Network Working Group R. Aggarwal (Juniper)
Internet Draft D. Papadimitriou (Alcatel)
Expiration Date: June 2005 S. Yasukawa (NTT)
Editors
Extensions to RSVP-TE for Point to Multipoint TE LSPs
draft-ietf-mpls-rsvp-te-p2mp-00.txt
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Abstract
This document describes extensions to Resource Reservation Protocol -
Traffic Engineering (RSVP-TE) for the setup of point-to-multipoint
(P2MP) Label Switched Paths (LSPs) in Multi-Protocol Label Switching
(MPLS) and Generalized MPLS (GMPLS) networks. The solution relies on
RSVP-TE without requiring a multicast routing protocol in the Service
Provider core. Protocol elements and procedures for this solution are
described. There can be various applications for P2MP TE LSPs such as
IP multicast. Specification of how such applications will use a P2MP
TE LSP is outside the scope of this document.
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Conventions used in this document
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 [KEYWORDS].
Authors' Note
Some of the text in the document needs further discussion between
authors and feedback from MPLS WG. This has been pointed out when
applicable. A change log and reviewed/updated text will be made
available online.
Table of Contents
1 Introduction............................................ 3
2 Terminology............................................. 3
3 Mechanisms.............................................. 4
3.1 P2MP Tunnels............................................ 4
3.2 P2MP LSP Tunnels........................................ 5
3.3 P2P Sub-LSPs............................................ 5
3.3.1 Representation of a P2P sub-LSP......................... 5
3.3.2 P2P Sub-LSPs and Path Messages.......................... 5
3.4 Explicit Route Encoding................................. 6
4 Sub-Groups.............................................. 8
5 Path Message Format..................................... 9
6 Path Message Processing................................. 10
6.1 Multiple Path Messages.................................. 10
6.1.1. Identifying Multiple Path Messages...................... 11
6.2 Multiple P2P Sub-LSPs in One Path Message............... 12
7 RESV Message Format..................................... 13
8 RESV Message Processing................................. 14
8.1 RRO Processing.......................................... 15
8.2 Resv Message Throttling................................. 15
9 Transit Fragmentation................................... 16
10 Grafting................................................ 16
11 Pruning................................................. 17
11.1 P2MP TE LSP Teardown.................................... 18
11.2 Path Tear Message Format................................ 19
12 Refresh Reduction....................................... 19
13 State Management........................................ 19
13.1 Incremental State Update................................ 19
13.2 Combing Multiple Path Messages.......................... 20
14 Error Processing........................................ 21
14.1 Branch Failure Handling................................. 21
15 Notify and ResvConf Messages............................ 22
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16 Control of Branch Fate Sharing.......................... 23
17 Admin Status Change..................................... 23
18 Label Allocation on LANs with Multiple Downstream Nodes. 24
19 Make-Before-Break....................................... 24
19.1 P2MP Tree re-optimization............................... 24
19.2 Re-optimization of a subset of P2P sub-LSPs ............ 24
20 Fast Reroute............................................ 25
20.1 Facility Backpup........................................ 25
20.2 One to One Backup....................................... 25
21 Support for LSRs that are not P2MP Capable.............. 26
22 Reduction in Control Plane Processing with LSP Hierarchy 28
23 P2MP LSP Tunnel Remerging and Cross-Over................ 28
23.1 PathErr Message Format.................................. 30
24 New and Updated Message Objects......................... 31
24.1 P2MP SESSION Object..................................... 31
24.2 P2MP LSP Tunnel SENDER_TEMPLATE Object.................. 32
24.2.1 P2MP LSP Tunnel IPv4 SENDER_TEMPLATE Object............. 33
24.2.2 P2MP LSP Tunnel IPv6 SENDER_TEMPLATE Object............. 33
24.3 P2P SUB-LSP Object...................................... 34
24.3.1 P2P IPv4 SUB-LSP Object................................. 34
24.3.2 P2P IPv6 SUB-LSP Object................................. 35
24.4 FILTER_SPEC Object...................................... 35
24.5 SUB EXPLICIT ROUTE Object (SERO)........................ 36
24.6 SUB RECORD ROUTE Object (SRRO).......................... 36
25 IANA Considerations..................................... 37
26 Security Considerations................................. 37
27 Acknowledgements........................................ 37
28 Appendix................................................ 37
28.1 Example................................................. 37
29 References....................................
.......... 39
30 Authors................................................. 40
31 Intellectual Property................................... 43
32 Full Copyright Statement................................ 43
33 Acknowledgement......................................... 44
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1. Introduction
[RFC3209] defines a mechanism for setting up P2P TE LSPs in MPLS
networks. [RFC3473] defines extensions to [RFC3209] for setting up
P2P TE LSPs in GMPLS networks. However these specifications do not
provide a mechanism for building P2MP TE LSPs.
This document defines extensions to RSVP-TE [RFC3209] and [RFC3473]
protocol to support P2MP TE LSPs satisfying the set of requirements
described in [P2MP-REQ].
This document relies on the semantics of RSVP that RSVP-TE inherits
for building P2MP LSP Tunnels. A P2MP LSP Tunnel is comprised of
multiple P2P sub-LSPs. These P2P sub-LSPs are set up between the
ingress and egress LSRs and are appropriately combined by the branch
LSRs using RSVP semantics to result in a P2MP TE LSP. One Path
message may signal one or multiple P2P sub-LSPs. Hence the P2P sub-
LSPs belonging to a P2MP LSP Tunnel can be signaled using one Path
message or split across multiple Path messages.
Path computation and P2MP application specific aspects are outside of
the scope of this document.
2. Terminology
This document uses terminologies defined in [RFC3031], [RFC2205],
[RFC3209], [RFC3473] and [P2MP-REQ]. In addition the following terms
are used in this document.
P2P sub-LSP: A P2MP TE LSP is constituted of one or more P2P sub-
LSPs. A P2P sub-LSP refers to the portion of the label switched path
from the ingress LSR to a particular egress LSR. The egress LSR is
the destination of the P2P sub-LSP.
3. Mechanism
This document describes a solution that optimizes data replication by
allowing non-ingress nodes in the network to be replication/branch
nodes. A branch node is a LSR that is capable of replicating the
incoming data on two or more outgoing interfaces. The solution uses
RSVP-TE in the core of the network for setting up a P2MP TE LSP.
The P2MP TE LSP is set up by associating multiple P2P TE sub-LSPs and
relying on data replication at branch nodes. This is described
further in the following sub-sections by describing P2MP tunnels and
how they relate to P2P sub-LSPs.
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3.1. P2MP Tunnels
The specific aspect related to P2MP TE LSP is the action required at
a branch node, where data replication occurs. For instance, in the
MPLS case, incoming labeled data is appropriately replicated to
several outgoing interfaces with different labels.
A P2MP TE tunnel comprises of one or more P2MP LSPs referred to as
P2MP LSP tunnels. A P2MP TE Tunnel is identified by a P2MP SESSION
object. This object contains the P2MP ID defined as a destination
identifier, a tunnel ID and an extended tunnel ID.
The fields of a P2MP SESSION object are identical to those of the
SESSION object defined in [RFC3209] except that the Tunnel Endpoint
Address field is replaced by the P2MP Identifier (P2MP ID) field.
This identifier encodes the P2MP ID and identifies the set of
destination(s) of the P2MP LSP Tunnel.
3.2. P2MP LSP Tunnel
A P2MP TE tunnel comprises of one or more P2MP LSPs referred to as
P2MP LSP Tunnels. A P2MP LSP Tunnel is identified by the combination
of the P2MP ID, Tunnel ID, and Extended Tunnel ID that are part of
the P2MP SESSION object, and the IPv4 or IPv6 tunnel sender address
and LSP ID fields of the P2MP SENDER_TEMPLATE object. The new P2MP
SENDER_TEMPLATE object is defined in section 24.2
3.3. P2P Sub-LSPs
A P2MP LSP Tunnel is constituted of one or more P2P sub-LSPs.
3.3.1. Representation of a P2P Sub-LSP
A P2P sub-LSP exists within the context of a P2MP LSP Tunnel. Thus it
is identified by the P2MP ID, Tunnel ID, and Extended Tunnel ID that
are part of the P2MP SESSION, the IPv4 or IPv6 tunnel sender address
and LSP ID fields of the P2MP SENDER_TEMPLATE object, and the P2P
sub-LSP destination address that is part of the P2P_SUB_LSP object.
The P2P_SUB_LSP object is defined in section 24.3.
Additionally, a sub-LSP ID contained in the P2P_SUB_LSP object may be
used depending on further discussions about the make-before-break
procedures described in section 19.
An EXPLICIT_ROUTE Object (ERO) or SUB_EXPLICIT_ROUTE Object (SERO) is
used to optionally specify the explicit route of a P2P sub-LSP. Each
ERO or a SERO that is signaled corresponds to a particular
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P2P_SUB_LSP object. Details of explicit route encoding are specified
in section 3.4.
3.3.2. P2P Sub-LSPs and Path Messages
The mechanism in this document allows a P2MP LSP Tunnel to be
signaled using one or more Path messages. Each Path message may
signal one or more P2P sub-LSPs. Multiple Path messages are desirable
as one Path message may not be large enough to fit all the P2P sub-
LSPs; and they also allow separate manipulation of sub-trees of the
P2MP LSP Tunnel. The reason for allowing a single Path message, to
signal multiple P2P sub-LSPs, is to optimize the number of control
messages needed to setup a P2MP LSP Tunnel.
3.4. Explicit Route Encoding
When a Path message signals a single P2P sub-LSP (that is, the Path
message is only targeting a single leaf in the P2MP tree), the
EXPLICIT_ROUTE object encodes the path from the ingress LSR to the
egress LSR. The Path message also includes the P2P_SUB_LSP object for
the P2P sub-LSP being signaled. The < [<EXPLICIT_ROUTE>],
<P2P_SUB_LSP> > tuple represents the P2P sub-LSP. The absence of the
ERO should be interpreted as requiring hop-by-hop routing for the
sub-LSP based on the P2P sub-LSP destination address field of the
P2P_SUB_LSP object.
The absence of the ERO should be interpreted as requiring hop-by-hop
routing for the sub-LSP based on the P2P sub-LSP destination address
field of the P2P_SUB_LSP object.
When a Path message signals multiple P2P sub-LSPs the path of the
first P2P sub-LSP, from the ingress LSR to the egress LSR, is encoded
in the ERO. The first P2P sub-LSP is the one that corresponds to the
first P2P_SUB_LSP object in the Path message. The P2P sub-LSPs
corresponding to the P2P_SUB_LSP objects that follow are termed as
subsequent P2P sub-LSPs. The path of each subsequent P2P sub-LSP is
encoded in a SUB_EXPLICIT_ROUTE object (SERO). The format of the SERO
is the same as an ERO (as defined in [RFC3209]). Each subsequent P2P
sub-LSP is represented by tuples of the form [<SUB_EXPLICIT_ROUTE>]
<P2P_SUB_LSP>. There is a one to one correspondence between a
P2P_SUB_LSP object and a SERO. The absence of a SERO should be
interpreted as requiring hop-by-hop routing for that sub-LSP. Note
that the destination address is carried in the P2P sub-LSP object.
The encoding of the SERO and P2P sub-LSP object are described in
detail in section 24.
The motivation behind the use of the SERO object is to provide
explicit route compression when a Path message signals simultaneously
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multiple P2P sub-LSPs. One approach to encode the explicit route of a
subsequent P2P sub-LSP is to in
clude the path from the ingress to the
egress of the P2P sub-LSP. However this implies potential repetition
of hops that can be learned from the ERO or explicit routes of other
P2P sub-LSPs. Explicit route compression using SEROs attempts to
minimize such repetition. A SERO for a particular P2P sub-LSP
includes only the path from a certain branch LSR to the egress LSR if
the path to that branch LSR can be derived from the ERO or other
SEROs.
Explicit route compression is illustrated using the following figure.
A
|
|
B
|
|
C----D----E
| | |
| | |
F G H-------I
| |\ |
| | \ |
J K L M
| | | |
| | | |
N O P Q--R
Figure 1. Explicit Route Compression
Figure 1. shows a P2MP LSP Tunnel with LSR A as the ingress LSR and
six egress LSRs: (F, N, O, P, Q and R). When all the six P2P sub-LSPs
are signaled in one Path message let us assume that the P2P sub-LSP
to LSR F is the first P2P sub-LSP and the rest are subsequent P2P
sub-LSPs. Following is one way for the ingress LSR A to encode the
P2P sub-LSP explicit routes using compression:
P2P sub-LSP-F: ERO = {B, E, D, C, F}, P2P_SUB_LSP Object-F
P2P sub-LSP-N: SERO = {D, G, J, N}, P2P_SUB_LSP Object-N
P2P sub-LSP-O: SERO = {E, H, K, O}, P2P_SUB_LSP Object-O
P2P sub-LSP-P: SERO = {H, L, P}, P2P_SUB_LSP Object-P,
P2P sub-LSP-Q: SERO = {H, I, M, Q}, P2P_SUB_LSP Object-Q,
P2P sub-LSP-R: SERO = {Q, R}, P2P_SUB_LSP Object-R,
After LSR E processes the incoming Path message from LSR B it sends a
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Path message to LSR D with the P2P sub-LSP explicit routes encoded as
follows:
P2P sub-LSP-F: ERO = {D, C, F}, P2P_SUB_LSP Object-F
P2P sub-LSP-N: SERO = {D, G, J, N}, P2P_SUB_LSP Object-N
LSR E also sends a Path message to LSR H and following is one way to
encode the P2P sub-LSP explicit routes using compression:
P2P sub-LSP-O: ERO = {H, K, O}, P2P_SUB_LSP Object-O
P2P sub-LSP-P: SERO = {H, L, P}, P2P_SUB_LSP Object-P,
P2P sub-LSP-Q: SERO = {H, I, M, Q}, P2P_SUB_LSP Object-Q,
P2P sub-LSP-R: SERO = {Q, R}, P2P_SUB_LSP Object-R,
After LSR H processes the incoming Path message from E it sends a
Path message to LSR K, LSR L and LSR I. The encoding for the Path
message to LSR K is as follows:
P2P sub-LSP-O: ERO = {K, O}, P2P_SUB_LSP Object-O
The encoding of the Path message sent by LSR H to LSR L is as
follows:
P2P sub-LSP-P: ERO = {L, P}, P2P_SUB_LSP Object-P,
Following is one way for LSR H to encode the P2P sub-LSP explicit
routes in the Path message sent to LSR I:
P2P sub-LSP-Q: ERO = {I, M, Q}, P2P_SUB_LSP Object-Q,
P2P sub-LSP-R: SERO = {Q, R}, P2P_SUB_LSP Object-R,
The explicit route encodings in the Path messages sent by LSRs D and
Q are left as an exercise to the reader.
This compression mechanism reduces the Path message size. It also
reduces extra processing that can result if explicit routes are
encoded from ingress to egress for each P2P sub-LSP. No assumptions
are placed on the ordering of the subsequent P2P sub-LSPs and hence
on the ordering of the SEROs in the Path message. All LSRs need to
process the ERO corresponding to the first P2P sub-LSP. A LSR needs
to process a P2P sub-LSP descriptor for a subsequent P2P sub-LSP only
if the first hop in the corresponding SERO is a local address of that
LSR. The branch LSR that is the first hop of a SERO propagates the
corresponding P2P sub-LSP downstream.
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4. Sub-Groups
As with all other RSVP controlled LSP Tunnels, P2MP LSP Tunnel state
is managed using RSVP messages. While use of RSVP messages is the
same, P2MP LSP Tunnel state differs from P2P LSP state in a number of
ways. The two most notable differences are that a P2MP LSP Tunnel is
targeted at multiple P2P Sub-LSPs and that, as a result of this, it
may not be possible to represent full state in a single IP datagram
and even more likely that it can't fit into a single IP packet. It
must also be possible to efficiently add and remove endpoints to and
from P2MP TE LSPs. An additional issue is that P2MP LSP Tunnels must
also handle the state "remerge" problem, see [P2MP-REQ].
These differences in P2MP state are addressed through the addition of
a sub-group identifier (Sub-Group ID) and sub-group originator (Sub-
Group Originator ID) to the SENDER_TEMPLATE and FILTER_SPEC objects.
Taken together the Sub-Group ID and Sub-Group Originator ID are
referred to as the Sub-Group fields.
The Sub-Group fields, together with rest of the SENDER_TEMPLATE and
SESSION objects, are used to represent a portion of a P2MP LSP
Tunnel's state. The portion of P2MP LSP Tunnel state identified by
specific subgroup field values is referred to as a signaling sub-
tree. It is important to note that the term "signaling sub-tree"
refers only to signaling state and not data plane replication or
branching. For example, it is possible for a node to "branch"
signaling state for a P2MP LSP Tunnel, but to not branch the data
associated with the P2MP LSP Tunnel. Typical applications for
generation and use of multiple subgroups are adding an egress and
semantic fragmentation to ensure that a Path message remains within a
single IP packet.
5. Path Message Format
This section describes modifications made to the Path message format
as specified in [RFC3209] and [RFC3473]. The Path message is enhanced
to signal one or more P2P sub-LSPs. This is done by including the P2P
sub-LSP descriptor list in the Path message as shown below.
<Path Message> ::= <Common Header> [ <INTEGRITY> ]
[ [<MESSAGE_ID_ACK> | <MESSAGE_ID_NACK>] ...]
[ <MESSAGE_ID> ]
<SESSION> <RSVP_HOP>
<TIME_VALUES>
[ <EXPLICIT_ROUTE> ]
<LABEL_REQUEST>
[ <PROTECTION> ]
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[ <LABEL_SET> ... ]
[ <SESSION_ATTRIBUTE> ]
[ <NOTIFY_REQUEST> ]
[ <ADMIN_STATUS> ]
[ <POLICY_DATA> ... ]
<sender descriptor>
[P2P sub-LSP descriptor list]
Following is the format of the P2P sub-LSP descriptor list.
<P2P sub-LSP descriptor list> ::= <P2P sub-LSP descriptor>
[ <P2P sub-LSP descriptor list> ]
<P2P sub-LSP descriptor> ::= <P2P_SUB_LSP> [ <SUB_EXPLICIT_ROUTE> ]
Each LSR MUST use the common objects in the Path message and the P2P
sub-LSP descriptors to process each P2P sub-LSP represented by the
P2P sub-LSP object and the SUB-/EXPLICIT_ROUTE object combination.
The first P2P_SUB_LSP object's explicit route is specified
by the
ERO. Explicit routes of subsequent P2P sub-LSPs are specified by the
corresponding SERO. A SERO corresponds to the following P2P_SUB_LSP
object.
The RRO in the sender descriptor contains the hops traversed by the
Path message and applies to all the P2P sub-LSPs signaled in the Path
message.
Path message processing is described in the next section.
6. Path Message Processing
The ingress-LSR initiates the set up of a P2P sub-LSP to each egress-
LSR that is the destination of the P2MP LSP Tunnel. Each P2P sub-LSP
is associated with the same P2MP LSP Tunnel using common P2MP SESSION
object and <Source Address, LSP-ID> fields in the SENDER_TEMPLATE
object. Hence it can be combined with other P2P sub-LSPs to form a
P2MP LSP Tunnel. Another P2P sub-LSP belonging to the same instance
of this P2P sub-LSP (i.e. the same P2MP LSP Tunnel) can share
resources with this LSP. The session corresponding to the P2MP TE
tunnel is determined based on the P2MP SESSION object. Each P2P sub-
LSP is identified using the P2P_SUB_LSP object. Explicit routing for
the P2P sub-LSPs is achieved using the ERO and SEROs.
As mentioned earlier, it is possible to signal P2P sub-LSPs for a
given P2MP LSP Tunnel in one or more Path messages. And a given Path
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message can contain one or more P2P sub-LSPs."
6.1. Multiple Path messages
As described in section 3, <EXPLICIT_ROUTE> <P2P SUB-LSP> or
<SUB_EXPLICIT_ROUTE> <P2P_SUB_LSP> tuple is used to specify a P2P
sub-LSP. Multiple Path messages can be used to signal a P2MP LSP
Tunnel. Each Path message can signal one or more P2P sub-LSPs. If a
Path message contains only one P2P sub-LSP, each LSR along the P2P
sub-LSP follows [RFC3209] procedures for processing the Path message
besides the P2P SUB-LSP object processing described in this document.
Processing of Path messages containing more than one P2P sub-LSP is
described in Section 6.2.
An ingress LSR may use multiple Path messages for signaling a P2MP
LSP. This may be because a single Path message may not be large
enough to signal the P2MP LSP Tunnel. Or it may be while adding
leaves to the P2MP LSP Tunnel the new leaves are signaled in a new
Path message. Or an ingress LSR MAY choose to break the P2MP tree
into separate manageable P2MP trees. These trees share the same root
and may share the trunk and certain branches. The scope of this
management decomposition of P2MP trees is bounded by a single tree
and multiple trees with a single leaf each. Per [P2MP-REQ], a P2MP
LSP Tunnel must have consistent attributes across all portions of a
tree. This implies that each Path message that is used to signal a
P2MP LSP Tunnel is signaled using the same signaling attributes with
the exception of the P2P sub-LSP information.
The resulting sub-LSPs from the different Path messages belonging to
the same P2MP LSP Tunnel SHOULD share labels and resources where they
share hops to prevent multiple copies of the data being sent.
In certain cases a transit LSR may need to generate multiple Path
messages to signal state corresponding to a single received Path
message. For instance ERO expansion may result in an overflow of the
resultant Path message. There are two cases occurring in such
circumstances, either the message can be decomposed into multiple
Path messages such that each of the message carries a subset of the
incoming P2P sub-LSPs carried by the incoming message or the message
can not be decomposed such that each of the outgoing Path message
fits its maximum size value."
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6.1.1. Identifying Multiple Path Messages
Multiple Path messages generated by a LSR that signal state for the
same P2MP LSP are signaled with the same SESSION object and have the
same <Source address, LSP-ID> in the SENDER_TEMPLATE object. In order
to disambiguate these Path messages a <Sub-Group Originator ID, sub-
Group ID> tuple is introduced (also referred to as the Sub-Group
field). Multiple Path messages generated by a LSR to signal state
for the same P2MP LSP have the same Sub-Group Originator ID and have
a different sub-Group ID. The Sub-Group Originator ID SHOULD be set
to the Router ID of the LSR that originates the Path message. This is
either the ingress LSR or a LSR which re-originates the Path message
with its own Sub-Group Originator ID. Cases when a transit LSR may
change the Sub-Group Originator ID of an incoming Path message are
described below. The <Sub-Group Originator ID, sub-Group ID> tuple is
globally unique. The sub-Group ID space is specific to the Sub-Group
Originator ID. Therefore the combination <Sub-Group Originator ID,
sub-Group ID> is network-wide unique. Also, a router that changes the
Sub-Group originator ID MUST use the same value of the Sub-Group
Originator ID for a particular P2MP LSP Tunnel and should not vary it
during the life of the P2MP LSP Tunnel.
Note: This version of the document assumes that these additional
fields i.e., <Sub-Group Originator ID, sub-Group ID> are part of the
SENDER_TEMPLATE object."
6.2. Multiple P2P Sub-LSPs in one Path message
The P2P sub-LSP descriptor list allows the signaling of one or more
P2P sub-LSPs.
in one Path message. It is possible to signal multiple P2P sub-LSP
object and ERO/SERO combinations in a single Path message. Note that
these two objects are the ones that differentiate a P2P sub-LSP. Each
LSR can use the common objects in the Path message and the P2P sub-
LSP descriptors to process each P2P sub-LSP.
All LSRs need to process, when it is present, the ERO corresponding
to the first P2P sub-LSP. If one or more SEROs are present an ERO
must be present. The first P2P sub-LSP is propagated in a Path
message by each LSR along the explicit route specified by the ERO. A
LSR needs to process a P2P sub-LSP descriptor for a subsequent P2P
sub-LSP only if the first hop in the corresponding SERO is a local
address of that LSR. If this is not the case the P2P sub-LSP
descriptor is included in the Path message sent to LSR that is the
next hop to reach the first hop in the SERO. This next hop is
determined by using the ERO or other SEROs that encode the path to
the SERO's first hop. If this is the case and the LSR is also the
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egress the P2P sub-LSP descriptor is not propagated downstream. If
this is the case and the LSR is not the egress the P2P sub-LSP
descriptor is included in a Path message sent to the next-hop
determined from the SERO. Hence a branch LSR only propagates the
relevant P2P sub-LSP descriptors on each downstream link. A P2P sub-
LSP descriptor that is propagated on a downstream link only contains
those P2P sub-LSPs that are routed using that link. This processing
may result in a subsequent P2P sub-LSP in an incoming Path message to
become the first P2P sub-LSP in an outgoing Path message.
Note that if one or more SEROs contains loose hops, expansion of such
loose hops may result in overflowing the Path message size. Section 9
describes how signaling of the set of P2P sub-LSPs can be split in
more than one Path message.
The Record Route Object (RRO) contains the hops traversed by the Path
message and applies to all the P2P sub-LSPs signaled in the path
message. A transit LSR appends its address in an incoming RRO and
propagates it downstream. A branch LSR forms a new RRO for each of
the outgoing Path messages. Each such updated RRO is formed by
appending the branch LSR's address to the incoming RRO.
If a LSR is unable to support a P2P sub-LSP setup, a PathErr message
MUST be sent for the impacted P2P sub-LSP, and normal processing of
the rest of the P2MP LSP Tunnel SHOULD continue. The default behavior
is that the remainder of the LSP is not impacted (that is, all other
branches are allowed to set up) and the failed branches are reported
in PathErr messages in which the Path_State_Reomved flag MUST NOT be
set. However, the ingress LSR may set a LSP Integrity flag (see
section 25) to request that if there is a setup failure on any branch
the entire LSP should fail to set up.
7. Resv Message Format
The Resv message follows the [RFC3209] and [RFC3473] format:
<Resv Message> ::= <Common Header> [ <INTEGRITY> ]
[ [<MESSAGE_ID_ACK> | <MESSAGE_ID_NACK>] ... ]
[ <MESSAGE_ID> ]
<SESSION> <RSVP_HOP>
<TIME_VALUES>
[ <RESV_CONFIRM> ] [ <SCOPE> ]
[ <NOTIFY_REQUEST> ]
[ <ADMIN_STATUS> ]
[ <POLICY_DATA> ... ]
<STYLE> <flow descriptor list>
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<flow descriptor list> ::= <FF flow descriptor list>
| <SE flow descriptor>
<FF flow descriptor list> ::= <FF flow descriptor>
| <FF flow descriptor list>
<FF flow descriptor>
<SE flow descriptor> ::= <FLOWSPEC> <SE filter spec list>
<SE filter spec list> ::= <SE filter spec>
| <SE filter spec list> <SE filter spec>
The FF flow descriptor and SE filter spec are modified as follows to
identify the P2P sub-LSPs that they correspond to:
<FF flow descriptor> ::= [ <FLOWSPEC> ] <FILTER_SPEC> <LABEL>
[ <RECORD_ROUTE> ] [ <P2P sub-LSP descriptor
list> ]
<SE filter spec> ::= <FILTER_SPEC> <LABEL> [ <RECORD_ROUTE> ]
[ <P2P sub-LSP descriptor list> ]
FILTER_SPEC is defined in section 24.4.
The P2P sub-LSP descriptor has the same format as in section 5.1 with
the difference that a SUB_RECORD_ROUTE object is used in place of a
SUB_EXPLICIT_ROUTE object. The SUB_RECORD_ROUTE objects follow the
same compression mechanism as the SUB_EXPLICIT_ROUTE objects. Note
that that a Resv message can signal multiple P2P sub-LSPs that may
belong to the same FILTER_SPEC object or different FILTER_SPEC
objects. The same label is allocated if the FILTER_SPEC object is the
same.
However different upstream labels are allocated if the <Source
Address, LSP-ID> of the FILTER_SPEC object is different as that
implies different P2MP LSP Tunnels.
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8. Resv Message Processing
The egress LSR follows normal RSVP procedures while originating a
Resv message. The Resv message carries the label allocated by the
egress LSR.
A subsequent node allocates its own label and passes it in the Resv
message upstream. The node may combine multiple flow descriptors,
from different Resv messages received from downstream, in one Resv
message sent upstream. A Resv message is not sent upstream until at
least one Resv message has been received from a downstream neighbor
except when the integrity bit is set in the LSP_ATTRIBUTE object.
Each FF flow descriptor or SE filter spec sent upstream in a Resv
message includes a P2P sub-LSP descriptor list. Each such FF flow
descriptor or SE filter spec for the same P2MP LSP Tunnel (whether on
one or multiple Resv messages) is allocated the same label.
This label is associated by that node with all the labels received
from downstream Resv messages for that P2MP LSP Tunnel. Note that a
transit node may become a replication point in the future when a
branch is attached to it. Hence this results in the setup of a P2MP
LSP Tunnel from the ingress-LSR to the egress LSRs.
The ingress LSR may need to understand when all desired egresses have
been reached. This is achieved using <P2P_SUB_LSP> objects.
Each branch node can potentially send one Resv message upstream for
each of the downstream receivers. This may result in overflowing the
Resv message, particularly when considering that the number of
messages increases the closer the branch node is to the ingress.
Transit nodes MUST replace the Sub-Group ID fields received in the
FILTER_SPEC objects with the value that was received in the Sub-Group
ID field of the Path message from the upstream neighbor, when the
node set the Sub-Group Originator field in the associated Path
message. ResvErr messages generation is unmodified. Nodes
propagating a received ResvErr message MUST use the Sub-Group field
values carried in the corresponding Resv message.
The solution for this issue is for further discussion.
8.1. RRO Processing
A Resv message contains a record route per P2P sub-LSP that is being
signaled by the Resv message if the sender node requests route
recording by including a RRO in the Path message. The same rule is
used during signaling of P2MP LSP Tunnels i.e. insertion of the RRO
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in the Path message used to signal one or more P2P sub-LSP triggers
the inclusion of an RRO for each sub-LSP.
The record route of the first P2P sub-LSP is encoded in the RRO.
Additional RROs for the subsequent P2P sub-LSPs are referred to as
SUB_RECORD_ROUTE objects (SRROs). Their format is specified in
section 24.5. The ingress node then receives the RRO and possibly
the SRRO corresponding to each subsequent P2P sub-LSP. Each
P2P_SUB_LSP object is followed by the RRO/SRRO. The ingress node can
then determine the record route corresponding to a particular P2P
sub-LSP. The RRO and SRROs can be used to construct the end to end
Path for each P2P sub-LSP.
8.2. Resv Message Throttling
A branch node may have to send the Resv message being sent upstream
whenever there is a change in a Resv message for a P2P sub-LSP
received from downstream. This can result in excessive Resv messages
sent upstream, particularly when the P2P sub-LSPs are established for
the first time. In order to mitigate this situation, branch nodes
can limit their transmission of Resv messages. Specifically, in the
case where the only change being sent in a Resv message is in one or
more SRRO objects, the branch node SHOULD transmit the Resv message
only after a delay time has passed since the transmission of the
previous Resv message for the same session. This delayed Resv message
SHOULD include SRROs for all branches. Specific mechanisms for Resv
message throttling are implementation dependent and are outside the
scope of this document.
9. Transit Fragmentation
In certain cases a transit LSR may need to generate multiple Path
messages to signal state corresponding to a single received Path
message. For instance ERO expansion may result in an overflow of the
resultant Path message. It is desirable not to rely on IP
fragmentation in this case. In order to achieve this, the multiple
Path messages generated by the transit LSR, are signaled with the
Sub-Group Originator ID set to the TE Router ID of the transit LSR
and a distin
ct sub-Group ID. Thus each distinct Path message that is
generated by the transit LSR for the P2MP LSP Tunnel carries a
distinct <Sub-Group Originator ID, Sub-Group ID> tuple.
When multiple Path messages are used by an ingress or transit node,
each Path message SHOULD be identical with the exception of the P2P
sub-LSP related information (e.g., SERO), message and hop information
(e.g., INTEGRITY, MESSAGE_ID and RSVP_HOP), and the SENDER_TEMPLATE
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objects. Except when performing a make-before-break operation, the
tunnel sender address and LSP ID fields MUST be the same in each
message, and for transit nodes, the same as the values in the Path
message.
As described above one case in which the Sub-Group Originator ID of a
received Path message is changed is that of transit fragmentation.
The Sub-Group Originator ID of a received Path message may also be
changed in the outgoing Path message and set to that of the LSR
originating the Path message based on a local policy. For instance a
LSR may decide to always change the Sub-Group Originator ID while
performing ERO expansion. The Sub-Group ID MUST not be changed if the
Sub-Group Originator ID is not being changed.
10. Grafting
The operation of adding egress LSR(s) to an existing P2MP LSP Tunnel
is termed as grafting. This operation allows egress nodes to join a
P2MP LSP Tunnel at different points in time.
There are two methods to add P2P sub-LSPs to a P2MP LSP Tunnel. The
first is to add new P2P sub-LSPs to the P2MP LSP Tunnel by adding
them to an existing Path message and refreshing the entire Path
message. Path message processing described in section 6 results in
adding these P2P sub-LSPs to the P2MP LSP Tunnel. Note that as a
result of adding one or more P2P sub-LSPs to a Path message the ERO
compression encoding may have to be recomputed.
The second is to use incremental updates described in section 13.1.
The egress LSRs can be added/removed by signaling only the impacted
P2P sub-LSPs in a new Path message. Hence other P2P sub-LSPs do not
have to be re-signaled.
11. Pruning
The operation of removing egress LSR(s) from an existing P2MP LSP
Tunnel is termed as pruning. This operation allows egress nodes to
leave a P2MP LSP Tunnel at different points in time.
The P2P sub-LSP(s) being removed from the P2MP LSP Tunnel are
signaled in a PathTear message. The PathTear message includes the P2P
sub-LSP descriptor list which is included before the sender
descriptor. Note that the PathTear message contains only the P2P sub-
LSP(s) being removed and rest of the P2MP LSP Tunnel does not have to
be re-signaled. This results in removal of the state corresponding to
these P2P sub-LSPs. State for rest of the P2P sub-LSPs is not
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modified.
This section describes various mechanisms to perform pruning. Further
discussion and feedback is needed to finesse these mechanisms. In the
first mechanism in order to delete one or more P2P Sub-LSPs, a
PathTear message is sent with the list of P2P sub-LSPs being deleted.
This is a form of explicit tear down. A single PathTear message can
only contain P2P sub-LSPs that were signaled by the ingress using the
same <Sub-Group Originator ID, Sub-Group ID> tuple. The PathTear
message is signaled with the SESSION and SENDER_TEMPLATE objects
corresponding to the P2MP LSP Tunnel and the <Sub-Group Originator
ID, Sub-Group ID> tuple corresponding to the P2P sub-LSPs that are
being deleted. A transit LSR that propagates the PathTear message
downstream MUST ensure that it sets the <Sub-Group Originator ID,
Sub-Group ID> tuple in the PathTear message to the values used to
generate the last Path message that corresponds to the P2P sub-LSPs
signaled in the PathTear message that it generates. The transit LSR
may need to generate multiple PathTear messages for an incoming
PathTear message if it had performed transit fragmentation for the
corresponding incoming Path message.
The Path messages from which the P2P sub-LSPs were deleted need to be
refreshed with the remaining P2P sub-LSPs. Note that as a result of
deleting one or more P2P sub-LSPs from a Path message the ERO
compression encoding may have to be recomputed.
When the last P2P sub-LSP is to be removed from a Path state, i.e.,
there are no remaining P2P sub-LSPs to send in a Path message, a
PathTear message SHOULD be sent carrying the Sub-Group ID of the Path
message that no longer has any P2P sub-LSPs.
The second mechanism to delete P2P sub-LSPs is implicit teardown
which uses standard RSVP message processing. Per standard RSVP
processing, a P2P sub-LSP may be removed from a P2MP TE LSP by
sending a modified message for the Path or Resv message that
previously advertised the P2P sub-LSP. This message MUST list all
P2P sub-LSPs that are not being removed. When using this approach, a
node processing a message that removes a P2P sub-LSP from a P2MP TE
LSP MUST ensure that the P2P sub-LSP is not included in any other
Path state associated with session before interrupting the data path
to that egress. All other message processing remains unchanged.
The third mechanism is an explicit teardown mechanism that defines
new syntax and semantics for a PathTear message. This new mechanism
minimizes signaling required to remove a subset of P2P sub-LSPs set
signaled in a Path message, and thereby reduces associated
processing. When using this mechanism each identified P2P sub-LSP is
removed from the P2MP LSP Tunnel state, even if the P2P sub-LSP is
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advertised in multiple Path message.
When using this approach, a PathTear message is generated. The
PathTear message MUST identify each P2P sub-LSP to be removed, via a
P2P_SUB_LSP object per P2P Sub-LSP, and include a SENDER_TEMPLATE
object corresponding to the Path state being modified. The Sub-Group
ID valued contained in the SENDER_TEMPLATE object message MUST be set
to zero (0). Subsequent Path messages associated with the P2MP LSP
Tunnel MUST NOT contain the removed P2P sub-LSPs, unless that P2P
sub-LSP is being re-added to the P2MP LSP.
To support the third mechanism, the receiver of PathTear message that
is associated with a P2MP LSP Tunnel MUST check the value of a
received Sub-Group ID fields. When there is no SENDER_TEMPLATE
object present or the value of the Sub-Group ID fields is non-zero,
then PathTear processing as defined in the above explicit tear down
mechanism must be followed. When the Sub-Group ID field is zero (0),
then the processing node MUST remove the identified egresses from all
control plane state associated with the P2MP LSP Tunnel and adjust
the data path appropriately.
11.1. P2MP TE LSP Tear Down
This operation is accomplished by listing all the P2P sub-LSPs in a
PathTear message.
A PathTear message must be generated for each Path message used to
signal the P2MP LSP Tunnel.
11.2. PathTear message Format
The format of the PathTear message is as follows:
<PathTear Message> ::= <Common Header> [ <INTEGRITY> ]
[ [ <MESSAGE_ID_ACK> | <MESSAGE_ID_NACK> ...
]
[ <MESSAGE_ID> ]
<SESSION> <RSVP_HOP>
[ <sender descriptor> ]
[ <P2P sub-LSP descriptor list> ]
<send
er descriptor> ::= (see earlier definition)
Note: it is assumed that the P2P sub-LSP descriptor will not include
the SUB_EXPLICIT_ROUTE object associated with each P2P_SUB_LSP being
deleted
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12. Refresh Reduction
The refresh reduction procedures described in [RFC2961] are equally
applicable to P2MP LSP Tunnels described in this document. Refresh
reduction applies to individual messages and the state they
install/maintain, and that continues to be the case for P2MP LSP
Tunnels.
13. State Management
State signaled by a P2MP Path message is managed by a local
implementation using the <P2MP ID, Tunnel ID, Extended Tunnel ID> as
part of the SESSION object and <Tunnel Sender Address, LSP ID, Sub-
Group Originator ID, Sub-Group ID> as part of the SENDER_TEMPLATE
object.
Additional information signaled in the Path message is part of the
state created by a local implementation. This mandatorily includes
PHOP and SENDER_TSPEC object.
13.1. Incremental State Update
RSVP as defined in [RFC2205] and as extended by RSVP-TE [RFC3209] and
GMPLS [RFC3473] uses the same basic approach to state communication
and synchronization, namely full state is sent in each state
advertisement message. Per [RFC2205] Path and Resv messages are
idempotent. Also, [RFC2961] categorizes RSVP messages into two types:
trigger and refresh messages and improves RSVP message handling and
scaling of state refreshes but does not modify the full state
advertisement nature of Path and Resv messages. The full state
advertisement nature of Path and Resv messages has many benefits, but
also has some drawbacks. One notable drawback is when an incremental
modification is being made to a previously advertised state. In this
case, there is the message overhead of sending the full state and the
cost of processing it. It is desirable to overcome this drawback and
add/delete P2P sub-LSPs to a P2MP LSP Tunnel by incrementally
updating the existing state.
It is possible to use the procedures described in this document to
allow P2P sub-LSPs to be incrementally added or deleted from the P2MP
LSP by allowing a Path or a PathTear message to incrementally change
the existing P2MP LSP Tunnel Path state.
As described in section 6.1, multiple Path messages can be used to
signal a P2MP LSP Tunnel. The Path messages are distinguished by
different <Sub-Group Originator ID, sub-Group ID> tuples in the
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SENDER_TEMPLATE object. In order to perform incremental P2P sub-LSP
state addition a separate Path message with a new sub-Group ID is
used to add the new P2P sub-LSPs, by the ingress LSR. The Sub-Group
Originator ID MUST be set to the TE Router ID [RFC3477] of the node
that sets the Sub-Group ID.
This maintains the idempotent nature of RSVP Path messages; avoids
keeping track of individual P2P sub-LSP state expiration and provides
the ability to perform incremental P2MP LSP Tunnel state updates.
13.2. Combining Multiple Path Messages
There is a tradeoff between the number of Path messages used by the
ingress to maintain the P2MP LSP Tunnel and using full state refresh
to add P2P sub- LSPs. It is possible to combine P2P sub-LSPs
previously advertised in different Path messages in a single Path
message in order to reduce the number of Path messages needed to
maintain the P2MP LSP. This can also be done by a transit node that
performed fragmentation and at a later point is able to combine
multiple Path messages that it generated into a single Path message.
This may happen when one or more P2P sub-LSPs are pruned from the
existing Path states.
The new Path message is signaled by the node that is combining
multiple Path messages with all the P2P sub-LSPs that are being
combined in a single Path message. This Path message contains a new
Sub-Group ID field value. When a new Path and Resv message that is
signaled for an existing P2P sub-LSP is received by a transit LSR,
state including the new instance of the P2P sub-LSP is created.
The P2P sub-LSP SHOULD continue to be advertised in both the old and
new Path messages until a Resv message listing the P2P sub-LSP and
corresponding to the new Path message is received by the combining
node. Hence until this point state for the P2P sub-LSP SHOULD be
maintained as part of the Path state for both the old and the new
Path message [Section 3.1.3, 2205]. At that point the P2P sub-LSP
SHOULD be deleted from the old Path state using a PathTear message.
The P2P sub-LSP should also be removed from the old Path message and
the old Path message should be signaled again, if there are other
remaining P2P sub-LSPs in the old Path message.
A Path message with a sub-Group_ID(n+1) may signal a set of P2P sub-
LSPs that belong partially or entirely to an already existing Sub-
Group_ID(i), i <= n, the SESSION object and <Sender Tunnel Address,
LSP-ID, Sub-Group Originator ID> being the same. Or it may signal a
strictly non-overlapping new set of P2P sub-LSPs with a strictly
higher sub-Group_ID value.
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1) If sub-Group_ID(i) = sub-Group_ID(n+1), i =< n then either a full
refresh is indicated by the Path message or a P2P Sub-LSP is added
to/deleted from the group signaled by sub-Group_ID(n+1)
2) If sub-Group_ID(i) != sub-Group_ID(n+1), i =< n then the Path
message is signaling a set of P2P sub-LSPs that belong partially or
entirely to an already existing Sub-Group_ID(i) or a strictly non-
overlapping set of P2P sub-LSPs.
14. Error Processing
PathErr and ResvErr messages are processed as per RSVP-TE procedures.
Note that a LSR on receiving a PathErr/ResvErr message for a
particular P2P sub-LSP changes the state only for that P2P sub-LSP.
Hence other P2P sub-LSPs are not impacted. In case the ingress node
requests the maintenance of the 'LSP integrity', any error reported
within the P2MP TE LSP must be reported at (least at) any other
branching nodes belonging to this LSP. Therefore, reception of an
error message for a particular P2P sub-LSP MAY change the state of
any other P2P sub- LSP of the same P2MP TE LSP.
14.1. Branch Failure Handling
During setup and during normal operation, PathErr messages may be
received at a branch node. In all cases, a received PathErr message
is first processed per standard processing rules. That is: the
PathErr message is sent hop-by-hop to the ingress/branch LSR for that
Path message. Intermediate nodes until this ingress/branch LSR MAY
inspect this message but take no action upon it. The behavior of a
branch LSR that generates a PathErr message is under the control of
the ingress LSR.
The default behavior is that the PathErr does not have the
Path_State_Removed flag set. However, if the ingress LSR has set the
'LSP integrity' flag on the Path message (see LSP_ATTRIBUTE object in
section 24) and if the Path_State_Removed flag is supported, the LSR
generating a PathErr to report the failure of a branch of the P2MP
LSP Tunnel SHOULD set the Path_State_Removed flag.
A branch LSR that receives a PathErr message with the
Path_State_Removed flag set MUST act according to the wishes of the
ingress LSR. The default behavior is that the branch LSR clears the
Path_State_Removed flag on the PathErr and sends it further upstream.
It does not tear any other branches of the LSP. However, if the LSP
integrity flag is set on the Path message, the branch LSR MUST send
PathTear on all downstream branches and send the PathErr message
upstream with the Path_State_Removed flag set.
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A branch LSR that receives a PathErr message with the
Path_State_Removed flag clear MUST act according to the wishes of the
ingress LSR. The default behavior is that the branch LSR forwards the
PathErr upstream and takes no further action. However, if the LSP
integrity flag is set on the Path message, the branch LSR MUST send
PathTear on all downstream branches and send the PathErr upstream
with the Path_State_Removed flag set (per [RFC3473]).
In all cases, the PathErr message forwarded by a branch LSR MUST
contain the P2P sub-LSP identification and explicit routes of all
branches that are errored (reported by received PathErr messages) and
all branches that are explicitly torn by the branch LSR.
15. Notify and ResvConf Messages
Notify messages, see [RFC3473], may contain either SENDER_TEMPLATE or
FILTER_SPEC objects, but are sent in a targeted fashion. This means
that the Sub-Group fields cannot be updated in transit and is
unlikely to provide any value to the Notify message recipient.
Therefore, the receiver of a Notify message MUST identify the sender
state referenced in the message based on the Source address and LSP
ID contained in the received SENDER_TEMPLATE or FILTER_SPEC objects
rather than, as is normally done, based on the whole objects.
ResvConf messages may contain FILTER_SPEC objects and may also be
sent in a targeted fashion. As with Notify messages, the receiver of
a ResvConf message MUST identify the state referenced in the message
based on the address and LSP ID contained in the received FILTER_SPEC
object rather than, as is normally done, based on the whole objects.
16. Control of Branch Fate Sharing
An ingress LSR can control the behavior of an LSP if there is a
failure during LSP setup or after an LSP has been established. The
default behavior is that only the branches downstream of the failure
are not established, but the ingress may request 'LSP integrity' such
that any failure anywhere within the LSP tree causes the entire P2MP
LSP Tunnel to fail.
The ingress LSP may request 'LSP integrity' by setting bit [TBD] of
the Attributes Flags TLV. The bit is set if LSP integrity is
required.
It is RECOMMENDED to use the LSP_ATTRIBUTES Object for this flag and
not the LSP_REQUIRED_ATTRIBUTES Object.
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A branch LSR that supports the Attributes Flags TLV and recognizes
this bit MUST support LSP integrity or reject the LSP setup with a
PathErr carrying the error "Routing Error"/"Unsupported LSP
Integrity"
17. Admin Status Change
A branch node that receives an ADMIN_STATUS object processes it
normally and also relays the ADMIN_STATUS object in a Path on every
branch. All Path messages may be concurrently sent to the downstream
neighbors.
Downstream nodes process the change in the status object per
[RFC3473], including generation of Resv messages. When the last
received upstream ADMIN_STATUS object had the R bit set, branch nodes
wait for a Resv message with a matching ADMIN_STATUS object to be
received (or a corresponding PathErr or ResvTear messsage) on all
branches before relaying a corresponding Resv message upstream.
18. Label Allocation on LANs with Multiple Downstream Nodes
A sender on a LAN uses a different label for sending traffic to each
node on the LAN that belongs to the P2MP LSP Tunnel. Thus the sender
performs replication. It may be considered desirable on a LAN to use
the same label for sending traffic to multiple nodes belonging to the
same P2MP LSP Tunnel, to avoid replication. Procedures for doing this
are for further study. Given the relatively small number of receivers
on LANs typically deployed in MPLS networks, this is not currently
seen as a practical problem. Furthermore avoiding replication at the
sender on a LAN requires significant complexity in the control plane.
Given the tradeoff we propose the use of replication by the sender on
a LAN.
19. Make-before-break
Let's consider the following cases where make-before-break is needed:
19.1. P2MP Tree Re-optimization
In this case all the P2P sub-LSPs are signaled with a different LSP
ID by the ingress-LSR and follow make-before-break procedure[RFC3209]
Thus a new P2MP LSP Tunnel instance is established. Each P2P sub-LSP
is signaled with a different LSP ID, corresponding to the new P2MP TE
LSP. The ingress can, after moving traffic to the new instance, tear
down the previous P2MP LSP Tunnel instance.
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19.2. Re-optimization of a subset of P2P sub-LSPs.
One way to accomplish re-optimization of a subset of P2P sub-LSPs
that belong to a P2MP LSP Tunnel is to resignal the entire tree with
a new LSP-ID as described in the previous subsection.
(There is NO-CONSENSUS between the authors on rest of the text in
this subsection and it needs further discussion.)
It is possible to accomplish re-optimization of one or more P2P sub-
LSPs without re-signaling rest of the P2MP LSP. To achieve this a
sub-LSP ID is used to identify each P2P sub-LSP. This is encoded in
the P2P sub-LSP object. Each re-optimized P2P sub-LSP is signaled
with a different sub-LSP ID and hence a new P2P sub-LSP is
established. Once the new setup is complete, the old P2P sub-LSP can
be torn down. In some cases this may result in transient data
duplication.
20. Fast Reroute
[RSVP-FR] extensions can be used to perform fast reroute for the
mechanism described in this document.
20.1. Facility Backup
Facility backup as described in [RSVP-FR] can be used to protect P2MP
LSP Tunnels.
If link protection is desired, a bypass tunnel is used to protect the
link between the PLR and next-hop. Thus all P2P sub-LSPs that use the
link can be protected in the event of link failure. Note that all
such P2P sub-LSPs belonging to a particular instance of a P2MP tunnel
will share the same outgoing label on the link between the PLR and
the next-hop. This is the P2MP LSP label on the link. Label stacking
is used to send data for each P2MP LSP in the bypass tunnel. The
inner label is the P2MP LSP Tunnel label allocated by the nhop.
During failure Path messages for each P2P sub-LSP, that is effected,
will be sent to the MP, by the PLR. It is recommended that the PLR
use the sender template specific method to identify these Path
messages. Hence the PLR will set the source address in the sender
template to a local PLR address. The MP will use the LSP-ID to
identify the corresponding P2P sub-LSPs.
The MP MUST not use the <sub-group originator ID, sub-group ID> while
identifying the corresponding P2P sub-LSPs.
In order to further process a P2P sub-LSP it will determine the
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protected P2P sub-LSP using the LSP-id and the P2P sub-LSP object.
If node protection is desired, the bypass tunnel must intersect the
path of the protected P2P sub-LSPs somewhere downstream of the PLR.
This constrains the set of P2P sub-LSPs being backed-up via that
bypass tunnel to those that pass through a common downstream MP. The
MP will alloca
te the same label to all such P2P sub-LSPs belonging to
a particular instance of a P2MP tunnel. This will be the inner label
used during label stacking. This may require the PLR to be branch
capable as multiple bypass tunnels may be required to backup the set
of P2P sub-LSPs passing through the protected node. Else all the P2P
sub-LSPs being backed up must pass through the same MP.
20.2. One to One Backup
One to one backup as described in [RSVP-FR] can be used to protect a
particular P2P sub-LSP against link and next-hop failure. Protection
may be used for one or more P2P sub-LSPs between the PLR and the
next-hop. All the P2P sub-LSPs corresponding to the same instance of
the P2MP tunnel, between the PLR and the next-hop share the same P2MP
LSP Tunnel label.
All or some of these P2P sub-LSPs may be protected.
The detour P2P sub-LSPs may or may not share labels, depending on the
detour path. Thus the set of outgoing labels and next-hops for a P2MP
LSP Tunnel that was using a single next-hop and label between the PLR
and next-hop before protection, may change once protection is
triggerred.
Its is recommended that the path specific method be used to identify
a backup P2P sub-LSP. Hence the DETOUR object will be inserted in the
backup Path message. A backup P2P sub-LSP MUST be treated as
belonging to a different P2MP tunnel instance than the one specified
by the LSP-id. Furthermore multiple backup P2P sub-LSPs MUST be
treated as part of the same P2MP tunnel instance if they have the
same LSP-id and the same DETOUR objects. Note that as specified in
section 3 P2P sub-LSPs between different P2MP tunnel instances use
different labels.
If there is only P2P sub-LSP in the Path message, the DETOUR object
applies to that sub-LSP. If there are multiple P2P sub-LSPs in the
Path message the DETOUR applies to all the P2P sub-LSPs.
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21. Support for LSRs that are not P2MP Capable
It may be that some LSRs in a network are capable of processing the
P2MP extensions described in this document, but do not support P2MP
branching in the data plane. If such an LSR is requested to become a
branch LSR by a received Path message, it MUST respond with a PathErr
message carrying the Error Value "Routing Error" and Error Code
"Unable to Branch".
Its also conceivable that some LSRs, in a network deploying P2MP
capability, may not support the extensions described in this
document. If a Path message for the establishment of a P2MP LSP
Tunnel reaches such an LSR it will reject it with a PathErr because
it will not recognize the C-Type of the P2MP SESSION object.
LSRs that do not support the P2MP extensions in this document may be
included as transit LSRs by the use of LSP-stitching and LSP-
hierarchy [LSP-HIER]. Note that LSRs that are required to play any
other role in the network (ingress, branch or egress) MUST support
the extensions defined in this document.
The use of LSP-stitching and LSP-hierarchy [LSP-HIER] allows to build
P2MP LSP Tunnels in such an environment. A P2P LSP segment is
signaled from the previous P2MP capable hop of a legacy LSR to the
next P2MP capable hop. Of course this assumes that intermediate
legacy LSRs are transit LSRs and cannot act as P2MP branch points.
Transit LSRs along this LSP segment do not process control plane
messages associated with a P2MP LSP Tunnel. Furthermore these LSRs
also do not need to have P2MP data plane capability as they only need
to process data belonging to the P2P LSP segment. Hence these LSRs do
not need to support P2MP MPLS. This P2P LSP segment is stitched to
the incoming P2MP LSP Tunnel. After the P2P LSP segment is
established the P2MP Path message is sent to the next P2MP capable
LSR as a directed Path message. The next P2MP capable LSR stitches
the P2P LSP segment to the outgoing P2MP LSP Tunnel.
In packet networks, the P2P sub-LSPs may be nested inside the outer
P2P LSP Tunnel. Hence label stacking can be used to enable use of the
same LSP Tunnel segment for multiple P2MP LSP Tunnels. Stitching and
nesting considerations and procedures are described further in [INT-
REG].
It may be an overhead for an operator to configure the P2P LSP
segments in advance, when it is desired to support legacy LSRs. It
may be desirable to do this dynamically. The ingress can use IGP
extensions to determine non P2MP capable LSRs. It can use this
information to compute P2P sub-LSP paths such that they avoid these
legacy LSRs. The explicit route object of a P2P sub-LSP path may
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contain loose hops if there are legacy LSRs along the path. The
corresponding explicit route contains a list of objects upto the P2MP
capable LSR that is adjacent to a legacy LSR followed by a loose
object with the address of the next P2MP capable LSR. The P2MP
capable LSR expands the loose hop using its TED. When doing this it
determines that the loose hop expansion requires a P2P LSP to tunnel
through the legacy LSR. If such a P2P LSP exists, it uses that P2P
LSP. Else it establishes the P2P LSP. The P2MP Path message is sent
to the next P2MP capable LSR using non-adjacent signaling. The P2MP
capable LSR that initiates the non-adjacent signaling message to the
next P2MP capable LSR may have to employ a fast detection mechanism
such as [BFD] to the next P2MP capable LSR.
This may be needed for the directed Path message Head-End to use node
protection FRR when the protected node is the directed Path message
tail.
Note that legacy LSRs along a P2P LSP segment cannot perform node
protection of the tail of the P2P LSP segment.
22. Reduction in Control Plane Processing with LSP Hierarchy
It is possible to take advantage of LSP hierarchy [LSP-HIER] while
setting up P2MP LSP Tunnels, as described in the previous section, to
reduce control plane processing along transit LSRs that are P2MP
capable. This is applicable only in environments where LSP hierarchy
can be used. Transit LSRs along a P2P LSP segment, being used by a
P2MP LSP Tunnel, do not process control plane messages associated
with the P2MP LSP Tunnel. Infact they are not aware of these messages
as they are tunneled over the P2P LSP segment. This reduces the
amount of control plane processing required on these transit LSRs.
Note that the P2P LSP segments can be dynamically setup as described
in the previous section or preconfigured. For example in Figure 2,
PE1 can setup a P2P LSP to P1 and use that as a LSP segment. The Path
messages for PE3 and PE4 can now be tunneled over the LSP segment.
Thus P3 is not aware of the P2MP LSP Tunnel and does not process the
P2MP control messages.
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23. P2MP LSP Tunnel Remerging and Cross-Over
The functional description described so far assumes that multiple
Path messages received by a LSR for the same P2MP LSP Tunnel arrive
on the same incoming interface. However this may not always be the
case. Further discussion is needed for this section.
P2MP tree remerging or cross-over occurs when a transit or egress
node receives the signaling state i.e. Path message for the same P2MP
TE LSP from more than one previous hop. If the re-merged P2P sub-LSPs
are sent out on different interfaces there is no data plane issue.
However if the re-merged P2P sub-LSPs are sent out on the same
interface it can
result in data duplication downstream. In order to
describe identification of cross over and remerging by a LSR let us
list the various cases when state for a P2P sub-LSP is received by a
LSR.
Case1: P2P sub-LSP already exist as part of an existing Path state.
The following are the various sub-cases.
a) The new P2P sub-LSP uses the same PHOP and outgoing interface
as the existing P2P sub-LSP. This is either a refresh or can occur
when multiple existing Path messages are combined in a new Path
message.
b) The new P2P sub-LSP uses the same PHOP but different outgoing
interface as the existing P2P sub-LSP. This is a case of re-routing.
c) The new P2P sub-LSP uses a different PHOP and same outgoing
interface as the existing P2P sub-LSP. This is a case of re-merging.
d) The new P2P sub-LSP uses a different PHOP and a different
outgoing interface as compared to the existing P2P sub-LSP. This is a
case of cross-over.
Case2: P2P sub-LSP does not exist as part of an existing Path state.
The following are the sub-cases.
a) The new P2P sub-LSP uses a PHOP and outgoing interface that is
same as the PHOP and outgoing interface used by an existing P2P sub-
LSP. This is a legal case of signaling a new P2P sub-LSP.
b) The new P2P sub-LSP uses a PHOP that is same as that used by an
existing P2P sub-LSP. However the outgoing interface is different
from the outgoing interfaces used by existing P2P sub-LSPs. This is a
legal case of signaling a new P2P sub-LSP.
c) The new P2P sub-LSP uses a different PHOP than that used by any
of the existing P2P sub-LSP. However the outgoing interface is same
as the outgoing interface used by an existing P2P sub-LSPs. This is a
case of remerging.
d) The new P2P sub-LSP uses a different PHOP than that used by any
of the existing P2P sub-LSP. Also the outgoing interface is different
from the outgoing interfaces used by existing P2P sub-LSPs. This is a
case of cross-over.
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Cases 1(d) and 2(d) above identify cross-over and this is considered
legal. Cases 1(c) and 2(c) above identify remerging in the data
plane. If the LSR is capable of remerging in the data plane this is
considered legal.
The below procedure applies for remerging.
The remerge error case is detected by checking incoming Path messages
that represent new P2MP TE LSP state and seeing if they represent
both known LSP state and a different P2P sub-LSP list. Specifically,
the remerge check MUST be performed when processing Path messages
that contain SESSION, SENDER_TEMPLATE and RSVP_HOP objects that have
not previously been seen on a particular interface. The remerge check
consists of attempting to locate state that has the same values in
the SESSION object and in the tunnel sender address and LSP ID fields
of the SENDER_TEMPLATE object.
If no matching state is located, then there is no remerge condition.
If matching state is found, then the list of P2P Sub-LSPs associated
with the new Path message is compared against the list present in the
located state. If any addresses in the lists of P2P sub-LSPs match,
then it is the legal LSP rerouting case mentioned here above.
If there are no overlap in the lists, and the LSR is capable of
remerging in the data plane, this is considered legal. Else the new
Path message MUST be handled according to remerge error processing as
described below.
The LSR generates a PathErr message with Error Code "Routing
Problem/P2MP Remerge Detected" towards the upstream node (i.e. the
node that sent the Path message) until it reaches the node that
caused the remerge condition. Identification of the offending node
requires special processing by the nodes upstream of the error. A
node that receives a PathErr message that contains a the error
"Routing Problem/P2MP Remerge Detected" MUST check to see if it is
the offending node. This check is done by comparing the P2P sub-LSPs
listed in the PathErr message with existing LSP state. If any of the
egresses are already present in any Path state associated with the
P2MP TE LSP other than the one associated with the <SESSION,
SENDER_TEMPLATE> objects signaled in the PathErr message, then the
node is the signaling branch node that caused the remerge condition.
This node SHOULD then correct the remerge condition by adding all P2P
sub-LSPs listed in the offending Path state to the Path state (and
Path message) associated to these P2P sub-LSPs. Note that the new
Path state may be sent out the same outgoing interface in different
Path messages in order to meet IP packet size limitations. If use of
a new outgoing interface violates one or more SERO constraint, then a
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PathErr message containing the associated egresses and any identified
valid egresses SHOULD be generated with the error code "Routing
Problem" and error value of "ERO Resulted in Remerge".
This process may continue hop-by-hop until the ingress is reached.
The only case where this process will fail is when all the listed P2P
sub-LSPs are deleted prior to the PathErr message propagating to the
ingress. In this case, the whole process will be corrected on the
next (refresh or trigger) transmission of the offending Path message.
In all cases where a remerge error is not detected, normal processing
continues.
23.1. PathErr Message Format
As described above, in the case where remerging is detected, a
PathErr message will include one or more P2P_SUB_LSP objects. The
resulting modified for a PathErr Message is:
<PathErr Message> ::= <Common Header> [ <INTEGRITY> ]
[ [<MESSAGE_ID_ACK> | <MESSAGE_ID_NACK>]
... ]
[ <MESSAGE_ID> ]
<SESSION> <ERROR_SPEC>
[ <ACCEPTABLE_LABEL_SET> ... ]
[ <POLICY_DATA> ... ]
<sender descriptor>
[ <P2P sub-LSP descriptor list> ]
PathErr messages generation is unmodified, but nodes that set the
Sub-Group Originator field and propagate a received PathErr message
upstream MUST replace the Sub-Group fields received in the PathErr
message with the value that was received in the Sub-Group fields of
the Path message from the upstream neighbor. Note the receiver of a
PathErr message is able to identify the errored outgoing Path
message, and outgoing interface, based on the Sub-Group fields
received in the error message.
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24. New and Updated Message Objects
This section presents the RSVP message related formats as modified by
this document.
24.1. P2MP LSP Tunnel SESSION Object
A P2MP LSP Tunnel SESSION object is used. This object uses the
existing SESSION C-Num. New C-Types are defined to accommodate a
logical P2MP destination identifier of the P2MP Tunnel. This SESSION
object has a similar structure as the existing point to point RSVP-TE
SESSION object. However the destination address is set to the P2MP ID
instead of the unicast Tunnel Endpoint address. All P2P sub-LSPs part
of the same P2MP LSP Tunnel share the same SESSION object. This
SESSION object identifies the P2MP Tunnel.
The combination of the SESSION object, the SENDER_TEMPLATE object and
the P2P SUB-LSP object, identifies each P2P sub-LSP. This follows the
existing P2P R
SVP-TE notion of using the SESSION object for
identifying a P2P Tunnel which in turn can contain multiple LSP
Tunnels, each distinguished by a unique SENDER_TEMPLATE object.
24.1.1. P2MP IPv4 LSP SESSION Object
Class = SESSION, P2MP_LSP_TUNNEL_IPv4 C-Type = TBD
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| P2MP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MUST be zero | Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
P2MP ID
A 32-bit identifier used in the SESSION object that remains
constant over the life of the P2MP tunnel. It encodes the
P2MP ID and identifies the set of destinations of the P2MP
LSP Tunnel.
Tunnel ID
A 16-bit identifier used in the SESSION object that remains
constant over the life of the P2MP tunnel.
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Extended Tunnel ID
A 32-bit identifier used in the SESSION object that remains
constant over the life of the P2MP tunnel. Normally set to
all zeros. Ingress nodes that wish to narrow the scope of a
SESSION to the ingress-PID pair may place their IPv4 address
here as a globally unique identifier [RFC3209].
24.1.2. P2MP IPv6 LSP SESSION Object
This is same as the P2MP IPv4 LSP SESSION Object with the difference
that the extended tunnel ID may be set to a 16 byte identifier
[RFC3209].
24.2. SENDER_TEMPLATE object
The sender template contains the ingress-LSR source address. LSP ID
can be can be changed to allow a sender to share resources with
itself. Thus multiple instances of the P2MP tunnel can be created,
each with a different LSP ID. The instances can share resources with
each other, but use different labels. The P2P sub-LSPs corresponding
to a particular instance use the same LSP ID.
As described in section 6.1 it is necessary to distinguish different
Path messages that are used to signal state for the same P2MP LSP
Tunnel by using a <Sub-Group ID Originator ID, Sub-Group ID> tuple.
There are various methods to encode this information. This document
proposes the use of the SENDER_TEMPLATE object and modifies it to
carry this information as shown below. This encoding is subject to
review by the MPLS WG.
24.2.1. P2MP IPv4 LSP Tunnel SENDER_TEMPLATE Object
Class = SENDER_TEMPLATE, P2MP_LSP_TUNNEL_IPv4 C-Type = TBD
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 tunnel sender address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | LSP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Sub-Group Originator ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Sub-Group ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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IPv4 tunnel sender address
See [RFC3209]
Sub-Group Originator ID
The Sub-Group Originator ID is set to the TE Router ID of
the LSR that originates the Path message. This is either the
ingress LSR or a LSR which re-originates the Path message
with its own Sub-Group Originator ID.
Sub-Group ID
An identifier of a Path message used to differentiate
multiple Path messages that signal state for the same P2MP
LSP. This may be seen as identifying a group of one or more
egress nodes targeted by this Path message. If the third
mechanism for pruning is used as described in section 11,
the Sub-Group ID value of zero (0) has special meaning and
MUST NOT be used with P2MP LSP Tunnels in messages other
than PathTear messages. Use of a Sub-Group ID value of zero
(0) in PathTear messages is defined below.
LSP ID
See [RFC3209]
24.2.2. P2MP LSP Tunnel IPv6 SENDER_TEMPLATE Object
Class = SENDER_TEMPLATE, P2MP_LSP_TUNNEL_IPv6 C-Type = TBD
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| IPv6 tunnel sender address |
+ +
| (16 bytes) |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | LSP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| Sub-Group Originator ID |
+ +
| (16 bytes) |
+ +
| |
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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Sub-Group ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv6 tunnel sender address
See [RFC3209]
Sub-Group Originator ID
The Sub-Group Originator ID is set to the IPv6 TE Router ID
of the LSR that originates the Path message. This is either
the ingress LSR or a LSR which re-originates the Path
message with its own Sub-Group Originator ID.
Sub-Group ID
As above.
LSP ID
See [RFC3209]
24.3. P2P SUB-LSP IPv4 Object
A new P2P Sub-LSP object identifies a particular P2P sub-LSP
belonging to the P2MP LSP Tunnel.
24.3.1. P2P SUB-LSP IPv4 Object
SUB_LSP Class = TBD, P2P_SUB_LSP_IPv4 C-Type = TBD
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 P2P Sub-LSP destination address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MUST be zero | Sub-LSP
ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPv4 Sub-LSP destination address
IPv4 address of the P2P sub-LSP destination.
(There is NO-CONSENSUS amongst the authors on the sub-LSP ID
described below and it needs more discussion)
Sub-LSP ID
A 16-bit identifier that identifies a particular instance
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of a P2P sub-LSP. It can be varied for P2P sub-LSP
make-before-break. Different P2P sub-LSPs, with the same SESSION
object and LSP ID, follow the label merge semantics described in
section 3 to form a particular instance of the P2MP tunnel.
24.3.2. P2P SUB-LSP IPv6 Object
SUB_LSP Class = TBD, P2P_SUB_LSP_IPv6 C-Type = TBD
This is same as the P2P IPv4 Sub-LSP object, with the difference that
the destination address is a 16 byte IPv6 address.
24.4. FILTER_SPEC Object
The FILTER_SPEC object is canonical to the P2MP SENDER_TEMPLATE
object.
24.4.1. P2MP LSP_TUNNEL_IPv4 FILTER_SPEC Object
Class = FILTER SPEC, P2MP LSP_TUNNEL_IPv4 C-Type = TBD
The format of the P2MP LSP_TUNNEL_IPv4 FILTER_SPEC object is
identical to the P2MP LSP_TUNNEL_IPv4 SENDER_TEMPLATE object.
24.4.2. P2MP LSP_TUNNEL_IPv4 FILTER_SPEC Object
Class = FILTER SPEC, P2MP LSP_TUNNEL_IPv6 C_Type = TBD
The format of the P2MP LSP_TUNNEL_IPv6 FILTER_SPEC object is
identical to the P2MP LSP_TUNNEL_IPv6 SENDER_TEMPLATE object.
24.5. SUB_EXPLICIT_ROUTE Object (SERO)
The SERO is defined as identical to the ERO. The CNums are TBD and
TBD of the form 11bbbbbb.
24.6. SUB_RECORD_ROUTE Object (SRRO)
The SRRO is defined as identical to the RRO. The CNums are TBD and
TBD of the form 11bbbbbb.
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25. IANA Considerations
25.1. New Message Objects
IANA considerations for new message objects will be specified after
the objects used are decided upon.
25.2. New Error Codes
Two new Error Codes are defined for use with the Error Value "Routing
Error". IANA is requested to assign values.
The Error Code "Unable to Branch" indicates that a P2MP branch cannot
be formed by the reporting LSR.
The Error Code "Unsupported LSP Integrity" indicates that a P2MP
branch does not support the requested LSP integrity function.
25.3. LSP Attributes Flags
IANA has been asked to manage the space of flags in the Attibutes
Flags TLV carried in the LSP_ATTRIBUTES Object [LSP-ATTRIB]. This
document defines two new flags as follows:
Suggested Bit Number: 3
Meaning: LSP Integrity Required
Used in Attributes Flags on Path: Yes
Used in Attributes Flags on Resv: No
Used in Attributes Flags on RRO: No
Referenced Section of this Doc: 16
Suggested Bit Number: 4
Meaning: Branch Reoptimization Allowed
Used in Attributes Flags on Path: Yes
Used in Attributes Flags on Resv: No
Used in Attributes Flags on RRO: No
Referenced Section of this Doc: 17.3
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26. Security Considerations
This document does not introduce any new security issues. The
security issues identified in [RFC3209] and [RFC3473] are still
relevant.
27. Acknowledgements
This document is the product of many people. The contributors are
listed in Section 26.
Thanks to Yakov Rekhter, Der-Hwa Gan, Arthi Ayyanger and Nischal
Sheth for their suggestions and comments. Thanks also to Dino
Farninacci for his comments.
28. Appendix
28.1. Example
Following is one example of setting up a P2MP LSP Tunnel using the
procedures described in this document.
Source 1 (S1)
|
PE1
| |
|L5 |
P3 |
| |
L3 |L1 |L2
R2----PE3--P1 P2---PE2--Receiver 1 (R1)
| L4
PE5----PE4----R3
|
|
R4
Figure 2.
The mechanism is explained using Figure 2. PE1 is the ingress-LSR.
PE2, PE3 and PE4 are Egress-LSRs.
a) PE1 learns that PE2, PE3 and PE4 are interested in joining a P2MP
tree with a P2MP ID of P2MP ID1. We assume that PE1 learns of the
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egress-LSRs at different points.
b) PE1 computes the P2P path to reach PE2.
c) PE1 establishes the P2P sub-LSP to PE2 along <PE1, P2, PE2>
d) PE1 computes the P2P path to reach PE3 when it discovers PE3. This
path is computed to share the same links where possible with the sub-
LSP to PE2 as they belong to the same P2MP session.
e) PE1 establishes the P2P sub-LSP to PE3 along <PE1, P3, P1, PE3>
f) PE1 computes the P2P path to reach PE4 when it discovers PE4. This
path is computed to share the same links where possible with the sub-
LSPs to PE2 and PE3 as they belong to the same P2MP session.
g) PE1 signals the Path message for PE4 sub-LSP along <PE1, P3, P1,
PE4>
e) P1 receives a Resv message from PE4 with label L4. It had
previously received a Resv message from PE3 with label L3. It had
allocated a label L1 for the sub-LSP to PE3. It uses the same label
and sends the Resv messages to P3. Note that it may send only one
Resv message with multiple flow descriptors in the flow descriptor
list. If this is the case and FF style is used, the FF flow
descriptor will contain the P2P sub-LSP descriptor list with two
entries: one for PE4 and the other for PE3. For SE style, the SE
filter spec will contain this P2P sub-LSP descriptor list. P1 also
creates a label mapping of (L1 -> {L3, L4}). P3 uses the existing
label L5 and sends the Resv message to PE1, with label L5. It reuses
the label mapping of {L5 -> L1}.
29. References
29.1. Normative References
[LSP-HIER] K. Kompella, Y. Rekhter, "LSP Hierarchy with Generalized
MPLS TE", draft-ietf-mpls-lsp-hierarchy-08.txt.
[LSP-ATTR] A. Farrel, et. al. , "Encoding of
Attributes for Multiprotocol Label Switching (MPLS)
Label Switched Path (LSP) Establishment Using RSVP-TE",
draft-ietf-mpls-rsvpte-attributes-03.txt, March 2004,
work in progress.
[RFC3209] D. Awduche, L. Berger, D. Gan, T. Li, V. Srinivasan,
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Internet Draft draft-ietf-mpls-rsvp-te-p2mp-00.txt November 2004
G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels",
RFC3209, December 2001
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2205] Braden, R., Zhang, L., Berson, S., Herzog, S. and S. Jamin,
"Resource ReSerVation Protocol (RSVP) -- Version 1,
Functional Specification", RFC 2205, September 1997.
[RFC3471] Lou Berger, et al., "Generalized MPLS - Signaling Functional
Description", RFC 3471, January 2003
[RFC3473] L. Berger et.al., "Generalized MPLS Signaling - RSVP-TE
Extensions", RFC 3473, January 2003.
[RFC2961] L. Berger, D. Gan, G. Swallow, P. Pan, F. Tommasi,
S. Molendini, "RSVP Refresh Overhead Reduction Extensions",
RFC 2961, April 2001.
[RFC3031] Rosen, E., Viswanathan, A. and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001.
[RSVP-FRR] P. Pan, G. Swallow, A. Atlas (Editors), "Fast Reroute Extensions
to RSVP-TE for LSP Tunnels",
draft-ietf-mpls-rsvp-lsp-fastreroute-07.txt.
[RFC3477] K. Kompella, Y. Rekther, "Signalling Unnumbered Links in
Resource ReSerVation Protocol - Traffic Engineering (RSVP-TE)".
29.2. Informative References
[BFD] D. Katz, D. Ward, "Bidirectional Forwarding Detection",
draft-katz-ward-bfd-01.txt.
[BFD-MPLS] R. Aggarwal, K. Kompella, "BFD for MPLS LSPs",
draft-raggarwa-mpls-bfd-00.txt
[IPR-1] Bradner, S., "IETF Rights in Contributions", BCP 78,
RFC 3667, February 2004.
[IPR-2] Bradner, S., Ed., "Intellectual Property Rights in IETF
Technology", BCP 79, RFC 3668, February 2004.
[INT-REG] JP Vasseur, A. Ayyangar, "Inter-area and Inter-AS MPLS Traffic
Engineering", draft-vasseur-ccamp-inter-area-as-te-00.txt.
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Internet Draft draft-ietf-mpls-rsvp-te-p2mp-00.txt November 2004
[P2MP-REQ] S. Yasukawa, et. al., "Requirements for Point-to-Multipoint
capability extension to MPLS",
draft-ietf-mpls-p2mp-requirement-04.txt.
[RFC2209] R. Braden, L. Zhang, "Resource Reservation Protocol (RSVP)
Version 1 Message Processing Rules", RFC 2209.
30. Author Information
30.1. Editor Information
Rahul Aggarwal
Juniper Networks
1194 North Mathilda Ave.
Sunnyvale, CA 94089
Email: rahul@juniper.net
Seisho Yasukawa
NTT Corporation
9-11, Midori-Cho 3-Chome
Musashino-Shi, Tokyo 180-8585 Japan
Phone: +81 422 59 4769
EMail: yasukawa.seisho@lab.ntt.co.jp
Dimitri Papadimitriou
Alcatel
Francis Wellesplein 1,
B-2018 Antwerpen, Belgium
Phone: +32 3 240-8491
Email: Dimitri.Papadimitriou@alcatel.be
30.2. Contributor Information
John Drake
Calient Networks
Email: jdrake@calient.net
Alan Kullberg
Motorola Computer Group
120 Turnpike Road 1st Floor
Southborough, MA 01772
EMail: alan.kullberg@motorola.com
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Lou Berger
Movaz Networks, Inc.
7926 Jones Branch Drive
Suite 615
McLean VA, 22102
Phone: +1 703 847-1801
EMail: lberger@movaz.com
Liming Wei
Redback Networks
350 Holger Way
San Jose, CA 95134
Email: lwei@redback.com
George Apostolopoulos
Redback Networks
350 Holger Way
San Jose, CA 95134
Email: georgeap@redback.com
Kireeti Kompella
Juniper Networks
1194 N. Mathilda Ave
Sunnyvale, CA 94089
Email: kireeti@juniper.net
George Swallow
Cisco Systems, Inc.
300 Beaver Brook Road
Boxborough , MA - 01719
USA
Email: swallow@cisco.com
JP Vasseur
Cisco Systems, Inc.
300 Beaver Brook Road
Boxborough , MA - 01719
USA
Email: jpv@cisco.com
Dean Cheng
Cisco Systems Inc.
170 W Tasman Dr.
San Jose, CA 95134
Phone 408 527 0677
Email: dcheng@cisco.com
Markus Jork
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Avici Systems
101 Billerica Avenue
N. Billerica, MA 01862
Phone: +1 978 964 2142
EMail: mjork@avici.com
Hisashi Kojima
NTT Corporation
9-11, Midori-Cho 3-Chome
Musashino-Shi, Tokyo 180-8585 Japan
Phone: +81 422 59 6070
EMail: kojima.hisashi@lab.ntt.co.jp
Andrew G. Malis
Tellabs
2730 Orchard Parkway
San Jose, CA 95134
Phone: +1 408 383 7223
Email: Andy.Malis@tellabs.com
Koji Sugisono
NTT Corporation
9-11, Midori-Cho 3-Chome
Musashino-Shi, Tokyo 180-8585 Japan
Phone: +81 422 59 2605
EMail: sugisono.koji@lab.ntt.co.jp
Masanori Uga
NTT Corporation
9-11, Midori-Cho 3-Chome
Musashino-Shi, Tokyo 180-8585 Japan
Phone: +81 422 59 4804
EMail: uga.masanori@lab.ntt.co.jp
Igor Bryskin
Movaz Networks, Inc.
7926 Jones Branch Drive
Suite 615
McLean VA, 22102
Adrian Farrel
Old Dog Consulting
Phone: +44 0 1978 860944
EMail: adrian@olddog.co.uk
Jean-Louis Le Roux
France Telecom
2, avenue Pierre-Marzin
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22307 Lannion Cedex
France
E-mail: jeanlouis.leroux@francetelecom.com
31. Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
32. Full Copyright Statement
Copyright (C) The Internet Society (2004). This document is subject
to the rights, licenses and restrictions contained in BCP 78 and
except as set forth therein, the authors retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUNG BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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33. Acknowledgement
Funding for the RFC Editor function is currently provided by the
Internet Society.
draft-ietf-mpls-rsvp-te-p2mp-00.txt [Page 45]
