draft-kumarkini-mpls-spring-lsp-ping-05.txt   draft-kumarkini-mpls-spring-lsp-ping-06.txt 
Network Work group N. Kumar Network Work group N. Kumar
Internet-Draft G. Swallow Internet-Draft G. Swallow
Intended status: Standards Track C. Pignataro Intended status: Standards Track C. Pignataro
Expires: August 3, 2016 Cisco Systems, Inc. Expires: September 22, 2016 Cisco Systems, Inc.
N. Akiya N. Akiya
Big Switch Networks Big Switch Networks
S. Kini S. Kini
Individual Individual
H. Gredler H. Gredler
Juniper Networks Juniper Networks
M. Chen M. Chen
Huawei Huawei
January 31, 2016 March 21, 2016
Label Switched Path (LSP) Ping/Trace for Segment Routing Networks Using Label Switched Path (LSP) Ping/Trace for Segment Routing Networks Using
MPLS Dataplane MPLS Dataplane
draft-kumarkini-mpls-spring-lsp-ping-05 draft-kumarkini-mpls-spring-lsp-ping-06
Abstract Abstract
Segment Routing architecture leverages the source routing and Segment Routing architecture leverages the source routing and
tunneling paradigms and can be directly applied to MPLS data plane. tunneling paradigms and can be directly applied to MPLS data plane.
A node steers a packet through a controlled set of instructions A node steers a packet through a controlled set of instructions
called segments, by prepending the packet with a Segment Routing called segments, by prepending the packet with a Segment Routing
header. header.
The segment assignment and forwarding semantic nature of Segment The segment assignment and forwarding semantic nature of Segment
skipping to change at page 2, line 4 skipping to change at page 2, line 4
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on August 3, 2016. This Internet-Draft will expire on September 22, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2016 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
skipping to change at page 2, line 30 skipping to change at page 2, line 30
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements notation . . . . . . . . . . . . . . . . . . . . 3 2. Requirements notation . . . . . . . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Challenges with Existing mechanism . . . . . . . . . . . . . 4 4. Challenges with Existing mechanism . . . . . . . . . . . . . 4
4.1. Path validation in Segment Routing networks . . . . . . . 4 4.1. Path validation in Segment Routing networks . . . . . . . 4
4.2. Service Label . . . . . . . . . . . . . . . . . . . . . . 5 4.2. Service Label . . . . . . . . . . . . . . . . . . . . . . 5
5. Segment ID sub-TLV . . . . . . . . . . . . . . . . . . . . . 5 5. Segment ID sub-TLV . . . . . . . . . . . . . . . . . . . . . 5
5.1. IPv4 Prefix Node Segment ID . . . . . . . . . . . . . . . 5 5.1. IPv4 IGP-Prefix Segment ID . . . . . . . . . . . . . . . 5
5.2. IPv6 Prefix Node Segment ID . . . . . . . . . . . . . . . 6 5.2. IPv6 IGP-Prefix Segment ID . . . . . . . . . . . . . . . 6
5.3. IGP Adjacency Segment ID . . . . . . . . . . . . . . . . 7 5.3. IGP-Adjacency Segment ID . . . . . . . . . . . . . . . . 7
6. Extension to Downstream Mapping TLV . . . . . . . . . . . . . 8 6. Extension to Downstream Mapping TLV . . . . . . . . . . . . . 8
7. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 9 7. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 9
7.1. FECs in Target FEC Stack TLV . . . . . . . . . . . . . . 9 7.1. FECs in Target FEC Stack TLV . . . . . . . . . . . . . . 9
7.2. FEC Stack Change sub-TLV . . . . . . . . . . . . . . . . 10 7.2. FEC Stack Change sub-TLV . . . . . . . . . . . . . . . . 10
7.3. Segment ID POP Operation . . . . . . . . . . . . . . . . 10 7.3. Segment ID POP Operation . . . . . . . . . . . . . . . . 10
7.4. Segment ID Check . . . . . . . . . . . . . . . . . . . . 10 7.4. Segment ID Check . . . . . . . . . . . . . . . . . . . . 10
7.5. TTL Consideration for traceroute . . . . . . . . . . . . 12 7.5. TTL Consideration for traceroute . . . . . . . . . . . . 12
8. Issues with non-forwarding labels . . . . . . . . . . . . . . 12 8. Issues with non-forwarding labels . . . . . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 9. Backward Compatibility with non Segment Routing devices . . . 13
9.1. New Target FEC Stack Sub-TLVs . . . . . . . . . . . . . . 13 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
10. Security Considerations . . . . . . . . . . . . . . . . . . . 13 10.1. New Target FEC Stack Sub-TLVs . . . . . . . . . . . . . 13
11. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 13 11. Security Considerations . . . . . . . . . . . . . . . . . . . 14
12. Contributing Authors . . . . . . . . . . . . . . . . . . . . 13 12. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 14
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 13. Contributing Authors . . . . . . . . . . . . . . . . . . . . 14
13.1. Normative References . . . . . . . . . . . . . . . . . . 14 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 14
13.2. Informative References . . . . . . . . . . . . . . . . . 15 14.1. Normative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 14.2. Informative References . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
[I-D.ietf-spring-segment-routing] introduces and explains Segment [I-D.ietf-spring-segment-routing] introduces and explains Segment
Routing architecture that leverages the source routing and tunneling Routing architecture that leverages the source routing and tunneling
paradigms. A node steers a packet through a controlled set of paradigms. A node steers a packet through a controlled set of
instructions called segments, by prepending the packet with Segment instructions called segments, by prepending the packet with Segment
Routing header. A detailed definition about Segment Routing Routing header. A detailed definition about Segment Routing
architecture is available in [I-D.ietf-spring-segment-routing] and architecture is available in [I-D.ietf-spring-segment-routing]
different use-cases are discussed in
[I-D.filsfils-spring-segment-routing-use-cases]
The Segment Routing architecture can be directly applied to MPLS data As defined in [I-D.ietf-spring-segment-routing-mpls], the Segment
plane in a way that, the Segment identifier (Segment ID) will be of Routing architecture can be directly applied to MPLS data plane in a
20-bits size and Segment Routing header is the label stack. way that, the Segment identifier (Segment ID) will be of 20-bits size
and Segment Routing header is the label stack.
Multi Protocol Label Switching (MPLS) has defined in [RFC4379] a "Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures"
simple and efficient mechanism to detect data plane failures in Label [RFC4379] defines a simple and efficient mechanism to detect data
Switched Paths (LSP) by specifying information to be carried in an plane failures in Label Switched Paths (LSP) by specifying
MPLS "echo request" and "echo reply" for the purposes of fault information to be carried in an MPLS "echo request" and "echo reply"
detection and isolation, and mechanisms for reliably sending the echo for the purposes of fault detection and isolation. Mechanisms for
reply. The functionality is modeled after the ping/traceroute reliably sending the echo reply are defined. The functionality
paradigm (ICMP echo request [RFC0792]) and is typically referred to defined in [RFC4379]is modeled after the ping/traceroute paradigm
as LSP ping and LSP traceroute. (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 Unlike LDP or RSVP which are the other well-known MPLS control plane
protocols, segment assignment in Segment Routing architecture is not protocols, segment assignment in Segment Routing architecture is not
hop-by-hop basis. hop-by-hop basis.
This nature of Segment Routing raises additional consideration for This nature of Segment Routing raises additional consideration for
fault detection and isolation in Segment Routing network. This fault detection and isolation in Segment Routing network. This
document illustrates the problem and describe a mechanism to perform document illustrates the problem and describe a mechanism to perform
LSP Ping and Traceroute on Segment Routing network over MPLS data LSP Ping and Traceroute on Segment Routing network over MPLS data
plane. plane.
skipping to change at page 5, line 19 skipping to change at page 5, line 19
helpful. For example if R3, due to misprogramming, forwards packet helpful. For example if R3, due to misprogramming, forwards packet
with Adjacency Segment ID 9236 via link L1 while it is expected to be with Adjacency Segment ID 9236 via link L1 while it is expected to be
forwarded over Link L2. forwarded over Link L2.
4.2. Service Label 4.2. Service Label
A Segment ID can represent a service based instruction. An Segment A Segment ID can represent a service based instruction. An Segment
Routing header can have label stack entries where the label Routing header can have label stack entries where the label
represents a service to be applied along the path. Since these represents a service to be applied along the path. Since these
labels are part of the label stack, they can influence the path taken labels are part of the label stack, they can influence the path taken
by a packet and consequently have implications on MPLS OAM. In by a packet and consequently have implications on MPLS OAM. Service
section 6.5 of this document, it is described how the procedures of Label is left for future study.
[RFC4379] can be applied to in the absence of service-labels in
Section 6.5. Additional considerations for service labels are
included in Section 7 and requires further discussion.
5. Segment ID sub-TLV 5. Segment ID sub-TLV
The format of the following Segment ID sub-TLVs follows the The format of the following Segment ID sub-TLVs follows the
philosophy of Target FEC Stack TLV carrying FECs corresponding to philosophy of Target FEC Stack TLV carrying FECs corresponding to
each label in the label stack. When operated with the procedures each label in the label stack. When operated with the procedures
defined in [RFC4379], this allows LSP ping/traceroute operations to defined in [RFC4379], this allows LSP ping/traceroute operations to
function when Target FEC Stack TLV contains more FECs than received function when Target FEC Stack TLV contains more FECs than received
label stack at responder nodes. label stack at responder nodes.
Three new sub-TLVs are defined for TLVs type 1, 16 and 21. 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 sub-Type Value Field
-------- --------------- -------- ---------------
TBD1 IPv4 Prefix Node Segment ID TBD1 IPv4 IGP-Prefix Segment ID
TBD2 IPv6 Prefix Node Segment ID TBD2 IPv6 IGP-Prefix Segment ID
TBD3 Adjacency Segment ID TBD3 IGP-Adjacency Segment ID
Service Segments and FRR will be considered in future version. Service Segments and FRR will be considered in future version.
5.1. IPv4 Prefix Node Segment ID 5.1. IPv4 IGP-Prefix Segment ID
The format is as below: The format is as below:
0 1 2 3 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 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 | | IPv4 Prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Prefix Length | Protocol | Reserved | |Prefix Length | Protocol | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv4 Prefix IPv4 Prefix
This field carries the IPv4 prefix to which the Node Segment ID is This field carries the IPv4 prefix to which the Segment ID is
assigned. If the prefix is shorter than 32 bits, trailing bits assigned. In case of Anycast Segment ID, this field will carry
SHOULD be set to zero. IPv4 Anycast address. If the prefix is shorter than 32 bits,
trailing bits SHOULD be set to zero.
Prefix Length Prefix Length
The Prefix Length field is one octet, it gives the length of the The Prefix Length field is one octet, it gives the length of the
prefix in bits (values can be 1 - 32). prefix in bits (values can be 1 - 32).
Protocol Protocol
Set to 1 if the IGP protocol is OSPF and 2 if IGP protocol is Set to 1 if the IGP protocol is OSPF and 2 if IGP protocol is
ISIS. ISIS.
5.2. IPv6 Prefix Node Segment ID 5.2. IPv6 IGP-Prefix Segment ID
The format is as below: The format is as below:
0 1 2 3 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 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 | | IPv6 Prefix |
| | | |
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Prefix Length | Protocol | Reserved | |Prefix Length | Protocol | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 Prefix IPv6 Prefix
This field carries the IPv6 prefix to which the Node Segment ID is This field carries the IPv6 prefix to which the Segment ID is
assigned. If the prefix is shorter than 128 bits, trailing bits assigned. In case of Anycast Segment ID, this field will carry
SHOULD be set to zero. IPv4 Anycast address. If the prefix is shorter than 128 bits,
trailing bits SHOULD be set to zero.
Prefix Length Prefix Length
The Prefix Length field is one octet, it gives the length of the The Prefix Length field is one octet, it gives the length of the
prefix in bits (values can be 1 - 128). prefix in bits (values can be 1 - 128).
Protocol Protocol
Set to 1 if the IGP protocol is OSPF and 2 if IGP protocol is Set to 1 if the IGP protocol is OSPF and 2 if IGP protocol is
ISIS. ISIS.
5.3. IGP Adjacency Segment ID 5.3. IGP-Adjacency Segment ID
The format is as below: The format is as below:
0 1 2 3 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 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 | | Adj. Type | Protocol | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface ID (4 or 16 octets) | | Local Interface ID (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Interface ID (4 or 16 octets) | | Remote Interface ID (4 or 16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~ ~ ~
| Advertising Node Identifier (4 or 6 octets) | | Advertising Node Identifier (4 or 6 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~ ~ ~
| Receiving Node Identifier (4 or 6 octets) | | Receiving Node Identifier (4 or 6 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Adj. Type Adj. Type (Adjacency Type)
Set to 1, when the Adjacency Segment is Parallel Adjacency as Set to 1, when the Adjacency Segment is Parallel Adjacency as
defined in section 3.5.1 of [I-D.ietf-spring-segment-routing]. 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 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 parallel adjacency. Set to 6, when the Adjacency segment is IPv6
based and is not a parallel adjacency. based and is not a parallel adjacency.
Protocol Protocol
Set to 1 if the IGP protocol is OSPF and 2 if IGP protocol is ISIS Set to 1 if the IGP protocol is OSPF and 2 if IGP protocol is ISIS
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1 Static 1 Static
2 BGP 2 BGP
3 LDP 3 LDP
4 RSVP-TE 4 RSVP-TE
With segment routing, OSPF or ISIS can be used for label With segment routing, OSPF or ISIS can be used for label
distribution, this document adds two new protocols as follows: distribution, this document adds two new protocols as follows:
Protocol # Signaling Protocol Protocol # Signaling Protocol
---------- ------------------ ---------- ------------------
5 OSPF TBD5 OSPF
6 ISIS TBD6 ISIS
7. Procedures 7. Procedures
This section describes aspects of LSP Ping and traceroute operations This section describes aspects of LSP Ping and traceroute operations
that require further considerations beyond [RFC4379]. that require further considerations beyond [RFC4379].
7.1. FECs in Target FEC Stack TLV 7.1. FECs in Target FEC Stack TLV
When LSP echo request packets are generated by an initiator, FECs When LSP echo request packets are generated by an initiator, FECs
carried in Target FEC Stack TLV may need to have deviating contents. carried in Target FEC Stack TLV may need to have deviating contents.
skipping to change at page 9, line 50 skipping to change at page 9, line 50
communicate the segments traversed. communicate the segments traversed.
Traceroute Traceroute
Initiator MUST initially include FECs corresponding to all of Initiator MUST initially include FECs corresponding to all of
segments imposed in the label stack. segments imposed in the label stack.
When a received echo reply contains FEC Stack Change TLV with When a received echo reply contains FEC Stack Change TLV with
one or more of original segment(s) being popped, initiator MAY one or more of original segment(s) being popped, initiator MAY
remove corresponding FEC(s) from Target FEC Stack TLV in the remove corresponding FEC(s) from Target FEC Stack TLV in the
next (TTL+1) traceroute request. next (TTL+1) traceroute request as defined in section 4.3.1.2
of [RFC6424].
When a received echo reply does not contain FEC Stack Change When a received echo reply does not contain FEC Stack Change
TLV, initiator MUST NOT attempt to remove FEC(s) from Target TLV, initiator MUST NOT attempt to remove FEC(s) from Target
FEC Stack TLV in the next (TTL+1) traceroute request. Note FEC Stack TLV in the next (TTL+1) traceroute request.
that Downstream Label field of DSMAP/DDMAP contains hints on
how initiator may be able to update the contents of next Target
FEC Stack TLV. However, such hints are ambiguous without full
understanding of PHP capabilities.
7.2. FEC Stack Change sub-TLV 7.2. FEC Stack Change sub-TLV
Section 3.3.1.3 of [RFC6424] defines a new sub-TLV that a router must Section 3.3.1.3 of [RFC6424] defines FEC Stack Change sub-TLV that a
include when the FEC stack changes. router must include when the FEC stack changes.
The network node which advertised the Node Segment ID is responsible The network node which advertised the Node Segment ID is responsible
for generating FEC Stack Change sub-TLV of &pop& operation for Node for generating FEC Stack Change sub-TLV of &pop& operation for Node
Segment ID, regardless of if PHP is enabled or not. Segment ID, regardless of if PHP is enabled or not.
The network node that is immediate downstream of the node which The network node that is immediate downstream of the node which
advertised the Adjacency Segment ID is responsible for generating FEC advertised the Adjacency Segment ID is responsible for generating FEC
Stack Change sub-TLV of &pop& operation for Adjacency Segment ID. Stack Change sub-TLV of &pop& operation for Adjacency Segment ID.
7.3. Segment ID POP Operation 7.3. Segment ID POP Operation
The forwarding semantic of Node Segment ID with PHP flag is The forwarding semantic of Node Segment ID with PHP flag is
equivalent to usage of implicit Null in MPLS protocols. Adjacency 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 Segment ID is also similar in a sense that it can be thought as next
hop destined locally allocated segment that has PHP enabled. hop destined locally allocated segment that has PHP enabled.
Procedures described in Section 4.4 of [RFC4379] relies on Stack-D Procedures described in Section 4.4 of [RFC4379] relies on Stack-D
and Stack-R explicitly having Implicit Null value. It may simplify and Stack-R explicitly having Implicit Null value. It may simplify
implementations to reuse Implicit Null for Node Segment ID PHP and implementations to reuse Implicit Null for Node Segment ID PHP and
Adjacency Segment ID cases. However, it is technically incorrect for Adjacency Segment ID cases.
Implicit Null value to externally appear. Therefore, implicit Null
MUST NOT be placed in Stack-D and Interface and Label Stack TLV for
Node Segment ID PHP and Adjacency Segment ID cases.
7.4. Segment ID Check 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- If the Label-stack-depth is 0 and Target FEC Stack Sub-TLV at FEC-
stack-depth is TBD1 (IPv4 Prefix Node Segment ID), the responder stack-depth is TBD1 (IPv4 IGP-Prefix Segment ID), the responder
should set Best return code to 10 if any below conditions fail: /* should set Best return code to 10, "Mapping for this FEC is not
The responder LSR is to check if it is the egress of the IPv4 the given label at stack-depth <RSC>" if any below conditions
Prefix Node Segment ID described in the Target FEC Stack Sub-TLV, 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.*/ 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 for IPv4 Prefix.
* Validate that Node Segment ID is advertisement of PHP bit. * Validate that Node Segment ID is advertised with No-PHP flag {
+ 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- If the Label-stack-depth is more than 0 and Target FEC Stack Sub-
TLV at FEC-stack-depth is TBD1 (IPv4 Prefix Node Segment ID), the 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 responder is to set Best return code to 10 if any below conditions
fail: fail:
* Validate that Node Segment ID is advertised for IPv4 Prefix. * 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- If the Label-stack-depth is 0 and Target FEC Sub-TLV at FEC-stack-
depth is TBD2 (IPv6 Prefix Node Segment ID), set Best return code 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 to 10 if any below conditions fail:
its being a tail-end for the LSP and have the prefix advertised
with PHP bit set*/ /* 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 for IPv6 Prefix.
* Validate that Node Segment ID is advertised of PHP bit. * Validate that Node Segment ID is advertised of PHP bit.
If the Label-stack-depth is 0 and Target FEC Sub-TLV at FEC-stack- If the Label-stack-depth is more than 0 and Target FEC Sub-TLV at
depth is TBD2 (IPv6 Prefix Node Segment ID), set Best return code FEC-stack-depth is TBD2 (IPv6 IGP-Prefix Segment ID), set Best
to 10 if any below conditions fail: return code to 10 if any below conditions fail:
* Validate that Node Segment ID is advertised for IPv6 Prefix. * 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- 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 depth is TBD3 (Adjacency Segment ID), set Best return code to
(error code TBD) if any below conditions fail: (error code TBD) if any below conditions fail:
When the Adj.Type is 1 (Parallel Adjacency): When the Adj. Type is 1 (Parallel Adjacency):
+ Validate that Receiving Node Identifier is local IGP + Validate that Receiving Node Identifier is local IGP
identifier. identifier.
+ Validate that Adjacency Segment ID is advertised by + Validate that Adjacency Segment ID is advertised by
Advertising Node Identifier of Protocol in local IGP Advertising Node Identifier of Protocol in local IGP
database. database.
When the Adj.Type is 4 or 6: When the Adj. Type is 4 or 6:
+ Validate that Remote Interface ID matches the local + Validate that Remote Interface ID matches the local
identifier of the interface (Interface-I) on which the identifier of the interface (Interface-I) on which the
packet was received. packet was received.
+ Validate that Receiving Node Identifier is local IGP + Validate that Receiving Node Identifier is local IGP
identifier. identifier.
+ Validate that IGP Adjacency Segment ID is advertised by + Validate that IGP-Adjacency Segment ID is advertised by
Advertising Node Identifier of Protocol in local IGP Advertising Node Identifier of Protocol in local IGP
database. database.
7.5. TTL Consideration for traceroute 7.5. TTL Consideration for traceroute
LSP Traceroute operation can properly traverse every hop of Segment LSP Traceroute operation can properly traverse every hop of Segment
Routing network in Uniform Model described in [RFC3443]. If one or Routing network in Uniform Model described in [RFC3443]. If one or
more LSRs employ Short Pipe Model described in [RFC3443], then LSP more LSRs employ Short Pipe Model described in [RFC3443], then LSP
Traceroute may not be able to properly traverse every hop of Segment Traceroute may not be able to properly traverse every hop of Segment
Routing network due to absence of TTL copy operation when outer label Routing network due to absence of TTL copy operation when outer label
is popped. In such scenario, following TTL manipulation technique is popped. Short Pipe being the most commonly used model. The
MAY be used. 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 When tracing a LSP according to the procedures in [RFC4379] the TTL
is incremented by one in order to trace the path sequentially along 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 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 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 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, 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 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 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 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 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. included it should contain only those for the inner stacked tunnels.
The lack of an echo response or the Return Code/Subcode should be The Return Code/Subcode and FEC Stack Change TLV should be used to
used to diagnose the tunnel as described in [RFC4379]. When the diagnose the tunnel as described in [RFC4379] and [RFC6424]. When
tracing of a tunnel in the stack is complete, then the next tunnel in the tracing of a tunnel in the stack is complete, then the next
the stack should be traced. The end of a tunnel can be detected from tunnel in the stack should be traced. The end of a tunnel can be
the "Return Code" when it indicates that the responding LSR is an detected from the "Return Code" when it indicates that the responding
egress for the stack at depth 1. Thus the traceroute procedures in LSR is an egress for the stack at depth 1. Thus the traceroute
[RFC4379] can be recursively applied to traceroute a source routed procedures in [RFC4379] can be recursively applied to traceroute a
LSP. source routed LSP.
8. Issues with non-forwarding labels 8. Issues with non-forwarding labels
Source stacking can be optionally used to apply services on the 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 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 trigger service application. A data plane failure detection and
isolation mechanism should provide its functionality without applying isolation mechanism should provide its functionality without applying
these services. This is mandatory for services that are stateful, these services. This is mandatory for services that are stateful,
though for stateless services [RFC4379] could be used as-is. It MAY though for stateless services [RFC4379] could be used as-is. It MAY
also provide a mechanism to detect and isolate faults within the also provide a mechanism to detect and isolate faults within the
service function itself. service function itself.
To prevent services from being applied to an "echo request" packet, How a node treats Service label is outside the scope of this document
the TTL of service labels MUST be 0. However TTL processing rules of and will be included in this or a different document later.
a service label must be the same as any MPLS label. Due to this a
TTL of 0 in the service label would prevent the packet from being
forwarded beyond the LSR that provides the service. To avoid this
problem, the originator of the "echo request" MUST NOT include the
service label in the label stack of an echo request above the tunnel
label of the tunnel that is being currently traced. In other words
the ingress must remove all service-labels above the label of the
tunnel being currently traced, but retain service labels below it
when sending the echo request. Note that load balancing may affect
the path when the service labels are removed, resulting in a newer
path being traversed. However this new path is potentially different
only up to the LSR that provides the service. Since this portion of
the path was traced when the tunnels above this tunnel in the stack
were traced and followed the exact path as the source routed LSP,
this should not be a major concern. Sometimes the newer path may
have a problem that was not in the original path resulting in a false
positive. In such a case the original path can be traversed by
changing the label stack to reach the intermediate LSR with labels
that route along each hop explicitly.
9. IANA Considerations 9. Backward Compatibility with non Segment Routing devices
9.1. New Target FEC Stack Sub-TLVs [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 IANA is requested to assign 3 new Sub-TLVs from "Sub-TLVs for TLV
Types 1, 16 and 21" sub-registry. Types 1, 16 and 21" sub-registry.
Sub-Type Sub-TLV Name Reference Sub-Type Sub-TLV Name Reference
---------- ----------------- ------------ ---------- ----------------- ------------
TBD1 IPv4 Prefix Node Segment ID Section 4.1 (this document) TBD1 IPv4 IGP-Prefix Segment ID Section 4.1 (this document)
TBD2 IPv6 Prefix Node Segment ID Section 4.2 (this document) TBD2 IPv6 IGP-Prefix Segment ID Section 4.2 (this document)
TBD3 Adjacency Segment ID Section 4.3 (this document) TBD3 IGP-Adjacency Segment ID Section 4.3 (this document)
10. Security Considerations 11. Security Considerations
This document defines additional Sub-TLVs and follows the mechanism This document defines additional Sub-TLVs and follows the mechanism
defined in [RFC4379]. So all the security consideration defined in defined in [RFC4379]. So all the security consideration defined in
[RFC4379] will be applicable for this document and in addition it [RFC4379] will be applicable for this document and in addition it
does not impose any security challenges to be considered. does not impose any security challenges to be considered.
11. Acknowledgement 12. Acknowledgement
The authors would like to thank Stefano Previdi, Les Ginsberg, Balaji The authors would like to thank Stefano Previdi, Les Ginsberg, Balaji
Rajagopalan and Harish Sitaraman for their review and comments. 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 The authors wold like to thank Loa Andersson for his comments and
recommendation to merge drafts. recommendation to merge drafts.
12. Contributing Authors 13. Contributing Authors
Tarek Saad Tarek Saad
Cisco Systems Cisco Systems
Email: tsaad@cisco.com Email: tsaad@cisco.com
Siva Sivabalan Siva Sivabalan
Cisco Systems Cisco Systems
Email: msiva@cisco.com Email: msiva@cisco.com
Balaji Rajagopalan Balaji Rajagopalan
Juniper Networks Juniper Networks
Email: balajir@juniper.net Email: balajir@juniper.net
13. References Faisal Iqbal
Cisco Systems
Email: faiqbal@cisco.com
13.1. Normative References 14. References
[I-D.filsfils-spring-segment-routing-use-cases] 14.1. Normative References
Filsfils, C., Francois, P., Previdi, S., Decraene, B.,
Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R., [I-D.ietf-isis-segment-routing-extensions]
Ytti, S., Henderickx, W., Tantsura, J., Kini, S., and E. Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
Crabbe, "Segment Routing Use Cases", draft-filsfils- Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS
spring-segment-routing-use-cases-01 (work in progress), Extensions for Segment Routing", draft-ietf-isis-segment-
October 2014. routing-extensions-06 (work in progress), December 2015.
[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-07 (work in progress), March 2016.
[I-D.ietf-spring-segment-routing] [I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Decraene, B., Litkowski, S., Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
and r. rjs@rob.sh, "Segment Routing Architecture", draft- and R. Shakir, "Segment Routing Architecture", draft-ietf-
ietf-spring-segment-routing-07 (work in progress), spring-segment-routing-07 (work in progress), December
December 2015. 2015.
[I-D.ietf-spring-segment-routing-ldp-interop]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., and
S. Litkowski, "Segment Routing interoperability with LDP",
draft-ietf-spring-segment-routing-ldp-interop-00 (work in
progress), October 2015.
[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, [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,
<http://www.rfc-editor.org/info/rfc792>. <http://www.rfc-editor.org/info/rfc792>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
skipping to change at page 15, line 20 skipping to change at page 16, line 15
[RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions [RFC5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions
in Support of Generalized Multi-Protocol Label Switching in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008, (GMPLS)", RFC 5307, DOI 10.17487/RFC5307, October 2008,
<http://www.rfc-editor.org/info/rfc5307>. <http://www.rfc-editor.org/info/rfc5307>.
[RFC6424] Bahadur, N., Kompella, K., and G. Swallow, "Mechanism for [RFC6424] Bahadur, N., Kompella, K., and G. Swallow, "Mechanism for
Performing Label Switched Path Ping (LSP Ping) over MPLS Performing Label Switched Path Ping (LSP Ping) over MPLS
Tunnels", RFC 6424, DOI 10.17487/RFC6424, November 2011, Tunnels", RFC 6424, DOI 10.17487/RFC6424, November 2011,
<http://www.rfc-editor.org/info/rfc6424>. <http://www.rfc-editor.org/info/rfc6424>.
13.2. Informative References 14.2. Informative References
[RFC6291] Andersson, L., van Helvoort, H., Bonica, R., Romascanu, [RFC6291] Andersson, L., van Helvoort, H., Bonica, R., Romascanu,
D., and S. Mansfield, "Guidelines for the Use of the "OAM" D., and S. Mansfield, "Guidelines for the Use of the "OAM"
Acronym in the IETF", BCP 161, RFC 6291, Acronym in the IETF", BCP 161, RFC 6291,
DOI 10.17487/RFC6291, June 2011, DOI 10.17487/RFC6291, June 2011,
<http://www.rfc-editor.org/info/rfc6291>. <http://www.rfc-editor.org/info/rfc6291>.
[RFC6425] Saxena, S., Ed., Swallow, G., Ali, Z., Farrel, A., [RFC6425] Saxena, S., Ed., Swallow, G., Ali, Z., Farrel, A.,
Yasukawa, S., and T. Nadeau, "Detecting Data-Plane Yasukawa, S., and T. Nadeau, "Detecting Data-Plane
Failures in Point-to-Multipoint MPLS - Extensions to LSP Failures in Point-to-Multipoint MPLS - Extensions to LSP
 End of changes. 48 change blocks. 
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