draft-ietf-mpls-mldp-recurs-fec-01.txt   draft-ietf-mpls-mldp-recurs-fec-02.txt 
Network Working Group IJsbrand Wijnands MPLS Working Group IJsbrand Wijnands
Internet Draft Eric C. Rosen Internet Draft Eric C. Rosen
Intended Status: Proposed Standard Cisco Systems, Inc. Intended Status: Proposed Standard Cisco Systems, Inc.
Expires: October 4, 2011 Expires: November 9, 2011
Maria Napierala Maria Napierala
AT&T AT&T
Nicolai Leymann Nicolai Leymann
Deutsche Telekom Deutsche Telekom
April 4, 2011 May 9, 2011
Using mLDP through a Backbone where there is no Route to the Root Using Multipoint LDP when the Backbone has no Route to the Root
draft-ietf-mpls-mldp-recurs-fec-01.txt draft-ietf-mpls-mldp-recurs-fec-02.txt
Abstract Abstract
The control protocol used for constructing Point-to-Multipoint and The control protocol used for constructing Point-to-Multipoint and
Multipoint-to-Multipoint Label Switched Paths ("MP LSPs") contains a Multipoint-to-Multipoint Label Switched Paths ("MP LSPs") contains a
field that identifies the address of a "root node". Intermediate field that identifies the address of a "root node". Intermediate
nodes are expected to be able to look up that address in their nodes are expected to be able to look up that address in their
routing tables. However, if the route to the root node is a BGP routing tables. However, if the route to the root node is a BGP
route, and the intermediate nodes are part of a BGP-free core, this route, and the intermediate nodes are part of a BGP-free core, this
is not possible. This document specifies procedures which enable a is not possible. This document specifies procedures which enable a
MP LSP to be constructed through a BGP-free core. In these MP LSP to be constructed through a BGP-free core. In these
procedures, the root node address is temporarily replaced by an procedures, the root node address is temporarily replaced by an
address which is known to the intermediate nodes. address that is known to the intermediate nodes and is on the path to
the true root node.
Status of this Memo Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the This Internet-Draft is submitted to IETF 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), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet- other groups may also distribute working documents as Internet-
Drafts. Drafts.
skipping to change at page 2, line 28 skipping to change at page 2, line 28
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1 Introduction .......................................... 3 1 Introduction .......................................... 3
2 The Recursive Opaque Value Type ....................... 5 2 The Recursive Opaque Value ............................ 5
2.1 Encoding .............................................. 5 2.1 Encoding .............................................. 5
2.2 Procedures ............................................ 5 2.2 Procedures ............................................ 5
3 The VPN-Recursive MP FEC Element ...................... 6 3 The VPN-Recursive Opaque Value ........................ 6
3.1 Encoding .............................................. 6 3.1 Encoding .............................................. 6
3.2 Procedures ............................................ 7 3.2 Procedures ............................................ 7
3.2.1 Unsegmented Inter-AS P-tunnels ........................ 7 3.2.1 Unsegmented Inter-AS P-tunnels ........................ 7
3.2.2 Limited Carrier's Carrier Function .................... 9 3.2.2 Limited Carrier's Carrier Function .................... 9
4 IANA Considerations ................................... 10 4 IANA Considerations ................................... 10
5 Security Considerations ............................... 11 5 Security Considerations ............................... 11
6 Acknowledgments ....................................... 11 6 Acknowledgments ....................................... 11
7 Authors' Addresses .................................... 11 7 Authors' Addresses .................................... 11
8 Normative References .................................. 12 8 Normative References .................................. 12
1. Introduction 1. Introduction
[MLDP] defines several LDP FEC element encodings: P2MP, MP2MP [mLDP] defines several LDP "Forwarding Equivalence Class" (FEC)
Upstream, and MP2MP Downstream. element encodings: Point-to-Multipoint (P2MP), Multipoint-to-
Multipoint (MP2MP) Upstream, and MP2MP Downstream.
The encoding for these three FEC elements is shown in Figure 1. The encoding for these three FEC elements is shown in Figure 1.
0 1 2 3 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 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 | Address Family | Address Length| | Type | Address Family | Address Length|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Root Node Address ~ ~ Root Node Address ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opaque Length | . | | Opaque Length | . |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +
~ ~ ~ ~
| Opaque Value | | Opaque Value |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
MLDP FEC Element Encoding mLDP FEC Element Encoding
Figure 1 Figure 1
Note that a P2MP or MP2MP label switched path ("MP LSP") is Note that a P2MP or MP2MP label switched path ("MP LSP") is
identified by the combination of a "root node" and a variable length identified by the combination of a "root node" and a variable length
"opaque value". The root node also plays a special role in the MLDP "opaque value". The root node also plays a special role in the mLDP
procedures - MLDP messages that are "about" a particular MP LSP are procedures - mLDP messages that are "about" a particular MP LSP are
forwarded to the LDP adjacency that is the next hop on the route to forwarded to the LDP adjacency that is the next hop on the route to
the root node. the root node.
Sometimes it is desirable for a MP LSP to pass through a part of the Sometimes it is desirable for a MP LSP to pass through a part of the
network in which there is no route to the root node. For instance, network in which there is no route to the root node. For instance,
consider the topology of Figure 2: consider the topology of Figure 2:
CE1----PE1---P1---- ...----P2 ----PE2----CE2----R CE1----PE1---P1---- ...----P2 ----PE2----CE2----R
Figure 2 Figure 2
skipping to change at page 4, line 12 skipping to change at page 4, line 13
hop. However, the provider's interior routers (such as P1 and P2) do hop. However, the provider's interior routers (such as P1 and P2) do
not have any BGP-learned routes, and in particular do not have any not have any BGP-learned routes, and in particular do not have any
routes to R. routes to R.
In such an environment, data packets from CE1 address to R would get In such an environment, data packets from CE1 address to R would get
encapsulated by PE1, tunneled to PE2, decapsulated by PE2, and encapsulated by PE1, tunneled to PE2, decapsulated by PE2, and
forwarded to CE2. forwarded to CE2.
Suppose now that CE1 is trying to set up a MP LSP whose root is R, Suppose now that CE1 is trying to set up a MP LSP whose root is R,
and the intention is that the provider's network will participate in and the intention is that the provider's network will participate in
the construction of the LSP. Then the MLDP messages identifying the the construction of the LSP. Then the mLDP messages identifying the
LSP must be passed from CE1 to PE1, from PE1 to P1, ..., from P2 to LSP must be passed from CE1 to PE1, from PE1 to P1, ..., from P2 to
PE2, from PE2 to CE2, and from CE2 to R. PE2, from PE2 to CE2, and from CE2 to R.
To begin the process, CE1 creates a MP FEC element with the address To begin the process, CE1 creates a MP FEC element with the address
of R as the root node address, and passes that FEC element via MLDP of R as the root node address, and passes that FEC element via mLDP
to PE1. However, PE1 cannot use this same FEC element to identify to PE1. However, PE1 cannot use this same FEC element to identify
the LSP in the LDP messages it sends to P1, because P1 does not have the LSP in the LDP messages it sends to P1, because P1 does not have
a route to R. a route to R.
However, PE1 does know that PE2 is the "BGP next hop" on the path to However, PE1 does know that PE2 is the "BGP next hop" on the path to
R. What is needed is a method whereby: R. What is needed is a method whereby:
- PE1 can tell P1 to set up an LSP as if the root node were PE2, - PE1 can tell P1 to set up an LSP as if the root node were PE2,
and and
- PE2 can determine that the LSP in question is really rooted at R, - PE2 can determine that the LSP in question is really rooted at R,
not at PE2 itself, not at PE2 itself,
- PE2 can determine the original FEC element that CE1 passed to - PE2 can determine the original FEC element that CE1 passed to
PE1, so that PE2 can pass it on to CE2. PE1, so that PE2 can pass it on to CE2.
This document defines the procedures that allow CE1 to create an LSP This document defines the procedures that allow CE1 to create an LSP
rooted at R. These procedures require PE1 to modify the MP FEC rooted at R. These procedures require PE1 to modify the MP FEC
element before sending an MLDP message to P1. The modified FEC element before sending an mLDP message to P1. The modified FEC
element has PE2 as the root, and the original FEC element as the element has PE2 as the root, and the original FEC element as the
opaque value. This requires a new type of opaque value. Since the opaque value. This requires a new type of opaque value. Since the
opaque value contains a FEC element, we call this a "Recursive Opaque opaque value contains a FEC element, we call this a "Recursive Opaque
Value". When PE2 sends an mLDP message to CE2, it replaces the FEC Value". When PE2 sends an mLDP message to CE2, it replaces the FEC
element with the opaque value, thus undoing the recursion. Details element with the opaque value, thus undoing the recursion. Details
are in section 2. are in section 2.
Section 3 defines a "VPN Recursive Opaque Value". Whereas the Section 3 defines a "Virtual Private Network (VPN) Recursive Opaque
"Recursive Opaque Value" carries the original FEC, the "VPN Recursive Value". Whereas the "Recursive Opaque Value" carries the original
Opaque Value" carries the original FEC plus a Route Distinguisher FEC, the "VPN Recursive Opaque Value" carries the original FEC plus a
(RD). This has several possible uses in an L3VPN context. Details Route Distinguisher (RD). This is applicable when MP LSPs are being
are in section 3. used to carry the multicast traffic of a VPN [MVPN]. Details are in
section 3.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
2. The Recursive Opaque Value Type 2. The Recursive Opaque Value
2.1. Encoding 2.1. Encoding
We define a new Opaque Value Type, the Recursive Opaque Value Type. We define a new type of Opaque Value, the Recursive Opaque Value.
This is a "basic type", identified by a one-octet type field.
0 1 2 3 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 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 = 6 | Length | | | Type = TBD | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ ~ ~ ~
| P2MP or MP2MP FEC Element | | P2MP or MP2MP FEC Element |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Recursive Opaque Value Type Recursive Opaque Value
Figure 3 Figure 3
The "opaque value" itself is a P2MP or MP2MP FEC element, encoded The value field of the "Recursive Opaque Value" is itself is a P2MP
exactly as specified in [MLDP], with a type field, a length field, or MP2MP FEC element, encoded exactly as specified in [mLDP], with a
and value field of is own. The length field of the Recursive Opaque type field, a length field, and value field of its own. The length
Value Type thus includes the type and length fields of the FEC of the Recursive Opaque Value thus includes the lengths of the type,
element that is the value field. length, and value fields of the contained FEC element.
2.2. Procedures 2.2. Procedures
In the topology of Figure 2, let us suppose that CE1 sends PE1 an MP In the topology of Figure 2, let us suppose that CE1 sends PE1 an MP
FEC element whose root node is R, and whose opaque value is Q. We FEC element whose root node is R, and whose opaque value is Q. We
will refer to this FEC element as "CE1-FEC". We may think of CE1-FEC will refer to this FEC element as "CE1-FEC". We may think of CE1-FEC
as an ordered pair, as follows: as an ordered pair, as follows:
CE1-FEC = <root=R, opaque_value=Q>. CE1-FEC = <root=R, opaque_value=Q>.
PE1 determines that the root node R matches a BGP route, with a BGP PE1 determines that the root node R matches a BGP route, with a BGP
next hop of PE2. PE1 also knows by its configuration that the next hop of PE2. PE1 also knows by its configuration that the
interior routers on the path to PE2 are "BGP-free", and thus have no interior routers on the path to PE2 are "BGP-free", and thus have no
route to R. route to R.
PE1 therefore MUST create a new MP FEC element, whose root node PE1 therefore MUST create a new MP FEC element, whose root node
address is the address of PE2, and whose opaque value is a Recursive address is the address of PE2, and whose opaque value is a Recursive
(type 6) Opaque Value whose value field contains CE1-FEC. We refer Opaque Value whose value field contains CE1-FEC. We refer to this
to this FEC element as PE2-FEC. PE1 then MUST send this FEC element FEC element as PE2-FEC. PE1 then MUST send this FEC element to P1.
to P1.
PE2-FEC = <root=PE2, opaque_value=CE1-FEC>, or PE2-FEC = <root=PE2, opaque_value=CE1-FEC>, or
PE2-FEC = <root=PE2, opaque_value=<root=R, PE2-FEC = <root=PE2, opaque_value=<root=R,
opaque_value=Q>> opaque_value=Q>>
As far as the interior routers are concerned, they are being As far as the interior routers are concerned, they are being
requested to build a MP LSP whose root node is PE2. They MUST NOT requested to build a MP LSP whose root node is PE2. They MUST NOT
interpret the opaque value at all. interpret the opaque value at all.
When PE2-FEC arrives at PE2, PE2 notes that it is the identified root When PE2-FEC arrives at PE2, PE2 notes that it (PE2) is the
node, and that the opaque value is a Recursive (type 6) opaque value. identified root node, and that the opaque value is a Recursive Opaque
Therefore it MUST replace PE2-FEC with the contents of the type 6 Value. Therefore PE2 MUST replace PE2-FEC with the contents of the
opaque value (i.e., with CE1-FEC) before doing any further Recursive Opaque Value (i.e., with CE1-FEC) before doing any further
processing. This will result in CE1-FEC being sent on to CE2, and processing. This will result in CE1-FEC being sent on to CE2, and
presumably further from CE2 to R. Note that CE1-FEC will contain the presumably further from CE2 to R. Note that CE1-FEC will contain the
LSP root node specified by CE1; the presumption is that PE2 has a LSP root node specified by CE1; the presumption is that PE2 has a
route to this root node. route to this root node.
3. The VPN-Recursive MP FEC Element 3. The VPN-Recursive Opaque Value
3.1. Encoding 3.1. Encoding
We define a new Opaque Value Type, the VPN-Recursive Opaque Value We define a new type of Opaque Value, the VPN-Recursive Opaque Value.
Type. This is a "basic type", identified by a one-octet type field.
0 1 2 3 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 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 = 7 | Length | | | Type = TBD | Length | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| | | |
| Route Distinguisher (8 octets) +-+-+-+-+-+-+-+-+ | Route Distinguisher (8 octets) +-+-+-+-+-+-+-+-+
| | | | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
~ ~ ~ ~
| P2MP or MP2MP FEC Element | | P2MP or MP2MP FEC Element |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
VPN-Recursive Opaque Value Type VPN-Recursive Opaque Value
Figure 3 Figure 3
The "opaque value" consists of an eight-octet Route Distinguisher The value field of the "VPN-Recursive Opaque Value" consists of an
(RD), followed by a P2MP or MP2MP FEC element, encoded exactly as eight-octet Route Distinguisher (RD), followed by a P2MP or MP2MP FEC
specified in [MLDP], with a type field, a length field, and value element, encoded exactly as specified in [mLDP], with a type field, a
field of is own. The length field of the Recursive Opaque Value Type length field, and value field of is own. The length of the VPN-
thus includes the 8 octets of RD plus the type and length fields of Recursive Opaque Value thus includes the 8 octets of RD plus the
the FEC element that is the value field. lengths of the type, length, and values fields of the contained FEC
element.
3.2. Procedures 3.2. Procedures
3.2.1. Unsegmented Inter-AS P-tunnels 3.2.1. Unsegmented Inter-AS P-tunnels
Consider the Inter-AS VPN scenario depicted in Figure 4. Consider the Inter-AS VPN scenario depicted in Figure 4.
PE1 --- P1 ---- ASBR1 ... ASBR2 ---- P2 ---- PE2 PE1 --- P1 ---- ASBR1 ... ASBR2 ---- P2 ---- PE2
Figure 4 Figure 4
skipping to change at page 8, line 27 skipping to change at page 8, line 27
Intra-AS I-PMSI A-D routes. Therefore one must use a Recursive FEC Intra-AS I-PMSI A-D routes. Therefore one must use a Recursive FEC
element that contains the RD as well as the as well as the address of element that contains the RD as well as the as well as the address of
PE2. The "VPN-Recursive FEC Element" defined herein is used for this PE2. The "VPN-Recursive FEC Element" defined herein is used for this
purpose. purpose.
This enables us to provide the same functionality, for mLDP P-tunnels This enables us to provide the same functionality, for mLDP P-tunnels
that is provided for PIM P-tunnels in section 8.1.3.2 of [MVPN] that is provided for PIM P-tunnels in section 8.1.3.2 of [MVPN]
though the use of the MVPN Join Attribute. though the use of the MVPN Join Attribute.
At PE1 in Figure 4, the LSP to be created is associated with a At PE1 in Figure 4, the LSP to be created is associated with a
particular VRF. PE1 looks up in that VRF the Intra-AS I-PMSI A-D particular VPN Routing/Forwarding Table (VRF). PE1 looks up in that
route originated by PE2. It finds that the BGP next hop of that VRF the Intra-AS I-PMSI A-D route originated by PE2. It finds that
route is ASBR1. So it creates a P2MP or MP2MP FEC element whose root the BGP next hop of that route is ASBR1. So it creates a P2MP or
is ASBR1, and whose opaque value is a VPN-Recursive FEC element. The MP2MP FEC element whose root is ASBR1, and whose opaque value is a
VPN-Recursive FEC element itself consists of a root, an RD, and an VPN-Recursive FEC element. The VPN-Recursive FEC element itself
opaque value, set as follows: consists of a root, an RD, and an opaque value, set as follows:
- The root is PE2 - The root is PE2
- The RD is the RD from the NLRI of the Intra-AS A-D route - The RD is the RD from the NLRI of the Intra-AS A-D route
originated by PE2. originated by PE2.
- The opaque value is chosen (by some method outside the scope of - The opaque value is chosen (by some method outside the scope of
this document) so as to be unique in the context of PE2. (E.g., this document) so as to be unique in the context of PE2. (E.g.,
it may have been specified in a PMSI tunnel attribute originated it may have been specified in a PMSI tunnel attribute originated
by PE2.) We will refer to this opaque value as "Q". by PE2.) We will refer to this opaque value as "Q".
The resulting FEC element can be informally represented as The resulting FEC element can be informally represented as
<root=ASBR1, opaque_value=<root=PE2, RD, opaque_value=Q>>. <root=ASBR1, opaque_value=<root=PE2, RD, opaque_value=Q>>.
PE1 can now begin setting up the LSP by using this FEC element in an PE1 can now begin setting up the LSP by using this FEC element in an
LDP label mapping message sent towards ASBR1. LDP label mapping message sent towards ASBR1.
When ASBR1 receives, over a non-VRF interface, an mLDP label mapping When ASBR1 receives, over a non-VRF interface, an mLDP label mapping
message containing this FEC element, it sees that it is the root, and message containing this FEC element, it sees that it is the root, and
that the opaque value is a VPN-Recursive (type 7) FEC element. It that the opaque value is a VPN-Recursive Opaque Value. It parses the
parses the VPN-Recursive FEC element and extracts the root value, VPN-Recursive Opaque value and extracts the root value, PE2.
PE2.
If ASBR1 has a route to PE2, it continues setting up the LSP by using If ASBR1 has a route to PE2, it continues setting up the LSP by using
the following FEC element: the following FEC element:
<root=PE2, opaque_value=Q> <root=PE2, opaque_value=Q>
However, if ASBR1 does not have a route to PE2, it looks for an However, if ASBR1 does not have a route to PE2, it looks for an
Intra-AS I-PMSI A-D route whose NLRI contains PE2's address along Intra-AS I-PMSI A-D route whose NLRI contains PE2's address along
with the specified RD value. Say the BGP next hop of that route is with the specified RD value. Say the BGP next hop of that route is
ASBR2. Then ASBR1 continues setting up the LSP by using the ASBR2. Then ASBR1 continues setting up the LSP by using the
skipping to change at page 9, line 41 skipping to change at page 9, line 40
refer to this FEC element as "CE1-FEC". However, PE1's route to R refer to this FEC element as "CE1-FEC". However, PE1's route to R
will be in a VRF ("Virtual Routing and Forwarding Table"). Therefore will be in a VRF ("Virtual Routing and Forwarding Table"). Therefore
the FEC-element created by PE1 must contain some identifier that PE2 the FEC-element created by PE1 must contain some identifier that PE2
can use to find the proper VRF in which to look up the address of R. can use to find the proper VRF in which to look up the address of R.
When PE1 looks up the address of R in a VRF, it will find a route in When PE1 looks up the address of R in a VRF, it will find a route in
the VPN-IP address family. The next hop will be PE2, but there will the VPN-IP address family. The next hop will be PE2, but there will
also be a Route Distinguisher (RD) as part of that NLRI of the also be a Route Distinguisher (RD) as part of that NLRI of the
matching route. In this case, the new FEC element created by PE1 matching route. In this case, the new FEC element created by PE1
MUST have the address of PE2 as the root node address, and MUST have MUST have the address of PE2 as the root node address, and MUST have
a VPN-Recursive (type 7) opaque value. The value field of the type 7 a VPN-Recursive Opaque Value. The value field of the VPN-Recursive
opaque value MUST consist of the 8-octet RD followed by CE1-FEC. Opaque Value MUST consist of the 8-octet RD followed by CE1-FEC.
As far as the interior routers are concerned, they are being As far as the interior routers are concerned, they are being
requested to build a MP LSP whose root node is PE2. They MUST NOT requested to build a MP LSP whose root node is PE2. They MUST NOT
interpret the opaque value at all. interpret the opaque value at all.
When an mLDP label mapping message containing PE2-FEC arrives at PE2 When an mLDP label mapping message containing PE2-FEC arrives at PE2
over a VRF interface, PE2 notes that it is the identified root node, over a VRF interface, PE2 notes that it is the identified root node,
and that the opaque value is a VPN-recursive (type 7) opaque value. and that the opaque value is a VPN-Recursive Opaque Value. Therefore
Therefore it MUST replace PE2-FEC with the contents of the VPN- it MUST replace PE2-FEC with the contents of the VPN-Recursive Opaque
recursive opaque value (i.e., with CE1-FEC) before doing any further Value (i.e., with CE1-FEC) before doing any further processing. It
processing. It uses the VRF to lookup up the path to R. This will uses the VRF to lookup up the path to R. This will result in CE1-FEC
result in CE1-FEC being sent on to CE2, and presumably further from being sent on to CE2, and presumably further from CE2 to R.
CE2 to R.
In this scenario, the RD in the VPN-Recursive Opaque Value also In this scenario, the RD in the VPN-Recursive Opaque Value also
ensures uniqueness of the FEC Element within the inner carrier's ensures uniqueness of the FEC Element within the inner carrier's
network. network.
This way of providing Carrier's Carrier service has limited This way of providing Carrier's Carrier service has limited
applicability, as it only works under the following conditions: applicability, as it only works under the following conditions:
- Both the inner carrier and the outer carrier are using - Both the inner carrier and the outer carrier are using
unsegmented mLDP P-tunnels unsegmented mLDP P-tunnels
skipping to change at page 10, line 31 skipping to change at page 10, line 29
- The inner carrier is not aggregating the P-tunnels of the outer - The inner carrier is not aggregating the P-tunnels of the outer
carrier, but is content to carry each such P-tunnel in a single carrier, but is content to carry each such P-tunnel in a single
P-tunnel of its own. P-tunnel of its own.
The carrier's carrier scenario can be distinguished from the inter-AS The carrier's carrier scenario can be distinguished from the inter-AS
scenario by the fact that in the former, the mLDP messages are being scenario by the fact that in the former, the mLDP messages are being
exchanged on VRF interfaces. exchanged on VRF interfaces.
4. IANA Considerations 4. IANA Considerations
[MLDP] defines a registry for "The LDP MP Opaque Value Element Type". [mLDP] defines a registry for "The LDP MP Opaque Value Element Basic
This document requires the assignment of two new code points in this Type". This document requires the assignment of two new code points
registry: in this registry:
- Type 6. - Recursive Opaque Value: Type TBD (requested value: 6)
An opaque value of this type is itself a TLV that encodes an mLDP An opaque value of this type is itself a TLV that encodes an mLDP
FEC type, as defined in [MLDP]. FEC type, as defined in [mLDP].
- Type 7 - VPN-Recursive Opaque Value: Type TBD (requested value: 7)
An opaque value of this type consists of an eight-octet Route An opaque value of this type consists of an eight-octet Route
Distinguisher as defined in [VPN], followed by a TLV that encodes Distinguisher as defined in [VPN], followed by a TLV that encodes
an mLDP FEC type, as defined in [MLDP]. an mLDP FEC type, as defined in [mLDP].
5. Security Considerations 5. Security Considerations
TBD The security considerations of [LDP] and [mLDP] apply.
Unauthorized modification of the FEC elements defined in this
document can disrupt the creation of the multipoint LSPs, or can
cause he multipoint LSPs to pass through parts of the network where
they are not supposed to go. This could potentially be used as part
of an attack to illegitimately insert or intercept multicast traffic.
However, since the FEC elements defined in this document are not
inherently more vulnerable to this form of attack than are the
previously defined FEC elements, this document does not add new
security vulnerabilities.
6. Acknowledgments 6. Acknowledgments
The authors wish to thank Toerless Eckert for his contribution to The authors wish to thank Toerless Eckert for his contribution to
this work. this work.
7. Authors' Addresses 7. Authors' Addresses
IJsbrand Wijnands IJsbrand Wijnands
Cisco Systems, Inc. Cisco Systems, Inc.
skipping to change at page 11, line 32 skipping to change at page 12, line 4
Eric C. Rosen Eric C. Rosen
Cisco Systems, Inc. Cisco Systems, Inc.
1414 Massachusetts Avenue 1414 Massachusetts Avenue
Boxborough, MA, 01719 Boxborough, MA, 01719
E-mail: erosen@cisco.com E-mail: erosen@cisco.com
Maria Napierala Maria Napierala
AT&T Labs AT&T Labs
200 Laurel Avenue, Middletown, NJ 07748 200 Laurel Avenue, Middletown, NJ 07748
E-mail: mnapierala@att.com E-mail: mnapierala@att.com
Nicolai Leymann Nicolai Leymann
Deutsche Telekom Deutsche Telekom
Winterfeldtstrasse 21 Winterfeldtstrasse 21
Berlin 10781 Berlin 10781
Germany Germany
E-mail: n.leymann@telekom.de E-mail: n.leymann@telekom.de
8. Normative References 8. Normative References
[MLDP] "Label Distribution Protocol Extensions for Point-to- [LDP] "LDP Specification", RFC 5036, Andersson, Minei, Thomas,
October 2007
[mLDP] "Label Distribution Protocol Extensions for Point-to-
Multipoint and Multipoint-to-Multipoint Label Switched Paths", Minei, Multipoint and Multipoint-to-Multipoint Label Switched Paths", Minei,
Kompella, Wijnands, Thomas, draft-ietf-mpls-ldp-p2mp-12.txt, February Kompella, Wijnands, Thomas, draft-ietf-mpls-ldp-p2mp-12.txt, February
2011 2011
[MVPN] "Multicast in MPLS/BGP IP VPNs", Rosen, Aggarwal, et. al., [MVPN] "Multicast in MPLS/BGP IP VPNs", Rosen, Aggarwal, et. al.,
draft-ietf-l3vpn-2547bis-mcast-10.txt, January 2009 draft-ietf-l3vpn-2547bis-mcast-10.txt, January 2009
[RFC2119] "Key words for use in RFCs to Indicate Requirement [RFC2119] "Key words for use in RFCs to Indicate Requirement
Levels.", Bradner, March 1997 Levels.", Bradner, March 1997
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