Hybrid OAM Using O-flag . . . . . . . 13
6.2.2. Traceroute to a SID . . . . . . . . . . . . . . . . . 11 3.4. Monitoring of SRv6 Paths . . . . . . . . . . . . . . . . 15
6.3. A Controller-Based Passive OAM Using O-flag . . . . . . . 13 4. Implementation Status . . . . . . . . . . . . . . . . . . . . 16
6.4. Monitoring of SRv6 Paths . . . . . . . . . . . . . . . . 15 5. Security Considerations . . . . . . . . . . . . . . . . . . . 16
7. Implementation Status . . . . . . . . . . . . . . . . . . . . 16 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 16 6.1. Segment Routing Header Flags . . . . . . . . . . . . . . 17
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
9.1. ICMPv6 type Numbers Registry . . . . . . . . . . . . . . 16 8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17
9.2. SRv6 OAM Endpoint Types . . . . . . . . . . . . . . . . . 17 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
9.3. Segment Routing Header Flags . . . . . . . . . . . . . . 17 9.1. Normative References . . . . . . . . . . . . . . . . . . 18
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 9.2. Informative References . . . . . . . . . . . . . . . . . 18
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
12.1. Normative References . . . . . . . . . . . . . . . . . . 18
12.2. Informative References . . . . . . . . . . . . . . . . . 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
This document defines building blocks for Operations, Administration, As Segment Routing with IPv6 data plane (SRv6) simply adds a new type
and Maintenance (OAM) in Segment Routing Networks with IPv6 Dataplane of Routing Extension Header, existing IPv6 OAM mechanisms can be used
(SRv6). in an SRv6 network. This document describes how the existing IPv6
mechanisms for ping and trace route can be used in an SRv6 network.
2. Requirements Language The document also introduces enhancements for controller-based OAM
mechanism for SRv6 networks. Specifically, the document describes an
OAM mechanism for performing controllable and predictable flow
sampling from segment endpoints using, e.g., IP Flow Information
Export (IPFIX) protocol [RFC7011]. The document also outlines how
centralized OAM technique in [RFC8403] can be extended for SRv6 to
perform a path continuity check between any nodes within an SRv6
domain from a centralized monitoring system, with minimal or no
control plane intervene on the nodes.
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].
3. 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.
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].
4. Terminology and Reference Topology 1.3. Terminology and Reference Topology
This document uses the terminology defined in [I-D.ietf- spring-srv6- This document uses the terminology defined in [I-D.ietf- spring-srv6-
network-programming]. The readers are expected to be familiar with network-programming]. The readers are expected to be familiar with
the same. the same.
Throughout the document, the following simple topology is used for Throughout the document, the following simple topology is used for
illustration. illustration.
+--------------------------| N100 |---------------------------------+ +--------------------------| N100 |---------------------------------+
| | | |
skipping to change at page 4, line 7 skipping to change at page 4, line 21
| | | | | | | |
---+-- | ------ | --+--- ---+-- | ------ | --+---
|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 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, and N4 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.
A SID at node k with locator block B and function F is represented A SID at node k with locator block 2001:DB8:B::/48 and function F
by 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::.
B:k:Cij:: is explicitly allocated as the END.X function at node k 2001:DB8:B:k:Cij:: is explicitly allocated as the END.X function
towards neighbor node i via jth Link between node i and node k. at node k towards neighbor node i via jth Link between node i and
e.g., B:2:C31:: represents END.X at N2 towards N3 via link3 (the node k. e.g., 2001:DB8:B:2:C31:: represents END.X at N2 towards
1st link between N2 and N3). Similarly, B:4:C52:: represents the N3 via link3 (the 1st link between N2 and N3). Similarly,
END.X at N4 towards N5 via link10. 2001:DB8:B:4:C52:: 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
skipping to change at page 5, line 9 skipping to change at page 5, line 26
use-case, it is simpler to use the <S1, S2, S3> notation. When use-case, it is simpler to use the <S1, S2, S3> notation. When
referring to an illustration of the detailed packet behavior, referring to an illustration of the detailed packet behavior,
the (S3, S2, S1; SL) notation is more convenient. the (S3, S2, S1; SL) notation is more convenient.
* (payload) represents the the payload of the packet. * (payload) represents the the payload of the packet.
SRH[SL] represents the SID pointed by the SL field in the first SRH[SL] represents the SID pointed by the SL field in the first
SRH. In our example SID list (S3, S2, S1; SL), SRH[2] represents SRH. In our example SID list (S3, S2, S1; SL), SRH[2] represents
S1, SRH[1] represents S2 and SRH[0] represents S3. S1, SRH[1] represents S2 and SRH[0] represents S3.
5. OAM Mechanisms 2. OAM Mechanisms
As Segment Routing with IPv6 data plane (SRv6) simply adds a new type
of Routing Extension Header, existing IPv6 OAM mechanisms can be used
in an SRv6 network.
This section defines OAM enhancement for the SRv6 networks. This section defines OAM enhancement for the SRv6 networks.
Specifically, it defines the O-flag for implementing a controller
based passive OAM mechanism and an OAM SID to more closely examine
the contents of packet at a segment endpoint for active OAM.
5.1. O-flag in Segment Routing Header 2.1. O-flag in Segment Routing Header
[I-D.ietf-6man-segment-routing-header] describes the Segment Routing [RFC8754] describes the Segment Routing Header (SRH) and how SR
Header (SRH) and how SR capable nodes use it. The SRH contains an capable nodes use it. The SRH contains an 8-bit "Flags" field. This
8-bit "Flags" field. This document defines the following bit in the document defines the following bit in the SRH.Flags to carry the
SRH.Flags to carry the O-flag: O-flag:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
| |O| | | |O| |
+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+
Where: Where:
O-flag: OAM flag. When set, it indicates that this packet is an O-flag: OAM flag.
Operation Administration and Maintenance (OAM) packet. This
document defines the usage of the O-flag in the SRH.Flags.
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.
5.1.1. O-flag Processing 2.1.1. O-flag Processing
The SRH.Flags.O-flag implements the "punt a timestamped copy of the The O-flag in SRH is used as a marking-bit in the user packets to
packet" behavior. This enables an SRv6 Endpoint node to send a trigger the telemetry data collection and export at the segment
timestamped copy of the packets marked with o-flag to a local OAM endpoints.
process. To prevent multiple evaluations of the datagram, the OAM
process MUST NOT process the packet or respond to any upper-layer
header (like ICMP, UDP, etc.) payload. However, the OAM process MAY
export the time-stamped copy of the packet to a controller using
e.g., IPFIX [RFC7011]. If data from the last node in the segment-
list (Egress node) is desired, the ingress uses an Ultimate Segment
Pop (USP) SID advertised by the Egress node. To avoid hitting any
performance impact, the processing node SHOULD rate-limit the number
of packets punted to the OAM process. Specification of the OAM
process or the external controller operations are beyond the scope of
this document. Section 6 illustrates use of the SRH.Flags.O-flag for
implementing a controller-based passive OAM mechanism.
Implementation of the O-flag is OPTIONAL. If a node does not support Without the loss of generality, this document assumes IP Flow
the O-flag, then upon reception it simply ignores it. Information Export (IPFIX) protocol [RFC7011] is used for exporting
the traffic flow information from the network devices to a controller
for monitoring and analytics. The requested information elements are
configured by the management plane through data set templates (e.g.,
as in IPFIX [RFC7012]).
If a node supports the O-flag, it can optionally advertise its Implementation of the O-flag is OPTIONAL. If a node does not support
potential via node capability advertisement in IGP [I-D.ietf-isis- the O-flag, then upon reception it simply ignores it. If a node
srv6- extensions] and BGP-LS [I-D.ietf-idr-bgpls-srv6-ext]. supports the O-flag, it can optionally advertise its potential via
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 [I-D.ietf-6man-segment-routing-header], is section 4.3.1.1 of [RFC8754], is modified as follows for the O-flag
modified as follows for the O-flag processing. processing.
S01.1. IF SRH.Flags.O-flag is set and local configuration permits S01.1. IF SRH.Flags.O-flag is set and local configuration permits
O-flag processing THEN O-flag processing THEN
a. Make a copy of the packet. a. Make a copy of the packet.
b. Send the copied packet, along with a timestamp b. Send the copied packet, along with a timestamp
to the OAM process. ;; Ref1 to the OAM process for telemetry data collection
and export. ;; Ref1
Ref1: An implementation SHOULD copy and record the timestamp as Ref1: An implementation SHOULD copy and record the timestamp as
soon as possible during packet processing. Timestamp is not soon as possible during packet processing. Timestamp or any other
metadata is not
carried in the packet forwarded to the next hop. carried in the packet forwarded to the next hop.
Please note that the O-flag processing happens before execution of Please note that the O-flag processing happens before execution of
regular processing of the local SID S. regular processing of the local SID S.
5.2. OAM Segments Based on the requested information elements configured by the
management plane through data set templates [RFC7012], the OAM
The presence of an OAM SID in the Destination address of the IPv6 process exports the requested information elements. The information
header instructs the segment endpoint implementing the OAM SID that elements include parts of the packet header and/or parts of the
the content of the packet is of interest. packet payload for flow identification. The OAM process uses
information elements defined in IPFIX [RFC7011] and PSAMP [RFC5476]
The document defines OAM Endpoint with Punt action. Additional OAM for exporting the requested sections of the mirrored packets.
SIDs may be defined in future documents.
5.3. End.OP: OAM Endpoint with Punt
When N receives a packet destined to S and S is a local End.OP SID, N
does:
S01. Send the packet to the OAM process If the telemetry data from the last node in the segment-list (egress
node) is desired, the ingress uses an Ultimate Segment Pop (USP) SID
advertised by the egress node.
The local OAM process further processes the packet, this MAY involve The processing node SHOULD rate-limit the number of packets punted to
processing protocol layers above IPv6. For example, ping and the OAM process to avoid hitting any performance impact.
traceroute will require ICMP or UDP protocol processing. Once the
packet leaves the IPv6 layer the processing is considered host
processing and the upper layer protocols MUST be processed as such.
As END.OP SID terminates the forwarding of the probe packets for the The OAM process MUST NOT process the copy of the packet or respond to
upper layer processing, it is used for the active OAM mechanisms. any upper-layer header (like ICMP, UDP, etc.) payload to prevent
For example, the END.OP SID SID is not designed for implementing In- multiple evaluations of the datagram.
situ OAM mechanisms defined in [I.D-draft-ietf-ippm-ioam-data].
6. Illustrations Specification of the OAM process or the external controller
operations are beyond the scope of this document. section 3
illustrates use of the SRH.Flags.O-flag for implementing a
controller-based hybrid OAM mechanism, where the "hybrid"
classification is based on RFC7799 [RFC7799]. 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
controller-based OAM mechanism using O-flag illustration in section 3
does not require the recording of OAM data in the packet.
This section illustrates the use of existing IPv6 OAM mechanisms in 3. Illustrations
the SRv6 network. It also illustrates the use of the END.OP SID and
O-flag at segment endpoints.
The document does not propose any changes to the standard ICMPv6 This section shows how some of the existing IPv6 OAM mechanisms can
[RFC4443], [RFC4884] or standard ICMPv4 [RFC792] or [RFC2151]. be used in an SRv6 network. It also illustrates an OAM mechanism for
performing controllable and predictable flow sampling from segment
endpoints. How centralized OAM technique in [RFC8403] can be
extended for SRv6 is also described in this Section.
6.1. 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.
6.1.1. Classic Ping 3.1.1. Classic Ping
The existing mechanism to query liveliness of a remote IP address, The existing mechanism to query liveliness of a remote IP address,
along the shortest path, continues to work without any modification. along the shortest path, continues to work without any modification.
The 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 capable node or a classic IPv6 the 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 prefix 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 <B:2:C31, B:4:C52>. loopback of node 5, via segment list <2001:DB8:B:2:C31::,
2001:DB8:B:4:C52::>.
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 <B:2:C31, N1 to the loopback address of node N5 via a segment list
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::,
2001:DB8:B:4:C52::
> ping A:5:: via segment-list B:2:C31, 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:
!!!!! !!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 0.625 Success rate is 100 percent (5/5), round-trip min/avg/max = 0.625
/0.749/0.931 ms /0.749/0.931 ms
Figure 2 A sample ping output at an SRv6 capable node Figure 2 A sample ping output at an SRv6 capable node
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. Furthermore, require any change to process the ICMPv6 echo request. For example,
there is no difference in processing of the ICMPv6 echo request at an in the ping example of Figure 2:
IPv6 classic node or an SRv6 capable node. For example, 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
(A:1::, B:2:C31)(A:5::, B:4:C52, B:2:C31, SL=2, NH = (2001:DB8:A:1::, 2001:DB8:B:2:C31::) (2001:DB8:A:5::,
ICMPv6)(ICMPv6 Echo Request). If B:4:C52 is a PSP SID, the OAM 2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::, SL=2, NH = ICMPv6)(ICMPv6
probes encodes the PSP SID in the packet (just mimicking data Echo Request). If 2001:DB8:B:4:C52:: is a PSP SID, the OAM probes
packets). No special consideration is needed to handle PSP SIDs. 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 function
(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 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 function
(B:4:C52) and forwards the packet on link10 towards N5. If (2001:DB8:B:4:C52::) and forwards the packet on link10 towards N5.
B:4:C52 is a PSP SID, The penultimate node (Node N4) does not, If 2001:DB8:B:4:C52:: is a PSP SID, The penultimate node (Node N4)
should no and cannot differentiate between the data packets and does not, should not and cannot differentiate between the data
OAM probes. Specifically, if B:4:C52 is a PSP SID, node N4 packets and OAM probes. Specifically, if 2001:DB8:B:4:C52:: is a
executes the SID like any other data packet with DA = B:4:C52 and PSP SID, node N4 executes the SID like any other data packet with
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. In either case, Node N5 performs the standard IPv6/ processing (SL=0). In either case, Node N5 performs the standard
ICMPv6 processing on the echo request. IPv6/ ICMPv6 processing on the echo request.
6.1.2. Pinging a SID 3.1.2. Pinging a SID
The following illustration uses END.OP SID for pinging a SID. The classic ping described in the previous section applies equally to
ping a remote SID function, as explained using an example in the
following.
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 B:4:C52, via B:2:C31, from node N1. The ICMPv6 echo request function 2001:DB8:B:4::, via 2001:DB8:B:2:C31::, from node N1. The
is processed at the individual nodes along the path as follows: ICMPv6 echo request is processed at the individual nodes along the
path as follows:
o To force a punt of the ICMPv6 echo request at the node N4, node N1 o Node N1 initiates an ICMPv6 ping packet with SRH as follows
inserts the END.OP SID just before the target SID B:4:C52 in the (2001:DB8:A:1::, 2001:DB8:B:2:C31::) (2001:DB8:B:4::,
SRH. Specifically, Node N1 initiates an ICMPv6 ping packet with 2001:DB8:B:2:C31::; SL=1; NH=ICMPv6)(ICMPv6 Echo Request). If
SRH as follows (A:1::, B:2:C31)(B:4:C52, B:4:OP, B:2:C31; SL=2; 2001:DB8:B:2:C31:: is a PSP SID, the OAM probes encodes the PSP
NH=ICMPv6)(ICMPv6 Echo Request). 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 function
(B:2:C31) on the echo request packet. (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
other data packet with DA = 2001:DB8:B:2:C31:: and removes the
SRH.
o Node N3 receives the packet as follows (A:1::, B:4:OP)(B:4:C52, o Node N3, which is a classic IPv6 node, performs the standard IPv6
B:4:OP, B:2:C31 ; SL=1; NH=ICMPv6)(ICMPv6 Echo Request). 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 B:4:OP in the IPv6 header. DA = 2001:DB8:B:4:: in the IPv6 header.
o When node N4 receives the packet (A:1::, B:4:OP)(B:4:C52, B:4:OP, o When node N4 receives the packet, it processes the 2001:DB8:B:4::
B:2:C31 ; SL=1; NH=ICMPv6)(ICMPv6 Echo Request), it processes the SID, as described in the pseudocode in [I-D.ietf-spring-srv6-
END.OP SID, as described in the pseudocode in Section 3. The network-programming].
packet gets punted to the OAM process for processing. The OAM
process checks if the next SID in SRH (the target SID B:4:C52) is
locally programmed.
o If the next SID is not locally programmed, the OAM process returns o If the 2001:DB8:B:4:: SID is not locally programmed, the packet is
an ICMPv6 error message type 4 (parameter problem) code 0 discarded
(erroneous header field encountered) with pointer set to the
target SID B:4:C52 and the packet is discarded.
o If the next SID is locally programmed, the node processes the o If the target SID (2001:DB8:B:4::) is locally programmed, the node
upper layer header, as a host. As part of the upper layer header processes the upper layer header. As part of the upper layer
(ICMPv6) processing node N4 sends the ICMPv6 Echo Reply message header processing node N4 respond to the ICMPv6 echo request
[RFC4443]. message.
6.2. 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
mechanisms work seamlessly in the SRv6 networks. mechanisms work seamlessly in the SRv6 networks.
The following subsections outline some use cases of the traceroute in The following subsections outline some use cases of the traceroute in
the SRv6 networks. the SRv6 networks.
6.2.1. Classic Traceroute 3.2.1. Classic Traceroute
The existing mechanism to traceroute a remote IP prefix, along the The existing mechanism to traceroute a remote IP address, along the
shortest path, continues to work without any modification. The shortest path, continues to work without any modification. The
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 prefix 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 <B:2:C31, from node N1 to a loopback of node 5, via segment list
B:4:C52>. Figure 3 contains sample output for the traceroute <2001:DB8:B:2:C31::, 2001:DB8:B:4:C52::>. Figure 3 contains sample
request. output for the traceroute request.
> traceroute A:5:: via segment-list B:2:C31, B:4:C52 > traceroute 2001:DB8:A:5:: via segment-list 2001:DB8:B:2:C31::,
Tracing the route to A:5:: 2001:DB8:B:4:C52::
1 2001:DB8:1:2:21:: 0.512 msec 0.425 msec 0.374 msec
SRH: (A:5::, B:4:C52, B:2:C31, SL=2)
2 2001:DB8:2:3:31:: 0.721 msec 0.810 msec 0.795 msec
SRH: (A:5::, B:4:C52, B:2:C31, SL=1)
3 2001:DB8:3:4:41:: 0.921 msec 0.816 msec 0.759 msec
SRH: (A:5::, B:4:C52, B:2:C31, SL=1)
4 2001:DB8:4:5:52:: 0.879 msec 0.916 msec 1.024 msec
Figure 3 A sample traceroute output at an SRv6 capable node
Please note that if B:4:C52 is a PSP SID, the traceroute probe Tracing the route to 2001:DB8:A:5::
encodes the PSP SID in the packet (just mimicking data packets). 1 2001:DB8:1:2:21:: 0.512 msec 0.425 msec 0.374 msec
Likewise, if B:4:C52 is a PSP SID, node N4 executes the SID like any DA: 2001:DB8:B:2:C31::,
other data packet with DA = B:4:C52. I.e., no special consideration SRH:(2001:DB8:A:5::, 2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::, SL=2)
is needed to handle PSP SIDs. 2 2001:DB8:2:3:31:: 0.721 msec 0.810 msec 0.795 msec
DA: 2001:DB8:B:4:C52::,
SRH:(2001:DB8:A:5::, 2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::, SL=1)
3 2001:DB8:3:4::41:: 0.921 msec 0.816 msec 0.759 msec
DA: 2001:DB8:B:4:C52::,
SRH:(2001:DB8:A:5::, 2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::, SL=1)
4 2001:DB8:4:5::52:: 0.879 msec 0.916 msec 1.024 msec
DA: 2001:DB8:A:5::
Figure 3 A sample traceroute output at an SRv6 capable node
Please note that information for hop2 is returned by N3, which is a Please note that information for hop2 is returned by N3, which is a
classic IPv6 node. Nonetheless, the ingress node is able to display classic IPv6 node. Nonetheless, the ingress node is able to display
SR header contents as the packet travels through the IPv6 classic SR header contents as the packet travels through the IPv6 classic
node. This is because the "Time Exceeded Message" ICMPv6 message can node. This is because the "Time Exceeded Message" ICMPv6 message can
contain as much of the invoking packet as possible without the ICMPv6 contain as much of the invoking packet as possible without the ICMPv6
packet exceeding the minimum IPv6 MTU [RFC4443]. The SR header is packet exceeding the minimum IPv6 MTU [RFC4443]. The SR header is
also included in these ICMPv6 messages initiated by the classic IPv6 also included in these ICMPv6 messages initiated by the classic IPv6
transit nodes that are not running SRv6 software. Specifically, a transit nodes that are not running SRv6 software. Specifically, a
node generating ICMPv6 message containing a copy of the invoking node generating ICMPv6 message containing a copy of the invoking
skipping to change at page 11, line 28 skipping to change at page 11, line 35
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 SID functions
B:2:C31 and B:4:C52 are executed correctly by N2 and N4, 2001:DB8:B:2:C31:: and 2001:DB8:B:4:C52:: are executed correctly by
respectively. Specifically, the information displayed for hop2 N2 and N4, respectively. Specifically, the information displayed for
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 function
B:2:C31 (link3). Similarly, the information displayed for hop5 2001:DB8:B:2:C31:: (link3). Similarly, the information displayed for
contains the incoming interface address 2001:DB8:4:5:52:: at N5. hop5 contains the incoming interface address 2001:DB8:4:5::52:: at
This matches with the expected interface bound to the END.X function N5. This matches with the expected interface bound to the END.X
B:4:C52 (link10). function 2001:DB8:B:4:C52:: (link10).
6.2.2. Traceroute to a SID 3.2.2. Traceroute to a SID
The following illustration uses END.OP SID for trace-routing a SID. The classic traceroute described in the previous section applies
The illustration assumes traceroute probe is UDP encoded but the equally to traceroute a remote SID function, as explained using an
procedure is equally applicable to other encoding types. example in the following.
Consider the example where the user wants to traceroute to a remote Please note that traceroute to a SID function is exemplified using
SID function B:4:C52, via B:2:C31, from node N1. The traceroute UDP probes. However, the procedure is equally applicable to other
probe is processed at the individual nodes along the path as follows: implementations of traceroute mechanism.
o To force a punt of the traceroute probe at the node N4, node N1 Consider the example where the user wants to traceroute a remote SID
inserts the END.OP SID just before the target SID B:4:C52 in the function 2001:DB8:B:4::, via 2001:DB8:B:2:C31::, from node N1. The
SRH. Specifically, Node N1 initiates a traceroute probe packet traceroute probe is processed at the individual nodes along the path
with a monotonically increasing value of hop-count and SRH as as follows:
follows (A:1::, B:2:C31)(B:4:C52, B:4:OP, B:2:C31; SL=2;
NH=UDP)(Traceroute probe). o Node N1 initiates a traceroute probe packet with a monotonically
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;
NH=UDP)(Traceroute probe). If 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 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-limit 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 SRv6 SID and SRH processing. Specifically, it the standard SRH processing. Specifically, it executes the END.X
executes the END.X function (B:2:C31) on the traceroute probe. function (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
other data packet with DA = 2001:DB8:B:2:C31:: and removes the
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
(A:1::, B:4:OP)(B:4:C52, B:4:OP, B:2:C31 ; HC=1, SL=1; with hop-count = 1, it processes the hop count expiry.
NH=UDP)(Traceroute probe) with hop-count = 1, it processes the Specifically, the node N3 responses with the ICMPv6 message (Type:
hop-limit expiry. Specifically, the node N3 responses with the "Time Exceeded", Code: "Time to Live exceeded in Transit").
ICMPv6 message (Type: "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 B:4:OP Specifically, it forwards the traceroute probe based on DA
in the IPv6 header. 2001:DB8:B:4:: in the IPv6 header.
o When node N4 receives the packet (A:1::, B:4:OP)(B:4:C52, B:4:OP, o When node N4 receives the packet with DA set to the local SID
B:2:C31 ; SL=1; HC=1, NH=UDP)(Traceroute probe), it processes the 2001:DB8:B:4::, it processes the END SID, as described in the
END.OP SID, as described in the pseudocode in Section 3, before pseudocode in [I-D.ietf-spring-srv6-network-programming].
hop-limit processing. The packet gets punted to the OAM process
for processing. The OAM process checks if the next SID in SRH
(the target SID B:4:C52) is locally programmed.
o If the next SID is not locally programmed, the OAM process returns o If the 2001:DB8:B:4:: SID is not locally programmed, the packet is
an ICMPv6 error message type 4 (parameter problem) code 0 discarded.
(erroneous header field encountered) with pointer set to the
target SID B:4:C52 and the packet is discarded.
o If the next SID is locally programmed, the node processes the o If the target SID (2001:DB8:B:4::) is locally programmed, the node
upper layer header. As part of the upper layer header processing processes the upper layer header. As part of the upper layer
node N4 responses with the ICMPv6 message (Type: Destination header processing node N4 responses with the ICMPv6 message (Type:
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 srv6 B:4:C52 via segment-list B:2:C31 > traceroute 2001:DB8:B:4:C52:: via segment-list 2001:DB8:B:2:C31::
Tracing the route to SID function B:4:C52
1 2001:DB8:1:2:21:: 0.512 msec 0.425 msec 0.374 msec
SRH: (B:4:C52, B:4:OP, B:2:C31; SL=2)
2 2001:DB8:2:3:31:: 0.721 msec 0.810 msec 0.795 msec
SRH: (B:4:C52, B:4:OP, B:2:C31; SL=1)
3 2001:DB8:3:4:41:: 0.921 msec 0.816 msec 0.759 msec
SRH: (B:4:C52, B:4:OP, B:2:C31; SL=1)
Figure 4 A sample output for traceroute to a SID
6.3. A Controller-Based Passive OAM Using O-flag Tracing the route to SID function 2001:DB8:B:4:C52::
1 2001:DB8:1:2:21:: 0.512 msec 0.425 msec 0.374 msec
DA: 2001:DB8:B:2:C31::,
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
DA: 2001:DB8:B:4:C52::,
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
DA: 2001:DB8:B:4:C52::,
SRH:(2001:DB8:B:4:C52::, 2001:DB8:B:2:C31::; SL=0)
This section illustrates a controller-based passive OAM mechanism Figure 4 A sample output for hop-by-hop traceroute to a SID
using the SRH.Flags.O-flag.
The mechanism is different than the passive In-situ OAM defined in 3.3. A Controller-Based Hybrid OAM Using O-flag
[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 controller-based OAM mechanism using O-flag
described in this section does not require the recording of OAM data
in the packet. Instead, a copy of the packet with the SRH.O-flag set
is sent to a local OAM process. The OAM process adds the required
metadata to the packet and sends the packet to a controller for
further processing. Specification of how the OAM process computes
the metadata and how the controller correlates and processes the copy
of the packets from different segment endpoints is beyond the scope
of this document.
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 B:2:C31 and B:4:C52. The VPN SID at P forces the packet via segments 2001:DB8:B:2:C31:: and
N7 associated with VPN100 is B:7:DT100. B:7:DT100 is a USP SID. N1, 2001:DB8:B:4:C52::. The VPN SID at N7 associated with VPN100 is
N4, and N7 are capable of processing SRH.Flags.O-flag but N2 is not 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
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
packets sent from nodes N1, N4, and N7. N100 is aware of packets sent from nodes N1, N4, and N7. N100 is aware of
SRH.Flags.O-flag processing capabilities. Controller N100 with the SRH.Flags.O-flag processing capabilities. Controller N100 with the
help from nodes N1, N4, N7 and implements a passive OAM mechanism help from nodes N1, N4, N7 and implements a hybrid OAM mechanism
using the SRH.Flags.O-flag as follows: using the SRH.Flags.O-flag as follows:
o A packet P1:(IPv4 header)(payload) is sent from CE1 to Node N1. o A packet P1:(IPv4 header)(payload) is sent from CE1 to Node N1.
o Node N1 steers the packet P1 through the Policy P. Based on a o Node N1 steers the packet P1 through the Policy P. Based on a
local configuration, Node N1 also implements logic to sample local configuration, Node N1 also implements logic to sample
traffic steered through policy P for passive OAM purposes. traffic steered through policy P for hybrid OAM purposes.
Specification for the sampling logic is beyond the scope of this Specification for the sampling logic is beyond the scope of this
document. Consider the case where packet P1 is classified as a document. Consider the case where packet P1 is classified as a
packet to be monitored via the passive OAM. Node N1 sets packet to be monitored via the hybrid OAM. Node N1 sets
SRH.Flags.O-flag during encapsulation required by policy P. As SRH.Flags.O-flag during encapsulation required by policy P. As
part of setting the SRH.Flags.O-flag, node N1 also send a part of setting the SRH.Flags.O-flag, node N1 also send a
timestamped copy of the packet P1: (A:1::, B:2:C31)(B:7:DT100, timestamped copy of the packet P1: (2001:DB8:A:1::,
B:4:C52, B:2:C31; SL=2; O-flag=1; NH=IPv4)(IPv4 header)(payload) 2001:DB8:B:2:C31::) (2001:DB8:B:7:DT100::, 2001:DB8:B:4:C52::,
2001:DB8:B:2:C31::; SL=2; O-flag=1; NH=IPv4)(IPv4 header)(payload)
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 N1 forwards the original packet any applicable metadata. Node N1 forwards the original packet
towards the next segment 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 (B:2:C31) and forwards the packet P1 (A:1::, function (2001:DB8:B:2:C31::) and forwards the packet P1
B:4:C52)(B:7:DT100, B:4:C52, B:2:C31; SL=1; O-flag=1; (2001:DB8:A:1::, 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 header)(payload) over link 3 towards Node N3. 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 B:4:C52 in the IPv6 header. forwards the packet P1 based on DA 2001:DB8:B:4:C52:: in the IPv6
header.
o When node N4 receives the packet P1 (A:1::, B:4:C52)(B:7:DT100, o When node N4 receives the packet P1 (2001:DB8:A:1::,
B:4:C52, B:2:C31; SL=1; O-flag=1; NH=IPv4)(IPv4 header)(payload), 2001:DB8:B:4:C52::) (2001:DB8:B:7:DT100::, 2001:DB8:B:4:C52::,
it processes the SRH.Flags.O-flag. As part of processing the 2001:DB8:B:2:C31::; SL=1; O-flag=1; NH=IPv4)(IPv4
O-flag, it sends a timestamped copy of the packet to a local OAM header)(payload), it processes the SRH.Flags.O-flag. As part of
process. The local OAM process sends a full or partial copy of processing the O-flag, it sends a timestamped copy of the packet
the packet P1 to the controller N100. The OAM process includes to a local OAM process. The local OAM process sends a full or
the recorded timestamp, additional OAM information like incoming partial copy of the packet P1 to the controller N100. The OAM
and outgoing interface, etc. along with any applicable metadata. process includes the recorded timestamp, additional OAM
Node N4 performs the standard SRv6 SID and SRH processing on the information like incoming and outgoing interface, etc. along with
original packet P1. Specifically, it executes the END.X function any applicable metadata. Node N4 performs the standard SRv6 SID
(B:4:C52) and forwards the packet P1 (A:1::, B:7:DT100)(B:7:DT100, and SRH processing on the original packet P1. Specifically, it
B:4:C52, B:2:C31; SL=0; O-flag=1; NH=IPv4)(IPv4 header)(payload) executes the END.X function (2001:DB8:B:4:C52::) and forwards the
over link 10 towards Node N5. 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::;
SL=0; O-flag=1; NH=IPv4)(IPv4 header)(payload) over link 10
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 B:7:DT100 in the IPv6 header. forwards the packet based on DA 2001:DB8:B:7:DT100:: in the IPv6
header.
o When node N7 receives the packet P1 (A:1::, B:7:DT100)(B:7:DT100, o When node N7 receives the packet P1 (2001:DB8:A:1::,
B:4:C52, B:2:C31; SL=0; O-flag=1; NH=IPv4)(IPv4 header)(payload), 2001:DB8:B:7:DT100::) (2001:DB8:B:7:DT100::, 2001:DB8:B:4:C52::,
it processes the SRH.Flags.O-flag. As part of processing the 2001:DB8:B:2:C31::; SL=0; O-flag=1; NH=IPv4)(IPv4
O-flag, it sends a timestamped copy of the packet to a local OAM header)(payload), it processes the SRH.Flags.O-flag. As part of
process. The local OAM process sends a full or partial copy of processing the O-flag, it sends a timestamped copy of the packet
the packet P1 to the controller N100. The OAM process includes to a local OAM process. The local OAM process sends a full or
the recorded timestamp, additional OAM information like incoming partial copy of the packet P1 to the controller N100. The OAM
and outgoing interface, etc. along with any applicable metadata. process includes the recorded timestamp, additional OAM
Node N4 performs the standard SRv6 SID and SRH processing on the information like incoming and outgoing interface, etc. along with
original packet P1. Specifically, it executes the VPN SID any applicable metadata. Node N4 performs the standard SRv6 SID
(B:7:DT100) and based on lookup in table 100 forwards the packet and SRH processing on the original packet P1. Specifically, it
P1 (IPv4 header)(payload) towards CE 2. executes the VPN SID (2001:DB8:B:7:DT100::) and based on lookup in
table 100 forwards the packet P1 (IPv4 header)(payload) towards CE
2.
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 passive 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.
6.4. 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 are interested in performing
network OAM functions in a centralized manner. Various data models network OAM functions in a centralized manner. [RFC8403] describes
like YANG are available to collect data from the network and manage such a centralized OAM mechanism. Specifically, the document
it from a centralized entity. describes a procedure that can be used to perform path continuity
check between any nodes within an SR domain from a centralized
SR technology enables a centralized OAM entity to perform path monitoring system, with minimal or no control plane intervene on the
monitoring from centralized OAM entity without control plane nodes. However, the document focuses on SR networks with MPLS data
intervention on monitored nodes. [RFC 8403] describes such a plane. This document describes how the concept can be used to
centralized OAM mechanism. Specifically, the draft describes a perform path monitoring in an SRv6 network from the centralized
procedure that can be used to perform path continuity check between controller.
any nodes within an SR domain from a centralized monitoring system,
with minimal or no control plane intervene on the nodes. However,
the draft focuses on SR networks with MPLS data plane. The same
concept applies to the SRv6 networks. This document describes how
the concept can be used to perform path monitoring in an SRv6
network. This document describes how the concept can be used to
perform path monitoring in an SRv6 network as follows.
In the above reference topology, N100 is the centralized monitoring
system implementing an END function B:100:1::. In order to verify a
segment list <B:2:C31, B:4:C52>, N100 generates a probe packet with
SRH set to (B:100:1::, B:4:C52, B:2:C31, SL=2). The controller
routes the probe packet towards the first segment, which is B:2:C31.
N2 performs the standard SRv6 SID and SRH processing and forward it
over link3 with the DA of IPv6 packet set to B:4:C52. N4 also
performs the normal SRH processing and forward it over link10 with
the DA of IPv6 packet set to B:100:1::. This makes the probe loops
back to the centralized monitoring system.
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. In other words, the controller leverages the visibility of topology. The controller leverages the visibility of the topology to
the topology to monitor the paths between the various endpoints monitor the paths between the various endpoints without control plane
without control plane intervention required at the monitored nodes. intervention required at the monitored nodes.
7. Implementation Status
This section is to be removed prior to publishing as an RFC. The controller N100 advertises an END SID 2001:DB8:B:100:1::. To
monitor any arbitrary SRv6 paths, the controller can create a
loopback probe that originates and terminates on Node N100. For
example, in order to verify a segment list <2001:DB8:B:2:C31::,
2001:DB8:B:4:C52::>:
See [I-D.matsushima-spring-srv6-deployment-status] for updated o N100 generates an OAM packet (2001:DB8:A:100::,
deployment and interoperability reports. 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
probe packet towards the first segment, which is
2001:DB8:B:2:C31::.
8. Security Considerations o Node N2 executes the END.X function (2001:DB8:B:2:C31::) and
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:2:C31::, SL=1)(OAM Payload) on link3 to N3.
This document does not define any new protocol extensions and relies o Node N3, which is a classic IPv6 node, performs the standard IPv6
on existing procedures defined for ICMP. This document does not processing. Specifically, it forwards the packet based on the DA
impose any additional security challenges to be considered beyond 2001:DB8:B:4:C52:: in the IPv6 header.
security considerations described in RFC4884, RFC4443, RFC792, RFCs
that updates these RFCs, [I-D.ietf-6man-segment-routing-header] and
[I-D.ietf-spring-srv6-network-programming].
9. IANA Considerations o Node N4 executes the END.X function (2001:DB8:B:4:C52::) and
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:2:C31::, SL=0)(OAM Payload) on link10 to N5.
9.1. ICMPv6 type Numbers Registry o Node N5, which is a classic IPv6 node, performs the standard IPv6
processing. Specifically, it forwards the packet based on the DA
2001:DB8:B:100:1:: in the IPv6 header.
This document defines one ICMPv6 type Number in the "ICMPv6 'type' o Node N100 executes the standard SRv6 END function. It
Numbers" registry of [RFC4443]. Specifically, the document requests decapsulates the header and consume the probe for OAM processing.
to add the following ICMPv6 type Number to the "ICMPv6 Type Numbers" The information in the OAM payload is used to detect any missing
registry: probes, round trip delay, etc.
TBA (suggested value: 162) SRv6 OAM Message. The OAM payload type or the information carried in the OAM probe is a
local implementation decision at the controller and is outside the
scope of this document.
The document also requests the creation of a new IANA registry to the 4. Implementation Status
"ICMPv6 'Code' Fields" against the "ICMPv6 Type Numbers TBA - SRv6
OAM Message" with the following codes:
Code Name Reference This section is to be removed prior to publishing as an RFC.
--------------------------------------------------------
0 No Error This document
1 SID is not locally implemented This document
9.2. SRv6 OAM Endpoint Types See [I-D.matsushima-spring-srv6-deployment-status] for updated
deployment and interoperability reports.
This I-D requests to IANA to allocate, within the "SRv6 Endpoint 5. Security Considerations
Behaviors Registry" sub-registry belonging to the top-level "Segment-
routing with IPv6 data plane (SRv6) Parameters" registry [I-D.ietf-
spring- srv6-network-programming], the following allocations:
+------------------+-------------------+-----------+ This document does not define any new protocol extensions and relies
| Value (Suggested | Endpoint Behavior | Reference | on existing procedures defined for ICMP. This document does not
| Value) | | | impose any additional security challenges to be considered beyond
+------------------+-------------------+-----------+ security considerations described in [RFC4884], [RFC4443], [RFC0792],
| TBA (40) | End.OP | [This.ID] | and [RFC8754].
+------------------+-------------------+-----------+
9.3. Segment Routing Header Flags 6. IANA Considerations
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 [I-D.draft-ietf- "Segment Routing Header Flags" registry defined in [RFC8754].
6man-segment-routing-header].
10. Acknowledgements 7. Acknowledgements
The authors would like to thank Gaurav Naik for his review comments. The authors would like to thank Joel M. Halpern, Greg Mirsky, Bob
Hinden, Loa Andersson and Gaurav Naik for their review comments.
11. 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
Individual Individual
Email: john@leddy.net Email: john@leddy.net
skipping to change at page 18, line 34 skipping to change at page 18, line 26
Email: ddukes@cisco.com Email: ddukes@cisco.com
Cheng Li Cheng Li
Huawei Huawei
Email: chengli13@huawei.com Email: chengli13@huawei.com
Faisal Iqbal Faisal Iqbal
Individual Individual
Email: faisal.ietf@gmail.com Email: faisal.ietf@gmail.com
12. References 9. References
12.1. Normative References 9.1. Normative References
[I-D.ietf-6man-segment-routing-header] [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Filsfils, C., Dukes, D., Previdi, S., Leddy, J., Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[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)", draft-ietf-6man-segment-routing-header-26 (work in (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
progress), October 2019. <https://www.rfc-editor.org/info/rfc8754>.
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-15 (work in
progress), March 2020. progress), March 2020.
[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>.
12.2. Informative References
[I-D.matsushima-spring-srv6-deployment-status] [I-D.matsushima-spring-srv6-deployment-status]
Matsushima, S., Filsfils, C., Ali, Z., and Z. Li, "SRv6 Matsushima, S., Filsfils, C., Ali, Z., Li, Z., and K.
Implementation and Deployment Status", draft-matsushima- Rajaraman, "SRv6 Implementation and Deployment Status",
spring-srv6-deployment-status-06 (work in progress), March draft-matsushima-spring-srv6-deployment-status-07 (work in
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>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet [RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
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>.
[RFC5476] Claise, B., Ed., Johnson, A., and J. Quittek, "Packet
Sampling (PSAMP) Protocol Specifications", RFC 5476,
DOI 10.17487/RFC5476, March 2009,
<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>.
[RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
"Specification of the IP Flow Information Export (IPFIX)
Protocol for the Exchange of Flow Information", STD 77,
RFC 7011, DOI 10.17487/RFC7011, September 2013,
<https://www.rfc-editor.org/info/rfc7011>.
[RFC7012] Claise, B., Ed. and B. Trammell, Ed., "Information Model
for IP Flow Information Export (IPFIX)", RFC 7012,
DOI 10.17487/RFC7012, September 2013,
<https://www.rfc-editor.org/info/rfc7012>.
[RFC7799] Morton, A., "Active and Passive Metrics and Methods (with
Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799,
May 2016, <https://www.rfc-editor.org/info/rfc7799>.
[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>.
[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>.
Authors' Addresses Authors' Addresses
Zafar Ali Zafar Ali
Cisco Systems Cisco Systems
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