MPLS Working Group H. Sitaraman
Internet-Draft V. Beeram
Intended status: Standards Track Juniper Networks
Expires: January 4, 2018 T. Parikh
Verizon
T. Saad
Cisco Systems
July 3, 2017
Signaling RSVP-TE tunnels on a shared MPLS forwarding plane
draft-sitaraman-mpls-rsvp-shared-labels-01.txt
Abstract
As the scale of MPLS RSVP-TE LSPs has grown, various implementation
recommendations have been proposed to manage control plane state.
However, the forwarding plane footprint of labels at a transit LSR
has remained proportional to the total LSP state in the control
plane. This draft defines a mechanism to prevent the label space
limit on an LSR from being a constraint to control plane scaling on
that node. It introduces the notion of pre-installed per TE link
'pop labels' that are shared by MPLS RSVP-TE LSPs that traverse these
links and thus significantly reducing the forwarding plane state
required. This couples the feature benefits of the RSVP-TE control
plane with the simplicity of the Segment Routing MPLS forwarding
plane. This document also introduces the ability to mix different
types of label operations along the path of the LSP, thereby allowing
the ingress or an external controller to influence how to optimally
place a LSP.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 4, 2018.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 4
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Allocation of pop labels . . . . . . . . . . . . . . . . . . 4
5. RSVP-TE pop and forward tunnel setup . . . . . . . . . . . . 5
6. Delegating label stack imposition . . . . . . . . . . . . . . 6
6.1. Stacking at the Ingress . . . . . . . . . . . . . . . . . 6
6.1.1. Stack to reach delegation hop . . . . . . . . . . . . 7
6.1.2. Stack to reach egress . . . . . . . . . . . . . . . . 7
6.2. Explicit Delegation . . . . . . . . . . . . . . . . . . . 8
6.3. Automatic Delegation . . . . . . . . . . . . . . . . . . 9
6.3.1. Effective Transport Label-Stack Depth (ETLD) . . . . 9
7. Mixing pop and swap labels in a RSVP-TE tunnel . . . . . . . 10
8. Construction of label stack . . . . . . . . . . . . . . . . . 11
9. Facility backup protection . . . . . . . . . . . . . . . . . 12
9.1. Link Protection . . . . . . . . . . . . . . . . . . . . . 12
9.2. Node Protection . . . . . . . . . . . . . . . . . . . . . 12
10. Quantifying pop labels . . . . . . . . . . . . . . . . . . . 13
11. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 13
11.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 13
11.2. Attribute Flags TLV: Pop Label . . . . . . . . . . . . . 14
11.3. RRO Label Subobject Flag: Pop Label . . . . . . . . . . 14
11.4. Attribute Flags TLV: LSI-D . . . . . . . . . . . . . . . 14
11.5. RRO Label Subobject Flag: Delegation Label . . . . . . . 15
11.6. Attributes Flags TLV: LSI-D-S2E . . . . . . . . . . . . 15
11.7. Attributes TLV: ETLD . . . . . . . . . . . . . . . . . . 15
12. OAM considerations . . . . . . . . . . . . . . . . . . . . . 16
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16
14. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 16
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
15.1. Attribute Flags: Pop Label, LSI-D, LSI-D-S2E . . . . . . 16
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15.2. Attribute TLV: ETLD . . . . . . . . . . . . . . . . . . 17
15.3. Record Route Label Sub-object Flags: Pop Label,
Delegation Label . . . . . . . . . . . . . . . . . . . . 17
16. Security Considerations . . . . . . . . . . . . . . . . . . . 17
17. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
17.1. Normative References . . . . . . . . . . . . . . . . . . 17
17.2. Informative References . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
Various RSVP-TE scaling recommendations [RFC2961]
[I-D.ietf-teas-rsvp-te-scaling-rec] have been proposed for
implementations to adopt guidelines that would allow the RSVP-TE
[RFC3209] control plane to scale better. The forwarding plane state
required to handle the equivalent control plane state remains
unchanged and is proportional to the total LSP state in the control
plane. The motivation of this draft is to prevent the platform
specific label space limit on an LSR from being a constraint to
pushing the limits of control plane scaling on that node.
This document proposes the allocation of a 'pop label' by a LSR for
each of its TE links. The label is installed in the MPLS forwarding
plane with a pop label operation and to forward the received packet
over the TE link. This label is sent normally by the LSR in the
Label object in the Resv message as LSPs are setup. The ingress LER
SHOULD construct and push a stack of labels [RFC3031] as received in
the Record Route object(RRO) in the Resv message.
This pop and forward data plane behavior is similar to that used by
Segment Routing (SR) [I-D.ietf-spring-segment-routing] using a MPLS
forwarding plane and a series of adjacency segments. The RSVP-TE pop
and forward tunnels can co-exist with SR LSPs as described in
[I-D.ietf-teas-sr-rsvp-coexistence-rec].
RSVP-TE using a pop and forward data plane offers the following
benefits:
1. Shared forwarding plane: The transit label on a TE link is shared
among RSVP-TE tunnels traversing the link and is used independent
of the ingress and egress of the LSPs.
2. Faster LSP setup time: The forwarding plane state is not
programmed during LSP setup and teardown resulting in faster LSP
setup time.
3. Hitless routes: New transit labels are not required on complete
path overlap during make-before-break (MBB) resulting in a faster
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MBB event. This avoids the ingress LER and the services that
might be using the tunnel from needing to update its forwarding
plane with new tunnel labels. Periodic MBB events are relatively
common in networks that deploy auto-bandwidth on RSVP-TE LSPs to
monitor bandwidth utilization and periodically adjust LSP
bandwidth.
4. Mix and match labels: Both 'pop' and 'swap' labels can be mixed
across transit hops for a single RSVP-TE tunnel (see Section 7).
This allows backwards compatibility with transit LSRs that
provides 'swap' labels.
No additional extensions are required to IGP-TE in order to support
this pop and forward data plane. Functionalities such as bandwidth
admission control, LSP priorities, preemption, auto-bandwidth and
Fast Reroute continue to work with this forwarding plane.
2. 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 [RFC2119].
3. Terminology
Pop label: An incoming label at a LSR that will be popped and
forwarded over a specific TE link to a neighbor.
Swap label: An incoming label at a LSR that will be swapped to an
outgoing label and forwarded over a specific downstream TE link.
Pop and forward data plane: A forwarding plane where every LSR along
the path uses a pop label.
RSVP-TE pop and forward tunnel: A MPLS RSVP-TE tunnel that uses a pop
and forward data plane.
4. Allocation of pop labels
A LSR SHOULD allocate a unique pop label for each TE link. The
forwarding action for the pop label should it appear on top of the
label stack MUST be to pop the label and forward the packet over the
TE link to the downstream neighbor of the RSVP-TE tunnel. Multiple
labels MAY be allocated for the TE link to accommodate tunnels
requesting no protection, link-protection and node-protection over
the specific TE link.
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5. RSVP-TE pop and forward tunnel setup
This section provides an example of how the RSVP-TE signaling
procedure works to setup a tunnel utilizing a pop and forward data
plane. The sample topology below will be used to explain the setup.
Labels shown at each node are pop labels for that neighbor
+---+100 +---+150 +---+200 +---+250 +---+
| A |-----| B |-----| C |-----| D |-----| E |
+---+ +---+ +---+ +---+ +---+
|110 |450 |550 |650 |850
| | | | |
| |400 |500 |600 |800
| +---+ +---+ +---+ +---+
+-------| F |-----|G |-----|H |-----|I |
+---+300 +---+350 +---+700 +---+
Figure 1: Pop and forward label topology
RSVP-TE tunnel T1: From A to E on path A-B-C-D-E
RSVP-TE tunnel T2: From F to E on path F-B-C-D-E
Both tunnels share the TE links B-C, C-D and D-E.
As RSVP-TE signals the setup (using the pop label attributes flag
defined in Section 11.2) of tunnel T1, when LSR D receives the Resv
message from the egress E, it checks the next-hop TE link (D-E) and
provides the pop label (250) in the Resv message for the tunnel. The
label is sent in the Label object and is also recorded in the Label
sub-object (using the pop label flag defined in Section 11.3) carried
in the RRO. Similarly, C provides the pop label (200) for the next-
hop TE link C-D and B provides the pop label (150) for the next-hop
TE link B-C. For the tunnel T2, the transit LSRs provide the same
pop labels as described for tunnel T1.
Both LER A and F will push the same stack of labels {150(top), 200,
250} for tunnels T1 and T2 respectively. It should be noted that a
transit LSR does not use the pop label provided in the label object
by its downstream LSR in the NHLFE as the outgoing label. The
recorded labels in the RRO are of interest to the ingress LER in
order to construct a stack of labels.
If there were another RSVP-TE tunnel T3 from F to I on path
F-B-C-D-E-I, then this would also share the TE links B-C, C-D and D-E
and additionally traverse link E-I. The label stack used by F would
be {150(top), 200, 250, 850}. Hence, regardless of the ingress and
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egress LERs from where the LSPs start and end, they will share LSR
labels at shared hops in the pop and forward data plane.
There MAY be local operator policy at the ingress LER that influences
the maximum depth of the label stack that can be pushed for a RSVP-TE
pop and forward tunnel. Prior to signaling the LSP, if the ingress
LER decides that it would be unable to push the entire label stack
should every transit hop provide a pop label, then the LER can choose
to either not signal a RSVP-TE pop and forward tunnel or can adopt
techniques mentioned in Section 6 or Section 7.
6. Delegating label stack imposition
One or more transit LSRs can assist the ingress LER by imposing part
of the label stack required for the path. From Figure 2, ingress LER
A can use the assistance of delegation hops LSR D and LSR I to impose
parts of the label stack. Each delegation hop allocates a delegation
label to represent a set of labels that will be pushed at this hop.
When a packet arrives at this LSR with a delegation label, this label
gets popped and the set of labels it represents gets pushed before
the packet is forwarded.
D and I - delegation hops; [Label]p - pop label; [Label]d -
delegation label
1250d
+---+100p +---+150p +---+200p +---+250p +---+300p +---+
| A |-----| B |-----| C |-----| D |-----| E |-----| F |
+---+ +---+ +---+ +---+ +---+ +---+
|350p
|
1500d |
+---+ 600p+---+ 550p+---+ 500p+---+ 450p+---+ 400p+---+
| L |-----| K |-----| J |-----| I |-----| H |-----+ G +
+---+ +---+ +---+ +---+ +---+ +---+
Figure 2: Delegating Label Stack Imposition
RSVP-TE tunnel: From A to L on path A-B-C-D-E-F-G-H-I-J-K-L
6.1. Stacking at the Ingress
When delegation labels come into play, there are a couple of stacking
approaches that the ingress can choose from. Section 8 explains how
the label stack can be constructed.
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6.1.1. Stack to reach delegation hop
In this approach, the stack pushed by the ingress carries a set of
labels that will take the packet to the first delegation hop (if
present). When this approach is employed, the set of labels
represented by a delegation label at a given delegation hop will
include the corresponding delegation label from the next delegation
hop (if present). As a result, this delegation label can only be
shared among LSPs that are destined to the same egress and traverse
the same downstream path.
Delegation label 1250 represents {300,350,400,450,1500}; Delegation
label 1500 represents {550, 600}
+---+ +---+ +---+
| A |-----.....-----| D |-----.....-----| I |-----.....
+---+ +---+ +---+
Pop 1250 & Pop 1500 &
Push Push Push
...... ...... ......
: 150: 1250->: 300: 1500->: 550:
: 200: : 350: : 600:
:1250: : 400: ......
...... : 450:
:1500:
......
Figure 3: Stack to reach delegation hop
With this approach, for the tunnel in Figure 2 the ingress LER A will
push {150,200,1250}. At LSR D, the delegation label 1250 will get
popped and {300,350,400,450,1500} will get pushed. And at LSR I, the
delegation label 1500 will get popped and the remaining set of labels
{550,600} will get pushed.
6.1.2. Stack to reach egress
In this approach, the stack pushed by the ingress carries a set of
labels that will take the packet all the way to the egress (all the
delegation labels are part of this stack). When this approach is
employed, the set of labels represented by a delegation label at a
given delegation hop will not include the corresponding delegation
label from the next delegation hop (if present). As a result, this
delegation label can be shared among all LSPs traversing the segment
between the two delegation hops. The downside of this approach is
that the number of hops that the LSP can traverse is dictated by the
label stack push limit of the ingress.
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Delegation label 1250 represents {300,350,400,450}; Delegation label
1500 represents {550, 600}
+---+ +---+ +---+
| A |-----.....-----| D |-----.....-----| I |-----.....
+---+ +---+ +---+
Pop 1250 & Pop 1500 &
Push Push Push
...... ...... ......
: 150: 1250->: 300: 1500->: 550:
: 200: : 350: : 600:
:1250: : 400: ......
:1500: : 450:
...... ......
|1500|
------
Figure 4: Stack to reach egress
With this approach, for the tunnel in Figure 2 the ingress LER A will
push {150,200,1250,1500}. At LSR D, the delegation label 1250 will
get popped and {300,350,400,450} will get pushed. And at LSR I, the
delegation label 1500 will get popped and the remaining set of labels
{550,600} will get pushed. The signaling extension required for the
ingress to indicate the chosen stacking approach is defined in
Section 11.6.
6.2. Explicit Delegation
In this delegation option, the ingress LER can explicitly delegate
one or more specific transit hops to handle pushing labels for a
certain number of its downstream hops. In order to accurately pick
the delegation hops, the ingress needs to be aware of the label stack
depth push limit of each of the transit LSRs prior to initiating the
signaling sequence. The mechanism by which the ingress or controller
(hosting the path computation element) learns this information is
outside the scope of this document.
Signaling extension required for the ingress LER to explicitly
delegate one or more specific transit hops is defined in
Section 11.4. The extension required for the delegation hop to
indicate that the recorded label is a delegation label is defined in
Section 11.5.
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6.3. Automatic Delegation
In this approach, the ingress LER lets the downstream hops
automatically pick suitable delegation hops during the initial
signaling sequence. The ingress need not be aware up front of the
label stack depth push limit of each of the transit LSRs. The
delegation hops are picked based on a per-hop signaled attribute
called the Effective Transport Label-Stack Depth (ETLD).
6.3.1. Effective Transport Label-Stack Depth (ETLD)
The ETLD is signaled as a per-hop attribute in the Path message.
When automatic delegation is requested, the ingress MUST populate the
ETLD with the maximum number of transport labels that it can
potentially send to its downstream hop. This value is then
decremented at each successive hop. If a node is reached where the
ETLD set from the previous hop is 1, then that node MUST select
itself as the delegation hop. If a node is reached and it is
determined that this hop cannot receive more than one transport
label, then that node MUST select itself as the delegation hop. If
there is a node or a sequence of nodes along the path of the LSP that
do not support ETLD, then the immediate hop that supports ETLD MUST
select itself as the delegation hop. The ETLD MUST be decremented at
each non-delegation transit hop by either 1 or some appropriate
number based on the limitations at that hop. At each delegation hop,
the ETLD MUST be reset to the maximum number of transport labels that
the hop can send and the ETLD decrements start again at each
successive hop until either a new delegation hop is selected or the
egress is reached. The net result is that by the time the Path
message reaches the egress, all delegation hops are selected. During
the Resv processing, at each delegation hop, a suitable delegation
label is selected (either an existing label is reused or a new label
is allocated) and recorded in the Resv message.
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Assumption: Ingress A can push up to 3 transport labels; Remaining
nodes can push up to 5 transport labels
ETLD:3 ETLD:2 ETLD:1 ETLD:5 ETLD:4
-----> -----> -----> -----> ----->
1250d
+---+100p +---+150p +---+200p +---+250p +---+300p +---+
| A |-----| B |-----| C |-----| D |-----| E |-----| F | ETLD:3
+---+ +---+ +---+ +---+ +---+ +---+ |
|350p |
| |
1500d | |
+---+ 600p+---+ 550p+---+ 500p+---+ 450p+---+ 400p+---+ v
| L |-----| K |-----| J |-----| I |-----| H |-----+ G +
+---+ +---+ +---+ +---+ +---+ +---+
ETLD:3 ETLD:4 ETLD:5 ETLD:1 ETLD:2
<----- <----- <----- <----- <-----
Figure 5: ETLD
Signaling extension for the ingress LER to request automatic
delegation is defined in Section 11.4. The extension for signaling
the ETLD is defined in Section 11.7. The extension required for the
delegation hop to indicate that the recorded label is a delegation
label is defined in Section 11.5.
7. Mixing pop and swap labels in a RSVP-TE tunnel
Labels can be mixed across transit hops in a single MPLS RSVP-TE LSP.
Certain LSRs can use pop labels and others can use swap labels. The
ingress can construct a label stack appropriately based on what type
of label is recorded from every transit LSR.
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Labels shown at each node are pop labels for that TE link. (#) are
swap labels.
(#) (#)
+---+100 +---+150 +---+200 +---+250 +---+
| A |-----| B |-----| C |-----| D |-----| E |
+---+ +---+ +---+ +---+ +---+
|110 |450 |550 |650 |850
| | | | |
| |400 |500 |600 |800
| +---+ +---+ +---+ +---+
+-------| F |-----|G |-----|H |-----|I |
+---+300 +---+350 +---+700 +---+
Figure 6: Mix pop and swap label topology
If the transit LSR allocates a swap label to be sent upstream in the
Resv, then the label operation in the NHLFE MUST be a swap to any
label received from the downstream LSR. If the transit LSR is using
a pop label to be sent upstream in the Resv, then the label operation
in the NHLFE MUST be a pop and forward regardless of any label
received from the downstream LSR.
Section 8 explains how the label stack can be constructed. For
example, the LSP from A to I using path A-B-C-D-E-I will use a label
stack of {150(top), 200}.
8. Construction of label stack
The ingress LER or delegation hop MUST check the type of label
received from each transit hop as recorded in the RRO in the Resv
message and generate the appropriate label stack to reach the next
delegation hop or egress, whichever is earlier.
The following logic could be used by the node constructing the label
stack:
Each RRO label sub-object SHOULD be processed starting with the label
sub-object from the first downstream hop. Any label provided by the
first downstream hop MUST always be pushed on the label stack
regardless of the label type. If the label type is a pop label, then
any label from the next downstream hop MUST also be pushed on the
constructed label stack. If the label type is a swap label, then any
label from the next downstream hop MUST NOT be pushed on the
constructed label stack. If the label type is a delegation label,
then the stacking procedure stops at that delegation hop. Approaches
in Section 6.1 SHOULD be used to determine how the delegation labels
are pushed in the label stack.
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9. Facility backup protection
The following section describe how link and node protection works
with facility backup protection [RFC4090] for the RSVP-TE pop and
forward tunnels.
9.1. Link Protection
To provide link protection at a PLR with a pop and forward data
plane, the LSR SHOULD allocate a separate pop label for the TE link
that will be used for RSVP-TE tunnels that request link-protection
from the ingress. No signaling extensions are required to support
link protection for RSVP-TE tunnels over the pop and forward data
plane.
(*) are pop labels to offer link protection for that TE link
101(*) 151(*) 201(*) 251(*)
+---+100 +---+150 +---+200 +---+250 +---+
| A |-----| B |-----| C |-----| D |-----| E |
+---+ +---+ +---+ +---+ +---+
|110 |450 |550 |650 |850
| | | | |
| |400 |500 |600 |800
| +---+ +---+ +---+ +---+
+-------| F |-----|G |-----|H |-----|I |
+---+300 +---+350 +---+700 +---+
Figure 7: Link protection topology
At each LSR, link protected pop labels can be allocated for each TE
link and a link protecting facility backup LSP can be created to
protect the TE link. This label can be sent by the LSR for LSPs
requesting link-protection over the specific TE link. Since the
facility backup terminates at the next-hop (merge point), the
incoming label on the packet will be what the merge point expects.
As an example, LSR B can install a facility backup LSP for the link
protected pop label 151. When the TE link B-C is up, LSR B will pop
151 and send the packet to C. If the TE link B-C is down, the LSR
can pop 151 and send the packet via the facility backup to C.
9.2. Node Protection
The solutions for the PLR to provide node-protection for the pop and
forward RSVP-TE tunnel will be explained in the next version of the
document.
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10. Quantifying pop labels
This section attempts to quantify the number of labels required in
the forwarding plane to provide sharing of labels across RSVP-TE pop
and forward tunnels. A MPLS RSVP-TE tunnel offers either no
protection, link protection or node protection and only one of these
labels is required per tunnel during signaling. The scale of the
number of pop labels required per LSR can be deduced as follows:
o For a LSR having X neighbors reachable across Y interfaces, the
number of unprotected pop labels = X
o For a PLR having X neighbors reachable across Y interfaces, number
of link protected pop labels = X
o For a PLR having X neighbors, each having Nx neighbors (i.e. next-
nexthop for PLR), number of node protected pop labels =
SUM_OF_ALL(Nx)
Total number of pop labels = Unprotected pop labels + link protected
pop labels + node protected pop labels = 2X + SUM_OF_ALL(Nx)
11. Protocol Extensions
11.1. Requirements
The functionality discussed in this document imposes the following
requirements on the signaling protocol.
o The Ingress of the LSP SHOULD have the ability to mandate/request
the use and recording of pop labels at all hops along the path of
the LSP.
o When the use of pop labels is mandated/requested for the path,
- the node recording the pop label SHOULD have the ability to
indicate if the recorded label is a pop label.
- the ingress SHOULD have the ability to delegate label stack
imposition by
* explicitly mandating specific hops to be delegation hops
(or)
* requesting automatic delegation
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- When explicit delegation is mandated or automatic delegation is
requested,
* the ingress SHOULD have the ability to indicate the chosen
stacking approach
* the delegation hop SHOULD have the ability to indicate that
the recorded label is a delegation label.
11.2. Attribute Flags TLV: Pop Label
Bit Number (TBD1): Pop Label
The presence of this in the LSP_ATTRIBUTES/LSP_REQUIRED_ATTRIBUTES
object of a Path message indicates that the ingress has requested/
mandated the use and recording of pop labels at all hops along the
path of this LSP. When a node that does not cater to the mandate
receives a Path message carrying the LSP_REQUIRED_ATTRIBUTES object
with this flag set, it MUST send a PathErr message with an error code
of 'routing problem' and an error value of 'pop label usage failure'.
11.3. RRO Label Subobject Flag: Pop Label
Bit Number (TBD2): Pop Label
The presence of this flag indicates that the recorded label is a pop
label. This flag MUST be used by a node only if the use and
recording of pop labels is requested/mandated for the LSP.
11.4. Attribute Flags TLV: LSI-D
Bit Number (TBD3): Label Stack Imposition - Delegation (LSI-D)
Automatic Delegation: The presence of this flag in the LSP_ATTRIBUTES
object of a Path message indicates that the ingress has requested
automatic delegation of label stack imposition. This flag MUST be
set in the LSP_ATTRIBUTES object of a Path message only if the use
and recording of pop labels is requested/mandated for this LSP.
Explicit Delegation: The presence of this flag in the HOP_ATTRIBUTES
subobject [RFC7570] of an ERO object in the Path message indicates
that the hop identified by the preceding IPv4 or IPv6 or Unnumbered
Interface ID subobject has been picked as an explicit delegation hop.
The HOP_ATTRIBUTES subobject carrying this flag MUST have the R
(Required) bit set. This flag MUST be set in the HOP_ATTRIBUTES
subobject of an ERO object in the Path message only if the use and
recording of pop labels is requested/mandated for this LSP. If the
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hop is not able to comply with this mandate, it MUST send a PathErr
message with an error code of 'routing problem' and an error value of
'label stack imposition failure'.
11.5. RRO Label Subobject Flag: Delegation Label
Bit Number (TBD4): Delegation Label
The presence of this flag indicates that the recorded label is a
delegation label. This flag MUST be used by a node only if the use
and recording of pop labels and delegation are requested/mandated for
the LSP.
11.6. Attributes Flags TLV: LSI-D-S2E
Bit Number (TBD5): Label Stack Imposition - Delegation - Stack to
reach egress (LSI-D-S2E)
The presence of this flag in the LSP_ATTRIBUTES object of a Path
message indicates that the ingress has chosen to use the "Stack to
reach egress" approach for stacking. The absence of this flag in the
LSP_ATTRIBUTES object of a Path message indicates that the ingress
has chosen to use the "Stack to reach delegation hop" approach for
stacking. This flag MUST be set in the LSP_ATTRIBUTES object of a
Path message only if the use and recording of pop labels and
delegation are requested/mandated for this LSP.
11.7. Attributes TLV: ETLD
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | ETLD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Attribute TLV Type: TBD6
The presence of this TLV in the HOP_ATTRIBUTES subobject of an RRO
object in the Path message indicates that the hop identified by the
preceding IPv4 or IPv6 or Unnumbered Interface ID subobject supports
automatic delegation. This attribute MUST be used only if the use
and recording of pop labels is requested/mandated and automatic
delegation is requested for the LSP. The ETLD field specifies the
maximum number of transport labels that this hop can potentially send
to its downstream hop.
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12. OAM considerations
MPLS LSP ping and traceroute [RFC8029] are applicable for RSVP-TE pop
and forward tunnels. The existing procedures allow for the label
stack imposed at a delegation hop to be reported back in the Label
Stack Sub-TLV in the MPLS echo reply for traceroute.
13. Acknowledgements
The authors would like to thank Adrian Farrel, Kireeti Kompella,
Markus Jork and Ross Callon for their input from discussions.
14. Contributors
The following individuals contributed to this document:
Raveendra Torvi
Juniper Networks
Email: rtorvi@juniper.net
Chandra Ramachandran
Juniper Networks
Email: csekar@juniper.net
George Swallow
Email: swallow.ietf@gmail.com
15. IANA Considerations
15.1. Attribute Flags: Pop Label, LSI-D, LSI-D-S2E
IANA manages the 'Attribute Flags' registry as part of the 'Resource
Reservation Protocol-Traffic Engineering (RSVP-TE) Parameters'
registry located at http://www.iana.org/assignments/rsvp-te-
parameters. This document introduces three new Attribute Flags.
Bit Name Attribute Attribute RRO ERO Reference
No. FlagsPath FlagsResv
TBD1 Pop Label Yes No No No This document
(Section 11.2)
TBD3 LSI-D Yes No No Yes This document
(Section 11.4)
TBD5 LSI-D-S2E Yes No No No This document
(Section 11.6)
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15.2. Attribute TLV: ETLD
IANA manages the "Attribute TLV Space" registry as part of the
'Resource Reservation Protocol-Traffic Engineering (RSVP-TE)
Parameters' registry located at http://www.iana.org/assignments/rsvp-
te-parameters. This document introduces a new Attribute TLV.
Type Name Allowed on Allowed on Allowed on Reference
LSP LSP REQUIRED LSP Hop
ATTRIBUTES ATTRIBUTES Attributes
TBD6 ETLD No No Yes This document
(Section 11.7)
15.3. Record Route Label Sub-object Flags: Pop Label, Delegation Label
IANA manages the 'Record Route Object Sub-object Flags' registry as
part of the 'Resource Reservation Protocol-Traffic Engineering (RSVP-
TE) Parameters' registry located at http://www.iana.org/assignments/
rsvp-te-parameters. This registry currently does not include Label
Sub-object Flags. This document proposes the addition of a new sub-
registry for Label Sub-object Flags as shown below.
Flag Name Reference
0x1 Global Label RFC 3209
TBD2 Pop Label This document (Section 11.3)
TBD4 Delegation Label This document (Section 11.5)
16. Security Considerations
This document does not introduce new security issues. The security
considerations pertaining to the original RSVP protocol [RFC2205] and
RSVP-TE [RFC3209] and those that are described in [RFC5920] remain
relevant.
17. References
17.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
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[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
September 1997, <http://www.rfc-editor.org/info/rfc2205>.
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001,
<http://www.rfc-editor.org/info/rfc3031>.
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<http://www.rfc-editor.org/info/rfc3209>.
[RFC4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
DOI 10.17487/RFC4090, May 2005,
<http://www.rfc-editor.org/info/rfc4090>.
[RFC7570] Margaria, C., Ed., Martinelli, G., Balls, S., and B.
Wright, "Label Switched Path (LSP) Attribute in the
Explicit Route Object (ERO)", RFC 7570,
DOI 10.17487/RFC7570, July 2015,
<http://www.rfc-editor.org/info/rfc7570>.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017,
<http://www.rfc-editor.org/info/rfc8029>.
17.2. Informative References
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
and R. Shakir, "Segment Routing Architecture", draft-ietf-
spring-segment-routing-12 (work in progress), June 2017.
[I-D.ietf-teas-rsvp-te-scaling-rec]
Beeram, V., Minei, I., Shakir, R., Pacella, D., and T.
Saad, "Implementation Recommendations to Improve the
Scalability of RSVP-TE Deployments", draft-ietf-teas-rsvp-
te-scaling-rec-04 (work in progress), March 2017.
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[I-D.ietf-teas-sr-rsvp-coexistence-rec]
Sitaraman, H., Beeram, V., Minei, I., and S. Sivabalan,
"Recommendations for RSVP-TE and Segment Routing LSP co-
existence", draft-ietf-teas-sr-rsvp-coexistence-rec-01
(work in progress), June 2017.
[RFC2961] Berger, L., Gan, D., Swallow, G., Pan, P., Tommasi, F.,
and S. Molendini, "RSVP Refresh Overhead Reduction
Extensions", RFC 2961, DOI 10.17487/RFC2961, April 2001,
<http://www.rfc-editor.org/info/rfc2961>.
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
<http://www.rfc-editor.org/info/rfc5920>.
Authors' Addresses
Harish Sitaraman
Juniper Networks
1133 Innovation Way
Sunnyvale, CA 94089
US
Email: hsitaraman@juniper.net
Vishnu Pavan Beeram
Juniper Networks
10 Technology Park Drive
Westford, MA 01886
US
Email: vbeeram@juniper.net
Tejal Parikh
Verizon
400 International Parkway
Richardson, TX 75081
US
Email: tejal.parikh@verizon.com
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Tarek Saad
Cisco Systems
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
Email: tsaad@cisco.com
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