BGP-LS extensions for IP Flexible Algorithms and Bandwidth, Delay, Metrics and Constraints

Flexible Algorithm is defined as a set of parameters consisting of calculation-type, metric-type and a set of constraints for allowing operators to have more control over the network path computation. defines further extensions to Flexible Algorithm that will allow operators additional control over their traffic flow, especially with respect to constraints about metric, delay and bandwidth. enables constraint based paths to be built in a network which is purely IP and does not support MPLS or SRv6 forwarding plane. This document defines BGP-LS related extensions to carry the information specific to Flexible Algorithms delay and bandwidth constraints as well as extensions related to IP Flexible-Algorithms.

Generic Metric as defined in is advertised as a Link attribute . The Generic Metric may be either sourced from ISIS, OSPFv2 or OSPFv3. When the Generic Metric is sourced from below TLVs in ISIS TLV-22 (Extended IS reachability) TLV-222 (MT-ISN) TLV-23 (IS Neighbor Attribute) TLV-223 (MT IS Neighbor Attribute) TLV-141 (inter-AS reachability information) OR is sourced from below TLVs in OSPF sub-TLV of the OSPF Link TLV of OSPF extended Link LSA . sub-TLV of TE Link TLV (2) of OSPF TE LSA . sub-TLV of the Router-Link TLV in the E-Router-LSA in OSPFv3 . It is advertised as link attribute TLV. When the Generic Metric is sourced from below TLV in ISIS and OSPF sub-TLV 16 (Application-Specific Link Attributes) of TLV 22/222/23/223/141 sub-sub-TLV of Application-Specific Link Attributes sub-TLV . It is advertised as a sub-TLV of Application Specific Link Attributes TLV

The sub-TLVs described in this section are advertised as the sub-TLV of the Flexible Algorithm Definition TLV . These sub-TLVs are either sourced from ISIS, OSPF or OSPFv3 as described in

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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Bandwidth Threshold 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Threshold Metric 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Bandwidth Threshold 2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Threshold Metric 2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Bandwidth Threshold 3 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ..... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Threshold Metric n-1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Bandwidth Threshold n | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Threshold Metric n | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ where: Type: TBD Length: 2 + n*8 octets. Here n is equal to number of Threshold Metrics specified. n MUST be greater than or equal to 1. Flags: 0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |G| | | | +-+-+-+-+-+-+-+-+ G-flag: when set, interface group Mode MUST be used to derive total link bandwidth. Staircase bandwidth threshold and associated metric values. Bandwidth Threshold 1: Minimum Link Bandwidth is encoded in 32 bits in IEEE floating point format. The units are bytes per second. Bandwidth Threshold 2: Maximum Link Bandwidth is encoded in 32 bits in IEEE floating point format. The units are bytes per second. Threshold Metric 1 : metric value range (1 - 4,294,967,296)

BGP-LS IP algorithm TLV is a node Attribute TLV and is encoded along with the Node NLRI. The TLV may be sourced from ISIS and/or OSPF as defined in section 5.1 and 5.2 of .

The IP algorithm Prefix Reachability TLV is advertised as a Prefix Attribute and may be associated with an IPv4 or an IPv6 Prefix. This TLV MUST appear only once in a Prefix NLRI. If the IP algorithm Prefix Reachability TLV is present, Prefix Metric TLV MUST NOT be added. IP algorithm Prefix Reachability TLV is present, IGP Flags TLV carries the flags for IP algorithm Prefix Reachability TLV.

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 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Algorithm| Reserved | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Metric | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type (2 octets) : The value is TBD. * Length (2 octet): 8 * Algorithm (1 octet): Associated Algorithm from 128 to 255. * Reserved: (3 octets). SHOULD be set to 0 on transmission and MUST be ignored on reception. * Metric (4 octets): The algorithm specific metric value. The metric value of 0XFFFFFFFF MUST be considered as unreachable. * Flags (1 octet): None defined

TBD

BGP-LS NLRI and Attribute TLV registry is updated to include newly defined Node, link and prefix attriute TLVs.