draft-ietf-ospf-segment-routing-msd-17.txt   draft-ietf-ospf-segment-routing-msd-18.txt 
OSPF Working Group J. Tantsura OSPF Working Group J. Tantsura
Internet-Draft Nuage Networks Internet-Draft Nuage Networks
Intended status: Standards Track U. Chunduri Intended status: Standards Track U. Chunduri
Expires: February 22, 2019 Huawei Technologies Expires: March 1, 2019 Huawei Technologies
S. Aldrin S. Aldrin
Google, Inc Google, Inc
P. Psenak P. Psenak
Cisco Systems Cisco Systems
August 21, 2018 August 28, 2018
Signaling MSD (Maximum SID Depth) using OSPF Signaling MSD (Maximum SID Depth) using OSPF
draft-ietf-ospf-segment-routing-msd-17 draft-ietf-ospf-segment-routing-msd-18
Abstract Abstract
This document defines a way for an Open Shortest Path First (OSPF) This document defines a way for an Open Shortest Path First (OSPF)
Router to advertise multiple types of supported Maximum SID Depths Router to advertise multiple types of supported Maximum SID Depths
(MSDs) at node and/or link granularity. Such advertisements allow (MSDs) at node and/or link granularity. Such advertisements allow
entities (e.g., centralized controllers) to determine whether a entities (e.g., centralized controllers) to determine whether a
particular SID stack can be supported in a given network. This particular SID stack can be supported in a given network. This
document defines only one type of MSD, but defines an encoding that document defines only one type of MSD, but defines an encoding that
can support other MSD types. Here the term OSPF means both OSPFv2 can support other MSD types. Here the term OSPF means both OSPFv2
skipping to change at page 1, line 42 skipping to change at page 1, line 42
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 22, 2019. This Internet-Draft will expire on March 1, 2019.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of (https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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head-ends. In order for BGP-LS to signal MSD for all the nodes and head-ends. In order for BGP-LS to signal MSD for all the nodes and
links in the network MSD is relevant, MSD capabilities should be links in the network MSD is relevant, MSD capabilities should be
advertised by every OSPF router in the network. advertised by every OSPF router in the network.
Other types of MSD are known to be useful. For example, Other types of MSD are known to be useful. For example,
[I-D.ietf-ospf-mpls-elc] defines Readable Label Depth Capability [I-D.ietf-ospf-mpls-elc] defines Readable Label Depth Capability
(RLDC) that is used by a head-end to insert an Entropy Label (EL) at (RLDC) that is used by a head-end to insert an Entropy Label (EL) at
a depth that can be read by transit nodes. a depth that can be read by transit nodes.
This document defines an extension to OSPF used to advertise one or This document defines an extension to OSPF used to advertise one or
more types of MSD at node and/or link granularity. It also defines more types of MSD at node and/or link granularity. In the future it
the Base MPLS Imposition MSD type. In the future it is expected, is expected, that new MSD types will be defined to signal additional
that new MSD types will be defined to signal additional capabilities capabilities e.g., entropy labels, SIDs that can be imposed through
e.g., entropy labels, SIDs that can be imposed through recirculation, recirculation, or SIDs associated with another dataplane e.g., IPv6.
or SIDs associated with another dataplane e.g., IPv6. Although MSD Although MSD advertisements are associated with Segment Routing, the
advertisements are associated with Segment Routing, the
advertisements MAY be present even if Segment Routing itself is not advertisements MAY be present even if Segment Routing itself is not
enabled. enabled. Note that in a non-SR MPLS network, label depth is what is
defined by the MSD advertisements.
1.1. Terminology 1.1. Terminology
This memo makes use of the terms defined in [RFC7770] This memo makes use of the terms defined in [RFC7770]
BGP-LS: Distribution of Link-State and TE Information using Border BGP-LS: Distribution of Link-State and TE Information using Border
Gateway Protocol Gateway Protocol
BMI: Base MPLS Imposition is the number of MPLS labels that can be
imposed inclusive of all service/transport/special labels
OSPF: Open Shortest Path First OSPF: Open Shortest Path First
MSD: Maximum SID Depth - the number of SIDs a node or one of its MSD: Maximum SID Depth - the number of SIDs a node or one of its
links can support links can support
PCC: Path Computation Client PCC: Path Computation Client
PCE: Path Computation Element PCE: Path Computation Element
PCEP: Path Computation Element Protocol PCEP: Path Computation Element Protocol
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSD-Type | MSD-Value | MSD-Type... | MSD-Value... | | MSD-Type | MSD-Value | MSD-Type... | MSD-Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Node MSD TLV Figure 1: Node MSD TLV
The Type: TBD1 Type: TBD1
Length: variable (multiple of 2 octets) and represents the total Length: variable (multiple of 2 octets) and represents the total
length of value field in octets. length of value field in octets.
Value: consists of one or more pairs of a 1 octet MSD-type and 1 Value: consists of one or more pairs of a 1 octet MSD-type and 1
octet MSD-Value. octet MSD-Value.
MSD-Type: one of the values defined in the IGP MSD Types registry MSD-Type: one of the values defined in the IGP MSD Types registry
defined in [I-D.ietf-isis-segment-routing-msd]. defined in [I-D.ietf-isis-segment-routing-msd].
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length | | Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSD-Type | MSD-Value | MSD-Type... | MSD-Value... | | MSD-Type | MSD-Value | MSD-Type... | MSD-Value... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Link MSD Sub-TLV Figure 2: Link MSD Sub-TLV
Type: Type:
For OSPFv2, the Link level MSD value is advertised as an optional For OSPFv2, the Link level MSD-Value is advertised as an optional
Sub-TLV of the OSPFv2 Extended Link TLV as defined in [RFC7684], and Sub-TLV of the OSPFv2 Extended Link TLV as defined in [RFC7684], and
has a type of TBD2. has a type of TBD2.
For OSPFv3, the Link level MSD value is advertised as an optional For OSPFv3, the Link level MSD-Value is advertised as an optional
Sub-TLV of the E-Router-LSA TLV as defined in [RFC8362], and has a Sub-TLV of the E-Router-LSA TLV as defined in [RFC8362], and has a
type of TBD3. type of TBD3.
Length: variable and same as defined in Section 2. Length: variable and same as defined in Section 2.
Value: consists of one or more pairs of a 1 octet MSD-type and 1 Value: consists of one or more pairs of a 1 octet MSD-type and 1
octet MSD-Value. octet MSD-Value.
MSD-Type: one of the values defined in the MSD Types registry defined MSD-Type: one of the values defined in the MSD Types registry defined
in [I-D.ietf-isis-segment-routing-msd]. in [I-D.ietf-isis-segment-routing-msd].
skipping to change at page 6, line 34 skipping to change at page 6, line 34
different OSPF Extended Link Opaque LSAs/E-Router-LSAs originated by different OSPF Extended Link Opaque LSAs/E-Router-LSAs originated by
the same OSPF router, the OSPFv2 Extended Link TLV in the OSPFv2 the same OSPF router, the OSPFv2 Extended Link TLV in the OSPFv2
Extended Link Opaque LSA with the smallest Opaque ID or in the OSPFv3 Extended Link Opaque LSA with the smallest Opaque ID or in the OSPFv3
E-Router-LSA with the smallest Link State ID is used by receiving E-Router-LSA with the smallest Link State ID is used by receiving
OSPF routers. This situation MAY be logged as a warning. OSPF routers. This situation MAY be logged as a warning.
4. Using Node and Link MSD Advertisements 4. Using Node and Link MSD Advertisements
When Link MSD is present for a given MSD type, the value of the Link When Link MSD is present for a given MSD type, the value of the Link
MSD MUST take preference over the Node MSD. When a Link MSD type is MSD MUST take preference over the Node MSD. When a Link MSD type is
not signalled but the Node MSD type is, then the value of that Link not signalled but the Node MSD type is, then the value of that Node
MSD type MUST be considered as the corresponding Node MSD type value. MSD type MUST be considered as the corresponding Link MSD type value.
In order to increase flooding efficiency, it is RECOMMENDED, that In order to increase flooding efficiency, it is RECOMMENDED, that
routers with homogenous link MSD values advertise just the Node MSD routers with homogenous Link MSD values advertise just the Node MSD
value. value.
The meaning of the absence of both Node and Link MSD advertisements The meaning of the absence of both Node and Link MSD advertisements
for a given MSD type is specific to the MSD type. Generally it can for a given MSD type is specific to the MSD type. Generally it can
only be inferred that the advertising node does not support only be inferred that the advertising node does not support
advertisement of that MSD type. However, in some cases the lack of advertisement of that MSD type. However, in some cases the lack of
advertisement might imply that the functionality associated with the advertisement might imply that the functionality associated with the
MSD type is not supported. The correct interpretation MUST be MSD type is not supported. The correct interpretation MUST be
specified when an MSD type is defined. specified when an MSD type is defined.
 End of changes. 12 change blocks. 
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