draft-ietf-ospf-segment-routing-msd-24.txt   draft-ietf-ospf-segment-routing-msd-25.txt 
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Internet-Draft Apstra, Inc. Internet-Draft Apstra, Inc.
Intended status: Standards Track U. Chunduri Intended status: Standards Track U. Chunduri
Expires: April 20, 2019 Huawei Technologies Expires: April 20, 2019 Huawei Technologies
S. Aldrin S. Aldrin
Google, Inc Google, Inc
P. Psenak P. Psenak
Cisco Systems Cisco Systems
October 17, 2018 October 17, 2018
Signaling MSD (Maximum SID Depth) using OSPF Signaling MSD (Maximum SID Depth) using OSPF
draft-ietf-ospf-segment-routing-msd-24 draft-ietf-ospf-segment-routing-msd-25
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(Segment Router to advertise multiple types of supported Maximum SID(Segment
Identifier) Depths (MSDs) at node and/or link granularity. Such Identifier) Depths (MSDs) at node and/or link granularity. Such
advertisements allow entities (e.g., centralized controllers) to advertisements allow entities (e.g., centralized controllers) to
determine whether a particular SID stack can be supported in a given determine whether a particular SID stack can be supported in a given
network. This document defines only one type of MSD, but defines an network. This document defines only one type of MSD, but defines an
encoding that can support other MSD types. Here the term OSPF means encoding that can support other MSD types. Here the term OSPF means
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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
Type: TBD1 Type: 12
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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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 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 6.
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 9.
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].
MSD-Value field contains Link MSD of the router originating the MSD-Value field contains Link MSD of the router originating the
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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 in specified when an MSD-type is defined in
[I-D.ietf-isis-segment-routing-msd]. [I-D.ietf-isis-segment-routing-msd].
5. IANA Considerations 5. IANA Considerations
This document requests IANA to allocate TLV type (TBD1) from the OSPF This specification updates several existing OSPF registries.
Router Information (RI) TLVs Registry as defined by [RFC7770]. IANA
has allocated the value 12 through the early assignment process. IANA has allocated TLV type 12 from the OSPF Router Information (RI)
TLVs Registry as defined by [RFC7770].
Value Description Reference Value Description Reference
----- --------------- ------------- ----- --------------- -------------
12 Node MSD This document 12 Node MSD This document
Figure 3: RI Node MSD Figure 3: RI Node MSD
Also, this document requests IANA to allocate a sub-TLV type (TBD2) IANA has allocated sub-TLV type 6 from the OSPFv2 Extended Link TLV
from the OSPFv2 Extended Link TLV Sub-TLVs registry. IANA has Sub-TLVs registry.
allocated the value 6 through the early assignment process.
Value Description Reference Value Description Reference
----- --------------- ------------- ----- --------------- -------------
6 OSPFv2 Link MSD This document 6 OSPFv2 Link MSD This document
Figure 4: OSPFv2 Link MSD Figure 4: OSPFv2 Link MSD
Finally, this document requests IANA to allocate a sub-TLV type IANA has allocated sub-TLV type 9 from the OSPFv3 Extended-LSA Sub-
(TBD3) from the OSPFv3 Extended-LSA Sub-TLV registry. TLV registry.
Value Description Reference Value Description Reference
----- --------------- ------------- ----- --------------- -------------
TBD3 OSPFv3 Link MSD This document 9 OSPFv3 Link MSD This document
Figure 5: OSPFv3 Link MSD Figure 5: OSPFv3 Link MSD
6. Security Considerations 6. Security Considerations
Security concerns for OSPF are addressed in [RFC7474], [RFC4552] and Security concerns for OSPF are addressed in [RFC7474], [RFC4552] and
[RFC7166]. Further security analysis for OSPF protocol is done in [RFC7166]. Further security analysis for OSPF protocol is done in
[RFC6863]. Security considerations, as specified by [RFC7770], [RFC6863]. Security considerations, as specified by [RFC7770],
[RFC7684] and [RFC8362] are applicable to this document. [RFC7684] and [RFC8362] are applicable to this document.
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