Network Work group N. Kumar
Internet-Draft G. Swallow
Intended status: Standards Track C. Pignataro
Expires: November 11, 2016 Cisco Systems, Inc.
N. Akiya
Big Switch Networks
S. Kini
Individual
H. Gredler
Juniper Networks
M. Chen
Huawei
May 10, 2016
Label Switched Path (LSP) Ping/Trace for Segment Routing Networks Using
MPLS Dataplane
draft-ietf-mpls-spring-lsp-ping-00
Abstract
Segment Routing architecture leverages the source routing and
tunneling paradigms and can be directly applied to MPLS data plane.
A node steers a packet through a controlled set of instructions
called segments, by prepending the packet with a Segment Routing
header.
The segment assignment and forwarding semantic nature of Segment
Routing raises additional consideration for connectivity verification
and fault isolation in LSP with Segment Routing architecture. This
document illustrates the problem and describe a mechanism to perform
LSP Ping and Traceroute on Segment Routing network over MPLS data
plane.
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 http://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."
Kumar, et al. Expires November 11, 2016 [Page 1]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
This Internet-Draft will expire on November 11, 2016.
Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Challenges with Existing mechanism . . . . . . . . . . . . . 4
4.1. Path validation in Segment Routing networks . . . . . . . 4
4.2. Service Label . . . . . . . . . . . . . . . . . . . . . . 5
5. Segment ID sub-TLV . . . . . . . . . . . . . . . . . . . . . 5
5.1. IPv4 IGP-Prefix Segment ID . . . . . . . . . . . . . . . 5
5.2. IPv6 IGP-Prefix Segment ID . . . . . . . . . . . . . . . 6
5.3. IGP-Adjacency Segment ID . . . . . . . . . . . . . . . . 7
6. Extension to Downstream Mapping TLV . . . . . . . . . . . . . 8
7. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. FECs in Target FEC Stack TLV . . . . . . . . . . . . . . 9
7.2. FEC Stack Change sub-TLV . . . . . . . . . . . . . . . . 10
7.3. Segment ID POP Operation . . . . . . . . . . . . . . . . 10
7.4. Segment ID Check . . . . . . . . . . . . . . . . . . . . 10
7.5. TTL Consideration for traceroute . . . . . . . . . . . . 12
8. Issues with non-forwarding labels . . . . . . . . . . . . . . 13
9. Backward Compatibility with non Segment Routing devices . . . 13
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
10.1. New Target FEC Stack Sub-TLVs . . . . . . . . . . . . . 13
11. Security Considerations . . . . . . . . . . . . . . . . . . . 14
12. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 14
13. Contributing Authors . . . . . . . . . . . . . . . . . . . . 14
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
14.1. Normative References . . . . . . . . . . . . . . . . . . 14
14.2. Informative References . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
Kumar, et al. Expires November 11, 2016 [Page 2]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
1. Introduction
[I-D.ietf-spring-segment-routing] introduces and explains Segment
Routing architecture that leverages the source routing and tunneling
paradigms. A node steers a packet through a controlled set of
instructions called segments, by prepending the packet with Segment
Routing header. A detailed definition about Segment Routing
architecture is available in [I-D.ietf-spring-segment-routing]
As defined in [I-D.ietf-spring-segment-routing-mpls], the Segment
Routing architecture can be directly applied to MPLS data plane in a
way that, the Segment identifier (Segment ID) will be of 20-bits size
and Segment Routing header is the label stack.
"Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures"
[RFC4379] defines a simple and efficient mechanism to detect data
plane failures in Label Switched Paths (LSP) by specifying
information to be carried in an MPLS "echo request" and "echo reply"
for the purposes of fault detection and isolation. Mechanisms for
reliably sending the echo reply are defined. The functionality
defined in [RFC4379]is modeled after the ping/traceroute paradigm
(ICMP echo request [RFC0792]) and is typically referred to as LSP
ping and LSP traceroute. [RFC6424] updates [RFC4379] to support
hierarchal and stitching LSPs.
Unlike LDP or RSVP which are the other well-known MPLS control plane
protocols, segment assignment in Segment Routing architecture is not
hop-by-hop basis.
This nature of Segment Routing raises additional consideration for
fault detection and isolation in Segment Routing network. This
document illustrates the problem and describe a mechanism to perform
LSP Ping and Traceroute on Segment Routing network over MPLS data
plane.
2. Requirements notation
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].
3. Terminology
This document uses the terminologies defined in
[I-D.ietf-spring-segment-routing], [RFC4379], and so the readers are
expected to be familiar with the same.
Kumar, et al. Expires November 11, 2016 [Page 3]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
4. Challenges with Existing mechanism
This document defines sub-TLVs for the Target FEC Stack TLV and
explains how they can be used to tackle below challenges.
4.1. Path validation in Segment Routing networks
[RFC4379] defines the OAM machinery that helps with fault detection
and isolation in MPLS dataplane path with the use of various Target
FEC Stack Sub-TLV that are carried in MPLS Echo Request packets and
used by the responder for FEC validation. While it is obvious that
new Sub-TLVs need to be assigned, the unique nature of Segment
Routing architecture raises a need for additional machinery for path
validation. This section discuss the challenges as below:
L1
+--------+
| L2 |
R3-------R6
/ \
/ \
R1----R2 R7----R8
\ /
\ /
R4-------R5
Figure 1: Segment Routing network
The Node segment IDs for R1, R2, R3, R4, R5, R6, R7 and R8 are 5001, 5002, 5003, 5004, 5005, 5006, 5007, 5008 respectively.
9136 --> Adjacency Segment ID from R3 to R6 over link L1.
9236 --> Adjacency Segment ID from R3 to R6 over link L2.
9124 --> Adjacency segment ID from R2 to R4.
9123 --> Adjacency Segment ID from R2 to R3.
The forwarding semantic of Adjacency Segment ID is to pop the segment
ID and send the packet to a specific neighbor over a specific link.
A malfunctioning node may forward packets using Adjacency Segment ID
to incorrect neighbor or over incorrect link. Exposed segment ID
(after incorrectly forwarded Adjacency Segment ID) might still allow
such packet to reach the intended destination, although the intended
strict traversal has been broken.
Assume in above topology, R1 sends traffic with segment stack as
{9124, 5008} so that the path taken will be R1-R2-R4-R5-R7-R8. If
the Adjacency Segment ID 9124 is misprogrammed in R2 to send the
Kumar, et al. Expires November 11, 2016 [Page 4]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
packet to R1 or R3, it will still be delivered to R8 but is not via
the expected path.
MPLS traceroute may help with detecting such deviation in above
mentioned scenario. However, in a different example, it may not be
helpful. For example if R3, due to misprogramming, forwards packet
with Adjacency Segment ID 9236 via link L1 while it is expected to be
forwarded over Link L2.
4.2. Service Label
A Segment ID can represent a service based instruction. An Segment
Routing header can have label stack entries where the label
represents a service to be applied along the path. Since these
labels are part of the label stack, they can influence the path taken
by a packet and consequently have implications on MPLS OAM. Service
Label is left for future study.
5. Segment ID sub-TLV
The format of the following Segment ID sub-TLVs follows the
philosophy of Target FEC Stack TLV carrying FECs corresponding to
each label in the label stack. When operated with the procedures
defined in [RFC4379], this allows LSP ping/traceroute operations to
function when Target FEC Stack TLV contains more FECs than received
label stack at responder nodes.
Three new sub-TLVs are defined for Target FEC Stack TLVs (Type 1),
Reverse-Path Target FEC Stack TLV (Type 16) and Reply Path TLV (Type
21).
sub-Type Value Field
-------- ---------------
TBD1 IPv4 IGP-Prefix Segment ID
TBD2 IPv6 IGP-Prefix Segment ID
TBD3 IGP-Adjacency Segment ID
Service Segments and FRR will be considered in future version.
5.1. IPv4 IGP-Prefix Segment ID
The format is as below:
Kumar, et al. Expires November 11, 2016 [Page 5]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Prefix Length | Protocol | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv4 Prefix
This field carries the IPv4 prefix to which the Segment ID is
assigned. In case of Anycast Segment ID, this field will carry
IPv4 Anycast address. If the prefix is shorter than 32 bits,
trailing bits SHOULD be set to zero.
Prefix Length
The Prefix Length field is one octet, it gives the length of the
prefix in bits (values can be 1 - 32).
Protocol
Set to 1 if the IGP protocol is OSPF and 2 if IGP protocol is
ISIS.
5.2. IPv6 IGP-Prefix Segment ID
The format is as below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| IPv6 Prefix |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Prefix Length | Protocol | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 Prefix
Kumar, et al. Expires November 11, 2016 [Page 6]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
This field carries the IPv6 prefix to which the Segment ID is
assigned. In case of Anycast Segment ID, this field will carry
IPv4 Anycast address. If the prefix is shorter than 128 bits,
trailing bits SHOULD be set to zero.
Prefix Length
The Prefix Length field is one octet, it gives the length of the
prefix in bits (values can be 1 - 128).
Protocol
Set to 1 if the IGP protocol is OSPF and 2 if IGP protocol is
ISIS.
5.3. IGP-Adjacency Segment ID
The format is as below:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Adj. Type | Protocol | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface ID (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface ID (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
| Advertising Node Identifier (4 or 6 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
| Receiving Node Identifier (4 or 6 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Adj. Type (Adjacency Type)
Set to 1, when the Adjacency Segment is Parallel Adjacency as
defined in section 3.5.1 of [I-D.ietf-spring-segment-routing].
Set to 4, when the Adjacency segment is IPv4 based and is not a
parallel adjacency. Set to 6, when the Adjacency segment is IPv6
based and is not a parallel adjacency.
Protocol
Set to 1 if the IGP protocol is OSPF and 2 if IGP protocol is ISIS
Kumar, et al. Expires November 11, 2016 [Page 7]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
Local Interface ID
An identifier that is assigned by local LSR for a link on which
Adjacency Segment ID is bound. This field is set to local link
address (IPv4 or IPv6). Incase of unnumbered, 32 bit link
identifier defined in [RFC4203], [RFC5307] is used. If the
Adjacency Segment ID represents parallel adjacencies
(Section 3.5.1 of [I-D.ietf-spring-segment-routing]) this field
MUST be set to zero.
Remote Interface ID
An identifier that is assigned by remote LSR for a link on which
Adjacency Segment ID is bound. This field is set to remote
(downstream neighbor) link address (IPv4 or IPv6). In case of
unnumbered, 32 bit link identifier defined in [RFC4203], [RFC5307]
is used. If the Adjacency Segment ID represents parallel
adjacencies (Section 3.5.1 of [I-D.ietf-spring-segment-routing])
this field MUST be set to zero.
Advertising Node Identifier
Specifies the advertising node identifier. When Protocol is set
to 1, then the 32 rightmost bits represent OSPF Router ID and if
protocol is set to 2, this field carries 48 bit ISIS System ID.
Receiving Node Identifier
Specifies the downstream node identifier. When Protocol is set to
1, then the 32 rightmost bits represent OSPF Router ID and if
protocol is set to 2, this field carries 48 bit ISIS System ID.
6. Extension to Downstream Mapping TLV
In an echo reply, the Downstream Mapping TLV [RFC4379] is used to
report for each interface over which a FEC could be forwarded. For a
FEC, there are multiple protocols that may be used to distribute
label mapping. The "Protocol" field of the Downstream Mapping TLV is
used to return the protocol that is used to distribute a specific a
label. The following protocols are defined in section 3.2 of
[RFC4379]:
Kumar, et al. Expires November 11, 2016 [Page 8]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
Protocol # Signaling Protocol
---------- ------------------
0 Unknown
1 Static
2 BGP
3 LDP
4 RSVP-TE
With segment routing, OSPF or ISIS can be used for label
distribution, this document adds two new protocols as follows:
Protocol # Signaling Protocol
---------- ------------------
TBD5 OSPF
TBD6 ISIS
7. Procedures
This section describes aspects of LSP Ping and traceroute operations
that require further considerations beyond [RFC4379].
7.1. FECs in Target FEC Stack TLV
When LSP echo request packets are generated by an initiator, FECs
carried in Target FEC Stack TLV may need to have deviating contents.
This document outlines expected Target FEC Stack TLV construction
mechanics by initiator for known scenarios.
Ping
Initiator MUST include FEC(s) corresponding to the destination
segment.
Initiator MAY include FECs corresponding to some or all of
segments imposed in the label stack by the initiator to
communicate the segments traversed.
Traceroute
Initiator MUST initially include FECs corresponding to all of
segments imposed in the label stack.
When a received echo reply contains FEC Stack Change TLV with
one or more of original segment(s) being popped, initiator MAY
remove corresponding FEC(s) from Target FEC Stack TLV in the
next (TTL+1) traceroute request as defined in section 4.3.1.2
of [RFC6424].
Kumar, et al. Expires November 11, 2016 [Page 9]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
When a received echo reply does not contain FEC Stack Change
TLV, initiator MUST NOT attempt to remove FEC(s) from Target
FEC Stack TLV in the next (TTL+1) traceroute request.
7.2. FEC Stack Change sub-TLV
Section 3.3.1.3 of [RFC6424] defines FEC Stack Change sub-TLV that a
router must include when the FEC stack changes.
The network node which advertised the Node Segment ID is responsible
for generating FEC Stack Change sub-TLV of &pop& operation for Node
Segment ID, regardless of if PHP is enabled or not.
The network node that is immediate downstream of the node which
advertised the Adjacency Segment ID is responsible for generating FEC
Stack Change sub-TLV of &pop& operation for Adjacency Segment ID.
7.3. Segment ID POP Operation
The forwarding semantic of Node Segment ID with PHP flag is
equivalent to usage of implicit Null in MPLS protocols. Adjacency
Segment ID is also similar in a sense that it can be thought as next
hop destined locally allocated segment that has PHP enabled.
Procedures described in Section 4.4 of [RFC4379] relies on Stack-D
and Stack-R explicitly having Implicit Null value. It may simplify
implementations to reuse Implicit Null for Node Segment ID PHP and
Adjacency Segment ID cases.
7.4. Segment ID Check
This section updates the procedure defined in Step 6 of section 4.4.
of [RFC4379]
If the Label-stack-depth is 0 and Target FEC Stack Sub-TLV at FEC-
stack-depth is TBD1 (IPv4 IGP-Prefix Segment ID), the responder
should set Best return code to 10, "Mapping for this FEC is not
the given label at stack-depth <RSC>" if any below conditions
fail:
/* The responder LSR is to check if it is the egress of the IPv4
IGP-Prefix Segment ID described in the Target FEC Stack Sub-TLV,
and if the FEC was advertised with the PHP bit set.*/
* Validate that Node Segment ID is advertised for IPv4 Prefix.
* Validate that Node Segment ID is advertised with No-PHP flag {
Kumar, et al. Expires November 11, 2016 [Page 10]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
+ When Protocol is OSPF, NP-flag defined in Section 5 of
[I-D.ietf-ospf-segment-routing-extensions] should be set to
0.
+ When Protocol is ISIS, P-Flag defined in Section 2.1 of
[I-D.ietf-isis-segment-routing-extensions] should be set to
0.
* }
If the Label-stack-depth is more than 0 and Target FEC Stack Sub-
TLV at FEC-stack-depth is TBD1 (IPv4 IGP-Prefix Segment ID), the
responder is to set Best return code to 10 if any below conditions
fail:
* Validate that Node Segment ID is advertised for IPv4 Prefix.
If the Label-stack-depth is 0 and Target FEC Sub-TLV at FEC-stack-
depth is TBD2 (IPv6 IGP-Prefix Segment ID), set Best return code
to 10 if any below conditions fail:
/* The LSR needs to check if its being a tail-end for the LSP and
have the prefix advertised with PHP bit set*/
* Validate that Node Segment ID is advertised for IPv6 Prefix.
* Validate that Node Segment ID is advertised of PHP bit.
If the Label-stack-depth is more than 0 and Target FEC Sub-TLV at
FEC-stack-depth is TBD2 (IPv6 IGP-Prefix Segment ID), set Best
return code to 10 if any below conditions fail:
* Validate that Node Segment ID is advertised for IPv6 Prefix.
If the Label-stack-depth is 0 and Target FEC sub-TLV at FEC-stack-
depth is TBD3 (Adjacency Segment ID), set Best return code to
(error code TBD) if any below conditions fail:
When the Adj. Type is 1 (Parallel Adjacency):
+ Validate that Receiving Node Identifier is local IGP
identifier.
+ Validate that Adjacency Segment ID is advertised by
Advertising Node Identifier of Protocol in local IGP
database.
Kumar, et al. Expires November 11, 2016 [Page 11]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
When the Adj. Type is 4 or 6:
+ Validate that Remote Interface ID matches the local
identifier of the interface (Interface-I) on which the
packet was received.
+ Validate that Receiving Node Identifier is local IGP
identifier.
+ Validate that IGP-Adjacency Segment ID is advertised by
Advertising Node Identifier of Protocol in local IGP
database.
7.5. TTL Consideration for traceroute
LSP Traceroute operation can properly traverse every hop of Segment
Routing network in Uniform Model described in [RFC3443]. If one or
more LSRs employ Short Pipe Model described in [RFC3443], then LSP
Traceroute may not be able to properly traverse every hop of Segment
Routing network due to absence of TTL copy operation when outer label
is popped. Short Pipe being the most commonly used model. The
following TTL manipulation technique MAY be used when Short Pipe
model is used.
When tracing a LSP according to the procedures in [RFC4379] the TTL
is incremented by one in order to trace the path sequentially along
the LSP. However when a source routed LSP has to be traced there are
as many TTLs as there are labels in the stack. The LSR that
initiates the traceroute SHOULD start by setting the TTL to 1 for the
tunnel in the LSP's label stack it wants to start the tracing from,
the TTL of all outer labels in the stack to the max value, and the
TTL of all the inner labels in the stack to zero. Thus a typical
start to the traceroute would have a TTL of 1 for the outermost label
and all the inner labels would have TTL 0. If the FEC Stack TLV is
included it should contain only those for the inner stacked tunnels.
The Return Code/Subcode and FEC Stack Change TLV should be used to
diagnose the tunnel as described in [RFC4379] and [RFC6424]. When
the tracing of a tunnel in the stack is complete, then the next
tunnel in the stack should be traced. The end of a tunnel can be
detected from the "Return Code" when it indicates that the responding
LSR is an egress for the stack at depth 1. Thus the traceroute
procedures in [RFC4379] can be recursively applied to traceroute a
source routed LSP.
Kumar, et al. Expires November 11, 2016 [Page 12]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
8. Issues with non-forwarding labels
Source stacking can be optionally used to apply services on the
packet at a LSR along the path, where a label in the stack is used to
trigger service application. A data plane failure detection and
isolation mechanism should provide its functionality without applying
these services. This is mandatory for services that are stateful,
though for stateless services [RFC4379] could be used as-is. It MAY
also provide a mechanism to detect and isolate faults within the
service function itself.
How a node treats Service label is outside the scope of this document
and will be included in this or a different document later.
9. Backward Compatibility with non Segment Routing devices
[I-D.ietf-spring-segment-routing-ldp-interop] describes how Segment
Routing operates in network where SR-capable and non-SR-capable nodes
coexist. In such networks, there may not be any FEC mapping in the
responder when the Initiator is SR-capable while the responder is not
(or vice-versa). But this is not different from RSVP and LDP interop
scenarios. When LSP Ping is triggered, the responder will set the
FEC-return-code to Return 4, "Replying router has no mapping for the
FEC at stack-depth".
Similarly when SR-capable node assigns Adj-SID for non-SR-capable
node, LSP trace may fail as the non-SR-capable node is not aware of
"IGP Adjacency Segment ID" sub-TLV and may not reply with FEC Stack
change. This may result in any further downstream nodes to reply
back with Return-code as 4, "Replying router has no mapping for the
FEC at stack-depth".
10. IANA Considerations
10.1. New Target FEC Stack Sub-TLVs
IANA is requested to assign 3 new Sub-TLVs from "Sub-TLVs for TLV
Types 1, 16 and 21" sub-registry.
Sub-Type Sub-TLV Name Reference
---------- ----------------- ------------
TBD1 IPv4 IGP-Prefix Segment ID Section 4.1 (this document)
TBD2 IPv6 IGP-Prefix Segment ID Section 4.2 (this document)
TBD3 IGP-Adjacency Segment ID Section 4.3 (this document)
Kumar, et al. Expires November 11, 2016 [Page 13]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
11. Security Considerations
This document defines additional Sub-TLVs and follows the mechanism
defined in [RFC4379]. So all the security consideration defined in
[RFC4379] will be applicable for this document and in addition it
does not impose any security challenges to be considered.
12. Acknowledgement
The authors would like to thank Stefano Previdi, Les Ginsberg, Balaji
Rajagopalan, Harish Sitaraman, Curtis Villamizar, Pranjal Dutta and
Lizhong Jin for their review and comments.
The authors wold like to thank Loa Andersson for his comments and
recommendation to merge drafts.
13. Contributing Authors
Tarek Saad
Cisco Systems
Email: tsaad@cisco.com
Siva Sivabalan
Cisco Systems
Email: msiva@cisco.com
Balaji Rajagopalan
Juniper Networks
Email: balajir@juniper.net
Faisal Iqbal
Cisco Systems
Email: faiqbal@cisco.com
14. References
14.1. Normative References
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS
Extensions for Segment Routing", draft-ietf-isis-segment-
routing-extensions-06 (work in progress), December 2015.
Kumar, et al. Expires November 11, 2016 [Page 14]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
[I-D.ietf-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", draft-ietf-ospf-segment-
routing-extensions-08 (work in progress), April 2016.
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
and R. Shakir, "Segment Routing Architecture", draft-ietf-
spring-segment-routing-07 (work in progress), December
2015.
[I-D.ietf-spring-segment-routing-ldp-interop]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., and
S. Litkowski, "Segment Routing interworking with LDP",
draft-ietf-spring-segment-routing-ldp-interop-01 (work in
progress), April 2016.
[I-D.ietf-spring-segment-routing-mpls]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., Horneffer, M., Shakir, R., Tantsura, J.,
and E. Crabbe, "Segment Routing with MPLS data plane",
draft-ietf-spring-segment-routing-mpls-04 (work in
progress), March 2016.
[RFC0792] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, DOI 10.17487/RFC0792, September 1981,
<http://www.rfc-editor.org/info/rfc792>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[RFC3443] Agarwal, P. and B. Akyol, "Time To Live (TTL) Processing
in Multi-Protocol Label Switching (MPLS) Networks",
RFC 3443, DOI 10.17487/RFC3443, January 2003,
<http://www.rfc-editor.org/info/rfc3443>.
[RFC4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, DOI 10.17487/RFC4203, October 2005,
<http://www.rfc-editor.org/info/rfc4203>.
[RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
DOI 10.17487/RFC4379, February 2006,
<http://www.rfc-editor.org/info/rfc4379>.
Kumar, et al. Expires November 11, 2016 [Page 15]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
[RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008,
<http://www.rfc-editor.org/info/rfc5307>.
[RFC6424] Bahadur, N., Kompella, K., and G. Swallow, "Mechanism for
Performing Label Switched Path Ping (LSP Ping) over MPLS
Tunnels", RFC 6424, DOI 10.17487/RFC6424, November 2011,
<http://www.rfc-editor.org/info/rfc6424>.
14.2. Informative References
[RFC6291] Andersson, L., van Helvoort, H., Bonica, R., Romascanu,
D., and S. Mansfield, "Guidelines for the Use of the "OAM"
Acronym in the IETF", BCP 161, RFC 6291,
DOI 10.17487/RFC6291, June 2011,
<http://www.rfc-editor.org/info/rfc6291>.
[RFC6425] Saxena, S., Ed., Swallow, G., Ali, Z., Farrel, A.,
Yasukawa, S., and T. Nadeau, "Detecting Data-Plane
Failures in Point-to-Multipoint MPLS - Extensions to LSP
Ping", RFC 6425, DOI 10.17487/RFC6425, November 2011,
<http://www.rfc-editor.org/info/rfc6425>.
Authors' Addresses
Nagendra Kumar
Cisco Systems, Inc.
7200 Kit Creek Road
Research Triangle Park, NC 27709
US
Email: naikumar@cisco.com
George Swallow
Cisco Systems, Inc.
1414 Massachusetts Ave
Boxborough, MA 01719
US
Email: swallow@cisco.com
Kumar, et al. Expires November 11, 2016 [Page 16]
Internet-Draft LSP Ping/Trace for SR on MPLS May 2016
Carlos Pignataro
Cisco Systems, Inc.
7200 Kit Creek Road
Research Triangle Park, NC 27709-4987
US
Email: cpignata@cisco.com
Nobo Akiya
Big Switch Networks
Email: nobo.akiya.dev@gmail.com
Sriganesh Kini
Individual
Email: sriganeshkini@gmail.com
Hannes Gredler
Juniper Networks
Email: hannes@juniper.net
Mach(Guoyi) Chen
Huawei
Email: mach.chen@huawei.com
Kumar, et al. Expires November 11, 2016 [Page 17]
