| Internet-Draft | BGP-LS extensions for IP Flexible Algori | March 2023 |
| Hegde, et al. | Expires 14 September 2023 | [Page] |
Flexible Algorithm is a mechanism that allows Link state routing protocols (viz. OSPF and IS-IS) to compute paths over a network based on user-defined (and hence, flexible) constraints and metrics. The computation is performed by routers participating in the specific network in a distributed manner using a Flexible Algorithm definition. This definition provisioned on one or more routers and propagated (viz. OSPF and IS- IS flooding) through the network. IP Flex-algo enables these constraint based paths to be built in a network which is purely IP and does not support MPLS or SRv6 forwarding plane. BGP Link-State (BGP-LS) enables the collection of various topology information from the network. This draft defines extensions to BGP- LS address-family to advertise bandwidth, delay and metric related constraints in Flexible algorithm definition. It also defines BGP-LS extensions required to advertise IP flexible algorithm related extensions in BGP-LS.¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119].¶
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Flexible Algorithm [RFC9350] 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. [I-D.ietf-lsr-flex-algo-bw-con] 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.¶
[I-D.ietf-lsr-ip-flexalgo] 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 [I-D.ietf-lsr-flex-algo-bw-con] is advertised as a Link attribute [RFC7752]. The Generic Metric may be either sourced from ISIS, OSPFv2 or OSPFv3. When the Generic Metric is sourced from below TLVs in ISIS¶
OR¶
is sourced from below TLVs in OSPF¶
It is advertised as link attribute TLV.¶
When the Generic Metric is sourced from below TLV in ISIS and OSPF¶
It is advertised as a sub-TLV of Application Specific Link Attributes TLV [I-D.ietf-idr-bgp-ls-app-specific-attr]¶
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| metric-type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type : TBD (To be assigned by IANA)
Length: 8 octets
metric-type = A value from the IGP metric type registry
Value : metric value (0- 4,294,967,295)
The sub-TLVs described in this section are advertised as the sub-TLV of the Flexible Algorithm Definition TLV [RFC9351].¶
These sub-TLVs are either sourced from ISIS, OSPF or OSPFv3 as described in [I-D.ietf-lsr-flex-algo-bw-con]¶
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Min Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type: TBD
Length: 4 octets.
Min Bandwidth: link bandwidth is encoded in 32 bits in IEEE
floating point format. The units are bytes per second.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Max Delay |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type: TBD
Length: 3 octets
Max link delay: Maximum link delay in microseconds
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reference Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Granularity Bandwidth |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
where:
Type: TBD
Length: 14 octets.
Reference Bandwidth: Bandwidth encoded in 32 bits in
IEEE floating point format.
The units are in bytes per second.
Granularity Bandwidth: Bandwidth encoded in 32 bits in
IEEE floating point format.
The units are in bytes per second.
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.
Metric calculation: (Reference_bandwidth) /
(Total_link_bandwidth -
(Modulus of
(Total_link_bandwidth, Granularity_bw)))
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 [I-D.ietf-lsr-ip-flexalgo] .¶
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Algorithm 1 | Algorithm... | Algorithm n | |
+- -+
| |
+ +
* Type: IP Algorithm TLV (Value TBD by IANA)
* Length: Variable
* Algorithm (1 octet): Value from 128 to 255.
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
BGP-LS NLRI and Attribute TLV registry is updated to include newly defined Node, link and prefix attriute TLVs.¶
+-----------+---------------------+------------------------------+
| TLV Code | Description | Reference |
| Point | | (RFC/Section) |
+------------+---------------------+------------------------------+
| TBD1 | IP Algorithm TLV | draft-ietf-lsr-ip-flexalgo |
| | | Section 5.1/5.2 |
| TBD2 | IPv4 Algorithm |draft-ietf-lsr-ip-flexalgo |
| | Prefix Reachability | section 6.1 to 6.4 |
| | TLV | |
| TBD3 | Generic Metric TLV |draft-ietf-lsr-flex-algo-bw-con
| | | Section 2.1 and 2.2 |
| TBD4 |Flexible Algorithm |draft-ietf-lsr-flex-algo-bw-con
| |Exclude Minimum |Section 3.1.1 and 3.2.1 |
| |Bandwidth | |
| TBD5 |Flexible Algorithm |draft-ietf-lsr-flex-algo-bw-con
| |Exclude Maximum |Section 3.1.2 and 3.2.2 |
| |Delay | |
| TBD6 |Flexible Algorithm |draft-ietf-lsr-flex-algo-bw-con
| |Reference Bandwidth |Section 4.1.3.1 and 4.1.4.1 |
| TBD7 |Flexible Algorithm |draft-ietf-lsr-flex-algo-bw-con
| | Bandwidth Threshold |Section 4.1.3.2 and 4.1.4.2 |
+------------+---------------------+------------------------------+