Advertising Tunnel Encapsulation Capabilities in
OSPFHuaweixuxiaohu@huawei.comOrangebruno.decraene@orange.comBloomberg LProbert@raszuk.netTelefonica I+Dluismiguel.contrerasmurillo@telefonica.comVerizonluay.jalil@verizon.com
Routing Area
OSPF Working GroupSampleDraftNetworks use tunnels for a variety of reasons. A large variety of
tunnel types are defined and the ingress tunnel router needs to select a
type of tunnel which is supported by the egress tunnel router and
itself. This document defines how to advertise the tunnel encapsulation
capabilities of egress tunnel routers in OSPF Router Information Link
State Advertisement (LSAs).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.Networks use tunnels for a variety of reasons, such as:Partial deployment of IPv6 in IPv4 networks or IPv4 in IPv6
networks as described in , where IPvx
tunnels are used between IPvx-enabled routers so as to traverse
non-IPvx routers.Remote Loop-Free Alternate (RLFA) repair tunnels as described in
, where tunnels are used between the Point
of Local Repair and the selected PQ node.The ingress tunnel router needs to select a type of tunnel which is
supported by the egress tunnel router and itself. This document
describes how to use OSPF Router Information Link State Advertisements
(LSAs) to advertise the tunneling capabilities of OSPF routers acting as
egress tunnel routers. In this document, OSPF refers to both OSPFv2
and OSPFv3 .This memo makes use of the terms defined in .Routers advertise their supported encapsulation type(s) by
advertising a new TLV of the OSPF Router Information (RI) Opaque LSA
, referred to as the Tunnel Encapsulation
Capabilities TLV. This TLV is applicable to both OSPFv2 and OSPFv3. The
Tunnel Encapsulation Capabilities TLV SHOULD NOT appear more than once
within a given OSPF Router Information (RI) Opaque LSA. If the Tunnel
Encapsulation Capabilities TLV appears more than once in an OSPF Router
Information LSA, only the first occurrence MUST be processed and others
SHOULD be ignored. The scope of the advertisement depends on the
application but it is recommended that it SHOULD be domain-wide. The
Type code of the Tunnel Encapsulation Capabilities TLV is TBD1, the
Length value is variable, and the Value field contains one or more
Tunnel Encapsulation Type Sub-TLVs (see ).
Each Encapsulation Type Sub-TLVs indicates a particular encapsulation
format that the advertising router supports along with the parameters to
be used for the tunnel.The Tunnel Encapsulation Type Sub-TLV is structured as follows:Tunnel Type (2 octets): Identifies the type of tunneling
technology being signaled. Tunnel types are shared with the BGP
extension and hence are
defined in the IANA registry "BGP Tunnel Encapsulation Attribute
Tunnel Types". Unknown types are to be ignored and skipped upon
receipt.Length (2 octets): Unsigned 16-bit integer indicating the total
number of octets of the value field. Note that this is a padding to
be ignored if the length field is longer than the field indicated by
the sub-TLVs.Value (variable): Zero or more Tunnel Encapsulation Attribute
Sub-TLVs as defined in .Tunnel Encapsulation Attribute Sub-TLV are structured as follows:Sub-TLV Type (2 octets): Each Sub-TLV type defines a certain
property of the tunnel TLV that contains this Sub-TLV. Types are
registered in the IANA registry "OSPF Tunnel Encapsulation Attribute
Sub-TLVs" .Sub-TLV Length (2 octets): Unsigned 16-bit integer indicating the
total number of octets of the Sub-TLV value field.Sub-TLV Value (variable): Encodings of the value field depend on
the Sub-TLV type as enumerated above. The following sub-sections
define the encoding in detail.Any unknown Sub-TLVs MUST be deemed as invalid Sub-TLVs and
therefore MUST be ignored and skipped upon receipt. When a reserved
value (See ) is seen in an LSA, it
SHOULD be treated as an invalid Sub-TLV. If a Sub-TLV is invalid, its
Tunnel Encapsulation Type TLV MUST be ignored and skipped. However,
other Tunnel Encapsulation Type TLVs MUST be considered.The advertisement of an Encapsulation Type Sub-TLV (See ) indicates that the advertising router
support a particular tunnel encapsulation along with the parameters to
be used for the tunnel. The decision to use that tunnel is driven by the
capability of the ingress router to support the encapsulation type and
the policy on the ingress router. The Color Sub-TLV (See ) may be used as an input to this policy. Note that
some tunnel types may require the execution of an explicit tunnel setup
protocol before they can be used to carry data. A tunnel MUST NOT be
used if there is no route toward the IP address specified in the
Endpoint Sub-TLV (See ) or if the route is
not advertised by the router advertising the Tunnel Encapsulation
Attribute Sub-TLVs for the tunnel.This Sub-TLV of type 1 is defined in Section 3.2 "Encapsulation
Sub-TLVs for Particular Tunnel Types" of from both a syntax and semantic
standpoint.This Sub-TLV of type 2 is defined in Section 3.4.1 "Protocol Type
sub-TLV" of from a
syntactic, semantic, and usage standpoint.Type is 3. The value field carries the Network Address to be used
as tunnel destination address.If length is 4, the tunnel endpoint is an IPv4 address.If length is 16, the tunnel endpoint is an IPv6 address.Type is 4. The value field is a 4-octet opaque unsigned
integer.The color value is user-defined and configured locally on the
advertising routers. It may be used by service providers to define
policies on the ingress tunnel routers, for example, to control the
selection of the tunnel to use.This color value can be referenced by BGP routes carrying Color
Extended Community . If the
tunnel is used to reach the BGP Next-Hop of BGP routes, then attaching
a Color Extended Community attached to those routes express the
willingness of the BGP speaker to use a tunnel of the same color.This Sub-TLV of type 5 is defined in from
a syntactic, semantic and usage standpoint.This Sub-TLV of type 6 is defined in Section 3.3.1 "IPv4 DS Field"
of from a syntactic,
semantic and usage standpoint.This Sub-TLV of type 7 is defined in Section 3.3.2 "UDP Destination
Port" of from a syntactic,
semantic and usage standpoint.This document requests IANA to allocate a new code point from the
OSPF Router Information (RI) registry.This document requests IANA to create a new registry "Tunnel
Encapsulation Attribute Sub-TLVs" with the following registration
procedure:The values in the range 1-255 are to be allocated using the
"Standards Action" registration procedure as defined in .The values in the range 256-65499 are to be allocated using the
"First Come, First Served" registration procedure.Security considerations applicable to softwires can be found in the
mesh framework . In general, security issues of
the tunnel protocols signaled through this OSPF capability extension are
inherited.If a third-party is able to modify any of the information that is
used to form encapsulation headers, to choose a tunnel type, or to
choose a particular tunnel for a particular payload type, user data
packets may end up getting misrouted, misdelivered, and/or dropped.
However, since an OSPF routing domain is usually well-controlled and
well-managed network, the possiblity of the above risk is very low.Security considerations for the base OSPF protocol are covered in
and .This document is partially inspired by .The authors would like to thank Greg Mirsky, John E Drake, Carlos
Pignataro and Karsten Thomann for their valuable comments on this
document. Special thanks should be given to Acee Lindem for his multiple
detailed reviews of this document and help. The authors would like to
thank Pete Resnick, Joe Touch, David Mandelberg, Sabrina Tanamal, Tim
Wicinski, Amanda Baber for their Last Call reviews and thank Spencer
Dawkins, Mirja Kühlewind, Ben Campbell, Benoit Claise, Alvaro
Retana, Adam Roach and Suresh Krishnan for their AD reviews.