IGP Flexible Algorithms Reverse Affinity Constraint

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Table of Contents

2. Requirements Language

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶

4. IS-IS Flexible Algorithm Exclude Reverse Admin Group Sub-TLV

The IS-IS Flexible Algorithm Exclude Reverse Admin Group (FAERAG) Sub-TLV is used to advertise the exclude rule that is used during the Flex-Algorithm path calculation as specified in Section 10.¶

The IS-IS FAERAG Sub-TLV is a Sub-TLV of the IS-IS FAD Sub-TLV. It has the following format:¶

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      Type     |    Length     |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      Extended Admin Group                     |
+-                                                             -+
|                            ...                                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:

Type: 10¶

Length: variable, dependent on the size of the Extended Admin Group. MUST be a multiple of 4 octets.¶

Extended Administrative Group: Extended Administrative Group as defined in [RFC7308].¶

The IS-IS FAERAG Sub-TLV MUST NOT appear more than once in a single IS-IS FAD Sub-TLV. If it appears more than once, the IS-IS FAD Sub-TLV MUST be ignored by the receiver.¶

The IS-IS FAERAG Sub-TLV MUST NOT appear more than once in the set of FAD sub-TLVs for a given Flex-Algorithm from a given IS. If it appears more than once in such set, the IS-IS FAERAG Sub-TLV in the first occurrence in the lowest numbered LSP from a given IS MUST be used and any other occurrences MUST be ignored.¶

5. IS-IS Flexible Algorithm Include-Any Reverse Admin Group Sub-TLV

The IS-IS Flexible Algorithm Include-Any Reverse Admin Group Sub-TLV is used to advertise include-any rule that is used during the Flex-Algorithm path calculation as specified in Section 10.¶

The format of the IS-IS Flexible Algorithm Include-Any Reverse Admin Group Sub-TLV is identical to the format of the FAERAG Sub-TLV in Section 4.¶

The IS-IS Flexible Algorithm Include-Any Reverse Admin Group Sub-TLV Type is 11.¶

The IS-IS Flexible Algorithm Include-Any Reverse Admin Group Sub-TLV MUST NOT appear more than once in a single IS-IS FAD Sub-TLV. If it appears more than once, the IS-IS FAD Sub-TLV MUST be ignored by the receiver.¶

The IS-IS Flexible Algorithm Include-Any Reverse Admin Group Sub-TLV MUST NOT appear more than once in the set of FAD sub-TLVs for a given Flex-Algorithm from a given IS. If it appears more than once in such set, the IS-IS Flexible Algorithm Include-Any Reverse Admin Group Sub-TLV in the first occurrence in the lowest numbered LSP from a given IS MUST be used and any other occurrences MUST be ignored.¶

6. IS-IS Flexible Algorithm Include-All Reverse Admin Group Sub-TLV

The IS-IS Flexible Algorithm Include-All Reverse Admin Group Sub-TLV is used to advertise include-any rule that is used during the Flex-Algorithm path calculation as specified in Section 10.¶

The format of the IS-IS Flexible Algorithm Include-All Reverse Admin Group Sub-TLV is identical to the format of the FAERAG Sub-TLV in Section 4.¶

The IS-IS Flexible Algorithm Include-All Reverse Admin Group Sub-TLV Type is 12.¶

The IS-IS Flexible Algorithm Include-All Reverse Admin Group Sub-TLV MUST NOT appear more than once in a single IS-IS FAD Sub-TLV. If it appears more than once, the IS-IS FAD Sub-TLV MUST be ignored by the receiver.¶

The IS-IS Flexible Algorithm Include-All Reverse Admin Group Sub-TLV MUST NOT appear more than once in the set of FAD sub-TLVs for a given Flex-Algorithm from a given IS. If it appears more than once in such set, the IS-IS Flexible Algorithm Include-All Reverse Admin Group Sub-TLV in the first occurrence in the lowest numbered LSP from a given IS MUST be used and any other occurrences MUST be ignored.¶

7. OSPF Flexible Algorithm Exclude Reverse Admin Group Sub-TLV

The OSPF Flexible Algorithm Exclude Reverse Admin Group (FAERAG) Sub-TLV is used to advertise the exclude rule that is used during the Flex-Algorithm path calculation as specified in Section 10.¶

The OSPF FAERAG Sub-TLV is a Sub-TLV of the OSPF FAD TLV. It has the following format:¶

 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              Type             |             Length            |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                      Extended Admin Group                     |
+-                                                             -+
|                            ...                                |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:

Type: 10¶

Length: variable, dependent on the size of the Extended Admin Group. MUST be a multiple of 4 octets.¶

Extended Administrative Group: Extended Administrative Group as defined in [RFC7308].¶

The OSPF FAERAG Sub-TLV MUST NOT appear more than once in an OSPF FAD TLV. If it appears more than once, the OSPF FAD TLV MUST be ignored by the receiver.¶

8. OSPF Flexible Algorithm Include-Any Reverse Admin Group Sub-TLV

The usage of this Sub-TLVs is described in Section 5.¶

The format of the OSPF Flexible Algorithm Include-Any Reverse Admin Group Sub-TLV is identical to the format of the OSPF FAERAG Sub-TLV in Section 7.¶

The OSPF Flexible Algorithm Include-Any Reverse Admin Group Sub-TLV Type is 11.¶

The OSPF Flexible Algorithm Include-Any Reverse Admin Group Sub-TLV MUST NOT appear more than once in an OSPF FAD TLV. If it appears more than once, the OSPF FAD TLV MUST be ignored by the receiver.¶

9. OSPF Flexible Algorithm Include-All Reverse Admin Group Sub-TLV

The usage of this Sub-TLVs is described in Section 6.¶

The format of the OSPF Flexible Algorithm Include-All Reverse Admin Group Sub-TLV is identical to the format of the OSPF FAERAG Sub-TLV in Section 7.¶

The OSPF Flexible Algorithm Include-All Reverse Admin Group Sub-TLV Type is 12.¶

The OSPF Flexible Algorithm Include-All Reverse Admin Group Sub-TLV MUST NOT appear more than once in an OSPF FAD TLV. If it appears more than once, the OSPF FAD TLV MUST be ignored by the receiver.¶

10. Calculation of Flexible Algorithm Paths

Three new rules are added to the existing rules specified in sec 13 of [RFC9350].¶

6. Check if any exclude reverse AG rule is part of the Flex-Algorithm definition. If such exclude rule exists, check if any color that is part of the exclude rule is also set on the link from the reverse direction. If such a color is set on the link from the reverse direction, the link MUST be pruned from the computation.¶

7. Check if any include-any reverse AG rule is part of the Flex-Algorithm definition. If such include-any rule exists, check if any color that is part of the include-any rule is also set on the link from the reverse direction. If no such color is set on the link from the reverse direction, the link MUST be pruned from the computation.¶

8. Check if any include-all reverse AG rule is part of the Flex-Algorithm definition. If such include-all rule exists, check if all colors that are part of the include-all rule are also set on the link from the reverse direction. If all such colors are not set on the link from the reverse direction, the link MUST be pruned from the computation.¶

11. IANA Considerations

12. Security Considerations

This document inherits security considerations from [RFC9350].¶

13. Acknowledgements

TBD¶

Authors' Addresses