| Internet-Draft | Abbreviated-Title | March 2022 |
| Li, et al. | Expires 6 September 2022 | [Page] |
[I-D.ietf-idr-link-bandwidth] defines a BGP link bandwidth extended community attribute, which can enable devices to implement unequal-cost load-balancing. However, the bandwidth value encapsulated by the extended community attribute is of the floating-point type, which is inconvenient to use. In this document, a set of new types of link bandwidth extended community are introduced to facilitate the configuration and calculation of link bandwidth.¶
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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In [I-D.ietf-idr-link-bandwidth], the link bandwidth extended community attribute is added to implement unequal-cost load balancing based on the bandwidth on a path. As defined in the draft, the bandwidth of a link is expressed in 4-octets in IEEE floating-point format.¶
In practice, the use of this floating-point format may result errors in configuration and computation. When an operator needs to manually specify the bandwidth, you also need to consider the conversion from the bandwidth value to the floating-point number. This mode is not user-friendly, especially when the routing policy is used for bandwidth matching.¶
This document introduce a more intuitive expression of link bandwidth in BGP. It uses an unsigned long integer value to describe the link bandwidth value. This is easier for operators to use and understand, and can avoid configuration and computation errors.¶
The type of Link Bandwidth Extended Community is 0x40, and the subtype is 0x04. In the attribute value, the global administrator subfield is set to the AS number of the route to which the Link Bandwidth attribute is added. In the local administrator subfield, the link bandwidth value [I-D.ietf-idr-link-bandwidth] is set to the IEEE floating-point type.¶
A new type of IPv6 Address Specific Extended Community[RFC5701] is added in this document. The ASN field of this attribute is set to the AS number of the route to which the link bandwidth attribute is added. The Link Bandwidth value field (8 bytes) is set to the link bandwidth. The following extended contents are added:¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x03 or 0x43 | Sub-Type | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 8 bytes Link Bandwidth value (cont.) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 8 bytes Link Bandwidth value (cont.) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 4 bytes ASN | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
The subtypes defined here can be used for both optional transitive and non-transitive extended community attributes.¶
The extended link bandwidth extended community attribute in this document should not be used together with the standard link bandwidth extended community attribute. If a route carries both the standard link bandwidth extended community attribute and the unit link bandwidth extended community attribute, the standard link bandwidth extended community attribute is ignored.¶
In actual deployment, if a routing policy is used to match link bandwidth attributes, you can directly perform exact value matching.¶
This document defines a specific application of the two-octet AS specific extended community. IANA is requested to assign new sub-types for both non-transitive and transitive extended communities.¶
SubType Description ------- ------------------------------- TBD Link Bandwidth EC in bytes per second¶
There are no additional security risks introduced by this design.¶