MVPN/EVPN Tunnel Aggregation with Common Labels
draft-ietf-bess-mvpn-evpn-aggregation-label-06
| Document | Type | Active Internet-Draft (bess WG) | |
|---|---|---|---|
| Authors | Zhaohui Zhang , Eric Rosen , Wen Lin , Zhenbin Li , IJsbrand Wijnands | ||
| Last updated | 2021-04-19 | ||
| Replaces | draft-zzhang-bess-mvpn-evpn-aggregation-label | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | Proposed Standard | ||
| Formats | plain text pdf htmlized bibtex | ||
| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Stephane Litkowski | ||
| Shepherd write-up | Show (last changed 2021-04-19) | ||
| IESG | IESG state | Publication Requested | |
| Action Holders |
(None)
|
||
| Consensus Boilerplate | Yes | ||
| Telechat date | |||
| Responsible AD | Martin Vigoureux | ||
| Send notices to | slitkows.ietf@gmail.com | ||
BESS Z. Zhang
Internet-Draft Juniper Networks
Updates: 7432, 6514, 7582 (if approved) E. Rosen
Intended status: Standards Track Individual
Expires: October 18, 2021 W. Lin
Juniper Networks
Z. Li
Huawei Technologies
I. Wijnands
Individual
April 16, 2021
MVPN/EVPN Tunnel Aggregation with Common Labels
draft-ietf-bess-mvpn-evpn-aggregation-label-06
Abstract
The MVPN specifications allow a single Point-to-Multipoint (P2MP)
tunnel to carry traffic of multiple VPNs. The EVPN specifications
allow a single P2MP tunnel to carry traffic of multiple Broadcast
Domains (BDs). These features require the ingress router of the P2MP
tunnel to allocate an upstream-assigned MPLS label for each VPN or
for each BD. A packet sent on a P2MP tunnel then carries the label
that is mapped to its VPN or BD. (In some cases, a distinct
upstream-assigned is needed for each flow.) Since each ingress
router allocates labels independently, with no coordination among the
ingress routers, the egress routers may need to keep track of a large
number of labels. The number of labels may need to be as large (or
larger) than the product of the number of ingress routers times the
number of VPNs or BDs. However, the number of labels can be greatly
reduced if the association between a label and a VPN or BD is made by
provisioning, so that all ingress routers assign the same label to a
particular VPN or BD. New procedures are needed in order to take
advantage of such provisioned labels. These new procedures also
apply to Multipoint-to-Multipoint (MP2MP) tunnels. This document
updates RFCs 6514, 7432 and 7582 by specifying the necessary
procedures.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Zhang, et al. Expires October 18, 2021 [Page 1]
Internet-Draft mvpn-evpn-aggregation-label April 2021
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 18, 2021.
Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Terminologies . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. Problem Description . . . . . . . . . . . . . . . . . . . 4
2.2. Proposed Solution . . . . . . . . . . . . . . . . . . . . 5
2.2.1. MP2MP Tunnels . . . . . . . . . . . . . . . . . . . . 6
2.2.2. Segmented Tunnels . . . . . . . . . . . . . . . . . . 7
2.2.3. Summary of Label Allocation Methods . . . . . . . . . 9
3. Specification . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1. Context Label Space ID Extended Community . . . . . . . . 9
3.2. Procedures . . . . . . . . . . . . . . . . . . . . . . . 10
4. Security Considerations . . . . . . . . . . . . . . . . . . . 11
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
7. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 12
Zhang, et al. Expires October 18, 2021 [Page 2]
Internet-Draft mvpn-evpn-aggregation-label April 2021
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
8.1. Normative References . . . . . . . . . . . . . . . . . . 13
8.2. Informative References . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Terminologies
Familiarity with MVPN/EVPN protocols and procedures is assumed. Some
terminologies are listed below for convenience.
o BUM: Broadcast, Unknown Unicast, or Multicast (traffic).
o BD: Broadcast Domain.
o PMSI: Provider Multicast Service Interface - a pseudo interface
for a PE to send overlay/customer multicast traffic via underlay/
provider tunnels. Includes I/S-PMSI (often referred to as x-PMSI)
for Inclusive/Selective-PMSI.
o IMET: Inclusive Multicast Ethernet Tag route. An EVPN specific
name for I-PMSI A-D route.
o PTA: PMSI Tunnel Attribute. A BGP attribute that may be attached
to an BGP-MVPN/EVPN A-D routes.
o ESI: Ethernet Segment Identifier.
2. Introduction
MVPN can use P2MP tunnels (set up by RSVP-TE, mLDP, or PIM) to
transport customer multicast traffic across a service provider's
backbone network. Often, a given P2MP tunnel carries the traffic of
only a single VPN. There are however procedures defined that allow a
single P2MP tunnel to carry traffic of multiple VPNs. In this case,
the P2MP tunnel is called an "aggregate tunnel". The PE router that
is the ingress node of an aggregate P2MP tunnel allocates an
"upstream-assigned MPLS label" [RFC5331] for each VPN, and each
packet sent on the P2MP tunnel carries the upstream-assigned MPLS
label that the ingress PE has bound to the packet's VPN.
Similarly, EVPN can use P2MP tunnels (set up by RSVP-TE, mLDP, or
PIM) to transport BUM traffic (Broadcast traffic, Unicast traffic
with an Unknown address, or Multicast traffic), across the provider
network. Often a P2MP tunnel carries the traffic of only a single
BD. However, there are procedures defined that allow a single P2MP
tunnel to be an "aggregate tunnel" that carries traffic of multiple
BDs. The procedures are analogous to the MVPN procedures -- the PE
router that is the ingress node of an aggregate P2MP tunnel allocates
Zhang, et al. Expires October 18, 2021 [Page 3]
Internet-Draft mvpn-evpn-aggregation-label April 2021
an upstream-assigned MPLS label for each BD, and each packet sent on
the P2MP tunnel carries the upstream-assigned MPLS label that the
ingress PE has bound to the packet's BD.
MVPN and EVPN can also use BIER [RFC8279] to transmit multicast
traffic or BUM traffic [RFC8556] [I-D.ietf-bier-evpn]. Although BIER
does not explicitly set up P2MP tunnels, from the perspective of
MVPN/EVPN, the use of BIER transport is very similar to the use of
aggregate P2MP tunnels. When BIER is used, the PE transmitting a
packet (the "BFIR" [RFC8279]) must allocate an upstream-assigned MPLS
label for each VPN or BD, and the packets transmitted using BIER
transport always carry the label that identifies their VPN or BD.
(See [RFC8556] and [I-D.ietf-bier-evpn] for the details.) In the
remainder of this document, we will use the term "aggregate tunnels"
to include both P2MP tunnels and BIER transport.
When an egress PE receives a packet from an aggregate tunnel, it must
look at the upstream-assigned label carried by the packet, and must
interpret that label in the context of the ingress PE. Essentially,
each ingress PE has its own "context label space" [RFC5331] from
which it allocates its upstream-assigned labels. When an egress PE
looks up the upstream-assigned label carried by a given packet, it
looks it up in the context label space owned by the packet's ingress
PE. How an egress PE identifies the ingress PE of a given packet
depends on the tunnel type.
2.1. Problem Description
Note that these procedures may require a very large number of labels.
Suppose an MVPN or EVPN deployment has 1001 PEs, each hosting 1000
VPN/BDs. Each ingress PE has to assign 1000 labels, and each egress
PE has to be prepared to interpret 1000 labels from each of the
ingress PEs. Since each ingress PE allocates labels from its own
context label space, and the ingress PEs do not coordinate their
label assignments, each egress PE must be prepared to interpret
1,000,000 upstream-assigned labels. This is an evident scaling
problem.
At the present time, few if any MVPN/EVPN deployments use aggregate
tunnels, so this problem has not surfaced. However, the use of
aggregate tunnels is likely to increase due to the following two
factors:
o In EVPN, a single customer ("tenant") may have a large number of
BDs, and the use of aggregate RSVP-TE or mLDP P2MP tunnels may
become important, since each tunnel creates state at the
intermediate nodes.
Zhang, et al. Expires October 18, 2021 [Page 4]
Internet-Draft mvpn-evpn-aggregation-label April 2021
o The use of BIER as transport for MVPN/EVPN is becoming more and
more attractive and feasible.
Note there are pros and cons with traditional P2MP tunnel aggregation
(vs. BIER), which are already discussed in Section 2.1.1 of
[RFC6513]. This document simply specifies a way to increase label
scaling when tunnel aggregation is used.
A similar problem also exists with EVPN ESI labels used for multi-
homing. A PE attached to a multi-homed Ethernet Segment (ES)
advertises an ESI label in its Ethernet Segment route for the ES.
The PE imposes the label when it sends frames received from the ES to
other PEs via a P2MP/BIER tunnel. A receiving PE that is attached to
the source ES will know from the ESI label that the packet originated
on the source ES, and thus will not transmit the packet on its local
attachment circuit to that ES. From the receiving PE's point of
view, the ESI label is (upstream-)allocated from the source PE's
label space, so the receiving PE needs to maintain context label
tables, one for each source PE, just like the VRF/BD label case
above. If there are 1,001 PEs, each attached to 1,000 ESes, this can
require each PE to understand 1,000,000 ESI labels. Notice that the
issue exists even when no P2MP tunnel aggregation (i.e. one tunnel
used for multiple BDs) is used.
2.2. Proposed Solution
The number of labels could be greatly reduced if a central authority
assigned a label to each VPN, BD, or ES, and if all PEs used that
same label to represent a given VPN , BD, or ES. Then the number of
total number of labels needed would just be the sum of the number of
VPNs, BD, and/or ESes.
One method of achieving this is to reserve a portion of the label
space for assignment by a central authority. We refer to this
reserved portion as the "Domain-wide Common Block" (DCB) of labels.
This is analogous to the "Segment Routing Global Block" (SRGB) that
is described in [RFC8402]. The DCB is taken from the same label
space that is used for downstream-assigned labels, but each PE would
know not to allocate labels from that block for other purposes (e.g.,
as a local label or for SRGB). A PE that is attached (via L3VPN VRF
interfaces or EVPN Access Circuits) would know by provisioning which
label from the DCB corresponds to which of its locally attached VPNs,
BDs, or ESes. The definition of "domain" is loose - it simply
includes all the routers that share the same DCB. In this document,
it only needs to includes all PEs of an MVPN/EVPN network. (Though
if tunnel segmentation [RFC6514] is used, each segmentation region
could have its own DCB. This will be explained in more detail
later.)
Zhang, et al. Expires October 18, 2021 [Page 5]
Internet-Draft mvpn-evpn-aggregation-label April 2021
The "domain" could also include all routers in the provider network,
making it not much different from a common SRGB across all the
routers. However, that is not necessarily as the labels used by PEs
for the purposes defined in this document will only rise to the top
of the label stack when traffic arrives the PEs. Therefore, it is
better to not include internal P routers in the "domain". That way
they do not have to aside the same DCB used for the purposes in this
document.
In some deployments, it may be impractical to allocate a DCB that is
large enough to contain labels for all the VPNs/BDs/ESes. In this
case, it may be necessary to allocate those labels from a context
label space. However, it is not necessary for each ingress PE to
have its own context label space. Instead, one (or some small
number) of context label spaces can be dedicated to such labels.
Each ingress PE would be provisioned to know both the context label
space identifier and the label for each VPN/BD/ES.
The MVPN/EVPN signaling defined in [RFC6514] and [RFC7432] assumes
that certain MPLS labels are allocated from a context label space
owned by a particular ingress PE. In this document, we augment the
signaling procedures so that it is possible to signal that a
particular label is from the DCB, rather than from an ingress PE's
context label space. We also augment the signaling so that it is
possible to indicate that a particular label is from an identified
context label space that is different than the ingress PE's own
context label space.
Notice that, the VPN/BD/ES-identifying labels from the DCB or from
those few context label spaces are very similar to VNIs in VXLAN.
Allocating a label from the DCB or from those a few context label
spaces and communicating them to all PEs should not be different from
allocating VNIs, and should be feasible in today's networks since
controllers are used more and more widely.
2.2.1. MP2MP Tunnels
MP2MP tunnels present the same problem that can be solved the same
way.
Per RFC 7582 ("MVPN: Using Bidirectional P-tunnels"), when MP2MP
tunnels are used for MVPN, the root of the MP2MP tunnel may need to
allocate and advertise "PE Distinguisher Labels". RFC 7582 states
that these labels are upstream-assigned, from the label space used by
the root node for its upstream-assigned labels.
Zhang, et al. Expires October 18, 2021 [Page 6]
Internet-Draft mvpn-evpn-aggregation-label April 2021
It is REQUIRED by this document that the PE Distinguisher labels
allocated by a particular node come from the same source that the
node uses to allocate its VPN-identifying labels.
2.2.2. Segmented Tunnels
There are some additional issues to be considered when MVPN or EVPN
is using "tunnel segmentation" (see [RFC6514], [RFC7524], and
[I-D.ietf-bess-evpn-bum-procedure-updates] Sections 5 and 6).
2.2.2.1. Selective Tunnels
For "selective tunnels" (see [RFC6513] Sections 2.1.1 and 3.2.1, and
[I-D.ietf-bess-evpn-bum-procedure-updates] Section 4), the procedures
outlined above work only if tunnel segmentation is not used.
A selective tunnel carries one or more particular sets of flows to a
particular subset of the PEs that attach to a given VPN or BD. Each
set of flows is identified by a Selective PMSI A-D route [RFC6514].
The PTA of the S-PMSI route identifies the tunnel used to carry the
corresponding set of flows. Multiple S-PMSI routes can identify the
same tunnel.
When tunnel segmentation is applied to a S-PMSI, certain nodes are
"segmentation points". A segmentation point is a node at the
boundary between two "segmentation regions". Let's call these
"region A" and "region B". A segmentation point is an egress node
for one or more selective tunnels in region A, and an ingress node
for one or more selective tunnels in region B. A given segmentation
point must be able to receive traffic on a selective tunnel from
region A, and label switch the traffic to the proper selective tunnel
in region B.
Suppose one selective tunnel (call it T1) in region A is carrying two
flows, Flow-1 and Flow-2, identified by S-PMSI route Route-1 and
Route-2 respectively. However, it is possible that, in region B,
Flow-1 is not carried by the same selective tunnel that carries Flow-
2. Let's suppose that in region B, Flow-1 is carried by tunnel T2
and Flow-2 by tunnel T3. Then when the segmentation point receives
traffic from T1, it must be able to label switch Flow-1 from T1 to
T2, while also label switching Flow-2 from T1 to T3. This implies
that Route-1 and Route-2 must signal different labels in the PTA.
In this case, it is not practical to have a central authority assign
domain-wide unique labels to individual S-PMSI routes. To address
this problem, all PEs can be assigned disjoint label blocks in those
few context label spaces, and each will allocate labels for segmented
S-PMSI independently from its assigned label block that is different
Zhang, et al. Expires October 18, 2021 [Page 7]
Internet-Draft mvpn-evpn-aggregation-label April 2021
from any other PE's. For example, PE1 allocates from label block
[101~200], PE2 allocates from label block [201~300], and so on.
Allocating from disjoint label blocks can be used for VPN/BD/ES
labels as well, though it does not address the original scaling
issue, because there would be one million labels allocated from those
a few context label spaces in the original example, instead of just
one thousand common labels.
2.2.2.2. Per-PE/Region Tunnels
Similarly, for segmented per-PE (MVPN (C-*,C-*) S-PMSI or EVPN IMET)
or per-AS/region (MVPN Inter-AS I-PMSI or EVPN per-Region I-PMSI)
tunnels, labels need to be allocated per PMSI route. In case of per-
PE PMSI route, the labels should be allocated from the label block
allocated to the advertising PE. In case of per-AS/region PMSI
route, different ASBR/RBRs attached to the same source AS/region will
advertise the same PMSI route. The same label could be used when the
same route is advertised by different ASBRs/RBRs, though a simpler
way is for each ASBR/RBR to allocate its own label from the label
block allocated to itself.
In the rest of the document, we call the label allocated for a
particular PMSI a (per-)PMSI label, just like we have (per-)VPN/BD/ES
labels. Notice that using per-PMSI label in case of per-PE PMSI
still has the original scaling issue associated with the upstream
allocated label, so per-region PMSIs should be preferred. Within
each AS/region, per-PE PMSIs are still used though they do not go
across border and per-VPN/BD labels can still be used.
Note that, when a segmentation point re-advertise a PMSI route to the
next segment, it does not need to re-advertise a new label unless the
upstream or downstream segment uses Ingress Replication. [note -
future revision may extend the applicability of this document to
Ingress Replication as well]
2.2.2.3. Alternative to the per-PMSI Label Allocation
The per-PMSI label allocation in case of segmentation, whether for
S-PMSI or for per-PE/Region I-PMSI, is for the segmentation points to
be able to label switch traffic w/o having to do IP or MAC lookup in
VRFs (the segmentation points typically do not have those VRFs at
all). If the label scaling becomes a concern, alternatively the
segmentation points could use (C-S,C-G) lookup in VRFs for flows
identified by the S-PMSIs. This allows the S-PMSIs for the same VPN/
BD to share the a VPN/BD-identifying label that leads to lookup in
the VRFs. That label should be different from the label used in the
per-PE/region I-PMSIs though, so that the segmentation points can
Zhang, et al. Expires October 18, 2021 [Page 8]
Internet-Draft mvpn-evpn-aggregation-label April 2021
label switch other traffic (not identified by those S-PMSIs).
However, this moves the scaling problem from the number of labels to
the number of (C-S/*,C-G) routes in VRFs on the segmentation points.
2.2.3. Summary of Label Allocation Methods
In summary, labels can be allocated and advertised the following
ways:
1. A central authority allocates per-VPN/BD/ES labels from the DCB.
PEs advertise the labels with an indication that they are from
the DCB.
2. A central authority allocates per-VPN/BD/ES labels from a few
common context label spaces, and allocate labels from the DCB to
identify those context label spaces. PEs advertise the VPN/BD
labels along with the context-identifying labels.
3. A central authority assigns disjoint label blocks from those a
few context label spaces to each PE, and allocate labels from the
DCB to identify the context label spaces. Each PE allocates
labels from its assigned label block independently for its
segmented S-PMSI, along with the context-identifying labels.
Option 1 is simplest, but it requires that all the PEs set aside a
common label block for the DCB that is large enough for all the
VPNs/BDs/ESes combined. Option 3 is needed only for segmented
selective tunnels that are set up dynamically. Multiple options
could be used in any combination depending on the deployment
situation.
3. Specification
3.1. Context Label Space ID Extended Community
Context Label Space ID Extended Community is a new Transitive Opaque
EC with the following structure (Sub-Type value to be assigned by
IANA):
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 0x03 or 0x43 | Sub-Type | ID-Type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ID-Value |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Zhang, et al. Expires October 18, 2021 [Page 9]
Internet-Draft mvpn-evpn-aggregation-label April 2021
o ID-Type: A 2-octet field that specifies the type of Label Space
ID. In this document, the ID-Type is 0, indicating that the ID-
Value field is a label.
o ID-Value: A 4-octet field that specifies the value of Label Space
ID. When it is a label (with ID-Value 0), the most significant
20-bit is set to the label value.
This document introduces a DCB-bit (to be assigned by IANA) in the
"Additional PMSI Tunnel Attribute Flags" BGP Extended Community
[RFC7902].
In the remainder of the document, when we say a BGP-MVPN/EVPN A-D
route "carries DCB-flag" or "has DCB-flag attached" we mean the
following:
o The route carries a PMSI Tunnel Attribute (PTA) and its Flags
field has the Extension bit set
o The route carries an "Additional PMSI Tunnel Attribute Flags" EC
and its DCB-bit is set
3.2. Procedures
The protocol and procedures specified in this section need not be
applied unless when BIER, or P2MP/MP2MP tunnel aggregation is used
for MVPN/EVPN, or BIER/P2MP/MP2MP tunnels are used with EVPN multi-
homing.
By means outside the scope of this document, each VPN/BD/ES is
assigned a label from the DCB or one of those few context label
spaces, and every PE that is part of the VPN/BD/ES is aware of the
assignment. The ES label and the BD label MUST be assigned from the
same source. If PE Distinguisher labels are used [RFC7582], they
MUST be allocated from the same source as well.
In case of tunnel segmentation, each PE is also assigned a disjoint
label block from one of those few context label spaces and it
allocates labels for its segmented PMSI routes from its assigned
label block.
When a PE originates/re-advertises an x-PMSI/IMET route, the route
MUST carry a DCB-flag if and only if the label in its PTA is assigned
from the DCB.
If the VPN/BD/PMSI label is assigned from one of those few context
label spaces, a Context Label Space ID Extended Community is attached
to the route. The ID-Type in the EC is set to 0 and the ID-Value is
Zhang, et al. Expires October 18, 2021 [Page 10]
Internet-Draft mvpn-evpn-aggregation-label April 2021
set to a label allocated from the DCB and identifies the context
label space. When an ingress PE sends traffic, it imposes the DCB
label that identifies the context label space after it imposes the
label (that is advertised in the PTA's Label field of the x-PMSI/IMET
route) for the VPN/BD and/or the label (that is advertised in the ESI
Label EC) for the ESI, and then imposes the encapsulation for the
transport tunnel.
When a PE receives an x-PMSI/IMET route with the Context Label Space
ID EC, it MUST program its default MPLS forwarding table to map the
label in the EC that identifies the context label space to a
corresponding context label table in which the next label lookup is
done for traffic that this PE receives.
Then, the receiving PE MUST program the label in the PTA or ESI Label
EC into either the default mpls forwarding table (if the route
carries the DCB-flag) or the context label table (if the Context
Label Space ID EC is present) according to the x-PMSI/IMET route.
A PE MUST NOT both carry the DCB-flag in an x-PMSI/IMET route and
attach the Context Label Space ID EC in the route. A PE MUST ignore
a received route with both the DCB-flag and the Context Label Space
ID EC attached, treating as if it was not received. If neither the
DCB-flag nor the Context Label Space ID EC is attached, the label in
the PTA or ESI Label EC MUST be treated as the upstream allocated
from the source PE's label space, and procedures in
[RFC6514][RFC7432] MUST be followed.
In case of MPLS P2MP tunnels, if two x-PMSI/IMET routes specify the
same tunnel, one of the following conditions MUST be met, so that a
receiving PE can correctly interpret the label that follows the
tunnel label in the right context.
o They MUST all have the DCB-flag, or,
o They MUST all carry the Context Label Space ID EC, or,
o None of them has the DCB-flag, or,
o None of them carry the Context Label Space ID EC.
4. Security Considerations
This document allows three methods (Section 2.2.3) of label
allocation for MVPN/EVPN PEs and specifies corresponding signaling
and procedures. The first method is the equivalent of using common
SRGBs from the regular per platform label space. The second one is
the equivalent of using common SRGBs from a third party's label
Zhang, et al. Expires October 18, 2021 [Page 11]
Internet-Draft mvpn-evpn-aggregation-label April 2021
space, which is also considered as an upstream-assigned label
allocation [RFC5331]. The third method is is a variation of the
second, in that the third party's label space is divided into
disjoint blocks for use by different PEs, who will use labels from
their respective block to send traffic. In all cases, a receiving PE
is able to identify one of a few LFIBs to forward incoming labeled
traffic.
Therefore, this document does not introduce new security issues
besides what have been discussed in existing specifications [RFC5331]
[RFC6514] [RFC7432] [RFC8402].
5. IANA Considerations
IANA is requested for the following assignments:
o Bit 47 (DCB-Bit) from the "Additional PMSI Tunnel Attribute Flags"
registry
Bit Name Reference
---- ---------------------- -------------
47 DCB-bit This document
o Sub-type 0x08 for "Context Label Space ID Extended Community" from
the "Transitive Opaque Extended Community Sub-Types" registry
Bit Name Reference
---- ---------------------- -------------
0x08 Context Label Space ID This document
6. Acknowledgements
The authors thank Stephane Litkowski, Ali Sajassi and Jingrong Xie
for their review of, comments on and suggestions for this document.
7. Contributors
The following also contributed to this document.
Selvakumar Sivaraj
Juniper Networks
Email: ssivaraj@juniper.net
Zhang, et al. Expires October 18, 2021 [Page 12]
Internet-Draft mvpn-evpn-aggregation-label April 2021
8. References
8.1. 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,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC6513] Rosen, E., Ed. and R. Aggarwal, Ed., "Multicast in MPLS/
BGP IP VPNs", RFC 6513, DOI 10.17487/RFC6513, February
2012, <https://www.rfc-editor.org/info/rfc6513>.
[RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
Encodings and Procedures for Multicast in MPLS/BGP IP
VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012,
<https://www.rfc-editor.org/info/rfc6514>.
[RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
2015, <https://www.rfc-editor.org/info/rfc7432>.
[RFC7524] Rekhter, Y., Rosen, E., Aggarwal, R., Morin, T.,
Grosclaude, I., Leymann, N., and S. Saad, "Inter-Area
Point-to-Multipoint (P2MP) Segmented Label Switched Paths
(LSPs)", RFC 7524, DOI 10.17487/RFC7524, May 2015,
<https://www.rfc-editor.org/info/rfc7524>.
[RFC7582] Rosen, E., Wijnands, IJ., Cai, Y., and A. Boers,
"Multicast Virtual Private Network (MVPN): Using
Bidirectional P-Tunnels", RFC 7582, DOI 10.17487/RFC7582,
July 2015, <https://www.rfc-editor.org/info/rfc7582>.
[RFC7902] Rosen, E. and T. Morin, "Registry and Extensions for
P-Multicast Service Interface Tunnel Attribute Flags",
RFC 7902, DOI 10.17487/RFC7902, June 2016,
<https://www.rfc-editor.org/info/rfc7902>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
8.2. Informative References
Zhang, et al. Expires October 18, 2021 [Page 13]
Internet-Draft mvpn-evpn-aggregation-label April 2021
[I-D.ietf-bess-evpn-bum-procedure-updates]
Zhang, Z., Lin, W., Rabadan, J., Patel, K., and A.
Sajassi, "Updates on EVPN BUM Procedures", draft-ietf-
bess-evpn-bum-procedure-updates-08 (work in progress),
November 2019.
[I-D.ietf-bier-evpn]
Zhang, Z., Przygienda, T., Sajassi, A., and J. Rabadan,
"EVPN BUM Using BIER", draft-ietf-bier-evpn-04 (work in
progress), December 2020.
[RFC5331] Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream
Label Assignment and Context-Specific Label Space",
RFC 5331, DOI 10.17487/RFC5331, August 2008,
<https://www.rfc-editor.org/info/rfc5331>.
[RFC8279] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A.,
Przygienda, T., and S. Aldrin, "Multicast Using Bit Index
Explicit Replication (BIER)", RFC 8279,
DOI 10.17487/RFC8279, November 2017,
<https://www.rfc-editor.org/info/rfc8279>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8556] Rosen, E., Ed., Sivakumar, M., Przygienda, T., Aldrin, S.,
and A. Dolganow, "Multicast VPN Using Bit Index Explicit
Replication (BIER)", RFC 8556, DOI 10.17487/RFC8556, April
2019, <https://www.rfc-editor.org/info/rfc8556>.
Authors' Addresses
Zhaohui Zhang
Juniper Networks
EMail: zzhang@juniper.net
Eric Rosen
Individual
EMail: erosen52@gmail.com
Zhang, et al. Expires October 18, 2021 [Page 14]
Internet-Draft mvpn-evpn-aggregation-label April 2021
Wen Lin
Juniper Networks
EMail: wlin@juniper.net
Zhenbin Li
Huawei Technologies
EMail: lizhenbin@huawei.com
IJsbrand Wijnands
Individual
EMail: ice@braindump.be
Zhang, et al. Expires October 18, 2021 [Page 15]