draft-ietf-mpls-ldp-ipv6-06.txt   draft-ietf-mpls-ldp-ipv6-07.txt 
MPLS Working Group Rajiv Asati MPLS Working Group Rajiv Asati
Internet Draft Cisco Internet Draft Cisco
Updates: 5036 (if approved) Updates: 5036 (if approved)
Intended status: Standards Track Vishwas Manral Intended status: Standards Track Vishwas Manral
Expires: July 23, 2012 Hewlett-Packard, Inc. Expires: December 8, 2012 Hewlett-Packard, Inc.
Rajiv Papneja Rajiv Papneja
Huawei Huawei
Carlos Pignataro Carlos Pignataro
Cisco Cisco
January 23, 2012 June 8, 2012
Updates to LDP for IPv6 Updates to LDP for IPv6
draft-ietf-mpls-ldp-ipv6-06 draft-ietf-mpls-ldp-ipv6-07
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
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Internet-Drafts are draft documents valid for a maximum of six Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents months and may be updated, replaced, or obsoleted by other documents
at any time. It is inappropriate to use Internet-Drafts as at any time. It is inappropriate to use Internet-Drafts as
reference material or to cite them other than as "work in progress." reference material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 23, 2012. This Internet-Draft will expire on December 8, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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interface. interface.
4. LDP Identifiers 4. LDP Identifiers
Section 2.2.2 of [RFC5036] specifies formulating at least one LDP Section 2.2.2 of [RFC5036] specifies formulating at least one LDP
Identifier, however, it doesn't provide any consideration in case of Identifier, however, it doesn't provide any consideration in case of
IPv6 (with or without dual-stacking). Additionally, section 2.5.2 of IPv6 (with or without dual-stacking). Additionally, section 2.5.2 of
[RFC5036] implicitly prohibits using the same label space for both [RFC5036] implicitly prohibits using the same label space for both
IPv4 and IPv6 FEC-label bindings. IPv4 and IPv6 FEC-label bindings.
The first four octets of the LDP identifier, the 32-bit LSR Id, The first four octets of the LDP identifier, the 32-bit LSR Id (e.g.
identify the LSR and is a globally unique value. This is regardless (i.e. LDP Router Id), identify the LSR and is a globally unique
of the address family used for the LDP session. Hence, this document value within the MPLS network. This is regardless of the address
preserves the usage of 32-bit LSR Id on an IPv6 only LSR. family used for the LDP session. Hence, this document preserves the
usage of 32-bit (unsigned non-zero integer) LSR Id on an IPv6 only
LSR (note that BGP has also mandated using 32-bit BGP Router ID on
an IPv6 only Router [RFC6286]).
Please note that 32-bit LSR Id value would not map to any IPv4- Please note that 32-bit LSR Id value would not map to any IPv4-
address in an IPv6 only LSR (i.e., single stack), nor would there address in an IPv6 only LSR (i.e., single stack), nor would there
be an expectation of it being DNS-resolvable. In IPv4 deployments, be an expectation of it being DNS-resolvable. In IPv4 deployments,
the LSR Id is typically derived from an IPv4 address, generally the LSR Id is typically derived from an IPv4 address, generally
assigned to a loopback interface. In IPv6 only deployments, this assigned to a loopback interface. In IPv6 only deployments, this
32-bit LSR Id must be derived by some other means that guarantees 32-bit LSR Id must be derived by some other means that guarantees
global uniqueness. global uniqueness within the MPLS network, similar to that of BGP
Identifier [RFC6286].
This document qualifies the first sentence of last paragraph of This document qualifies the first sentence of last paragraph of
Section 2.5.2 of [RFC5036] to be per address family and therefore Section 2.5.2 of [RFC5036] to be per address family and therefore
updates that sentence to the following: "For a given address family updates that sentence to the following: "For a given address family
over which a Hello is sent, and a given label space, an LSR MUST over which a Hello is sent, and a given label space, an LSR MUST
advertise the same transport address." This rightly enables the per- advertise the same transport address." This rightly enables the per-
platform label space to be shared between IPv4 and IPv6. platform label space to be shared between IPv4 and IPv6.
In summary, this document not only allows the usage of a common LDP In summary, this document not only allows the usage of a common LDP
identifier i.e. same LSR-Id, but also the common Label space id for identifier i.e. same LSR-Id (aka LDP Router-Id), but also the common
both IPv4 and IPv6 on a dual-stack LSR. Label space id for both IPv4 and IPv6 on a dual-stack LSR.
This document reserves 0.0.0.0 as the LSR-Id, and prohibits its This document reserves 0.0.0.0 as the LSR-Id, and prohibits its
usage. usage.
5. Peer Discovery 5. Peer Discovery
5.1. Basic Discovery Mechanism 5.1. Basic Discovery Mechanism
Section 2.4.1 of [RFC5036] defines the Basic Discovery mechanism for Section 2.4.1 of [RFC5036] defines the Basic Discovery mechanism for
directly connected LSRs. Following this mechanism, LSRs periodically directly connected LSRs. Following this mechanism, LSRs periodically
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and IPv6 transport address optional objects, but MUST use only and IPv6 transport address optional objects, but MUST use only
the transport address whose address family is the same as that the transport address whose address family is the same as that
of the IP packet carrying Hello. of the IP packet carrying Hello.
3. An LSR MUST send separate Hellos (each containing either IPv4 3. An LSR MUST send separate Hellos (each containing either IPv4
or IPv6 transport address optional object) for each IP address- or IPv6 transport address optional object) for each IP address-
family, if LDP was enabled for both IP address-families. family, if LDP was enabled for both IP address-families.
4. An LSR MUST use a global unicast IPv6 address in IPv6 transport 4. An LSR MUST use a global unicast IPv6 address in IPv6 transport
address optional object of outgoing targeted hellos, and check address optional object of outgoing targeted hellos, and check
for the same in incoming targeted hellos. for the same in incoming targeted hellos (i.e. MUST discard the
hello, if it failed the check).
5. An LSR MUST prefer using global unicast IPv6 address for an LDP 5. An LSR MUST prefer using global unicast IPv6 address for an LDP
session with a remote LSR, if it had to choose between global session with a remote LSR, if it had to choose between global
unicast IPv6 address and link-local IPv6 address (pertaining to unicast IPv6 address and link-local IPv6 address (pertaining to
the same LDP Identifier) for the transport connection. the same LDP Identifier) for the transport connection.
6. An LSR SHOULD NOT create (or honor the request for creating) a 6. An LSR SHOULD NOT create (or honor the request for creating) a
TCP connection for a new LDP session with a remote LSR, if they TCP connection for a new LDP session with a remote LSR, if they
already have an LDP session (for the same LDP Identifier) already have an LDP session (for the same LDP Identifier)
established over whatever IP version transport. established over whatever IP version transport.
This means that only one transport connection is established, This means that only one transport connection is established,
even if there are two Hello adjacencies (one for IPv4 and even if there are two Hello adjacencies (one for IPv4 and
another for IPv6). This is independent of whether the Hello another for IPv6). This is independent of whether the Hello
Adjacencies are created over a single interface (scenarios 1 in Adjacencies are created over a single interface (scenario 1 in
section 1.1) or multiple interfaces (scenario 2 in section 1.1) section 1.1) or multiple interfaces (scenario 2 in section 1.1)
between two LSRs. between two LSRs.
7. An LSR SHOULD prefer the LDP/TCP connection over IPv6 for a new 7. An LSR SHOULD prefer the LDP/TCP connection over IPv6 for a new
LDP session with a remote LSR, if it has both IPv4 and IPv6 LDP session with a remote LSR, if it has both IPv4 and IPv6
hello adjacencies for the same LDP Identifier (over a dual- hello adjacencies for the same LDP Identifier (over a dual-
stack interface, or two or more single-stack IPv4 and IPv6 stack interface, or two or more single-stack IPv4 and IPv6
interfaces). This applies to the section 2.5.2 of RFC5036. interfaces). This applies to the section 2.5.2 of RFC5036.
8. An LSR SHOULD prefer the LDP/TCP connection over IPv6 for a new 8. An LSR SHOULD prefer the LDP/TCP connection over IPv6 for a new
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adjacency for IPv4 and IPv6 on that interface. adjacency for IPv4 and IPv6 on that interface.
This ensures successful labeled IPv4 and labeled IPv6 traffic This ensures successful labeled IPv4 and labeled IPv6 traffic
forwarding on a dual-stacked interface, as well as successful LDP forwarding on a dual-stacked interface, as well as successful LDP
peering using the appropriate transport on a multi-access peering using the appropriate transport on a multi-access
interface (even if there are IPv4-only, IPv6-only and dual-stack interface (even if there are IPv4-only, IPv6-only and dual-stack
LSRs connected to that multi-access interface). LSRs connected to that multi-access interface).
6.3. Maintaining LDP Sessions 6.3. Maintaining LDP Sessions
Two LSRs maintain a single LDP session between them, as described in Two LSRs maintain a single LDP session between them (i.e. not tear
section 6.1, whether they are connected via a dual-stack LDP enabled down an existing session), as described in section 6.1, whether
interface or via two single-stack LDP enabled interfaces. This is
also true when a single-stack interface is converted to a dual-stack
interface (e.g. figure 1), or when another interface is added
between two LSRs (e.g. figure 2).
Needless to say that the procedures defined in section 6.1 would - they are connected via a dual-stack LDP enabled interface or via
always result in preferring LDPoIPv6 session after the loss of an two single-stack LDP enabled interfaces;
- a single-stack interface is converted to a dual-stack interface
(e.g. figure 1) on either LSR;
- an additional single-stack or dual-stack interface is added or
removed between two LSRs (e.g. figure 2).
Needless to say that the procedures defined in section 6.1 should
result in preferring LDPoIPv6 session only after the loss of an
existing LDP session (because of link failure, node failure, reboot existing LDP session (because of link failure, node failure, reboot
etc.). etc.).
On the other hand, if a dual-stack interface is converted to a On the other hand, if a dual-stack interface is converted to a
single-stack interface (by disabling IPv4 or IPv6 routing), then the single-stack interface (by disabling IPv4 or IPv6 routing), then the
LDP session should be torn down ONLY if the disabled IP version was LDP session should be torn down ONLY if the disabled IP version was
the same as that of the transport connection. Otherwise, the LDP the same as that of the transport connection. Otherwise, the LDP
session should stay intact. session should stay intact.
If the LDP session is torn down for whatever reason (LDP disabled If the LDP session is torn down for whatever reason (LDP disabled
for the corresponding transport, hello adjacency expiry etc.), then for the corresponding transport, hello adjacency expiry etc.), then
the LSRs should initiate establishing a new LDP session as per the the LSRs should initiate establishing a new LDP session as per the
procedures described in section 6.1 of this document along with procedures described in section 6.1 of this document along with
RFC5036. RFC5036.
7. Label Distribution 7. Label Distribution
An LSR MAY NOT advertise both IPv4 and IPv6 FEC-label bindings (as An LSR SHOULD NOT advertise both IPv4 and IPv6 FEC-label bindings
well as interface addresses via ADDRESS message) from/to the peer (as well as interface addresses via ADDRESS message) from/to the
over an LDP session (using whatever transport), unless it has valid peer over an LDP session (using whatever transport), unless it has
IPv4 and IPv6 Hello Adjacencies for that peer, as specified in valid IPv4 and IPv6 Hello Adjacencies for that peer, as specified in
section 6.2. section 6.2.
Another solution for getting the same result as above is by Another solution for getting the same result as above is by
negotiating the IP Capability for a given AFI, as specified in negotiating the IP Capability for a given AFI, as specified in
[IPPWCap]. [IPPWCap].
An LSR MUST NOT allocate and advertise FEC-Label bindings for link- An LSR MUST NOT allocate and advertise FEC-Label bindings for link-
local IPv6 address, and ignore such bindings, if ever received. An local IPv6 address, and ignore such bindings, if ever received. An
LSR MUST treat the IPv4-mapped IPv6 address, defined in section LSR MUST treat the IPv4-mapped IPv6 address, defined in section
2.5.1 of [RFC4291], the same as that of a global IPv6 address and 2.5.5.2 of [RFC4291], the same as that of a global IPv6 address and
not mix it with the 'corresponding' IPv4 address. not mix it with the 'corresponding' IPv4 address.
Additionally, to ensure backward compatibility (and interoperability Additionally, to ensure backward compatibility (and interoperability
with IPv4-only LDP implementations), this document specifies that - with IPv4-only LDP implementations), this document specifies that -
1. An LSR MUST NOT send a label mapping message with a FEC TLV 1. An LSR MUST NOT send a label mapping message with a FEC TLV
containing FEC Elements of different address-family. In other containing FEC Elements of different address-family. In other
words, a FEC TLV in the label mapping message MUST contain the words, a FEC TLV in the label mapping message MUST contain the
FEC Elements belonging to the same address-family. FEC Elements belonging to the same address-family.
2. An LSR MUST NOT send an Address message (or Address Withdraw 2. An LSR MUST NOT send an Address message (or Address Withdraw
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RFC5036 section 2.7 specifies logic for mapping between a peer LDP RFC5036 section 2.7 specifies logic for mapping between a peer LDP
Identifier and the peer's addresses to find the correct LIB entry Identifier and the peer's addresses to find the correct LIB entry
for any prefix by using a database populated by the Address message. for any prefix by using a database populated by the Address message.
However, this logic is insufficient to deal with overlapping IPv6 However, this logic is insufficient to deal with overlapping IPv6
(link-local) addresses used by two or more peers. One may note that (link-local) addresses used by two or more peers. One may note that
all interior IP routing protocols specify using link-local IPv6 all interior IP routing protocols specify using link-local IPv6
addresses as the next-hops. addresses as the next-hops.
This document specifies that the logic is enhanced with the usage of This document specifies that the logic is enhanced with the usage of
(Hello Adjacency) database populated by the Hello messages. This (Hello Adjacency) database populated by the Hello messages. This
additional database lookup is useful only if/when two or more peers additional database lookup is useful if/when two or more peers use
use the same link-local IPv6 address as the IP routing next-hops the same link-local IPv6 address as the IP routing next-hops
(causing duplicate next-hop entries). (causing duplicate next-hop entries).
Specifically, this document specifies that an LSR should (continue Specifically, this document specifies that an LSR should (continue
to) use the machinery described in RFC5036 section 2.7 to map to) use the machinery described in RFC5036 section 2.7 to map
between a peer LDP Identifier and the peer's addresses (learned via between a peer LDP Identifier and the peer's addresses (learned via
ADDRESS message) for any prefix. However, if this mapping fails (for ADDRESS message) for any prefix. However, if this mapping fails (for
reasons such as the one described earlier), then an LSR can find the reasons such as the one described earlier), then an LSR can find the
peer LDP Identifier by checking for the particular link-local IPv6 peer LDP Identifier by checking for the particular link-local IPv6
address in the hello adjacency database. address and interface (corresponding to the next-hop in the unicast
routing table) in the hello adjacency database.
If an LSR can't find such a mapping in either database, then LSR If an LSR can't find such a mapping in either database, then LSR
should follow procedures specified in RFC5036 (e.g. not resolve the should follow procedures specified in RFC5036 (e.g. not resolve the
label). label).
Lastly, for better scale and optimization, an LSR may advertise only Lastly, for better scale and optimization, an LSR may advertise only
the link-local IPv6 addresses in the Address message, assuming that the link-local IPv6 addresses in the Address message, assuming that
the peer uses only the link-local IPv6 addresses as static and/or the peer uses only the link-local IPv6 addresses as static and/or
dynamic IP routing next-hops. dynamic IP routing next-hops.
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