MPLS Working Group L. Jin
Internet-Draft ZTE Corporation
Intended status: Standards Track F. Jounay
Expires: November 8, 2012 France Telecom
M. Bhatia
Alcatel-Lucent
May 7, 2012
Extensions to Resource Reservation Protocol - Traffic Engineering
(RSVP-TE) for Hub and Spoke Multipoint Label Switched Paths (LSPs)
draft-jjb-mpls-rsvp-te-hsmp-lsp-01
Abstract
In Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS)
environment, the RSVP-TE based Point-to-Multipoint (P2MP) LSP allows
traffic to transmit from root to leaf node, but there is no co-routed
reverse path for traffic from leaf to root node. This draft
introduces a Hub and Spoke Multipoint (HSMP) LSP, which allows
traffic from both the root to the leaves through a P2MP LSP and also
the leaves to the root along a co-routed reverse path.
Status of this Memo
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This Internet-Draft will expire on November 8, 2012.
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Table of Contents
1. Application . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Time Synchronization . . . . . . . . . . . . . . . . . . . 3
1.2. P2MP Pseudowire based L2VPNs (VPMS and VPLS) . . . . . . . 4
2. Comparing Hub-Spoke MP LSP with P2MP and Unidirectional
Reverse LSP . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Number of Path and Resv State Blocks . . . . . . . . . . . 5
2.2. Hardware Programming and Label Utilization . . . . . . . . 6
2.3. RSVP Control Traffic . . . . . . . . . . . . . . . . . . . 7
3. Setting up a Hub and Spoke Multipoint LSP with RSVP-TE . . . . 7
3.1. Hub and Spoke Multipoint LSP and Path Messages . . . . . . 7
3.2. Procedures for Hub and Spoke Multipoint LSP . . . . . . . 7
3.3. Symmetric Bandwidth Allocation . . . . . . . . . . . . . . 8
3.4. Asymmetric bandwidth allocation . . . . . . . . . . . . . 8
3.4.1. Packet Format . . . . . . . . . . . . . . . . . . . . 9
3.4.2. UPSTREAM_FLOWSPEC processing . . . . . . . . . . . . . 10
3.4.3. UPSTREAM_TSPEC and UPSTREAM_ADSPEC processing . . . . 10
4. Setting up the Hub Spoke Multipoint LSP . . . . . . . . . . . 10
5. Grafting . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
6. Pruning . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
7. Refresh Reduction . . . . . . . . . . . . . . . . . . . . . . 13
8. Fast Reroute . . . . . . . . . . . . . . . . . . . . . . . . . 13
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
10. Security Considerations . . . . . . . . . . . . . . . . . . . 14
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
12.1. Normative References . . . . . . . . . . . . . . . . . . . 14
12.2. Informative References . . . . . . . . . . . . . . . . . . 14
Appendix 1. Appendix: Alternate Mechanism to set up a reverse
LSP . . . . . . . . . . . . . . . . . . . . . . . . . 15
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15
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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 RFC2119 [RFC2119].
When used in lower case, these words convey their typical use in
common language, and are not to be interpreted as described in
RFC2119 [RFC2119].
1. Application
The proposed technique targets one-to-many applications that require
reverse one-to-one traffic flow (thus many one-to-one in the reverse
direction).
There are a few applications that could use such kind of Resource
Reservation Protocol - Traffic Engineering (RSVP-TE) based Hub and
Spoke Multipoint LSPs.
1.1. Time Synchronization
The delivery of time synchronization to end equipments, such as base
stations, can be achieved using a time protocol as [IEEE] (also known
as PTP). This protocol defines Transparent Clock (TC) function,
which can be used in transport nodes to improve the accuracy of time
synchronization. Two types of TCs exist in [IEEE]: End-to-end
Transparent Clock (E2E TC) and Peer-to-peer Transparent Clock (P2P
TC). P2P TCs assume that the link delays between the different nodes
are calculated
Assuming that a chain of P2P TCs is used between a PTP master and a
PTP slave, time synchronization can be delivered to the PTP slave by
sending timestamps only in the direction master to slave (one way
mode), via PTP Sync messages. This is possible because of the link
delay calculation performed locally by each node, which enables it to
calculate the propagation delay over the path. This scenario permits
that the same PTP Sync messages would be sent by the PTP master to
all the PTP slaves.
In this scenario (chain of P2P TCs), the PTP slave might have to send
also messages (not carrying timestamps) back to the PTP master in
some cases. For instance, PTP Signaling messages could be sent back
to the PTP master. These PTP Signaling messages are not intended to
be received by the other PTP slaves.
By using Point-to-Multipoint (P2MP) technology to transmit PTP Sync
messages will greatly improve the bandwidth usage for above
applications. This will also be useful for monitoring performance
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metrics for two-way delay and related metrics such as delay variation
and loopback measurement. Current RSVP-TE based Point-to-Multipoint
LSP mechanism only provides unidirectional path from the root to the
leaf nodes, which cannot fulfill the above new requirement (i.e. need
for a reverse path for the PTP Signaling messages).
This draft attempts to solve this problem. RSVP-TE based Hub and
Spoke P2MP LSP described in this draft provides a co-routed reverse
path from the leaf to the root based on current unidirectional Point-
to-Multipoint LSP.
1.2. P2MP Pseudowire based L2VPNs (VPMS and VPLS)
Point-to-Multipoint (P2MP) Pseudowires (PW) described in
[I-D.ietf-pwe3-p2mp-pw] requires an additional reverse LSP to be set
up from the leaf node (referred as egress PE) to root node (referred
as ingress PE). Instead, if HSMP LSP is used to multiplex P2MP PW,
the reverse path can also be multiplexed to HSMP upstream path to
avoid setting up an independent reverse path. In that case, the
operational cost will be reduced for maintaining only one HSMP LSP,
instead of P2MP LSP and n (number of leaf nodes) P2P reverse LSPs
The VPMS defined in [I-D.ietf-l2vpn-vpms-frmwk-requirements] requires
reverse path from the leaf to the root node. The P2MP PW multiplexed
to HSMP LSP can provide VPMS with reverse path, without introducing
independent reverse paths from each leaf to the root.
The P2MP PW multiplexed to HSMP LSP can also be used for VPLS
[RFC4672], which will reduce the overall broadcast/multicast
utilization for VPLS. In current VPLS implementations with a full
mesh of P2P LSPs between PEs, broadcast, unknown and multicast (BUM)
traffic is efficiently distributed over the physical links between
Provider (P) and Provider Edge (PE) routers.
[I-D.ietf-l2vpn-vpls-mcast] and
[I-D.ietf-l2vpn-ldp-vpls-broadcast-exten] leverages this constraint
by introducing the usage of P2MP PW and/or P2MP LSP. But a specific
P2P PW over P2P LSP is still needed for unicast traffic between the
PEs.
In the VPLS implementation scenario with P2MP PW multiplexed to HSMP
LSPs, each PE signals a P2MP PW with itself as a root to all other
PEs in the VPLS. Thereafter, all BUM traffic from this PE will use
this P2MP PW. Unicast (learnt) traffic from a particular PE (e.g.
PE1) to another PE (e.g. PE2) will be sent from leaf to root using
the reverse path of P2MP PW where PE2 is the root.
This simplifies the VPLS implementation by reducing (a) link
utilization for the BUM traffic and (b) the total number of LSPs
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maintained by each PE (i.e. instead of requiring a full mesh of LSPs,
PEs now only require one HSMP LSP). It also helps in avoiding the
unnecessary MAC learning that happens on the hub PE routers in case
of H-VPLS.
2. Comparing Hub-Spoke MP LSP with P2MP and Unidirectional Reverse LSP
An HSMP LSP provides a Point-to-Multipoint reachability from the root
node to the leaf nodes and a unicast reachability from all the leaf
nodes back to the root node. An obvious question that comes up is
that how is this better than setting up a P2MP LSP from a root node
and Unidirectional reverse LSPs back from the leaves to the root
node. This section compares the two mechanisms and demonstrates how
establishing one HSMP LSP is better than establishing a P2MP LSP with
reverse LSPs from the leaves back to the root.
Consider the topology as shown in Figure 1. Router A wants to
establish a Point-to-Multipoint connectivity to Routers E, F, G and H
and also wants a Unicast path back from these routers to itself.
There are two ways to accomplish this. In the first, we set up a
HSMP LSP between A, E, F, G and H. In the second, we set up a P2MP
LSP between A, E, F, G and H and establish regular LSPs back from
these routers to A.
A
|
B
/ \
C D
/ \ / \
E F G H
Figure 1
2.1. Number of Path and Resv State Blocks
When an RSVP-capable router receives an initial Path message, it
creates a path state block (PSB) for that particular session. Each
PSB consists of parameters derived from the received Path message
such as SESSION, SENDER_TEMPLATE, SENDER_TSPEC, RSVP_HOP objects, and
the outgoing interface provided by the IGP routing. Similarly, as a
Resv message travels upstream toward the sender, it creates a
reservation state block (RSB) in each RSVP-capable node along the way
which stores information derived from the objects in the received
Resv message, such as SESSION, RSVP_HOP, FLOWSPEC, FILTERSPEC, STYLE,
etc objects. The PSB and the RSB need to be periodically refreshed
by the Path and the Resv messages.
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In case of HSMP LSP, the number of PSBs and the RSBs is the same as
that for establishing a single P2MP LSP and is a function of how the
P2MP LSP is signaled. It is equal to the number of S2L sub-LSPs of
the P2MP LSP if each S2L sub-lsp is signaled independently. It is
one, if an aggregated mode is used where multiple sub-lsps of the
P2MP LSP are signaled togethar.
In the second case routers need to maintain this state for the P2MP
LSP and all the Unidirectional LSPs that go via it.
Lets look at the state that branch node B needs to maintain. In case
of HSMP LSP it is the same as a P2MP LSP. In the other approach it
needs to maintain state for the following LSPs:
1. P2MP LSP from A and E, F, G and H
2. Reverse LSP ECBA
3. Reverse LSP FCBA
4. Reverse LSP GDBA
5. Reverse LSP HDBA
We can thus clearly see that the amount of state that routers need to
maintain in the second approach is much more than the HSMP LSP. It
becomes all the more pronounced when the P2MP LSP is signalled using
the aggregated approach described in [RFC4875] where a single Path
and Resv message is used to signal the entire P2MP LSP. In such
cases the amount of state that such branch nodes need to maintain
increase linearly with the leaf nodes that get added to the P2MP LSP.
2.2. Hardware Programming and Label Utilization
In the HSMP LSP the LSR B advertises the same (upstream) label to C
and D, thus consumes only one label and needs to only program one
entry in the ILM table.
In the second approach, LSR B needs to advertise two different labels
to LSRs C and D and will thus consume 2 ILM entries in HW.
We can clearly see that the number of labels consumed in the second
approach will increase linearly with the amount of branching that
happens on that LSR. It will further aggravate as the number of P2MP
LSPs increase.
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2.3. RSVP Control Traffic
In the second approach, LSR B will have RSVP control traffic for the
P2MP LSP and all the Unidirectional reverse LSPs that pass through
it. In case of HSMP LSR B will only have the RSVP traffic for the
P2MP LSP.
3. Setting up a Hub and Spoke Multipoint LSP with RSVP-TE
The Hub and Spoke Multipoint LSP comprises of one downstream
unidirectional P2MP LSP from ingress LSR to each of egress LSR, and a
co-routed upstream path from each of egress LSR to ingress LSR.
[RFC3473] describes a point-to-point bidirectional LSP mechanism for
the GMPLS architecture, where a bidirectional LSP setup is indicated
by the presence of an Upstream_Label object in the Path message. The
Upstream_Label object has the same format as the generalized label,
and uses Class-Number 35 (of form 0bbbbbbb) and the C-Type of the
label being used. Hub and Spoke Multipoint LSP describe in this
draft will use similar mechanism, and reuse the Upstream_Label object
defined in [RFC3473]. Note: the downstream label assignment is still
applied, and upstream direction is based on the h&s topology (hub =
upstream, spoke= downstream), rather on forwarding direction.
3.1. Hub and Spoke Multipoint LSP and Path Messages
[RFC4875] allows a P2MP LSP to be signaled using one or more Path
messages . Each Path message may signal one or more source to leaf
(S2L) sub-LSPs. This document assumes that a unique Path message is
being used to signal each individual sub-LSP of the HSMP LSP. Later
versions of this document can describe mechanisms to use a single
Path message to describe each component sub LSP of the HSMP LSP.
3.2. Procedures for Hub and Spoke Multipoint LSP
The process of establishing a Hub and Spoke Multipoint LSP follows
the establishment of a unidirectional P2MP LSP define in [RFC4875]
with some additions. To support Hub and Spoke Multipoint LSPs an
Upstream_Label object is added to the Path message. The
Upstream_Label object MUST indicate a label that is valid for
forwarding at the time the Path message is sent. When a Path message
containing an Upstream_Label object is received, the receiver first
verifies that the upstream label is acceptable. If the label is not
acceptable, the receiver MUST issue a PathErr message with a "Routing
problem/Unacceptable label value" indication.
The generated PathErr message MAY include an Acceptable Label Set
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defined in [RFC3473] section 4.1.
The transit node must also allocate one label for the co-routed
upstream path before propagating the Path message to all downstream
nodes. If a transit node is unable to allocate a label or internal
resources, then it MUST issue a PathErr message with a "Routing
problem/MPLS label allocation failure" indication. With regards to
the co-routed return path from the leafs to the root, the forwarding
table on transit node will have one incoming labels allocated for all
of the outgoing interfaces, and one outgoing label received from
Upstream_Label object in Path message sent by upstream node. That
means the traffic from different egress LSRs will be merged at each
transit node, and will be sent together to upstream node, see section
3.3 for more detail of bandwidth guarantee in this case.
The Path messages sending downstream with same [P2MP ID, Tunnel ID,
Extended Tunnel ID] tuple as part of the SESSION object and the
[Tunnel Sender Address, LSP ID] tuple as part of the SENDER_TEMPLATE
object, but may different [Sub-Group Originator ID, Sub-Group ID]
MUST use same allocated label value for Upstream_Label object.
Leaf nodes process Path messages as usual, with the exception that
the upstream label should be used to transport data traffic
associated with the Hub and Spoke Multipoint LSP upstream towards the
root node.
When a Hub and Spoke Multipoint LSP is removed, both upstream and
downstream labels are invalidated and it is no longer valid to send
data using the associated labels.
3.3. Symmetric Bandwidth Allocation
The bandwidth allocation for upstream path from leaf to root could be
same as the downstream path from root to leaf node [RFC3473], and the
bandwidth will be guarantee only when there is no traffic merging
happened on transit node. If there are cases where leaf nodes send
traffic to root node at the same time which may cause traffic to be
merged on one physical link at transit node, then traffic overload
may happen on these links.
3.4. Asymmetric bandwidth allocation
There are several casse to require asymmetric bandwidth allocation
for HSMP LSP. For example, when HSMP LSP is used in VPLS
application, each leaf node may send reverse traffic to root node at
the same time. The reverse path bandwidth allocation MUST fullfill
the traffic requirement, with the assumption that traffic from all
leaf nodes will be merged at each link. Some applications may not
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require bandwidth guarantee for the upstream path from leaf to root
(only use reverse path for signaling), then it is not necessary to
allocate bandwidth for the upstream path.
The mechanism of allocating asymmetric bandwidth for point-to-point
link is described in[I-D.ietf-ccamp-asymm-bw-bidir-lsps-bis], and
this draft will have some extension to support asymmetric bandwidth
allocation for HSMP LSP.
Each S2L sub-LSP should have its own traffic bandwidth requirement
for the reverse path of HSMP LSP, and the S2L sub-LSP should carry
the bandwidth information.
3.4.1. Packet Format
The sender descriptor in path message is modified as follows to add
bandwidth information to each S2L sub-LSPs.
<sender descriptor> ::= <SENDER_TEMPLATE> <SENDER_TSPEC>
[ <ADSPEC> ]
[ <RECORD_ROUTE> ]
[ <SUGGESTED_LABEL> ]
[ <RECOVERY_LABEL> ]
<UPSTREAM_LABEL>
<UPSTREAM_FLOWSPEC>
S2L sub-LSP descriptor list in path message should have the following
format.
<S2L sub-LSP descriptor list> ::= <S2L sub-LSP descriptor>
[ <S2L sub-LSP descriptor list> ]
<S2L sub-LSP descriptor> ::= <S2L_SUB_LSP>
[ <P2MP SECONDARY_EXPLICIT_ROUTE> ]
<UPSTREAM_FLOWSPEC>
FF flow descriptor in resv message is modified as follows to add
bandwidth information to each S2L sub-LSPs.
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<FF flow descriptor> ::= [ <FLOWSPEC> ]
[ <UPSTREAM_TSPEC>] [ <UPSTREAM_ADSPEC> ]
<FILTER_SPEC> <LABEL>
[ <RECORD_ROUTE> ]
[ <S2L sub-LSP flow descriptor list> ]
<S2L sub-LSP flow descriptor list> ::=
<S2L sub-LSP flow descriptor>
[ <S2L sub-LSP flow descriptor list> ]
<S2L sub-LSP flow descriptor> ::= <S2L_SUB_LSP>
[ <P2MP_SECONDARY_RECORD_ROUTE> ]
[ <UPSTREAM_TSPEC>] [ <UPSTREAM_ADSPEC> ]
3.4.2. UPSTREAM_FLOWSPEC processing
The Path message of an asymmetric bandwidth HSMP LSP MUST contain an
UPSTREAM_FLOWSPEC object defined
in[I-D.ietf-ccamp-asymm-bw-bidir-lsps-bis]. Nodes processing a Path
message containing an UPSTREAM_FLOWSPEC object MUST allocate the
upstream bandwidth with the sum of bandwidth of all S2L sub-LSP
traversing this node. A node that is unable to allocate the internal
resources based on the contents of the UPSTREAM_FLOWSPEC object MUST
issue a PathErr message with a "Routing problem/MPLS label allocation
failure" indication.
3.4.3. UPSTREAM_TSPEC and UPSTREAM_ADSPEC processing
The process of UPSTREAM_TSPEC and UPSTREAM_ADSPEC Object is same as
defined in[I-D.ietf-ccamp-asymm-bw-bidir-lsps-bis].
When an UPSTREAM_TSPEC object is received by the root node, the root
MAY determine that the original reservation is insufficient to
satisfy the traffic flow. In this case, the root MAY require the LSP
to be re-routed, and in extreme cases might result in the LSP being
torn down when sufficient resources are not available.
4. Setting up the Hub Spoke Multipoint LSP
The Following is an example of establishing a HSMP LSP using the
procedures described in the previous sections.
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Receiver
|
|
PE2 PE3 --- Receiver
| |
P1 -- P3
/
Source --- PE1
\
P2 -- PE5 --- Receiver
|
PE4 --- Receiver
Figure 2
The mechanism is explained using Figure 1. PE1 is a root LER (head
end) node. PE2, PE3, PE4 and PE5 are the leaf LER nodes. P1 and P2
are branch LSR nodes and P3 is a plain LSR node.
1. PE1 learns that PE2, PE3, PE4 and PE5 are interested in joining a
HSMP tree with a P2MP ID of P2MP ID1. We assume that PE1 learns
of the egress LERs at different points in time.
2. PE1 computes the P2P path to reach PE3 and sends a Path message
with ERO [PE1, P1, P3, PE3]. It also provides an Upstream Label
UL1 in the Upstream_Label object that P1 should use when
forwarding packets to PE1.
3. The Path message traverses hop-by-hop and finally reaches PE3.
Assume that the Path message from P1 to P3 uses upstream label of
UL3, in which case P1 must program the ILM to swap UL3 with UL1.
The Path message from P3 to PE3 uses upstream label UL4, and thus
P3 programs the ILM to swap UL4 with UL3.
4. PE3 responds with a Resv message that contains label L4, that P3
should use when forwarding packets to PE3. Similarly, the Resv
from P3 to P1 contains label L3, that P1 should use when
forwarding packets to P3.
5. Similarly when setting up the component sub-LSP from PE1 to PE2,
PE1 will use the same Upstream label UL1 as it knows that this
sub-LSP belongs to the same HSMP LSP because of the same P2MP
session object that both sub-LSPs carry.
6. The Path message, thus for this component sub-LSP goes with ERO
[PE1, P1, PE2] along with the Upstream label UL1 that P1 should
use when forwarding packets to PE1.
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7. P1 forwards the Path message with a new Upstream label UL2.
Finally, PE2 sends a Resv message containing label L2, that P1
should use when forwarding packets to PE2. P1 also understands
that the Resv messages from PE2 and PE3 refer to the same HSMP
LSP, because of the P2MP Session Object carried in each. [
8. P1 sends a separate Resv message to PE1 corresponding to each of
the sub-LSPs, but uses the same label L1 since the two sub LSPs
belong to the same HSMP LSP.
9. The other component sub LSPs are set up in a similar way as
described above.
5. Grafting
The operation of adding leaf LER(s) to an existing HSMP LSP is termed
grafting. This operation allows leaf nodes to join a HSMP LSP at
different points in time.
The leaf LER(s) can be added by signaling only the impacted component
sub- LSPs in a new Path message. Hence, the existing component sub-
LSPs do not have to be re-signaled.
Receiver
|
|
PE2 PE3 --- Receiver
| |
P1 -- P3 -- P6 -- PE6 --- Receiver
/
Root --- PE1
\
P2 -- PE5 --- Receiver
|
PE4 --- Receiver
Figure 3
Assume PE1 needs to set up another sub-LSP from PE1 to PE6. Being a
part of the same HSMP LSP, PE1 MUST advertise the same Upstream Label
to P1 in its Path message. P1 advertises the same Upstream Label to
P3. P3 when sending the Path message to P6 would advertise a fresh
Upstream label and similarly P6 would use a new upstream label when
forwarding the Path message to PE6.
PE6 sends a Resv message with a label back to P6. P6, would send a
new label back to P3. P3 because of this new component sub-LSP (PE1-
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PE6) is now a branch LSR node that performs MPLS multicast
replication.
6. Pruning
The operation of removing egress LER nodes from an existing HSMP LSP
is termed as pruning. This operation allows leaf nodes to be removed
from a HSMP LSP at different points in time. This section describes
the mechanisms to perform pruning.
Assume that the LER PE6 wants to be removed from the HSMP LSP. Since
we used a unique Path message for each component sub LSP, the
teardown will rely on generating a PathTear message for the
corresponding Path message. PE6 will send a Path Tear message with
the SESSION and SENDER_TEMPLATE objects corresponding to the HSMP LSP
and the [Sub-Group Originator ID, Sub-Group ID] tuple corresponding
to the Path message. P3 upon receiving the PathTear message would
prune the MPLS multicast replication list and will become a normal
RSVP LSR node.
In the P2MP and HSMP context the PathTear is used for a specific
component sub LSP teardown. This does not necessarily mean the whole
path's breakdown from upstream; hence the LSRs MUST retain the
Upstream label until all the component sub LSPs of the HSMP LSP are
torn down.
When a HSMP LSP is removed by the root, a PathTear message MUST be
generated for each Path message used to signal the HS Multipoint LSP.
7. Refresh Reduction
The refresh reduction procedures described in [RFC2961] are equally
applicable to HS Multipoint LSPs described in this document. Refresh
reduction applies to individual messages and the state they install/
maintain, and that continues to be the case for HS Multipoint LSPs.
8. Fast Reroute
[RFC4090] extensions can be used to perform fast reroute for the
mechanism described in this document when applied within packet
networks.
This is still TBD.
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9. Acknowledgements
We would like to thank Dimitri Papadimitriou, Yuji Kamite, Sebastien
Jobert for their comments and feedback on the document.
10. Security Considerations
The same security considerations apply as for the RSVP-TE P2MP LSP
specification, as described in [RFC4875].
11. IANA Considerations
No requests for IANA at this point of time.
12. References
12.1. Normative References
[I-D.ietf-ccamp-asymm-bw-bidir-lsps-bis]
Takacs, A., Berger, L., Caviglia, D., Fedyk, D., and J.
Meuric, "GMPLS Asymmetric Bandwidth Bidirectional Label
Switched Paths (LSPs)",
draft-ietf-ccamp-asymm-bw-bidir-lsps-bis-03 (work in
progress), August 2011.
[IEEE] "IEEE Standard for a Precision Clock Synchronization
Protocol for Networked Measurement and Control Systems",
2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC4875] Aggarwal, R., Papadimitriou, D., and S. Yasukawa,
"Extensions to Resource Reservation Protocol - Traffic
Engineering (RSVP-TE) for Point-to-Multipoint TE Label
Switched Paths (LSPs)", RFC 4875, May 2007.
12.2. Informative References
[I-D.ietf-l2vpn-ldp-vpls-broadcast-exten]
Key, R., Kamite, Y., Liu, Z., Paul, M., Kunze, R., and L.
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Jin, "Extension to LDP-VPLS for Ethernet Broadcast and
Multicast", draft-ietf-l2vpn-ldp-vpls-broadcast-exten-03
(work in progress), December 2011.
[I-D.ietf-l2vpn-vpls-mcast]
Aggarwal, R., Rekhter, Y., Kamite, Y., and L. Fang,
"Multicast in VPLS", draft-ietf-l2vpn-vpls-mcast-10 (work
in progress), February 2012.
[I-D.ietf-l2vpn-vpms-frmwk-requirements]
Kamite, Y., JOUNAY, F., Niven-Jenkins, B., Brungard, D.,
and L. Jin, "Framework and Requirements for Virtual
Private Multicast Service (VPMS)",
draft-ietf-l2vpn-vpms-frmwk-requirements-04 (work in
progress), July 2011.
[I-D.ietf-pwe3-p2mp-pw]
Sivabalan, S., Boutros, S., and L. Martini, "Signaling
Root-Initiated Point-to-Multipoint Pseudowire using LDP",
draft-ietf-pwe3-p2mp-pw-04 (work in progress), March 2012.
[RFC2961] Berger, L., Gan, D., Swallow, G., Pan, P., Tommasi, F.,
and S. Molendini, "RSVP Refresh Overhead Reduction
Extensions", RFC 2961, April 2001.
[RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute
Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
May 2005.
[RFC4672] De Cnodder, S., Jonnala, N., and M. Chiba, "RADIUS Dynamic
Authorization Client MIB", RFC 4672, September 2006.
1. Appendix: Alternate Mechanism to set up a reverse LSP
We had considered another approach where the leaves could set up a
unidirectional LSP by reversing the RRO that they recieve in the S2L
sub-LSP Path message and use that as the ERO in their Path message.
This approach was rejected because this would have entailed setting
up another reverse LSP which leads to more state being maintained on
all the intermediate routers. The reader is suggested to go through
Section 2 which discusses this in detail.
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Authors' Addresses
Lizhong Jin
ZTE Corporation
Bibo Road, Shanghai 201203
China
Email: lizhong.jin@zte.com.cn
Frederic Jounay
France Telecom
Lannion Cedex 95134
France
Email: frederic.jounay@orange.ch
Manav Bhatia
Alcatel-Lucent
Bangalore,
India
Email: manav.bhatia@alcatel-lucent.com
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