Export of IGP Algorithm Information in IPFIX ZTE
Nanjing China liu.yao71@zte.com.cn
ZTE
zhao.liman@zte.com.cn
OPS OPSAWG IPFIX IGP Algorithm Flexible Algorithm(Flex-Algorithm) This document introduces a new IPFIX information element (IE) to identify the IGP Algorithm information related with the Segment Identifier (SID) or the IPv4/IPv6 prefix.
Introduction IGP Algorithms represent the triplet (calculation-type, metric-type, and constraints), where the second and third elements of the triplet MAY be unspecified. Flexible Algorithm is one type of IGP Algorithm. introduces the concept of Flexible Algorithm that allows IGPs (ISIS, OSPFv2 and OSPFv3) to compute constraint-based path over an SR-MPLS or an SRv6 network. In SR, the same prefix can be associated with multiple algorithms. comments that, besides the SR-MPLS prefix SID, the algorithm can be also included as part of an SR-MPLS Adjacency-SID advertisement in scenarios where multiple algorithms share the same link resource. further extends IGP Flexible Algorithm so that it can be used with regular IPv4 and IPv6 forwarding. The IANA "IGP Algorithm Types" registry defines the set of values for IGP Algorithms. The registry currently includes the default algorithm (value 0), Strict Shortest Path First (Strict-SPF, value 1), and Flexible Algorithms (values 128-255), while other values (e.g., 2-127) are reserved for future IGP Algorithm Types. Below are the typical use cases when monitoring a traffic flow in a network with IGP Algorithm (especially Flexible Algorithm) enabled.
  • Which IGP Algorithm does the SR-MPLS SID or the SRv6 SID locator belong to?
  • Which IGP Algorithm is the IPv4/IPv6 prefix related with?
By only looking at the SR SID or the IP address itself, the above questions could not be answered. This document introduces a new IP Flow Information Export (IPFIX) information element (IE) to identify the IGP Algorithm related with the SR segment identifier (SID) or the IPv4/IPv6 prefix.
Terminology 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 when, and only when, they appear in all capitals, as shown here. This document makes use of the terms defined in , and . The following terms are used as defined in :
  • IPFIX
  • IPFIX Information Elements
  • Metering Process
  • Template Record
  • Data Record
  • Collector
The following terms are used as defined in :
  • Segment Routing (SR)
  • Segment List
  • SRv6
  • SR-MPLS
  • Segment Identifier (SID)
The following terms are used as defined in :
  • (IGP) Algorithm
The following terms are used as defined in :
  • Flexible Algorithm
IGP Algorithm Information in IPFIX A new IE "igpAlgo" is defined in this document to identify the IGP Algorithm information related with an SR-MPLS SID, an SRv6 locator or an IPv4/IPv6 prefix, the IE carries the value of the IGP Algorithm Types as in the IANA "IGP Algorithm Types" registry.
Name:
igpAlgo
ElementID:
TBD1
Description:
The 8-bit value that represents an IGP Algorithm type related with an SR-MPLS SID, an SRv6 locator or an IPv4/IPv6 prefix. The values of the IGP Algorithm types are specified in the IANA "IGP Algorithm Types" registry, i.e., the value is 0 if the default algorithm is used, the value is 1 if Strict Shortest Path First (Strict-SPF) algorithm is used, and the value 128-255 for Flex-Algorithms.
Abstract Data Type:
unsigned8
Data Type Semantics:
identifier
Additional Information:
Specified in and .
Reference:
This document.
Operational Considerations
Generic Considerations When used for monitoring SR-MPLS traffic flows: The IE "igpAlgo" indicates the IGP Algorithm of the active SR-MPLS prefix/adjacency SID or the IGP prefix related with the SR-MPLS SID, as in , and . And the "igpAlgo" is valid when the value of IE "IPFIX MPLS label type (Value 46) " in the data record is 7 (OSPFv2 Segment Routing), 8 (OSPFv3 Segment Routing) or 9 (IS-IS Segment Routing). In the absence of the IE "IPFIX MPLS label type" in the IPFIX template record, how to process the "igpAlgo" is implementation specific. When used for monitoring SRv6 traffic flows: The IE "igpAlgo" indicates the IGP Algorithm related with the locator of the active SRv6 SID as in , and . And the IE "igpAlgo" is valid when the value of IE "IPFIX IPv6 SRH Segment Type (Value 500)" in the data record is 3 (OSPFv3 Segment Routing) or 4 (IS-IS Segment Routing). In the absence of the IE "IPv6 SRH Segment Type", how to process the "igpAlgo" is implementation specific. When monitoring pure IPv4/IPv6 traffic flows, the IE "igpAlgo" can be used to indicate the IGP Algorithm related with the destination IPv4/IPv6 address or the IPv4/IPv6 next hop address.
Security Considerations There are no additional security considerations regarding allocation of these new IPFIX IEs compared to . Other security considerations for IGP Algorithm in and apply to this document.
IANA Considerations This document requests IANA to create a new IE under the "IPFIX Information Elements" registry available at .
Acknowledgements The authors would like to thank Thomas Graf for his helpful comments and suggestions.
References Normative References IP Flow Information Export (IPFIX) Entities IANA Informative References