BGP Classful Transport
PlanesJuniper Networks, Inc.1133 Innovation Way,SunnyvaleCA94089USkaliraj@juniper.netJuniper Networks, Inc.1133 Innovation Way,SunnyvaleCA94089USnatv@juniper.netThis document specifies a mechanism, referred to as "Intent Driven
Service Mapping" to express association of overlay routes with underlay
routes satisfying a certain SLA using BGP. The document describes a
framework for classifying underlay routes into transport classes and
mapping service routes to specific transport class.The "Transport class" construct maps to a desired SLA and can be used
to realize the "Topology Slice" in 5G Network slicing architecture.This document specifies BGP protocol procedures that enable
dissemination of such service mapping information that may span multiple
cooperating administrative domains. These domains may be administetered
by the same provider or by closely co-ordinating provider networks.A new BGP transport layer address family (SAFI 76) is defined for
this purpose that uses RFC-4364 technology and follows RFC-8277 NLRI
encoding. This new address family is called "BGP Classful Transport",
aka BGP CT.BGP CT makes it possible to advertise multiple tunnels to the same
destination address, thus avoiding need of multiple loopbacks on the
egress node.It carries transport prefixes across tunnel domain boundaries (e.g.
in Inter-AS Option-C networks), which is parallel to BGP LU (SAFI 4) .
It disseminates "Transport class" information for the transport prefixes
across the participating domains, which is not possible with BGP LU.
This makes the end-to-end network a "Transport Class" aware tunneled
network.Though BGP CT family is used only in the option-C inter-AS neworks,
the Service Mapping procedures described in this document apply in the
same manner to Intra-AS service end points as well as Inter-AS option-A,
option-B and option-C variations.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.The mechanisms defined in this document enable brownfiled networks
deployed using existing technologies like RSVP-TE and greenfield
networks that use technologies like SPRING achieve 'Intent Driven
Service Mapping'.To facilitate this, the tunnels in a network can be grouped by the
purpose they serve into a "Transport Class". These tunnels could be
created using any signaling protocol including but not limited to LDP,
RSVP-TE, BGP LU or SPRING. The tunnels could also use native IP or IPv6
as long as they can carry MPLS payload. Tunnels may exist between
different pair of end points. Multiple tunnels may exist between the
same pair of end points.Thus, a Transport Class consists of tunnels created by various
protocols that satisfy the properties of the class. For example, a
"Gold" transport class may consist of tunnels that traverse the shortest
path with fast re-route protection. A "Silver" transport class may hold
tunnels that traverse shortest paths without protection. A "To NbrAS
Foo" transport class may hold tunnels that exit to neighboring AS Foo
and so on.The extensions specified in this document can be used to create a BGP
transport tunnel that potentially spans domains while preserving its
Transport Class. Examples of domain are Autonomous System (AS) or IGP
area. Within each domain, there is a second level underlay tunnel used
by BGP to cross the domain. The second level underlay tunnels could be
hetrogeneous; each domain may use a different type of tunnel (e.g. MPLS,
IP, GRE or SRv6) or use a differnet signaling protocol. A domain
boundary is demarcated by a rewrite of BGP nexthop to 'self' while
readvertising tunnel routes in BGP CT. Examples of domain boundary are
inter-AS links and inter-region ABRs. The path uses MPLS label-switching
when crossing domain boundaries and uses the native intra-AS tunnel of
the desired transport class when traversing within a domain.Overlay routes carry sufficient indication of the desired Transport
Classes in the form of a BGP community called the "Mapping community".
The "route resolution" procedure on the ingress node selects an
appropriate tunnel whose destination matches (LPM) the nexthop of the
overlay route belonging to the corresponding Transport Class. If the
overlay route is carried in BGP, the protocol nexthop (or PNH) is
carried as an attribute of the route.The PNH of the overlay route is also referred to as "Service
Endpoint" (SEP). The SEP may exist in the same domain as the service
ingress node or lie in a different domain, which is adjacent or
non-adjacent. In the former case, reachability to the SEP is provided by
an intra-domain tunneling protocol and in the latter case, reachability
to the SEP is via BGP transport families (e.g. SAFI 4 or 76).In this architecture, the intra-domain transport protocols (e.g.
RSVP-TE, SRTE) are also "Transport Class aware". They publish ingress
routes in the Transport Route Database associated with the Transport
Class at the tunnel ingress node. These routes are used to resolve BGP
routes inluding BGP CT which may be further readvertised to adjacent
domains to extend this tunnel. How exactly the transport protocols are
made transport class aware is outside the scope of this document.This document describes mechanisms to: Model a "Transport Class" as a "Transport Route Database" on a
router and to collect tunnel ingress routes of a certain class.Enable service routes to resolve over an intended Transport Class
by virtue of carrying the appropriate "Mapping Community", which
results in using the corresponding Transport Route Database for
finding nexthop reachability.Publish tunnel ingress routes in a Transport Route Database via
BGP without any path hiding using BGP VPN and Add-path procedures,
such that overlay routes in the receiving domains can also resolve
over tunnels of the associated Transport Class.Provide a way for cooperating domains to reconcile any
differences in extended community namespaces and interoperate
between different transport signaling protocols in each domain.In this document we focus mainly on MPLS as the intra-domain
transport tunnel forwarding technology, but the mechanisms described
here would work in similar manner for non-MPLS (e.g. IP, GRE, UDP or
SRv6) transport tunnel forwarding technologies too.This document assumes MPLS forwarding as the defacto standard when
crossing domain boundaries. However mechanisms specified in this
document can also support different forwarding technologies (e.g. SRv6).
Section 17 (SRv6 support) in this document describes the application of
BGP CT over SRv6 data plane.The document Seamless Segment
Routing describes various use cases and applications of
procedures described in this document.LSP: Label Switched Path.TE : Traffic Engineering.SN : Service Node. A router that sends or receives BGP Service routes
(e.g. SAFI 1, 128) with self as nexthop.BN : Border Node. A router that sends or receives BGP Transport
routes (e.g. SAFI 4, 76) with self as nexthop.TN : Transport Node, P-router.BGP-VPN : VPNs built using RFC4364 mechanisms.RT : Route-Target extended community.RD : Route-Distinguisher.VRF: Virtual Router Forwarding Table.CsC: Carrier serving Carrier VPN.PNH : Protocol-Nexthop address carried in a BGP Update message.EP : End point, a loopback address in the network.SEP : Service End point, the PNH of a Service route.LPM : Longest Prefix Match.SLA: Service Level Agreement.EPE: Egress Peer Engineering.Service Family : BGP address family used for advertising routes for
"data traffic" as opposed to tunnels (e.g. SAFI 1 or 128).Transport Family : BGP address family used for advertising tunnels,
which are in turn used by service routes for resolution (e.g. SAFI 4 or
76).Transport Tunnel : A tunnel over which a service may place traffic
(e.g. GRE, UDP, LDP, RSVP-TE or SPRING).Tunnel Ingress Route: Route to Tunnel Destination/Endpoint installed
at the headend (ingress) of the tunnel by the tunneling protocol.Tunnel Domain : A domain of the network containing SNs and BNs under
a single administrative control that has tunnels between them. An
end-to-end tunnel spanning several adjacent tunnel domains can be
created by "stitching" them together using labels.Transport Class : A group of transport tunnels offering the same
SLA.Transport Class RT : A Route-Target extended community used to
identify a specific Transport Class.Transport Route Database : At the SN and BN, a Transport Class has an
associated Transport Route Database that collects its tunnel ingress
routes.Transport Plane : An end to end plane comprising of transport tunnels
belonging to same Transport Class. Tunnels of same Transport Class are
stitched together by BGP CT route readvertisements with nexthop self to
enable Label-Swap forwarding across domain boundaries.Mapping Community : BGP Community/Extended-community on a service
route that maps it to resolve over a Transport Class.A Transport Class is defined as a set of transport tunnels that share
the same SLA. It is encoded as the Transport Class RT, which is a new
Route-Target extended community.A Transport Class is configured at SN and BN with RD and Route Target
attributes. Creation of a Transport Class instantiates its corresponding
Transport Route Database.The operator may configure an SN/BN to classify a tunnel into an
appropriate Transport Class, which causes the tunnel's ingress route to
be installed in the corresponding Transport Route Database. These routes
are used to resolve BGP routes inluding BGP CT which may be further
readvertised to adjacent domains to extend this tunnel.Alternatively, a router receiving the transport routes in BGP with
appropriate signaling information can associate those ingress routes to
the appropriate Transport Class. E.g. for Classful Transport family
(SAFI 76) routes, the Transport Class RT indicates the Transport Class.
For BGP LU family(SAFI 4) routes, import processing based on Communities
or inter-AS source-peer may be used to place the route in the desired
Transport Class.When the ingress route is received via SRTE with "Color:Endpoint" as the NLRI that encodes
the Transport Class as an integer 'Color', the 'Color' is mapped to a
Transport Class during import processing. SRTE ingress route for
'Endpoint' is installed in the corresponding Transport Route Database.
The SRTE tunnel will be extended by a BGP CT advertisement with NLRI
'RD:Endpoint', Transport Class RT and a new label. The MPLS swap route
thus installed for the new label will pop the label and deliver
decapsulated traffic into the path determined by SRTE route.RFC8664 extends PCEP to carry SRTE
Color. This color association learnt from PCEP is also mapped to a
Transport Class thus associating the PCEP signaled SRTE LSP with the
desired Transport Class.Similarly, PCEP-RSVP-COLOR
extends PCEP to carry RSVP Color. This color association learnt from
PCEP is also mapped to a Transport Class thus associating the PCEP
signaled RSVP-TE LSP with the desired Transport Class.This document defines a new type of Route Target, called "Transport
Class" Route Target Extended Community."Transport Class" Route Target extended community is a transitive
extended community EXT-COMM of
extended-type, with a new Format (Type high = 0xa) and SubType as 0x2
(Route Target).This new Route Target Format has the following encoding:
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= 0xa | SubType= 0x02 | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transport Class ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fig 1: "Transport Class" Route Target Extended Community
Type: 1 octet
Type field contains value 0xa.
SubType: 1 octet
Subtype field contain 0x2. This indicates 'Route Target'.
Transport Class ID: 4 octets
The least significant 32-bits of the value field contain the
"Transport Class" identifier, which is a 32-bit integer.
The remaining 2 octets after SubType field are Reserved. They MUST
be set to zero on transmission, SHOULD be ignored on reception and
left unaltered.
The "Transport class" Route Target Extended community follows the
mechanisms for VPN route import/export as specified in BGP-VPN and follows the Constrained Route
Distribution mechanisms as specified in Route
Target ConstraintsA BGP speaker that implements RT Constraint Route Target Constraints MUST apply the RT
Constraint procedures to the "Transport class" Route Target Extended
community as well.The Transport Class Route Target Extended community is carried on
Classful Transport family routes and allows associating them with
appropriate Transport Route Databases at receiving BGP speakers.Use of the Transport Class Route Target Extended community with a new
Type code avoids conflicts with any VPN Route Target assignments already
in use for service families.A Transport Route Database is a logical collection of transport
routes pertaining to the same Transport Class. Tunnel endpoint addresses
in this database belong to the "Provider Namespace".Overlay routes that want to use a specific Transport Class confine
the scope of nexthop resolution to the set of routes contained in the
corresponding Transport Route Database.The Transport Route Database can be realized as a "Routing Table"
referred in Section
9.1.2.1 of RFC4271 which is a control plane only database.
However, an implementation may choose a different methodology to realize
this logical construct in such a way that it supports the procedures
defined in this document.SN or BN originate routes for 'Classful Transport' address family
from the Transport Route Database. These routes have NLRI "RD:Endpoint",
Transport Class RT and an MPLS label. 'Classful Transport' family routes
received with Transport Class RT are imported into its corresponding
Transport Route Database.An implementation may provide an option for the service route to
resolve over less preferred Transport Classes, should the resolution
over preferred or "primary" Transport Class fail.To accomplish this, the set of service routes may be associated with
a user-configured "Resolution Scheme" that consists of the primary
Transport Class and an optional ordered list of fallback Transport
Classes.A community called as "Mapping Community" is configured for a
"resolution scheme". A Mapping Community maps to exactly one Resolution
Scheme. A Resolution Scheme comprises of one primary transport class and
optionally, one or more fallback transport classes.A BGP route is associated with a resolution scheme during import
processing. The first community on the route that matches a Mapping
Community of a locally configured Resolution Scheme is considered the
effective Mapping Community for the route. The Resolution Scheme thus
found is used when resolving the route's PNH. If a route contains more
than one Mapping Community, it indicates that the route considers these
multiple Mapping Communities as equivalent. So, the first community that
maps to a Resolution Scheme is chosen.A transport route received in BGP Classful Transport family SHOULD
use a Resolution Scheme that contains the primary Transport Class
without any fallback to best effort tunnels. The primary Transport Class
is identified by the Transport Class RT carried on the route. Thus,
Transport Class RT serves as the Mapping Community for BGP CT
routes.A service route received in a BGP service family MAY map to a
Resolution Scheme that contains the primary Transport Class identified
by the Mapping Community on the route and a fallback to best effort
Transport Class. The primary Transport Class is identified by the
Mapping Community carried on the route. For e.g. the Extended Color
community may serve as the Mapping Community for service routes.
Color:0:<n> MAY map to a Resolution Scheme that has primary
Transport Class <n> and a fallback to best-effort Transport
Class.The Classful Transport (CT) family will use the existing AFI of IPv4
or IPv6 and a new SAFI 76 "Classful Transport" that will apply to both
IPv4 and IPv6 AFIs. These AFI, SAFI pair of values MUST be negotiated in
Multiprotocol Extensions capability described in to be able to send and receive BGP CT routes.The "Classful Transport" SAFI NLRI itself is encoded as specified in
https://tools.ietf.org/html/rfc8277#section-2.When AFI/SAFI is 1/76, the Classful Transport NLRI Prefix consists of
an 8-byte RD followed by an IPv4 prefix. When AFI/SAFI is 2/76, the
Classful Transport NLRI Prefix consists of an 8-byte RD followed by an
IPv6 prefix.For better readability, the following figure illustrates a BGP
Classful Transport family NLRI when single Label is advertised:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | Label |Rsrv |S|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Route Distinguisher (8 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4/IPv6 Prefix ~
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Fig 2: SAFI 76 "Classful Transport" NLRI
Length: 1 octet
The Length field consists of a single octet. It specifies the
length in bits of the remainder of the NLRI field.
Note that the length will always be the sum of 20 (number of bits
in Label field), plus 3 (number of bits in Rsrv field), plus 1
(number of bits in S field), plus the length in bits of the
Prefix (RD:IP prefix).
In an MP_REACH_NLRI attribute whose SAFI is 76, the Prefix
(RD + IP prefix) will be 96 bits or less if the AFI is 1
and will be 192 bits or less if the AFI is 2.
As specified in [RFC4760], the actual length of the NLRI field
will be the number of bits specified in the Length field, rounded
up to the nearest integral number of octets.
Label:
The Label field is a 20-bit field containing an MPLS label value
(see [RFC3032]).
Rsrv:
This 3-bit field SHOULD be set to zero on transmission and MUST be
ignored on reception.
S:
When single label is advertised, this 1-bit field MUST be set to
one on transmission and MUST be ignored on reception.
Route Distinguihser:
8 byte RD as defined in [RFC4364 Sec 4.2].
IPv4/IPv6 Prefix:
IPv4 prefix, if AFI/SAFI 1/76.
IPv6 prefix, if AFI/SAFI 2/76.
Attributes on a Classful Transport route include the Transport Class
Route-Target extended community, which is used to associate the route
with the correct Transport Route Databases on SNs and BNs in the
network.SAFI 76 routes can be sent with either IPv4 or IPv6 nexthop. The type
of nexthop is inferred from the length of the nexthop.When the length of Next Hop Address field is 24 (or 48) the nexthop
address is of type VPN-IPv6 with 8-octet RD set to zero (potentially
followed by the link-local VPN-IPv6 address of the next hop with an
8-octet RD set to zero).When the length of the Next Hop Address field is 12 the nexthop
address is of type VPN-IPv4 with 8-octet RD set to zero.RD aids in troubleshooting a BGP CT network by uniquely identifying
the originator of a route across a multi domain network.Use of RD also allows the option for signaling forwarding diversity
within the same Transport Class. The same Egress PE can advertise
multiple BGP CT routes for an EP belonging to the same Transport
Class.E.g. multiple RDx:EP1 prefixes can be advertised for an EP1 to
different set of BGP peers in order to collect traffic statistics for
them. In absense of RD, duplicated Transport Class/Color values will be
needed in the transport network to achieve such use cases.SAFI 128 (Inet-VPN) is an RFC8277 encoded family that carries service
prefixes in the NLRI, where the prefixes come from the customer
namespaces and are contexualized into separate user virtual service RIBs
called VRFs using RFC4364 procedures.SAFI 4 (BGP LU) is an RFC8277 encoded family that carries transport
prefixes in the NLRI, where the prefixes come from the provider
namespace.SAFI 76 (Classful Transport) is an RFC8277 encoded family that
carries transport prefixes in the NLRI, where the prefixes come from the
provider namespace and are contexualized into separate Transport Route
Databases using RFC4364 procedures.It is worth noting that SAFI 128 has been used to carry transport
prefixes in "L3VPN Inter-AS Carrier's carrier" scenario, where BGP
LU/LDP prefixes in CsC VRF are advertised in SAFI 128 towards the
remote-end client carrier.In this document a new AFI/SAFI is used instead of reusing SAFI 128
to carry these transport routes because it is operationally advantageous
to segregate transport and service prefixes into separate address
families. E.g. It allows to safely enable "per-prefix" label allocation
scheme for Classful Transport prefixes without affecting SAFI 128
service prefixes which may have huge scale. The "per prefix" label
allocation scheme keeps the routing churn local during topology
changes.A new family also facilitates having a different readvertisement path
of the transport family routes in a network than the service route
readvertisement path. Service routes (Inet-VPN) are exchanged over an
EBGP multihop session between Autonomous systems with nexthop unchanged;
whereas Classful Transport routes are readvertised over EBGP single hop
sessions with "nexthop self" rewrite over inter-AS links.The Classful Transport family is similar in vein to BGP LU, in that
it carries transport prefixes. The only difference is that it also
carries in Route Target, an indication of which Transport Class the
transport prefix belongs to and uses RD to disambiguate multiple
instances of the same transport prefix in a BGP Update.This section summarizes the procedures followed by various nodes
speaking Classful Transport family.Operator decides on the Transport Classes that exist in the
network and allocates a Transport Class Route Target to identify
each Transport Class.Operator configures Transport Classes on the SNs and BNs in the
network with Transport Class Route Targets and unique
Route-Distinguishers.Implementations MAY provide automatic generation and assignment
of RD, RT values; they MAY also provide a way to manually override
the automatic mechanism in order to deal with any conflicts that
may arise with existing RD, RT values in different network domains
participating in the deployment.At the ingress node of the tunnel's home domain, the tunneling
protocols install tunnel ingress routes in the Transport Route
Database associated with the Transport Class the tunnel belongs
to.The egress node of the tunnel i.e. the tunnel endpoint
originates the BGP Classful Transport route with NLRI containing
RD:TunnelEndpoint, Transport Class RT and PNH TunnelEndpoint,
which will resolve over the tunnel route in Transport Route
Database at the ingress node. When the tunnel is up, the Classful
Transport BGP route will become usable and get re-advertised.Alternatively, the ingress node may advertise this tunnel
destination into BGP as a Classful Transport family route with
NLRI RD:TunnelEndpoint, attaching a 'Transport Class' Route Target
that identifies the Transport Class. This BGP CT route is
advertised to EBGP peers and IBGP peers in neighboring domains.
This route SHOULD NOT be advertised to the IBGP core that contains
the tunnel.Unique RD SHOULD be used by the originator of a Classful
Transport route to disambiguate the multiple BGP advertisements
for a transport end point.On receiving a BGP Classful Transport route with a PNH that is
not directly connected (e.g. an IBGP-route), a Mapping Community on
the route (the Transport Class RT) indicates which Transport Class
this route maps to. The routes in the associated Transport Route
Database are used to resolve the received PNH. If there does not
exist a route in the Transport Route Database matching the PNH, the
Classful Transport route is considered unusable and MUST NOT be
advertised further.The BN allocates an MPLS label to advertise upstream in Classful
Transport NLRI. The BN also installs an MPLS route for that label
that swaps the incoming label with a label received from the
downstream BGP speaker or pops the incoming label. It then pushes
received traffic to the transport tunnel or direct interface that
the Classful Transport route's PNH resolved over.The label SHOULD be allocated with "per-prefix" label allocation
semantics. RD is stripped from the BGP CT NLRI prefix when a BGP CT
route is added to a Transport Route Database. The IP prefix in the
Transport Route Database context (Transport-Class, IP-prefix) is
used as the key to do per-prefix label allocation. This helps in
avoiding BGP CT route churn through out the CT network when a
failure happens in a domain. The failure is not propagated further
than the BN closest to the failure.The value of advertised MPLS label is locally significant, and is
dynamic by default. The BN may provide option to allocate a value
from a statically carved out range. This can be achieved using
locally configured export policy, or via mechanisms described in
BGP Prefix-SID.If the route is received with PNH that is known to be directly
connected (e.g. EBGP single-hop peering address), the directly
connected interface is checked for MPLS forwarding capability. No
other nexthop resolution process is performed as the inter-AS link
can be used for any Transport Class.If the inter-AS links should honor Transport Class, then the BN
SHOULD follow procedures of an Ingress node described above and
perform nexthop resolution process. The interface routes SHOULD be
installed in the Transport Route Database belonging to the
associated Transport Class.When multiple BNs exist such that theu advertise a RD:EP prefix
to RRs, the RRs may hide all but one of the BNs, unless ADDPATH is used for the Classful Transport
family. This is similar to L3VPN option-B scenarios. Hence ADDPATH
SHOULD be used for Classful Transport family, to avoid path-hiding
through RRs.Pair of redundant ABRs, each acting as an RR with nexthop self
may chose each other as best path instead of the upstream ASBR,
causing a traffic forwarding loop.Implementations SHOULD provide a way to alter the tie-breaking
rule specified in BGP RR to tie-break
on CLUSTER_LIST step before ROUTER-ID step, when performing path
selection for BGP CT routes. RFC4456 considers pure RR which is not
in forwarding path. When RR is in forwarding path and reflects
routes with nexthop self as is the case for ABR BNs in a BGP
transport network, this rule may cause loops. This document suggests
the following modification to the BGP Decision Process Tie Breaking
rules (Sect. 9.1.2.2, ) when doing path
selection for BGP CT family routes:The following rule SHOULD be inserted between Steps e) and f): a
BGP Speaker SHOULD prefer a route with the shorter CLUSTER_LIST
length. The CLUSTER_LIST length is zero if a route does not carry
the CLUSTER_LIST attribute.Some deployment considerations can also help in avoiding this
problem: IGP metric should be assigned such that "ABR to redundant
ABR" cost is inferior than "ABR to upstream ASBR" cost.Tunnels belonging to non best effort Transport Classes SHOULD
NOT be provisioned between ABRs. This will ensure that the route
received from an ABR with nexthop self will not be usable at a
redundant ABR. This avoids possibility of such loops altogether.Service routes received with Mapping Community resolve using
Transport Route Databases determined by the Resolution Scheme. If
the resolution process does not find a Tunnel Ingress Route in any
of the Transport Route Databases, the service route MUST be
considered unusable for forwarding purpose and be withdrawn.Cooperating option-C domains may sometimes not agree on RT, RD,
Mapping-community or Transport Route Target values because of
differences in community namespaces (e.g. during network mergers or
renumbering for expansion). Such deployments may deploy mechanisms
to map and rewrite the Route Target values on domain boundaries,
using per ASBR import policies. This is no different than any other
BGP VPN family. Mechanisms used in inter-AS VPN deployments may be
used with the Classful Transport family also.The Resolution Schemes SHOULD allow association with multiple
Mapping Communities. This helps with renumbering, network mergers or
transitions.Deploying unique RDs is strongly RECOMMENDED because it helps in
troubleshooting by uniquely identifying originator of a route and
avoids path-hiding.This document defines a new format of Route-Target
extended-community to carry Transport Class, this avoids collision
with regular Route Target namespace used by service routes.Flowspec routes using Redirect to IP nexthop is described in BGP Flow-Spec Redirect to IP
ActionSuch Flowspec BGP routes with Redirect to IP nexthop can be attached
with a Mapping Community (e.g. Color:0:100), which allows redirecting
the flow traffic over a tunnel to the IP nexthop satisfying the desired
SLA (e.g. Transport Class color 100).Flowspec BGP family acts as just another service that can make use of
BGP CT architecture to achieve Flow based forwarding with SLAs.Mechanisms described in BGP LU EPE
also applies to BGP CT family.The Peer/32 or Peer/128 EPE route MAY be originated in BGP CT family
with appropriate Mapping Community (e.g. transport-target:0:100), thus
allowing an EPE path to the peer that satisfies the desired SLA.The Tunnel Encapsulation Attribute described in RFC9012 can be used to request a specific type
of tunnel encapsulation. Usage of this attribute may apply to BGP
service routes or transport routes, including BGP Classful Transport
family routes.Mechanisms described in BGP MultiNexthop
Attribute allow a BGP route to carry multiple nexthop addresses.
It also allows specifying 'Transport Class ID' as a qualifier for each
Nexthop address.It should be noted that in such cases "Transport Class/Color" can
exist in multiple places on the same route, and a precedence order needs
to be established to determine which Transport class the route's nexthop
should resolve over. This document suggests the following order of
precedence, more preferred first: Transport Class ID SubTLV, in MultiNexthop Attribute.Color SubTLV, in Tunnel Encapsulation Attribute.Transport Target Extended community, on BGP CT route.Color Extended community, on BGP service route. The above precedence order follows more specific scoping of
Color to less specific scoping.Transport Class ID specified for Nexthop-Leg subTLV in a MultiNextHop
attribute is more specific indication of Color than Color subTLV in a
TEA, which inturn is more specific than Mapping Community (Transport
Target) on a BGP CT transport route, which is inturn more specific than
a Service route scoped Mapping Community (Color Extended community).RFC8212 suggests BGP speakers
require explicit configuration of both BGP Import and Export
Policies in order to receive or send routes over EBGP sessions.It is recommended to follow this for BGP CT routes. It will
prohibit unintended advertisement of transport routes throughout the
BGP CT transport domain which may span across multiple AS domains.
This will conserve usage of MPLS label and nexthop resources in the
network. An ASBR of a domain can be provisioned to allow routes with
only the Transport Route Targets that are required by SNs in the
domain.This section describes how the number of Protocol Nexthops
advertised to a SN or BN can be constrained using BGP Classsful
Transport and Route Target
Constraints.An egress SN MAY advertise BGP CT route for RD:eSN with two Route
Targets: transport-target:0:<TC> and a RT carrying
<eSN>:<TC>. Where TC is the Transport Class identifier,
and eSN is the IP-address used by SN as BGP nexthop in its service
route advertisements.The transport-target:0:<TC> is the new type of route target
(Transport Class RT) defined in this document. It is carried in BGP
extended community attribute (BGP attribute code 16).The RT carrying <eSN>:<TC> MAY be an IP-address
specific regular RT (BGP attribute code 16), IPv6-address specific
RT (BGP attribute code 25), or a Wide-communities based RT (BGP
attribute code 34) as described in Route
Target Constrain Extension. This document recommends using
Wide-communities based RT for the same.An ingress SN MAY import BGP CT routes with Route Target carrying
<eSN>:<TC>. The ingress SN MAY learn the eSN values
either by configuration, or it MAY discover them from the BGP
nexthop field in the BGP VPN service routes received from eSN. A BGP
ingress SN receiving a BGP service route with nexthop of eSN SHOULD
generate a RTC/Extended-RTC route for Route Target prefix <Origin
ASN>:<eSN>/[80|176] in order to learn BGP CT transport
routes to reach eSN. This allows constrained distribution of the
transport routes to the PNHs actually required by iSN.When path of route propogation of BGP CT routes is same as the
RTC routes, a BN would learn the RTC routes advertised by ingress
SNs and propagate further. This will allow constraining distribution
of BGP CT routes for a PNH to only the necessary BNs in the network,
closer to the egress SN.This mechanism provides "On Demand Nexthop" of BGP CT routes,
which help with the scaling of MPLS forwarding state at SN and
BN.However, the amount of state carried in RTC family may become
proportional to number of PNHs in the network. To strike a balance,
the RTC route advertisements for <Origin
ASN>:<eSN>/[80|176] MAY be confined to the BNs in home
region of ingress-SN, or the BNs of a super core.Such a BN in the core of the network SHOULD import BGP CT routes
with Transport-Target:0:<TC> and generate a RTC route for
<Origin ASN>:0:<TC>/96, while not propagating the more
specific RTC requests for specific PNHs. This will let the BN learn
transport routes to all eSN nodes. But confine their propagation to
ingress-SNs.It may be even more desirable to limit the number of PNHs that
are globaly visible in the network. This is possible using mechanism
described in MPLS
NamespacesSuch that advertisement of PE loopback addresses as next-hop in
BGP service routes is confined to the region they belong to. An
anycast IP-address called "Context Protocol Nexthop Address" (CPNH)
abstracts the SNs in a region from other regions in the network,
swapping the SN scoped service label with a CPNH scoped private
namespace label.This provides much greater advantage in terms of scaling and
convergence. Changes to implement this feature are required only on
the local region's BNs and RRs.Standard MPLS OAM procedures specified in
also apply to BGP Classful Transport.The 'Target FEC Stack' sub-TLV for IPv4 Classful Transport has a
Sub-Type of [TBD], and a length of 13. The Value field consists of the
RD advertised with the Classful Transport prefix, the IPv4 prefix (with
trailing 0 bits to make 32 bits in all) and a prefix length encoded as
follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Route Distinguisher |
| (8 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 prefix |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | Must Be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The 'Target FEC Stack' sub-TLV for IPv6 Classful Transport has a
Sub-Type of [TBD], and a length of 25. The Value field consists of the
RD advertised with the Classful Transport prefix, the IPv6 prefix (with
trailing 0 bits to make 128 bits in all) and a prefix length encoded as
follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Route Distinguisher |
| (8 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 prefix |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Prefix Length | Must Be Zero |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In Network Slicing, the Transport Slice Controller (TSC) sets up the
Topology (e.g. RSVP-TE, SR-TE tunnels with desired characteristics) and
resources (e.g. polices/shapers) in a transport network to create a
Transport Slice. The Transport Class construct described in this
document represents the "Topology Slice" portion of this equation.The TSC can use the Transport Class Identifier (Color value) to
provision a transport tunnel in a specific Topology Slice.Further, Network Slice Controller can use the Mapping Community on
the service route to map traffic to the desired Transport Slice.This section describes how BGP CT may be used to set up inter domain
tunnels of a certain Transport Class, when using Segment Routing over
IPv6 (SRv6) data plane on the inter AS links or as an intra AS tunneling
mechanism. specifies the SRv6 Endpoint behaviors (End
USD, End.BM, End.B6.Encaps and End.Replace, End.ReplaceB6,
respectively). specify the SRv6
Endpoint behaviors (END.REPLACE, END.REPLACEB6 and END.DB6). These are
leveraged for BGP CT with SRv6 data plane.The BGP Classful Transport route update for SRv6 MUST include the BGP
Prefix-SID attribute along with SRv6 SID information as specified in
. It may also include SRv6 SID structure
for Transposition as specified in . It
should be noted that prefixes carried in BGP CT family are transport
layer end-points, e.g. PE loopback addresses. Thus the SRv6 SID carried
in a BGP CT route is also a transport layer identifier.This document extends the usage of "SRv6 label route tunnel" TLV to
AFI=1/2 SAFI 76. "SRv6 label route tunnel" is the TLV of the BGP
Prefix-SID Attribute as specified in .
[RR26] [RR27] [RR16]
| | |
| | |
|+-[ABR23]--+|+--[ASBR21]---[ASBR13]-+|+--[PE11]--+
|| ||| ` / ||| |
[CE41]--[PE25]--[P28] [P29] `/ [P15] [CE31]
| | | /` | | |
| | | / ` | | |
| | | / ` | | |
+--[ABR24]--+ +--[ASBR22]---[ASBR14]-+ +--[PE12]--+
| | | |
+ + + +
CE | region-1 | region-2 | |CE
AS4 ...AS2... AS1 AS3
41.41.41.41 ------------ Traffic Direction ----------> 31.31.31.31
This example shows a provider network that comprises of two
Autonomous systems, AS1, AS2. They are serving customers AS3, AS4
respectively. Traffic direction being described is CE41 to CE31. CE31
may request a specific SLA (e.g. Gold for this traffic), when
traversing these provider networks.AS2 is further divided into two regions. So, there are three tunnel
domains in provider space. AS1 uses ISIS Flex-Algo intra-domain
tunnels, whereas AS2 uses RSVP-TE intra-domain tunnels.The network has two Transport classes: Gold with transport class id
100, Bronze with transport class id 200. These transport classes are
provisioned at the PEs and the Border nodes (ABRs, ASBRs) in the
network.Following tunnels exist for Gold transport class.PE25_to_ABR23_gold - RSVP-TE tunnelPE25_to_ABR24_gold - RSVP-TE tunnelABR23_to_ASBR22_gold - RSVP-TE tunnelASBR13_to_PE11_gold - ISIS FlexAlgo tunnelASBR14_to_PE11_gold - ISIS FlexAlgo tunnelFollowing tunnels exist for Bronze transport class.PE25_to_ABR23_bronze - RSVP-TE tunnelABR23_to_ASBR21_bronze - RSVP-TE tunnelABR23_to_ASBR22_bronze - RSVP-TE tunnelABR24_to_ASBR21_bronze - RSVP-TE tunnelASBR13_to_PE12_bronze - ISIS FlexAlgo tunnelASBR14_to_PE11_bronze - ISIS FlexAlgo tunnelThese tunnels are either provisioned or auto-discovered to belong
to transport class 100 or 200.Service nodes PE11, PE12 negotiate service families (SAFI 1, 128)
on the BGP session with RR16. Service helpers RR16, RR26 have multihop
EBGP session to exchange service routes between the two AS. Similarly
PE25 negotiates service families with RR26.Forwarding happens using service routes at service nodes PE25,
PE11, PE12 only. Routes received from CEs are not present in any other
nodes' FIB in the network.CE31 advertises a route for example prefix 31.31.31.31 with nexthop
self to PE11, PE12. CE31 can attach a Mapping Community Color:0:100 on
this route, to indicate its request for Gold SLA. Or, PE11 can attach
the same using locally configured policies.Consider CE31 is getting VPN service from PE11. The 31.31.31.31
route is readvertised in SAFI 128 by PE11 with nexthop self (1.1.1.1)
and label V-L1, to RR16 with the Mapping Community Color:0:100
attached. This SAFI 128 route reaches PE25 via RR16, RR26 with the
nexthop unchanged, as PE11 and label V-L1. Now PE25 can resolve the
PNH 1.1.1.1 using transport routes received in BGP CT or BGP LU.The IP FIB at PE25 VRF will have a route for 31.31.31.31 with a
nexthop when resolved, that points to a Gold tunnel in ingress
domain.Egress nodes PE11, PE12 negotiate BGP CT family with transport
ASBRs ASBR13, ASBR14. These egress nodes originate BGP CT routes for
tunnel endpoint addresses, that are advertised as nexthop in BGP
service routes. In this example both PEs participate in transport
classes Gold and Bronze. The protocol procedures are explained using
Gold SLA plane and the Bronze SLA plane is used to highlight the path
hiding aspects.PE11 is provisioned with transport class 100, RD value 1.1.1.1:10
and a transport-target:0:100 for Gold tunnels. And a Transport class
200 with RD value 1.1.1.1:20, and transport route target 0:200 for
Bronze tunnels. Similarly, PE12 is provisioned with transport class
100, RD value 1.1.1.2:10 and a transport-target:0:100 for Gold
tunnels. And transport class 200, RD value 1.1.1.2:20 with
transport-target:0:200 for Bronze tunnelsSimilarly, these transport classes are also configured on ASBRs,
ABRs and PEs with same Transport Route Target and unique RDs.ASBR13 and ASBR14 negotiate BGP CT family with transport ASBRs
ASBR21, ASBR22 in neighboring AS. They negotiate BGP CT family with
RR27 in region 2, which reflects BGP CT routes to ABR23, ABR24. ABR23,
ABR24 negotiate BGP CT family with Ingress node PE25 in region 1. BGP
LU family is also negotiated on these sessions alongside BGP CT
family. BGP LU carries "best effort" transport class routes, BGP CT
carries gold, bronze transport class routes.PE11 is provisioned to originate BGP CT route with Gold SLA to
endpoint PE11. This route is sent with NLRI RD prefix
1.1.1.1:10:1.1.1.1, Label B-L0, nexthop 1.1.1.1 and a route target
extended community transport-target:0:100. Label B-L0 can either be
Implicit Null (Label 3) or a Ultimate Hop Pop (UHP) label.This route is received by ASBR13 and it resolves over the tunnel
ASBR13_to_PE11_gold. The route is then readvertised by ASBR13 in BGP
CT family to ASBRs ASBR21, ASBR22 according to export policy. This
route is sent with same NLRI RD prefix 1.1.1.1:10:1.1.1.1, Label B-L1,
nexthop self, and transport-target:0:100. MPLS swap route is installed
at ASBR13 for B-L1 with a nexthop pointing to ASBR13_to_PE11_gold
tunnel.Similarly ASBR14 also receives BGP CT route for 1.1.1.1:10:1.1.1.1
from PE11 and it resolves over the tunnel ASBR14_to_PE11_gold. The
route is then readvertised by ASBR14 in BGP CT family to ASBRs ASBR21,
ASBR22 according to export policy. This route is sent with same NLRI
RD prefix 1.1.1.1:10:1.1.1.1, Label B-L2, nexthop self, and
transport-target:0:100. MPLS swap route is installed at ASBR14 for
B-L1 with a nexthop pointing to ASBR14_to_PE11_gold tunnel.In the Bronze plane, BGP CT route with Bronze SLA to endpoint PE11
is originated by PE11 with a NLRI containing RD prefix
1.1.1.1:20:1.1.1.1, and appropriate label. The RD allows both Gold and
Bronze advertisements traverse path selection pinchpoints without any
path hiding at RRs or ASBRs. And route target extended community
transport-target:0:200 lets the route resolve over Bronze tunnels in
the network, similar to the process being described for Gold SLA
path.Moving back to the Gold plane, ASBR21 receives the Gold SLA BGP CT
routes for NLRI RD prefix 1.1.1.1:10:1.1.1.1 over the single hop EBGP
sessions from ASBR13, ASBR14, and can compute ECMP/FRR towards them.
ASBR21 readvertises BGP CT route for 1.1.1.1:10:1.1.1.1 with nexthop
self (loopback adderss 2.2.2.1) to RR27, advertising a new label B-L3.
MPLS swap route is installed for label B-L3 at ASBR21 to swap to
received label B-L1, B-L2 and forward to ASBR13, ASBR14 respectively.
RR27 readvertises this BGP CT route to ABR23, ABR24 with label and
nexthop unchanged.Similarly, ASBR22 receives BGP CT route 1.1.1.1:10:1.1.1.1 over the
single hop EBGP sessions from ASBR13, ASBR14, and readvertises with
nexthop self (loopback adderss 2.2.2.2) to RR27, advertising a new
label B-L4. MPLS swap route is installed for label B-L4 at ASBR22 to
swap to received label B-L1, B-L2 and forward to ASBR13, ASBR14
respectively. RR27 readvertises this BGP CT route also to ABR23, ABR24
with label and nexthop unchanged.Addpath is enabled for BGP CT family on the sessions between RR27
and ASBRs, ABRs such that routes for 1.1.1.1:10:1.1.1.1 with the
nexthops ASBR21 and ASBR22 are reflected to ABR23, ABR24 without any
path hiding. Thus giving ABR23 visibiity of both available nexthops
for Gold SLA.ABR23 receives the route with nexthop 2.2.2.1, label B-L3 from
RR27. The route target "transport-target:0:100" on this route acts as
Mapping Community, and instructs ABR23 to strictly resolve the nexthop
using transport class 100 routes only. ABR23 is unable to find a route
for 2.2.2.1 with transport class 100. Thus it considers this route
unusable and does not propagate it further. This prunes ASBR21 from
Gold SLA tunneled path.ABR23 also receives the route with nexthop 2.2.2.2, label B-L4 from
RR27. The route target "transport-target:0:100" on this route acts as
Mapping Community, and instructs ABR23 to strictly resolve the nexthop
using transport class 100 routes only. ABR23 successfully resolves the
nexthop to point to ABR23_to_ASBR22_gold tunnel. ABR23 readvertises
this BGP CT route with nexthop self (loopback address 2.2.2.3) and a
new label B-L5 to PE25. Swap route for B-L5 is installed by ABR23 to
swap to label B-L4, and forward into ABR23_to_ASBR22_gold tunnel.PE25 receives the BGP CT route for prefix 1.1.1.1:10:1.1.1.1 with
label B-L5, nexthop 2.2.2.3 and transport-target:0:100 from RR26. And
it similarly resolves the nexthop 2.2.2.3 over transport class 100,
pushing labels associated with PE25_to_ABR23_gold tunnel.In this manner, the Gold transport LSP "ASBR13_to_PE11_gold" in
egress-domain is extended by BGP CT until the ingress-node PE25 in
ingress domain, to create an end-to-end Gold SLA path. MPLS swap
routes are installed at ASBR13, ASBR22 and ABR23, when propagating the
PE11 BGP CT Gold transport class route 1.1.1.1:10:1.1.1.1 with nexthop
self towards PE25.The BGP CT LSP thus formed, originates in PE25, and terminates in
ASBR13 (assuming PE11 advertised Implicit Null), traversing over the
Gold underlay LSPs in each domain. ASBR13 uses UHP to stitch the BGP
CT LSP into the "ASBR13_to_PE11_gold" LSP to traverse the last domain,
thus satisfying Gold SLA end-to-end.When PE25 receives service routes from RR26 with nexthop 1.1.1.1
and mapping community Color:0:100, it resolves over this BGP CT route
1.1.1.1:10:1.1.1.1. Thus pushing label B-L5, and pushing as top label
the labels associated with PE25_to_ABR23_gold tunnel.This section describes how the data plane looks like in steady
state.CE41 transmits an IP packet with destination as 31.31.31.31. On
receiving this packet PE25 performs a lookup in the IP FIB
associated with the CE41 interface. This lookup yeids the service
route that pushes the VPN service label V-L1, BGP CT label B-L5, and
labels for PE25_to_ABR23_gold tunnel. Thus PE25 encapsulates the IP
packet in MPLS packet with label V-L1(innermost), B-L5, and top
label as PE25_to_ABR23_gold tunnel. This MPLS packet is thus
transmitted to ABR23 using Gold SLA.ABR23 decapsulates the packet received on PE25_to_ABR23_gold
tunnel as required, and finds the MPLS packet with label B-L5. It
performs lookup for label B-L5 in the global MPLS FIB. This yields
the route that swaps label B-L5 with label B-L4, and pushes top
label provided by ABR23_to_ASBR22_gold tunnel. Thus ABR23 transmits
the MPLS packet with label B-L4 to ASBR22, on a tunnel that
satisfies Gold SLA.ASBR22 similarly performs a lookup for label B-L4 in global MPLS
FIB, finds the route that swaps label B-L4 with label B-L2, and
forwards to ASBR13 over the directly connected MPLS enabled
interface. This interface is a common resource not dedicated to any
specific transport class, in this example.ASBR13 receives the MPLS packet with label B-L2, and performs a
lookup in MPLS FIB, finds the route that pops label B-L2, and pushes
labels associated with ASBR13_to_PE11_gold tunnel. This transmits
the MPLS packet with VPN label V-L1 to PE11 using a tunnel that
preserves Gold SLA in AS 1.PE11 receives the MPLS packet with V-L1, and performs VPN
forwarding. Thus transmitting the original IP payload from CE41 to
CE31. The payload has traversed path satisfying Gold SLA
end-to-end.This section describes how the data plane at ASBR22 reacts when
link between ASBR22 and ASBR13 experiences a failure, and an
alternate path exists.Assuming ASBR22_to_ASBR13 link goes down, such that traffic with
Gold SLA going to PE11 needs repair. ASBR22 has an alternate BGP CT
route for 1.1.1.1:10:1.1.1.1 from ASBR14. This has been
preprogrammed in forwarding by ASBR22 as FRR backup nexthop for
label B-L4. This allows the Gold SLA traffic to be locally repaired
at ASBR22 without the failure event propagated in the BGP CT
network. In this case, ingress node PE25 will not know there was a
failure, and traffic restoration will be independent of prefix scale
(PIC).This section describes how the data plane reacts when gold path
experiences a failure, but no alternate path exists.Assuming tunnel ABR23_to_ASBR22_gold goes down, such that now
end-to-end Gold path does not exist in the network. This makes the
BGP CT route for RD prefix 1.1.1.1:10:1.1.1.1 unusable at ABR23.
This makes ABR23 send a BGP withdrawal for 1.1.1.1:10:1.1.1.1 to
PE25.Withdrawal for 1.1.1.1:10:1.1.1.1 allows PE25 to react to the
loss of gold path to 1.1.1.1. Assuming PE25 is provisioned to use
best-effort transport class as the backup path, this withdrawal of
BGP CT route allows PE25 to adjust the nexthop of the VPN
Service-route to push the labels provided by the BGP LU route. That
repairs the traffic to go via best effort path. PE25 can also be
provisioned to use Bronze transport class as the backup path. The
repair will happen in similar manner in that case as-well.Traffic repair to absorb the failure happens at ingress node
PE25, in a service prefix scale independent manner. This is called
PIC (Prefix scale Independent Convergence). The repair time will be
proportional to time taken for withdrawing the BGP CT route.The above examples demostrate the various levels of failsafe
mechanisms available to protect traffic in a BGP CT network.This document makes following requests of IANA.New BGP SAFI code for "Classful Transport". Value 76.This will be used to create new AFI,SAFI pairs for IPv4, IPv6
Classful Transport families. viz:"Inet, Classful Transport". AFI/SAFI = "1/76" for carrying IPv4
Classful Transport prefixes."Inet6, Classful Transport". AFI/SAFI = "2/76" for carrying
IPv6 Classful Transport prefixes.Please assign a new Format (Type high = 0xa) of extended community
EXT-COMM called "Transport Class" from
the following registries:the "BGP Transitive Extended Community Types" registry, andthe "BGP Non-Transitive Extended Community Types" registry.Please assign the same low-order six bits for both allocations.This document uses this new Format with subtype 0x2 (route target),
as a transitive extended community.The Route Target thus formed is called "Transport Class" route
target extended community.Taking reference of RFC7153 ,
following requests are made:This registry contains values of the high-order octet (the
"Type" field) of a Transitive Extended Community.Registry Name: BGP Transitive Extended Community Types
TYPE VALUE NAME
+ 0x0a Transitive Transport Class Extended
+ Community (Sub-Types are defined in the
+ "Transitive Transport Class Extended
+ Community Sub-Types" registry)
This registry contains values of the high-order octet (the
"Type" field) of a Non-transitive Extended Community.
Registry Name: BGP Non-Transitive Extended Community Types
TYPE VALUE NAME
+ 0x4a Non-Transitive Transport Class Extended
+ Community (Sub-Types are defined in the
+ "Non-Transitive Transport Class Extended
+ Community Sub-Types" registry)
This registry contains values of the second octet (the "Sub-Type"
field) of an extended community when the value of the first octet
(the "Type" field) is 0x07.
Registry Name: Transitive Transport Class Extended
Community Sub-Types
RANGE REGISTRATION PROCEDURE
0x00-0xBF First Come First Served
0xC0-0xFF IETF Review
SUB-TYPE VALUE NAME
0x02 Route Target
This registry contains values of the second octet (the "Sub-Type"
field) of an extended community when the value of the first octet
(the "Type" field) is 0x47.
Registry Name: Non-Transitive Transport Class Extended
Community Sub-Types
RANGE REGISTRATION PROCEDURE
0x00-0xBF First Come First Served
0xC0-0xFF IETF Review
SUB-TYPE VALUE NAME
0x02 Route Target
The following two code points are sought for Target FEC Stack
sub-TLVs:IPv4 BGP Classful TransportIPv6 BGP Classful TransportMechanisms described in this document carry Transport routes in a new
BGP address family. That minimizes possibility of these routes leaking
outside the expected domain or mixing with service routes.When redistributing between SAFI 4 and SAFI 76 Classful Transport
routes, there is a possibility of SAFI 4 routes mixing with SAFI 1
service routes. To avoid such scenarios, it is RECOMMENDED that
implementations support keeping SAFI 4 routes in a separate transport
RIB, distinct from service RIB that contain SAFI 1 service routes.Advertising Segment Routing Policies in BGPRoute Target Constrain ExtensionSeamless Segment RoutingBGP signalled
MPLS-namespacesEgress Peer Engineering using
BGP-LUPath Computation Element
Protocol(PCEP) Extension for RSVP ColorSRv6 inter-domain mapping
SIDsSRv6 BGP based Overlay
ServicesSRv6 and MPLS interworkingBGP Flow-Spec Redirect to IP
ActionBGP MultiNexthop AttributeAT&T2212 Avenida Mara,Chula VistaCalifornia91914USAisrael.means@att.comHungarian NREN35 Vaci street,Budapest1134Hungaryietf@nop.huExtreme Networks55 Commerce Valley Drive West, Suite 300,Thornhill, Toronto,OntarioL3T 7V9Canadadgowda@extremenetworks.comJuniper Networks, Inc.Electra, Exora Business Park~Marathahalli - Sarjapur Outer
Ring Road,BangaloreKA560103Indiabalajir@juniper.netJuniper Networks, Inc.1133 Innovation Way,SunnyvaleCA94089USdreshma@juniper.netJuniper Networks, Inc.Electra, Exora Business Park~Marathahalli - Sarjapur Outer
Ring Road,BangaloreKA560103Indiamrajesh@juniper.netAT&T200 S Laurel Ave,Middletown,NJ07748USAcy098d@att.comVerizon Inc.13101 Columbia PikeSilver SpringMD20904USAgyan.s.mishra@verizon.comCox Communications Inc.AtlantaGAUSAmazen.khaddam@cox.comGoogle.1160 N Mathilda Ave, Bldg 5,Sunnyvale,CA94089USAszarecki@google.comCapitalonline.BeijingChinaxiaohu.xu@capitalonline.netThe authors thank Jeff Haas, John Scudder, Susan Hares, Moses Nagarajah,
Navaneetha Krishnan, Ravi M R, Chandrasekar Ramachandran, Shradha Hegde,
Richard Roberts, Krzysztof Szarkowicz, John E Drake, Srihari Sangli,
Vijay Kestur, Santosh Kolenchery, Robert Raszuk, Ahmed Darwish, Aravind
Srinivas Srinivasa Prabhakar, Moshiko Nayman, Chris Trip for the
valuable discussions and review comments.The decision to not reuse SAFI 128 and create a new address-family to
carry these transport-routes was based on suggestion made by Richard
Roberts and Krzysztof Szarkowicz.