draft-ietf-mpls-spring-entropy-label-01.txt   draft-ietf-mpls-spring-entropy-label-02.txt 
Network Working Group S. Kini, Ed. Network Working Group S. Kini, Ed.
Internet-Draft Ericsson Internet-Draft Ericsson
Intended status: Informational K. Kompella Intended status: Standards Track K. Kompella
Expires: March 9, 2016 Juniper Expires: July 29, 2016 Juniper
S. Sivabalan S. Sivabalan
Cisco Cisco
S. Litkowski S. Litkowski
Orange Orange
R. Shakir R. Shakir
X. Xu X. Xu
Huawei Huawei
W. Hendrickx W. Hendrickx
Alcatel-Lucent Alcatel-Lucent
J. Tantsura J. Tantsura
Ericsson Ericsson
September 6, 2015 January 26, 2016
Entropy labels for source routed stacked tunnels Entropy labels for source routed tunnels with label stacks
draft-ietf-mpls-spring-entropy-label-01 draft-ietf-mpls-spring-entropy-label-02
Abstract Abstract
Source routed tunnel stacking is a technique that can be leveraged to Source routed tunnels with label stacking is a technique that can be
provide a method to steer a packet through a controlled set of leveraged to provide a method to steer a packet through a controlled
segments. This can be applied to the Multi Protocol Label Switching set of segments. This can be applied to the Multi Protocol Label
(MPLS) data plane. Entropy label (EL) is a technique used in MPLS to Switching (MPLS) data plane. Entropy label (EL) is a technique used
improve load balancing. This document examines and describes how ELs in MPLS to improve load balancing. This document examines and
are to be applied to source routed stacked tunnels. describes how ELs are to be applied to source routed tunnels with
label stacks.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on March 9, 2016. This Internet-Draft will expire on July 29, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2016 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Abbreviations and Terminology . . . . . . . . . . . . . . . . 3 2. Abbreviations and Terminology . . . . . . . . . . . . . . . . 3
3. Use-case requiring multipath load balancing in source stacked 3. Use-case requiring multipath load balancing . . . . . . . . . 4
tunnels . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Recommended EL solution for SPRING . . . . . . . . . . . . . 5 4. Recommended EL solution for SPRING . . . . . . . . . . . . . 5
5. Options considered . . . . . . . . . . . . . . . . . . . . . 6 5. Options considered . . . . . . . . . . . . . . . . . . . . . 6
5.1. Single EL at the bottom of the stack of tunnels . . . . . 6 5.1. Single EL at the bottom of the stack of tunnels . . . . . 6
5.2. An EL per tunnel in the stack . . . . . . . . . . . . . . 7 5.2. An EL per tunnel in the stack . . . . . . . . . . . . . . 7
5.3. A re-usable EL for a stack of tunnels . . . . . . . . . . 7 5.3. A re-usable EL for a stack of tunnels . . . . . . . . . . 8
5.3.1. EL at top of stack . . . . . . . . . . . . . . . . . 8 5.3.1. EL at top of stack . . . . . . . . . . . . . . . . . 8
5.4. ELs at readable label stack depths . . . . . . . . . . . 8 5.4. ELs at readable label stack depths . . . . . . . . . . . 8
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Security Considerations . . . . . . . . . . . . . . . . . . . 9 8. Security Considerations . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9 9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 10 9.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction 1. Introduction
The source routed stacked tunnels paradigm is leveraged by techniques The source routed tunnels with label stacking paradigm is leveraged
such as Segment Routing (SR) [I-D.filsfils-spring-segment-routing] to by techniques such as Segment Routing (SR)
steer a packet through a set of segments. This can be directly [I-D.ietf-spring-segment-routing] to steer a packet through a set of
applied to the MPLS data plane, but it has implications on label segments. This can be directly applied to the MPLS data plane, but
stack depth. it has implications on the label stack depth.
Clarifying statements on label stack depth have been provided in Clarifying statements on label stack depth have been provided in
[RFC7325] but they do not address the case of source routed stacked [RFC7325] but the RFC does not address the case of source routed
MPLS tunnels as described in [I-D.filsfils-spring-segment-routing] stacked MPLS tunnels as described in
where deeper label stacks are more prevalent.
[I-D.ietf-spring-segment-routing] where deeper label stacks are more
prevalent.
Entropy label (EL) [RFC6790] is a technique used in the MPLS data Entropy label (EL) [RFC6790] is a technique used in the MPLS data
plane to provide entropy for load balancing. When using LSP plane to provide entropy for load balancing. When using LSP
hierarchies there are implications on how [RFC6790] should be hierarchies there are implications on how [RFC6790] should be
applied. One such issue is addressed by applied. The current document addresses the case where the hierarchy
[I-D.ravisingh-mpls-el-for-seamless-mpls] but that is when different is created at a single LSR as required by source routed tunnels with
levels of the hierarchy are created at different LSRs. The current label stacks.
document addresses the case where the hierarchy is created at a
single LSR as required by source stacked tunnels.
A use-case requiring load balancing with source stacked tunnels is A use-case requiring load balancing with source routed tunnels with
given in Section 3. A recommended solution is described in Section 4 label stacks is given in Section 3. A recommended solution is
keeping in consideration the limitations of implementations when described in Section 4 keeping in consideration the limitations of
applying [RFC6790] to deeper label stacks. Options that were implementations when applying [RFC6790] to deeper label stacks.
considered to arrive at the recommended solution are documented for Options that were considered to arrive at the recommended solution
historical purposes in Section 5. are documented for historical purposes in Section 5.
1.1. Requirements Language 1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Although this document is not a protocol specification, the use of Although this document is not a protocol specification, the use of
this language clarifies the instructions to protocol designers this language clarifies the instructions to protocol designers
producing solutions that satisfy the requirements set out in this producing solutions that satisfy the requirements set out in this
skipping to change at page 4, line 4 skipping to change at page 3, line 50
SR - Segment Routing SR - Segment Routing
ECMP - Equal Cost Multi Paths ECMP - Equal Cost Multi Paths
MPLS - Multiprotocol Label Switching MPLS - Multiprotocol Label Switching
SID - Segment Identifier SID - Segment Identifier
RLD - Readable Label Depth RLD - Readable Label Depth
OAM - Operation, Administration and Maintenance OAM - Operation, Administration and Maintenance
3. Use-case requiring multipath load balancing in source stacked 3. Use-case requiring multipath load balancing
tunnels
+------+ +------+
| | | |
+-------| P3 |-----+ +-------| P3 |-----+
| +-----| |---+ | | +-----| |---+ |
L3| |L4 +------+ L1| |L2 +----+ L3| |L4 +------+ L1| |L2 +----+
| | | | +--| P4 |--+ | | | | +--| P4 |--+
+-----+ +-----+ +-----+ | +----+ | +-----+ +-----+ +-----+ +-----+ | +----+ | +-----+
| S |-----| P1 |------------| P2 |--+ +--| D | | S |-----| P1 |------------| P2 |--+ +--| D |
| | | | | |--+ +--| | | | | | | |--+ +--| |
+-----+ +-----+ +-----+ | +----+ | +-----+ +-----+ +-----+ +-----+ | +----+ | +-----+
+--| P5 |--+ +--| P5 |--+
+----+ +----+
S=Source LSR, D=Destination LSR, P1,P2,P3,P4,P5=Transit LSRs, S=Source LSR, D=Destination LSR, P1,P2,P3,P4,P5=Transit LSRs,
L1,L2,L3,L4=Links L1,L2,L3,L4=Links
Figure 1: Traffic engineering use-case Figure 1: Traffic engineering use-case
Traffic-engineering (TE) is one of the applications of MPLS and is Traffic-engineering (TE) is one of the applications of MPLS and is
also a requirement for source stacked tunnels. Consider the topology also a requirement for source routed tunnels with label stacks.
shown in Figure 1. Lets say the LSR P1 has a limitation that it can Consider the topology shown in Figure 1. Lets say the LSR P1 has a
only look four labels deep in the stack to do multipath decisions. limitation that it can only look four labels deep in the stack to do
All other transit LSRs in the figure can read deep label stacks and multipath decisions. All other transit LSRs in the figure can read
the LSR S can insert as many <ELI, EL> pairs as needed. The LSR S deep label stacks and the LSR S can insert as many <ELI, EL> pairs as
requires data to be sent to LSR D along a traffic-engineered path needed. The LSR S requires data to be sent to LSR D along a traffic-
that goes over the link L1. Good load balancing is also required engineered path that goes over the link L1. Good load balancing is
across equal cost paths (including parallel links). To engineer also required across equal cost paths (including parallel links). To
traffic along a path that takes link L1, the label stack that LSR S engineer traffic along a path that takes link L1, the label stack
creates consists of a label to the node SID of LSR P3, stacked over that LSR S creates consists of a label to the node SID of LSR P3,
the label for the adjacency SID of link L1 and that in turn is stacked over the label for the adjacency SID of link L1 and that in
stacked over the label to the node SID of LSR D. For simplicity lets turn is stacked over the label to the node SID of LSR D. For
assume that all LSRs use the same label space for source stacked simplicity lets assume that all LSRs use the same label space for
tunnels. Lets L_N-P denote the label to be used to reach the node source routed label stacks. Lets L_N-P denote the label to be used
SID of LSR P. Let L_A-Ln denote the label used for the adjacency SID to reach the node SID of LSR P. Let L_A-Ln denote the label used for
for link Ln. The LSR S must use the label stack <L_N-P3, L_A-L1, the adjacency SID for link Ln. The LSR S must use the label stack
L_N-D> for traffic-engineering. However to achieve good load <L_N-P3, L_A-L1, L_N-D> for traffic-engineering. However to achieve
balancing over the equal cost paths P2-P4-D, P2-P5-D and the parallel good load balancing over the equal cost paths P2-P4-D, P2-P5-D and
links L3, L4, a mechanism such as Entropy labels [RFC6790] should be the parallel links L3, L4, a mechanism such as Entropy labels
adapted for source stacked tunnels. Multiple ways to apply entropy [RFC6790] should be adapted for source routed label stacks. Multiple
labels were considered and are documented in Section 5 along with ways to apply entropy labels were considered and are documented in
their tradeoffs. A recommended solution is described in Section 4. Section 5 along with their tradeoffs. A recommended solution is
described in Section 4.
4. Recommended EL solution for SPRING 4. Recommended EL solution for SPRING
The solution described in this section follows [RFC6790]. The solution described in this section follows [RFC6790].
An LSR may have a limitation in its ability to read and process the An LSR may have a limitation in its ability to read and process the
label stack in order to do multipath load balancing. This limitation label stack in order to do multipath load balancing. This limitation
expressed in terms of the number of label stack entries that the LSR expressed in terms of the number of label stack entries that the LSR
can read is henceforth referred to as the Readable Label Depth (RLD) can read is henceforth referred to as the Readable Label Depth (RLD)
capability of that LSR. If an EL does not occur within the RLD of an capability of that LSR. If an EL does not occur within the RLD of an
skipping to change at page 5, line 30 skipping to change at page 5, line 30
corresponding to a label stack, multiple <ELI, EL> pairs MAY be corresponding to a label stack, multiple <ELI, EL> pairs MAY be
inserted in the label stack as long as the tunnel's label below which inserted in the label stack as long as the tunnel's label below which
they are inserted are advertised with entropy label capability they are inserted are advertised with entropy label capability
enabled. The LSR that inserts <ELI, EL> pairs MAY have limitations enabled. The LSR that inserts <ELI, EL> pairs MAY have limitations
on the number of such pairs that it can insert and also the depth at on the number of such pairs that it can insert and also the depth at
which it can insert them. If due to any limitation, the inserted ELs which it can insert them. If due to any limitation, the inserted ELs
are at positions such that an LSR along the path receives an MPLS are at positions such that an LSR along the path receives an MPLS
packet without an EL in the label stack within that LSR's RLD, then packet without an EL in the label stack within that LSR's RLD, then
the load balancing performed by that LSR would be poor. Special the load balancing performed by that LSR would be poor. Special
attention should be paid when a forwarding adjacency LSP (FA-LSP) attention should be paid when a forwarding adjacency LSP (FA-LSP)
[RFC4206] is used as a link along the path of a source stacked LSP, [RFC4206] is used as a link along the path of a source routed LSP's
since the labels of the FA-LSP would additionally count towards the label stack, since the labels of the FA-LSP would additionally count
depth of the label stack when calculating the appropriate positions towards the depth of the label stack when calculating the appropriate
to insert the ELs. The recommendations for inserting <ELI, EL> pairs positions to insert the ELs. The recommendations for inserting <ELI,
are: EL> pairs are:
o An LSR that is limited in the number of <ELI, EL> pairs that it o An LSR that is limited in the number of <ELI, EL> pairs that it
can insert SHOULD insert such pairs deeper in the stack. can insert SHOULD insert such pairs deeper in the stack.
o An LSR SHOULD try to insert <ELI, EL> pairs at positions so that o An LSR SHOULD try to insert <ELI, EL> pairs at positions so that
for the maximum number of transit LSRs, the EL occurs within the for the maximum number of transit LSRs, the EL occurs within the
RLD of the incoming packet to that LSR. RLD of the incoming packet to that LSR.
o An LSR SHOULD try to insert the minimum number of such pairs while o An LSR SHOULD try to insert the minimum number of such pairs while
trying to satisfy the above criteria. trying to satisfy the above criteria.
skipping to change at page 6, line 24 skipping to change at page 6, line 24
set current insertion point to new insertion point set current insertion point to new insertion point
} }
Figure 2: Algorithm to insert <ELI, EL> pairs in a label stack Figure 2: Algorithm to insert <ELI, EL> pairs in a label stack
When this algorithm is applied to the example described in Section 3 When this algorithm is applied to the example described in Section 3
it will result in ELs being inserted in two positions, one below the it will result in ELs being inserted in two positions, one below the
label L_N-D and another below L_N-P3. Thus the resulting label stack label L_N-D and another below L_N-P3. Thus the resulting label stack
would be <L_N-P3, ELI, EL, L_A-L1, L_N-D, ELI, EL> would be <L_N-P3, ELI, EL, L_A-L1, L_N-D, ELI, EL>
The RLD can be advertised via protocols and those extensions would be The RLD can be advertised via protocols and those extensions are
described in separate documents [I-D.xu-isis-mpls-elc] and described in separate documents [I-D.xu-isis-mpls-elc] and
[I-D.xu-ospf-mpls-elc]. [I-D.xu-ospf-mpls-elc].
The recommendations above are not expected to bring any additional The recommendations above are not expected to bring any additional
OAM considerations beyond those described in section 6 of [RFC6790]. OAM considerations beyond those described in section 6 of [RFC6790].
However, the OAM requirements and solutions for source stacked However, the OAM requirements and solutions for source routed tunnels
tunnels are still under discussion and future revisions of this formed by label stacking are still under discussion and future
document will address those if needed. revisions of this document will address those if needed.
5. Options considered 5. Options considered
Different options that were considered to arrive at the recommended
solution are documented in this section.
5.1. Single EL at the bottom of the stack of tunnels 5.1. Single EL at the bottom of the stack of tunnels
In this option a single EL is used for the entire label stack. The In this option a single EL is used for the entire label stack. The
source LSR S encodes the entropy label (EL) below the labels of all source LSR S encodes the entropy label (EL) at the bottom of the
the stacked tunnels. In the example described in Section 3 it will label stack. In the example described in Section 3 it will result in
result in the label stack at LSR S to look like <L_N-P3, L_A-L1, L_N- the label stack at LSR S to look like <L_N-P3, L_A-L1, L_N-D, ELI,
D, ELI, EL> <remaining packet header>. Note that the notation in EL> <remaining packet header>. Note that the notation in [RFC6790]
[RFC6790] is used to describe the label stack. An issue with this is used to describe the label stack. An issue with this approach is
approach is that as the label stack grows due an increase in the that as the label stack grows due an increase in the number of SIDs,
number of SIDs, the EL goes correspondingly deeper in the label the EL goes correspondingly deeper in the label stack. Hence transit
stack. Hence transit LSRs have to access a larger number of bytes in LSRs have to access a larger number of bytes in the packet header
the packet header when making forwarding decisions. In the example when making forwarding decisions. In the example described in
described in Section 3 the LSR P1 would poorly load-balance traffic Section 3 the LSR P1 would poorly load-balance traffic on the
on the parallel links L3, L4 since the EL is below the RLD of the parallel links L3, L4 since the EL is below the RLD of the packet
packet received by P1. A load balanced network design using this received by P1. A load balanced network design using this approach
approach must ensure that all intermediate LSRs have the capability must ensure that all intermediate LSRs have the capability to
to traverse the maximum label stack depth as required for that traverse the maximum label stack depth as required for that
application that uses source routed stacking. application that uses source routed stacking.
In the case where the hardware is capable of pushing a single <ELI, In the case where the hardware is capable of pushing a single <ELI,
EL> pair at any depth, this option is the same as the recommended EL> pair at any depth, this option is the same as the recommended
solution in Section 4. solution in Section 4.
This option was discounted since there exist a number of hardware This option was discounted since there exist a number of hardware
implementations which have a low maximum readable label depth. implementations which have a low maximum readable label depth.
Choosing this option can lead to a loss of load-balancing using EL in Choosing this option can lead to a loss of load-balancing using EL in
a significant part of the network but that is a critical requirement a significant part of the network but that is a critical requirement
skipping to change at page 7, line 26 skipping to change at page 7, line 28
5.2. An EL per tunnel in the stack 5.2. An EL per tunnel in the stack
In this option each tunnel in the stack can be given its own EL. The In this option each tunnel in the stack can be given its own EL. The
source LSR pushes an <ELI, EL> before pushing a tunnel label when source LSR pushes an <ELI, EL> before pushing a tunnel label when
load balancing is required to direct traffic on that tunnel. In the load balancing is required to direct traffic on that tunnel. In the
example described in Section 3, the source LSR S encoded label stack example described in Section 3, the source LSR S encoded label stack
would be <L_N-P3, ELI, EL, L_A-L1, L_N-D, ELI, EL> where all the ELs would be <L_N-P3, ELI, EL, L_A-L1, L_N-D, ELI, EL> where all the ELs
can be the same. Accessing the EL at an intermediate LSR is can be the same. Accessing the EL at an intermediate LSR is
independent of the depth of the label stack and hence independent of independent of the depth of the label stack and hence independent of
the specific application that uses source stacking on that network. the specific application that uses source routed tunnels with label
A drawback is that the depth of the label stack grows significantly, stacking in that network. A drawback is that the depth of the label
almost 3 times as the number of labels in the label stack. The stack grows significantly, almost 3 times as the number of labels in
network design should ensure that source LSRs should have the the label stack. The network design should ensure that source LSRs
capability to push such a deep label stack. Also, the bandwidth should have the capability to push such a deep label stack. Also,
overhead and potential MTU issues of deep label stacks should be the bandwidth overhead and potential MTU issues of deep label stacks
accounted for in the network design. should be accounted for in the network design.
In the case where the RLD is the minimum value (3) for all LSRs, all In the case where the RLD is the minimum value (3) for all LSRs, all
LSRs are EL capable and the LSR that is inserting <ELI, EL> pairs has LSRs are EL capable and the LSR that is inserting <ELI, EL> pairs has
no limit on how many it can insert then this option is the same as no limit on how many it can insert then this option is the same as
the recommended solution in Section 4. the recommended solution in Section 4.
This option was discounted due to the existence of hardware This option was discounted due to the existence of hardware
implementations that can push a limited number of labels on the label implementations that can push a limited number of labels on the label
stack. Choosing this option would result in a hardware requirement stack. Choosing this option would result in a hardware requirement
to push two additional labels per tunnel label. Hence it would to push two additional labels per tunnel label. Hence it would
restrict the number of tunnels that can form a LSP and constrain the restrict the number of tunnels that can form a LSP and constrain the
types of LSPs that can be created. This was considered unacceptable. types of LSPs that can be created. This was considered unacceptable.
5.3. A re-usable EL for a stack of tunnels 5.3. A re-usable EL for a stack of tunnels
In this option an LSR that terminates a tunnel re-uses the EL of the In this option an LSR that terminates a tunnel re-uses the EL of the
terminated tunnel for the next inner tunnel. It does this by storing terminated tunnel for the next inner tunnel. It does this by storing
the EL from the outer tunnel when that tunnel is terminated and re- the EL from the outer tunnel when that tunnel is terminated and re-
inserting it below the next inner tunnel label during the label swap inserting it below the next inner tunnel label during the label swap
operation. The LSR that stacks tunnels SHOULD insert an EL below the operation. The LSR that stacks tunnels should insert an EL below the
outermost tunnel. It SHOULD NOT insert ELs for any inner tunnels. outermost tunnel. It should not insert ELs for any inner tunnels.
Also, the penultimate hop LSR of a segment MUST NOT pop the ELI and Also, the penultimate hop LSR of a segment must not pop the ELI and
EL even though they are exposed as the top labels since the EL even though they are exposed as the top labels since the
terminating LSR of that segment would re-use the EL for the next terminating LSR of that segment would re-use the EL for the next
segment. segment.
In Section 3 above, the source LSR S encoded label stack would be In Section 3 above, the source LSR S encoded label stack would be
<L_N-P3, ELI, EL, L_A-L1, L_N-D>. At P1 the outgoing label stack <L_N-P3, ELI, EL, L_A-L1, L_N-D>. At P1 the outgoing label stack
would be <L_N-P3, ELI, EL, L_A-L1, L_N-D> after it has load balanced would be <L_N-P3, ELI, EL, L_A-L1, L_N-D> after it has load balanced
to one of the links L3 or L4. At P3 the outgoing label stack would to one of the links L3 or L4. At P3 the outgoing label stack would
be <L_N-D, ELI, EL>. At P2 the outgoing label stack would be <L_N-D, be <L_N-D, ELI, EL>. At P2 the outgoing label stack would be <L_N-D,
ELI, EL> and it would load balance to one of the nexthop LSRs P4 or ELI, EL> and it would load balance to one of the nexthop LSRs P4 or
P5. Accessing the EL at an intermediate LSR (e.g. P1) is P5. Accessing the EL at an intermediate LSR (e.g. P1) is
independent of the depth of the label stack and hence independent of independent of the depth of the label stack and hence independent of
the specific use-case to which the stacked tunnels are applied. the specific use-case to which the label stack is applied.
This option was discounted due to the significant change in label This option was discounted due to the significant change in label
swap operations that would be required for existing hardware. swap operations that would be required for existing hardware.
5.3.1. EL at top of stack 5.3.1. EL at top of stack
A slight variant of the re-usable EL option is to keep the EL at the A slight variant of the re-usable EL option is to keep the EL at the
top of the stack rather than below the tunnel label. In this case top of the stack rather than below the tunnel label. In this case
each LSR that is not terminating a segment should continue to keep each LSR that is not terminating a segment should continue to keep
the received EL at the top of the stack when forwarding the packet the received EL at the top of the stack when forwarding the packet
skipping to change at page 9, line 22 skipping to change at page 9, line 28
labels that need to be pushed against the requirement for entropy. labels that need to be pushed against the requirement for entropy.
6. Acknowledgements 6. Acknowledgements
The authors would like to thank John Drake, Loa Andersson, Curtis The authors would like to thank John Drake, Loa Andersson, Curtis
Villamizar, Greg Mirsky, Markus Jork, Kamran Raza and Nobo Akiya for Villamizar, Greg Mirsky, Markus Jork, Kamran Raza and Nobo Akiya for
their review comments and suggestions. their review comments and suggestions.
7. IANA Considerations 7. IANA Considerations
This memo includes no request to IANA. This memo includes no request to IANA. Note to RFC Editor: Remove
this section before publication.
8. Security Considerations 8. Security Considerations
This document does not introduce any new security considerations This document does not introduce any new security considerations
beyond those already listed in [RFC6790]. beyond those already listed in [RFC6790].
9. References 9. References
9.1. Normative References 9.1. Normative References
[I-D.filsfils-spring-segment-routing] [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., Requirement Levels", BCP 14, RFC 2119,
Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R., DOI 10.17487/RFC2119, March 1997,
Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe, <http://www.rfc-editor.org/info/rfc2119>.
"Segment Routing Architecture", draft-filsfils-spring-
segment-routing-04 (work in progress), July 2014.
[I-D.ravisingh-mpls-el-for-seamless-mpls] [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
Singh, R., Shen, Y., and J. Drake, "Entropy label for L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
seamless MPLS", draft-ravisingh-mpls-el-for-seamless- RFC 6790, DOI 10.17487/RFC6790, November 2012,
mpls-04 (work in progress), October 2014. <http://www.rfc-editor.org/info/rfc6790>.
9.2. Informative References
[I-D.ietf-spring-segment-routing]
Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
and r. rjs@rob.sh, "Segment Routing Architecture", draft-
ietf-spring-segment-routing-07 (work in progress),
December 2015.
[I-D.xu-isis-mpls-elc] [I-D.xu-isis-mpls-elc]
Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
Litkowski, "Signaling Entropy Label Capability Using IS- Litkowski, "Signaling Entropy Label Capability Using IS-
IS", draft-xu-isis-mpls-elc-02 (work in progress), April IS", draft-xu-isis-mpls-elc-02 (work in progress), April
2015. 2015.
[I-D.xu-ospf-mpls-elc] [I-D.xu-ospf-mpls-elc]
Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S. Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
Litkowski, "Signaling Entropy Label Capability Using Litkowski, "Signaling Entropy Label Capability Using
OSPF", draft-xu-ospf-mpls-elc-01 (work in progress), OSPF", draft-xu-ospf-mpls-elc-01 (work in progress),
October 2014. October 2014.
[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>.
[RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP) [RFC4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206, (GMPLS) Traffic Engineering (TE)", RFC 4206,
DOI 10.17487/RFC4206, October 2005, DOI 10.17487/RFC4206, October 2005,
<http://www.rfc-editor.org/info/rfc4206>. <http://www.rfc-editor.org/info/rfc4206>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, DOI 10.17487/RFC6790, November 2012,
<http://www.rfc-editor.org/info/rfc6790>.
9.2. Informative References
[I-D.filsfils-spring-segment-routing-use-cases]
Filsfils, C., Francois, P., Previdi, S., Decraene, B.,
Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R.,
Ytti, S., Henderickx, W., Tantsura, J., Kini, S., and E.
Crabbe, "Segment Routing Use Cases", draft-filsfils-
spring-segment-routing-use-cases-01 (work in progress),
October 2014.
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
Litkowski, S., Decraene, B., and J. Tantsura, "IS-IS
Extensions for Segment Routing", draft-ietf-isis-segment-
routing-extensions-05 (work in progress), June 2015.
[I-D.ietf-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", draft-ietf-ospf-segment-
routing-extensions-05 (work in progress), June 2015.
[RFC7325] Villamizar, C., Ed., Kompella, K., Amante, S., Malis, A., [RFC7325] Villamizar, C., Ed., Kompella, K., Amante, S., Malis, A.,
and C. Pignataro, "MPLS Forwarding Compliance and and C. Pignataro, "MPLS Forwarding Compliance and
Performance Requirements", RFC 7325, DOI 10.17487/RFC7325, Performance Requirements", RFC 7325, DOI 10.17487/RFC7325,
August 2014, <http://www.rfc-editor.org/info/rfc7325>. August 2014, <http://www.rfc-editor.org/info/rfc7325>.
Authors' Addresses Authors' Addresses
Sriganesh Kini (editor) Sriganesh Kini (editor)
Ericsson Ericsson
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