wdiff draft-ietf-6man-spring-srv6-oam-02.txt draft-ietf-6man-spring-srv6-oam-03.txt

6man Z. Ali
Internet-Draft C. Filsfils
Intended status: Standards Track Cisco Systems
Expires: May 23, June 20, 2020 S. Matsushima
Softbank
D. Voyer
Bell Canada
M. Chen
Huawei
November 20,
December 18, 2019

Operations, Administration, and Maintenance (OAM) in Segment Routing
Networks with IPv6 Data plane (SRv6)
draft-ietf-6man-spring-srv6-oam-02
draft-ietf-6man-spring-srv6-oam-03

Abstract

This document defines building blocks for Operations, Administration,
and Maintenance (OAM) in Segment Routing Networks with IPv6 Dataplane
(SRv6). The document also describes some SRv6 OAM mechanisms.

Requirements Language

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

Status of This Memo

This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.

Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."

This Internet-Draft will expire on May 23, June 20, 2020.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3
2.1. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Terminology and Reference Topology . . . . . . . . . . . 3
3. OAM Building Blocks . . . . . . . . . . . . . . . . . . . . . 5
3.1. O-flag in Segment Routing Header . . . . . . . . . . . . 5
3.1.1. O-flag Processing . . . . . . . . . . . . . . . . . . 6
3.2. OAM Segments . . . . . . . . . . . . . . . . . . . . . . 6
3.3. End.OP: OAM Endpoint with Punt . . . . . . . . . . . . . 6 7
3.4. End.OTP: OAM Endpoint with Timestamp and Punt . . . . . . 7
3.5. SRH TLV . . . . . . . . . . . . . . . . . . . . . . . . . 8
4. OAM Mechanisms . . . . . . . . . . . . . . . . . . . . . . . 8 7
4.1. Ping . . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1.1. Classic Ping . . . . . . . . . . . . . . . . . . . . 8
4.1.2. Pinging a SID Function . . . . . . . . . . . . . . . 10
4.1.3. Error Reporting . . . . . . . . . . . . . . . . . . . 12 9
4.2. Traceroute . . . . . . . . . . . . . . . . . . . . . . . 13 11
4.2.1. Classic Traceroute . . . . . . . . . . . . . . . . . 13 11
4.2.2. Traceroute to a SID Function . . . . . . . . . . . . 15 . . . . . 12
4.3. Monitoring of SRv6 Paths . . . . . . . . . . . . . . . . 18 15
5. Implementation Status . . . . . . . . . . . . . . . . . . . . 19 16
6. Security Considerations . . . . . . . . . . . . . . . . . . . 19 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 16
7.1. ICMPv6 type Numbers RegistrySEC . . . . . . . . . . . . . 20 16
7.2. SRv6 OAM Endpoint Types . . . . . . . . . . . . . . . . . 20 16
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20 17
9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 20 17
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 18
10.1. Normative References . . . . . . . . . . . . . . . . . . 22 18
10.2. Informative References . . . . . . . . . . . . . . . . . 22 19
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 23 19

1. Introduction

2. Conventions Used in This Document

2.1. Abbreviations

The following abbreviations are used in this document:

SID: Segment ID.

SL: Segment Left.

SR: Segment Routing.

SRH: Segment Routing Header.

SRv6: Segment Routing with IPv6 Data plane.

TC: Traffic Class.

ICMPv6: multi-part ICMPv6 messages [RFC4884]. Specification [RFC4443].

2.2. Terminology and Reference Topology

This document uses the terminology defined in [I-D.ietf- spring-srv6-
network-programming]. The readers are expected to be familiar with
the same.

Throughout the document, the following simple topology is used for
illustration.

+--------------------------| N100 |------------------------+
| |
====== link1====== link3------ link5====== link9------
||N1||======||N2||======| N3 |======||N4||======| N5 |
|| ||------|| ||------| |------|| ||------| |
====== link2====== link4------ link6======link10------
| |
| ------ |
+-------| N6 |---------+
link7 | | link8
------

Figure 1 Reference Topology

In the reference topology:

Nodes N1, N2, and N4 are SRv6 capable nodes.

Nodes N3, N5 and N6 are classic IPv6 nodes.

Node N100 is a controller.

Node k has a classic IPv6 loopback address A:k::/128.

A SID at node k with locator block B and function F is represented
by B:k:F::.

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
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
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
towards neighbor node i via jth Link between node i and node j.
e.g., B:2:C31:: represents END.X at N2 towards N3 via link3 (the
1st link between N2 and N3). Similarly, 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
SID to visit, S2 is the second SID to visit and S3 is the last SID
to visit along the SR path.

(SA,DA) (S3, S2, S1; SL)(payload) represents an IPv6 packet with:

* IPv6 header with source address SA, destination addresses DA
and SRH as next-header

* SRH with SID list <S1, S2, S3> with SegmentsLeft = SL

* Note the difference between the < > and () symbols: <S1, S2,
S3> represents a SID list where S1 is the first SID and S3 is
the last SID to traverse. (S3, S2, S1; SL) represents the same
SID list but encoded in the SRH format where the rightmost SID
in the SRH is the first SID and the leftmost SID in the SRH is
the last SID. When referring to an SR policy in a high-level
use-case, it is simpler to use the <S1, S2, S3> notation. When
referring to an illustration of the detailed packet behavior,
the (S3, S2, S1; SL) notation is more convenient.

* (payload) represents the the payload of the packet.

SRH[SL] represents the SID pointed by the SL field in the first
SRH. In our example, SRH[2] represents S1, SRH[1] represents S2
and SRH[0] represents S3.

3. OAM Building Blocks

This section defines the various building blocks for implementing OAM
mechanisms in SRv6 networks.

3.1. O-flag in Segment Routing Header

[I-D.ietf-6man-segment-routing-header] describes the Segment Routing
Header (SRH) and how SR capable nodes use it. The SRH contains an
8-bit "Flags" field [I-D.draft-ietf-6man-segment- routing-header].
This document defines the following bit in the SRH.Flags to carry the
O-flag:

0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
| |O| |
+-+-+-+-+-+-+-+-+

Where:

O-flag: OAM flag. When set, it indicates that this packet is an
operations and management (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
meaning and processing of any other bit in SRH.Flags is outside of
the scope of this document.

3.1.1. O-flag Processing

The SRH.Flags.O-flag implements the "punt a timestamped copy and
forward" of the
packet" behavior. This enables an SRv6 Endpoint node to send a
timestamped copy of the packets marked with o-flag to a local OAM
process. To prevent multiple evaluations of the datagram, the OAM
process MUST NOT 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]. 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.

Implementation of the O-flag is OPTIONAL. If a node does not support
the O-flag, then upon reception it simply ignores it. It is also
possible that a node is capable of supporting the O-bit but based on
a local decision it MAY ignore it during processing on some local
SIDs.

If a node supports the O-flag, it can optionally advertise its
potential via node capability advertisement in IGP [I-D.ietf-isis-
srv6- extensions] and BGP-LS [I-D.ietf-idr-bgpls-srv6-ext].

When N receives a packet whose IPv6 DA is S and S is a local SID, the
line S01 of the 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
modified as follows for the O-flag processing.

S01.1. IF SRH.Flags.O-flag is set and local configuration permits
O-flag processing THEN
a. Make a copy of the packet.
b. Send the copied packet, along with an accurate a timestamp
to the OAM process. ;; Ref1, Ref2 Ref1
Ref1: An implementation SHOULD copy and record the timestamp as soon as
possible during packet processing. Timestamp is not carried in the packet
forwarded to the next hop.
Ref2: An implementation SHOULD NOT generate ICMP error during
local SID S processing. If local SID S processing requires generation
of an ICMP error, the error is generated by the local OAM process.

Please note that the O-flag processing happens before execution of
regular processing of the local SID S.

3.2. OAM Segments

The presence of an OAM Segment IDs (SIDs) is another component SID in the Destination address of the SRv6 IPv6
header instructs the segment endpoint implementing the OAM building
Blocks. This document defines a couple SID that
the content of OAM SIDs. the packet is of interest to the node and to process
the upper-layer payload, accordingly.

3.3. End.OP: OAM Endpoint with Punt

Many scenarios require punting of SRv6 OAM packets at the desired
nodes in the network. The "OAM Endpoint with Punt" function (End.OP
for short) represents a particular OAM function to implement the punt
behavior for an OAM packet. It is described using the pseudocode as
follows:

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 ;; Ref1

Ref1:

The local OAM process SHOULD NOT generate further processes the packet, this MAY involve
processing protocol layers above IPv6. For example, ping and
traceroute will require ICMP error during
local SID S or UDP protocol processing.

Please note that in an SRH containing END.OP SID, it Once the
packet leaves the IPv6 layer the processing is RECOMMENDED
to set considered host
processing and the SRH.Flags.O-flag = 0. upper layer protocols MUST be processed as such.

3.4. End.OTP: OAM Endpoint with Timestamp and Punt

Scenarios demanding performance management of an SR policy/ path
requires hardware timestamping before hardware punts the packet to
the software for OAM processing. The "OAM Endpoint with Timestamp
and Punt" function (End.OTP for short) represents an OAM SID function
to implement the timestamp and punt behavior for an OAM packet. It
is described using the pseudocode as follows:

When N receives a packet destined to S and S is a local End.OTP SID,
N does:

S01.1. Timestamp the packet ;; Ref1

2.
S01.2. Send the packet, along with an accurate a timestamp, to the
OAM process ;; Ref2
Ref1: Timestamping SHOULD be done in hardware, as soon as possible
during the packet processing.
Ref2:

Please note that in an SRH containing END.OTP SID, it is RECOMMENDED
to set Once the SRH.Flags.O-flag = 0.

3.5. SRH TLV

[I-D.ietf-6man-segment-routing-header] defines TLVs of
packet leaves the Segment
Routing Header.

SRH TLV plays an important role in carrying OAM IPv6 layer the processing is considered host
processing and Performance
Management (PM) metadata. the upper layer protocols MUST be processed as such.

4. OAM Mechanisms

This section describes how OAM mechanisms can be implemented using
the OAM building blocks described in the previous section.
Additional OAM mechanisms will be added in a future revision of the
document.

[RFC4443] describes Internet Control Message Protocol for IPv6
(ICMPv6) that is used by IPv6 devices for network diagnostic and
error reporting purposes. As Segment Routing with IPv6 data plane
(SRv6) simply adds a new type of Routing Extension Header, existing
ICMPv6 ping mechanisms can be used in an SRv6 network. This section
describes the applicability of ICMPv6 in the SRv6 network and how the
existing ICMPv6 mechanisms can be used for providing OAM
functionality.

The document does not propose any changes to the standard ICMPv6
[RFC4443], [RFC4884] or standard ICMPv4 [RFC792].

4.1. Ping

There is no hardware or software change required for ping operation
at

The following subsections outline some use cases of the classic IPv6 nodes ICMP ping in an
the SRv6 network. That includes the
classic IPv6 node with ingress, egress or transit roles.
Furthermore, no protocol changes are required to the standard ICMPv6
[RFC4443], [RFC4884] or standard ICMPv4 [RFC792]. In other words,
existing ICMP ping mechanisms work seamlessly in the SRv6 networks.

The following subsections outline some use cases of the ICMP ping in
the SRv6 networks.

4.1.1. Classic Ping

The existing mechanism to ping a remote IP prefix, along networks.

4.1.1. Classic Ping

The existing mechanism to ping a remote IP prefix, along the shortest
path, continues to work without any modification. 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 node.

If an SRv6 capable ingress node wants to ping an IPv6 prefix via an
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
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 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>.

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,
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:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max = 0.625
/0.749/0.931 ms

Figure 2 A sample ping output at an SRv6 capable node

All transit nodes process the echo request message like any other
data packet carrying SR header and hence do not require any change.
Similarly, the egress node (IPv6 classic or SRv6 capable) does not
require any change to process the ICMPv6 echo request. For example,
in the ping example of Figure 2:

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 =
ICMPv6)(ICMPv6 Echo Request).

o Node N2, which is an SRv6 capable node, performs the standard SRH
processing. Specifically, it executes the END.X function
(B:2:C31) and forwards the packet on link3 to N3.

o Node N3, which is a classic IPv6 node, performs the standard IPv6
processing. Specifically, it forwards the echo request based on
DA B:4:C52 in the IPv6 header.

o Node N4, which is an SRv6 capable node, performs the standard SRH
processing. Specifically, it observes the END.X function
(B:4:C52) with PSP (Penultimate Segment POP) on the echo request
packet and removes the SRH and forwards the packet across link10
to N5.

o The echo request packet at N5 arrives as an IPv6 packet without an
SRH. Node N5, which is a classic IPv6 node, performs the standard
IPv6/ ICMPv6 processing on the echo request and responds,
accordingly.

4.1.2. Pinging a SID Function

The classic ping described in the previous section cannot be used to
ping a remote SID function, as explained using an example in the
following.

Consider the case where the user wants to ping the remote SID
function B:4:C52, via B:2:C31, B:4:C52 from node N1. Node N1 constructs the ping packet
(A:1::, B:2:C31)(B:4:C52, B:2:C31, SL=1;
NH=ICMPv6)(ICMPv6 B:4:C52)(ICMPv6 Echo Request). The ping fails because the
node N4 receives the ICMPv6 echo request with DA set to B:4:C52 but
the next header is ICMPv6, instead of SRH.

To solve this problem, the
initiator needs to mark the perform ICMPv6 ping to a target SID an echo request as an OAM packet.

The OAM packets are identified either message is
generated by setting the O-flag in SRH or
by inserting initiator with the END.OP/ END.OP or END.OTP SIDs at an appropriate place SID in the
SRH. The following illustration uses END.OTP SID but
segment-list of the procedures
are equally applicable to SRH immediately preceding the END.OP target SID.

In an SRv6 network, the user can exercise two flavors of the ping:
end-to-end ping There
MAY or segment-by-segment ping, as outlined in MAY NOT be additional segments preceding the
following subsection.

4.1.2.1. End-to-end ping using END.OP/ END.OTP

The end-to-end ping illustration uses
SID.

When the END.OTP node instantiating a SID but S of type END.OP or END.OTP
receives a packet with S in the
procedures are equally applicable destination address of the IPv6
header it sends it to the END.OP OAM process. The OAM process verifies the
segment following S is a locally instantiated SID.

Consider It then processes
the same example where Upper layer header of the user wants to ping a remote SID
function B:4:C52, via B:2:C31, from node N1. To force packet, as a punt of host, responding to the
ICMPv6
echo request at the node N4, node N1 inserts the END.OTP SID
just before the target SID B:4:C52 message in the SRH. The ICMPv6 echo
request payload.

When the segment following S is processed at not verified by the individual nodes OAM process an
ICMPv6 error message type 4 (parameter problem) code 0 (erroneous
header field encountered) with pointer set to the segment following S
(the target SID) is generated for the packet and the packet is
discarded.

An implementation of the OAM process SID verification SHOULD do the
following:

o Verify that the SID is locally instantiated.

o Verify that the SID is instantiated in the data plane (this may
include verification of the SID in NPUs or forwarding hardware, as
applicable).

4.1.2.1. Ping using END.OP/ END.OTP

This section uses END.OTP SID for the ping illustration but the
procedures are equally applicable to the END.OP SID.

Consider the example where the user wants to ping a remote SID
function B:4:C52, via B:2:C31, from node N1. To force a punt of the
ICMPv6 echo request at the node N4, node N1 inserts the END.OTP SID
just before the target SID B:4:C52 in the SRH. The ICMPv6 echo
request is processed at the individual nodes along the path as
follows:

o Node N1 initiates an ICMPv6 ping packet with SRH as follows
(A:1::, B:2:C31)(B:4:C52, B:4:OTP, B:2:C31; SL=2;
NH=ICMPv6)(ICMPv6 Echo Request).

o Node N2, which is an SRv6 capable node, performs the standard SRH
processing. Specifically, it executes the END.X function
(B:2:C31) on the echo request packet.

o Node N3 receives the packet as follows (A:1::, B:4:OTP)(B:4:C52,
B:4:OTP, 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
DA B:4:OTP in the IPv6 header.

o When node N4 receives the packet (A:1::, B:4:OTP)(B:4:C52,
B:4:OTP, B:2:C31 ; SL=1; NH=ICMPv6)(ICMPv6 Echo Request), it
processes the END.OTP SID, as described in the pseudocode in
Section 3. The packet gets time-stamped and punted to the ICMPv6 OAM
process for processing. The ICMPv6 OAM process checks if the next SID in
SRH (the target SID B:4:C52) is locally programmed.

o If the target next SID is not locally programmed, N4 responses with the OAM process returns
an ICMPv6 error message (Type: "SRv6 OAM (TBA)", Code: "SID not locally
implemented (TBA)"); otherwise a success is returned.

4.1.2.2. Segment-by-segment ping using O-flag (Proof of Transit)

Consider type 4 (parameter problem) code 0
(erroneous header field encountered) with pointer set to the same example where
target SID B:4:C52 and the user wants to ping a remote packet is discarded.

o If the next SID
function B:4:C52, via B:2:C31, from node N1. However, in this ping, is locally programmed, the node N1 wants to get a response from each segment node in processes the SRH
as a "proof
upper layer header. As part of transit". In other words, in the segment-by-segment
ping case, the node N1 expects a response from node N2 and upper layer header (ICMPv6)
processing node N4
for their respective local SID function. When a response to O-bit is
desired from sends the last SID in a SID-list, it ICMPv6 Echo Reply message [RFC4443].

4.2. Traceroute

There is no hardware or software change required for traceroute
operation at the responsibility of classic IPv6 nodes in an SRv6 network. That
includes the ingress classic IPv6 node with ingress, egress or transit roles.
Furthermore, no protocol changes are required to use USP as the last SID. E.g., standard
traceroute operations. In other words, existing traceroute
mechanisms work seamlessly in this example, the target SID B:4:C52 is a USP SID.

To force a punt SRv6 networks.

The following subsections outline some use cases of the ICMPv6 echo request at node N2 and node N4,
node N1 sets the O-flag traceroute in SRH. The ICMPv6 echo request is processed
at
the individual nodes SRv6 networks.

4.2.1. Classic Traceroute

The existing mechanism to traceroute a remote IP prefix, along the path as follows:

o Node N1 initiates
shortest path, continues to work without any modification. The
initiator may be an ICMPv6 ping packet with SRH as follows
(A:1::, B:2:C31)(B:4:C52, B:2:C31; SL=1, Flags.O=1;
NH=ICMPv6)(ICMPv6 Echo Request).

o When SRv6 node N2 receives or a classic IPv6 node. Similarly, the packet (A:1::, B:2:C31)(B:4:C52,
B:2:C31; SL=1, Flags.O=1; NH=ICMPv6)(ICMPv6 Echo Request) packet,
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
via an arbitrary segment list <S1, S2, S3>, it processes needs to initiate
traceroute probe with an SR header containing the O-flag in SRH, as described in SID list <S1, S2,
S3>. That is illustrated using the pseudocode topology in
Section 3. A time-stamped copy of Figure 1. Assume all
the packet gets punted links have IGP metric 10 except both links between node2 and
node3, which have IGP metric set to the
ICMPv6 process for processing. Node N2 continues to apply the
B:2:C31 SID function on the original packet and forwards it,
accordingly. As B:4:C52 is a USP SID, N2 does not remove the SRH.
The ICMPv6 process at node N2 checks if its local SID (B:2:C31) is
locally programmed or not and responds to the ICMPv6 Echo Request.

o If the target SID is not locally programmed, N4 responses with the
ICMPv6 message (Type: "SRv6 OAM (TBA)", Code: "SID not locally
implemented (TBA)"); otherwise a success is returned. Please note
that, as mentioned in Section 3, if node N2 does not support the
O-flag, it simply ignores it and process the local SID, B:2:C31.

o Node N3, which is a classic IPv6 node, performs the standard IPv6
processing. Specifically, it forwards the echo request based on
DA B:4:C52 in the IPv6 header.

o When node N4 receives the packet (A:1::, B:4:C52)(B:4:C52,
B:2:C31; SL=0, Flags.O=1; NH=ICMPv6)(ICMPv6 Echo Request), it
processes the O-flag in SRH, as described in the pseudocode in
Section 3. A time-stamped copy of the packet gets punted to the
ICMPv6 process for processing. The ICMPv6 process at node N4
checks if its local SID (B:4:C52) is locally programmed or not and
responds to the ICMPv6 Echo Request.

o If the target SID is not locally programmed, N4 responses with the
ICMPv6 message (Type: "SRv6 OAM (TBA)", Code: "SID not locally
implemented (TBA)"); otherwise a success is returned.

Support for O-flag is part of node capability advertisement. That
enables node N1 to know which segment nodes are capable of responding
to the ICMPv6 echo request. Node N1 processes the echo responses and
presents data to the user, accordingly.

Please note that segment-by-segment ping can be used to address proof
of transit use-case.

4.1.3. Error Reporting

Any IPv6 node can use ICMPv6 control messages to report packet
processing errors to the host that originated the datagram packet.
To name a few such scenarios:

o If the router receives an undeliverable IP datagram, or

o If the router receives a packet with a Hop Limit of zero, or

o If the router receives a packet such that if the router decrements
the packet's Hop Limit it becomes zero, or

o If the router receives a packet with problem with a field in the
IPv6 header or the extension headers such that it cannot complete
processing the packet, or

o If the router cannot forward a packet because the packet is larger
than the MTU of the outgoing link.

In the scenarios listed above, the ICMPv6 response also contains the
IP header, IP extension headers and leading payload octets of the
"original datagram" to which the ICMPv6 message is a response.
Specifically, the "Destination Unreachable Message", "Time Exceeded
Message", "Packet Too Big Message" and "Parameter Problem Message"
ICMPV6 messages can contain as much of the invoking packet as
possible without the ICMPv6 packet exceeding the minimum IPv6 MTU
[RFC4443], [RFC4884]. In an SRv6 network, the copy of the invoking
packet contains the SR header. The packet originator can use this
information for diagnostic purposes. For example, traceroute can use
this information as detailed in the following subsection.

4.2. Traceroute

There is no hardware or software change required for traceroute
operation at the classic IPv6 nodes in an SRv6 network. That
includes the classic IPv6 node with ingress, egress or transit roles.
Furthermore, no protocol changes are required to the standard
traceroute operations. In other words, existing traceroute
mechanisms work seamlessly in the SRv6 networks.

The following subsections outline some use cases of the traceroute in
the SRv6 networks.

4.2.1. Classic Traceroute

The existing mechanism to traceroute a remote IP prefix, along the
shortest path, continues to work without any modification. 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.

If an SRv6 capable ingress node wants to traceroute to IPv6 prefix
via an arbitrary segment list <S1, S2, S3>, it needs to initiate
traceroute probe with an SR header containing the SID list <S1, S2,
S3>. That is 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 set to 100. User issues a traceroute
from node N1 to a loopback of node 5, via segment list <B:2:C31,
B:4:C52>. Figure 3 contains sample output for the traceroute
request.

> traceroute A:5:: via segment-list B:2:C31, B:4:C52

Tracing the route to B5::
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 information for hop2 is returned by N3, which is a
classic IPv6 node. Nonetheless, the ingress node is able to display
SR header contents as the packet travels through the IPv6 classic
node. This is because the "Time Exceeded Message" ICMPv6 message can
contain as much of the invoking packet as possible without the ICMPv6
packet exceeding the minimum IPv6 MTU [RFC4443]. The SR header is
also included in these ICMPv6 messages initiated by the classic IPv6
transit nodes that are not running SRv6 software. Specifically, a
node generating ICMPv6 message containing a copy of the invoking
packet does not need to understand the extension header(s) in the
invoking packet.

The segment list information returned for hop1 is returned by N2,
which is an SRv6 capable node. Just like for hop2, the ingress node
is able to display SR header contents for hop1.

There is no difference in processing of the traceroute probe at an
IPv6 classic node and an SRv6 capable node. Similarly, both IPv6
classic and SRv6 capable nodes may use the address of the interface
on which probe was received as the source address in the ICMPv6
response. ICMP extensions defined in [RFC5837] can be used to also
display information about the IP interface through which the datagram
would have been forwarded had it been forwardable, and the IP next
hop to which the datagram would have been forwarded, the IP interface
upon which a datagram arrived, the sub-IP component of an IP
interface upon which 100. User issues a datagram arrived.

The information about the IP address of the incoming interface on
which the traceroute probe was received by the reporting
from node is very
useful. This information can also be used N1 to verify if SID functions
B:2:C31 and B:4:C52 are executed correctly by N2 and N4,
respectively. Specifically, the information displayed for hop2 a loopback of node 5, via segment list <B:2:C31,
B:4:C52>. Figure 3 contains sample output for the incoming interface address 2001:DB8:2:3:31:: at N3.
This matches with traceroute
request.

> traceroute A:5:: via segment-list B:2:C31, B:4:C52

Tracing the expected interface bound route to END.X function
B:2:C31 (link3). Similarly, the information displayed for hop5
contains the incoming interface address A:5::
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 N5.
This matches with the expected interface bound to the END.X function
B:4:C52 (link10).

4.2.2. Traceroute to an SRv6 capable node

Please note that information for hop2 is returned by N3, which is a SID Function

The
classic traceroute described in IPv6 node. Nonetheless, the previous section cannot be
used ingress node is able to traceroute a remote SID function, display
SR header contents as explained using an
example in the following.

Consider the case where the user wants to traceroute packet travels through the remote SID
function B:4:C52, via B:2:C31, from node N1. The trace route fails
at N4. IPv6 classic
node. This is because the node N4 trace route probe where next
header is UDP or ICMPv6, instead "Time Exceeded Message" ICMPv6 message can
contain as much of SRH (even though the hop limit is
set to 1). To solve this problem, the initiator needs to mark invoking packet as possible without the ICMPv6 echo request as an OAM packet.

The OAM packets are identified either by setting
packet exceeding the O-flag minimum IPv6 MTU [RFC4443]. The SR header is
also included in SRH or these ICMPv6 messages initiated by inserting the END.OP or END.OTP SID at an appropriate place classic IPv6
transit nodes that are not running SRv6 software. Specifically, a
node generating ICMPv6 message containing a copy of the invoking
packet does not need to understand the extension header(s) in the
SRH.

In
invoking packet.

The segment list information returned for hop1 is returned by N2,
which is an SRv6 network, capable node. Just like for hop2, the user can exercise two flavors ingress node
is able to display SR header contents for hop1.

There is no difference in processing of the
traceroute: hop-by-hop traceroute or overlay traceroute.

o In hop-by-hop traceroute, user gets responses from all nodes
including probe at an
IPv6 classic node and an SRv6 capable node. Similarly, both IPv6 transit nodes,
classic and SRv6 capable transit nodes may use the address of the interface
on which probe was received as well as SRv6 capable segment endpoints. E.g., consider the
example where source address in the user wants to traceroute ICMPv6
response. ICMP extensions defined in [RFC5837] can be used to a remote SID
function B:4:C52, via B:2:C31, from node N1. The traceroute
output will also
display information about node3, the IP interface through which is a
transit (underlay) node.

o The overlay traceroute, on the other hand, does not trace datagram
would have been forwarded had it been forwardable, and the
underlay nodes. In other words, IP next
hop to which the overlay traceroute only
displays datagram would have been forwarded, the nodes that acts as SRv6 segments along IP interface
upon which a datagram arrived, the route.
I.e., in sub-IP component of an IP
interface upon which a datagram arrived.

The information about the example where IP address of the user wants to traceroute to a
remote SID function B:4:C52, via B:2:C31, from node N1, incoming interface on
which the
overlay traceroute would only display probe was received by the traceroute information
from reporting node is very
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 node N4; it will not display N4,
respectively. Specifically, the information from
node 3.

4.2.2.1. Hop-by-hop traceroute using END.OP/ END.OTP

In this section, hop-by-hop traceroute displayed for hop2
contains the incoming interface address 2001:DB8:2:3:31:: at N3.
This matches with the expected interface bound to a SID END.X function is
exemplified using UDP probes. However,
B:2:C31 (link3). Similarly, the procedure is equally
applicable to other implementation of traceroute mechanism.

Furthermore, information displayed for hop5
contains the illustration uses incoming interface address 2001:DB8:4:5::52:: at N5.
This matches with the expected interface bound to the END.OTP END.X function
B:4:C52 (link10).

4.2.2. Traceroute to a SID but

The classic traceroute described in the procedures
are equally applicable previous section cannot be
used to traceroute a remote SID function, as explained using an
example in the END.OP SID. following.

Consider the same example case where the user wants to traceroute to a the remote SID
function B:4:C52, via B:2:C31, B:4:C52 from node N1. To force a
punt of the traceroute probe only at the node N4, node N1 inserts the
END.OTP SID just before the target SID B:4:C52 in the SRH. The
traceroute probe is processed trace route fails at N4. This is
because the individual nodes along the path
as follows:

o Node N1 initiates node N4 receives a traceroute trace route probe packet with a monotonically
increasing value where next header is
UDP or ICMPv6, instead of hop count and SRH as follows (A:1::,
B:2:C31)(B:4:C52, B:4:OTP, B:2:C31; SL=2; NH=UDP)(Traceroute
probe).

o When node N2 receives the packet with hop-count = 1, it processes (even though the hop count expiry. Specifically, the node N2 responses with
the ICMPv6 message (Type: "Time Exceeded", Code: "Time to Live
exceeded in Transit").

o When Node N2 receives the packet with hop-count > 1, it performs
the standard SRH processing. Specifically, it executes the END.X
function (B:2:C31) on the traceroute probe.

o When node N3, which limit is a classic IPv6 node, receives the packet
(A:1::, B:4:OTP)(B:4:C52, B:4:OTP, B:2:C31 ; HC=1, SL=1;
NH=UDP)(Traceroute probe) with hop-count = 1, it processes the hop
count expiry. Specifically, the node N3 responses with the ICMPv6
message (Type: "Time Exceeded", Code: "Time set to Live exceeded in
Transit").

o When node N3, which is
1).

To traceroute a classic IPv6 node, receives target SID a probe message is generated by the packet
initiator with hop-count > 1, it performs the standard IPv6 processing.
Specifically, it forwards the traceroute probe based on DA B:4:OTP END.OP or END.OTP SID in the IPv6 header.

o When node N4 receives segment-list of the packet (A:1::, B:4:OTP)(B:4:C52,
B:4:OTP, B:2:C31 ; SL=1; HC=1, NH=UDP)(Traceroute probe), it
processes
SRH immediately preceding the END.OTP SID, as described in target SID. There MAY or MAY NOT be
additional segments preceding the pseudocode in
Section 3. END.OP/ END.OTP SID.

The node instantiating a SID S of type END.OP or END.OTP receives a
packet gets timestamped with S in the destination address of the IPv6 header and punted sends
it to the
traceroute OAM process for processing. (before processing the TTL). The traceroute OAM process checks
if
verifies the next SID in SRH (the target SID B:4:C52) segment following S is a locally
programmed.

o If instantiated SID. It
then processes the target SID B:4:C52 is locally programmed, node N4 responses
with Upper layer header of the ICMPv6 message (Type: Destination unreachable, Code: Port
Unreachable). If packet, as a host,
responding to the target SID B:4:C52 probe message.

When the segment following S is not a local SID, node
N4 silently drops the traceroute probe.

Figure 4 displays a sample traceroute output for this example.

> traceroute srv6 B:4:C52 via segment-list B:2:C31

Tracing verified by 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:OTP, 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:OTP, 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:OTP, B:2:C31; SL=1)

Figure OAM process an
ICMPv6 error message type 4 A sample output for hop-by-hop traceroute (parameter problem) code 0 (erroneous
header field encountered) with pointer set to a the segment following S
(the target SID) is generated for the packet and the packet is
discarded.

An implementation of the OAM process SID function

4.2.2.2. Tracing SRv6 Overlay

The overlay traceroute does not trace verification SHOULD do the underlay nodes, i.e., only
displays
following:

o Verify that the nodes SID is locally instantiated.

o Verify that acts as SRv6 segments along the path. This SID is achieved by setting instantiated in the data plane (this may
include verification of the SRH.Flags.O bit. SID in NPUs or forwarding hardware, as
applicable).

4.2.2.1. Traceroute using END.OP/ END.OTP

In this section, overlay hop-by-hop traceroute to a SID function is
exemplified using UDP probes. However, the procedure is equally
applicable to other implementation of traceroute mechanism.
Furthermore, the illustration uses the END.OTP SID but the procedures
are equally applicable to the END.OP SID.

Consider the same example where the user wants to traceroute to a
remote SID function B:4:C52, via B:2:C31, from node N1. To force a
punt of the traceroute probe only at the node N4, node N1 inserts the
END.OTP SID just before the target SID B:4:C52 in the SRH. The
traceroute probe is processed at the individual nodes along the path
as follows:

o Node N1 initiates a traceroute probe packet with a monotonically
increasing value of hop count and SRH as follows (A:1::,
B:2:C31)(B:4:C52, B:4:OTP, B:2:C31; HC=64, SL=1, Flags.O=1; SL=2; NH=UDP)(Traceroute Probe). Please note that the hop-count is set
to 64 to skip the underlay nodes from tracing. The O-flag in SRH
is set to make the overlay nodes (nodes processing the SRH)
respond.
probe).

o When node N2 receives the packet (A:1::, B:2:C31)(B:4:C52,
B:2:C31; SL=1, HC=64, Flags.O=1; NH=UDP)(Traceroute Probe), with hop-count = 1, it processes
the O-flag in SRH, as described in hop count expiry. Specifically, the pseudocode node N2 responses with
the ICMPv6 message (Type: "Time Exceeded", Code: "Time to Live
exceeded in
Section 3. A time-stamped copy of Transit").

o When Node N2 receives the packet gets punted to with hop-count > 1, it performs
the
traceroute process for standard SRH processing. Node N2 continues to apply Specifically, it executes the
B:2:C31 SID END.X
function (B:2:C31) on the original packet and forwards it,
accordingly. The traceroute process at node N2 checks if its
local SID (B:2:C31) is locally programmed. If the SID probe.

o When node N3, which is not
locally programmed, it silently drops a classic IPv6 node, receives the packet. Otherwise, packet
(A:1::, B:4:OTP)(B:4:C52, B:4:OTP, B:2:C31 ; HC=1, SL=1;
NH=UDP)(Traceroute probe) with hop-count = 1, it
performs processes the egress check by looking at hop
count expiry. Specifically, the SL value in SRH.

o As SL is not equal to zero (i.e., it's not egress node), node N2 N3 responses with the ICMPv6
message (Type: "SRv6 OAM (TBA)", "Time Exceeded", Code:
"O-flag punt at Transit (TBA)"). Please note that, as mentioned "Time to Live exceeded in Section 3, if node N2 does not support the O-flag, it simply
ignores it and processes the local SID, B:2:C31.
Transit").

o When node N3 N3, which is a classic IPv6 node, receives the packet (A:1::, B:4:C52)(B:4:C52,
B:2:C31; SL=0, HC=63, Flags.O=1; NH=UDP)(Traceroute Probe),
with hop-count > 1, it performs the standard IPv6 processing.
Specifically, it forwards the traceroute probe based on DA B:4:C52 B:4:OTP
in the IPv6 header.
Please note that there is no hop-count expiration at the transit
nodes.

o When node N4 receives the packet (A:1::, B:4:C52)(B:4:C52,
B:2:C31; SL=0, HC=62, Flags.O=1; B:4:OTP)(B:4:C52,
B:4:OTP, B:2:C31 ; SL=1; HC=1, NH=UDP)(Traceroute Probe), probe), it
processes the O-flag in SRH, END.OTP SID, as described in the pseudocode in
Section 3. A time-stamped copy of Before hop-limit processing, the packet gets
timestamped and punted to the
traceroute OAM process for processing. The traceroute OAM
process at node
N4 checks if its local the next SID (B:2:C31) in SRH (the target SID B:4:C52) is
locally programmed.

o If the next SID is not locally programmed, it silently drops the
packet. Otherwise, it performs OAM process returns
an ICMPv6 error message type 4 (parameter problem) code 0
(erroneous header field encountered) with pointer set to the egress check by looking at
target SID B:4:C52 and the
SL value in SRH. As SL packet is equal to zero (i.e., N4 discarded.

o If the next SID is locally programmed, the egress
node), node N4 tries to consume processes the UDP probe.
upper layer header. As UDP probe is
set to access an invalid port, part of the upper layer header processing
node N4 responses with the ICMPv6 message (Type: Destination
unreachable, Code: Port
Unreachable) Unreachable).

Figure 5 4 displays a sample overlay traceroute output for this example. Please note that the underlay node N3 does not appear in
the output.

> traceroute srv6 B:4:C52 via segment-list B:2:C31

Tracing the route to SID function B:4:C52
1 2001:DB8:1:2:21:: 2001:DB8:1:2:21 0.512 msec 0.425 msec 0.374 msec
SRH: (B:4:C52, B:4:OTP, B:2:C31; SL=1) SL=2)
2 2001:DB8:3:4::41:: 2001:DB8:2:3:31 0.721 msec 0.810 msec 0.795 msec
SRH: (B:4:C52, B:4:OTP, 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:OTP, B:2:C31; SL=0) SL=1)

Figure 5 4 A sample output for overlay hop-by-hop traceroute to a SID function

4.3. Monitoring of SRv6 Paths

In the recent past, network operators are interested in performing
network OAM functions in a centralized manner. Various data models
like YANG are available to collect data from the network and manage
it from a centralized entity.

SR technology enables a centralized OAM entity to perform path
monitoring from centralized OAM entity without control plane
intervention on monitored nodes. [RFC 8403] describes such a
centralized OAM mechanism. Specifically, the draft describes a
procedure that can be used to perform path continuity check between
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 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
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
topology. In other words, the controller leverages the visibility of
the topology to monitor the paths between the various endpoints
without control plane intervention required at the monitored nodes.

5. Implementation Status

This section is to be removed prior to publishing as an RFC.

See [I-D.matsushima-spring-srv6-deployment-status] for updated
deployment and interoperability reports.

6. Security Considerations

This document does not define any new protocol extensions and relies
on existing procedures defined for ICMP. This document does not
impose any additional security challenges to be considered beyond
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].

7. IANA Considerations

7.1. ICMPv6 type Numbers RegistrySEC

This document defines one ICMPv6 Message, a type that has been
allocated from the "ICMPv6 'type' Numbers" registry of [RFC4443].
Specifically, it requests to add the following to the "ICMPv6 Type
Numbers" registry:

TBA (suggested value: 162) SRv6 OAM Message.

The document also requests the creation of a new IANA registry to the
"ICMPv6 'Code' Fields" against the "ICMPv6 Type Numbers TBA - SRv6
OAM Message" with the following codes:

Code Name Reference
--------------------------------------------------------
0 No Error This document
1 SID is not locally implemented This document
2 O-flag punt at Transit This document

7.2. SRv6 OAM Endpoint Types

This I-D requests to IANA to allocate, within the "SRv6 Endpoint
Behaviors Registry" sub-registry belonging to the top-level "Segment-
routing with IPv6 dataplane (SRv6) Parameters" registry [I-D.ietf-
spring- srv6-network-programming], the following allocations:

8. Acknowledgements

The authors would like to thank Gaurav Naik for his review comments.

9. Contributors

The following people have contributed to this document:

Robert Raszuk
Bloomberg LP
Email: robert@raszuk.net

John Leddy
Individual
Email: john@leddy.net

Gaurav Dawra
LinkedIn
Email: gdawra.ietf@gmail.com

Bart Peirens
Proximus
Email: bart.peirens@proximus.com

Nagendra Kumar
Cisco Systems, Inc.
Email: naikumar@cisco.com

Carlos Pignataro
Cisco Systems, Inc.
Email: cpignata@cisco.com
Rakesh Gandhi
Cisco Systems, Inc.
Canada
Email: rgandhi@cisco.com

Frank Brockners
Cisco Systems, Inc.
Germany
Email: fbrockne@cisco.com

Darren Dukes
Cisco Systems, Inc.
Email: ddukes@cisco.com

Cheng Li
Huawei
Email: chengli13@huawei.com

Faisal Iqbal
Individual
Email: faisal.ietf@gmail.com

10. References

10.1. Normative References

[I-D.ietf-6man-segment-routing-header]
Filsfils, C., Dukes, D., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", draft-ietf-6man-segment-routing-header-26 (work in
progress), October 2019.

[I-D.ietf-spring-srv6-network-programming]
Filsfils, C., Camarillo, P., Leddy, J., Voyer, D.,
Matsushima, S., and Z. Li, "SRv6 Network Programming",
draft-ietf-spring-srv6-network-programming-05
draft-ietf-spring-srv6-network-programming-06 (work in
progress), October December 2019.

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.

10.2. Informative References

[I-D.matsushima-spring-srv6-deployment-status]
Matsushima, S., Filsfils, C., Ali, Z., and Z. Li, "SRv6
Implementation and Deployment Status", draft-matsushima-
spring-srv6-deployment-status-02
spring-srv6-deployment-status-04 (work in progress),
October
December 2019.

[RFC0792] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, DOI 10.17487/RFC0792, September 1981,
<https://www.rfc-editor.org/info/rfc792>.

[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", STD 89,
RFC 4443, DOI 10.17487/RFC4443, March 2006,
<https://www.rfc-editor.org/info/rfc4443>.

[RFC4884] Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
"Extended ICMP to Support Multi-Part Messages", RFC 4884,
DOI 10.17487/RFC4884, April 2007,
<https://www.rfc-editor.org/info/rfc4884>.

[RFC5837] Atlas, A., Ed., Bonica, R., Ed., Pignataro, C., Ed., Shen,
N., and JR. Rivers, "Extending ICMP for Interface and
Next-Hop Identification", RFC 5837, DOI 10.17487/RFC5837,
April 2010, <https://www.rfc-editor.org/info/rfc5837>.

[RFC8403] Geib, R., Ed., Filsfils, C., Pignataro, C., Ed., and N.
Kumar, "A Scalable and Topology-Aware MPLS Data-Plane
Monitoring System", RFC 8403, DOI 10.17487/RFC8403, July
2018, <https://www.rfc-editor.org/info/rfc8403>.

Authors' Addresses

Zafar Ali
Cisco Systems

Email: zali@cisco.com

Clarence Filsfils
Cisco Systems

Email: cfilsfil@cisco.com
Satoru Matsushima
Softbank

Email: satoru.matsushima@g.softbank.co.jp

Daniel Voyer
Bell Canada

Email: daniel.voyer@bell.ca

Mach Chen
Huawei

Email: mach.chen@huawei.com