Network Working Group Y. Gu
Internet-Draft Huawei
Intended status: Standards Track J. Chen
Expires: September 12, 2019 Tencent
P. Mi
S. Zhuang
Z. Li
Huawei
March 11, 2019
VPN Traffic Engineering Using BMP
draft-gu-grow-bmp-vpn-te-00
Abstract
The BGP Monitoring Protocol (BMP) is designed to monitor BGP running
status, such as BGP peer relationship establishment and termination
and route updates. This document provides a traffic engineering (TE)
method in the VPN (Virtual Private Network) scenario using BMP.
Requirements Language
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].
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 September 12, 2019.
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Copyright Notice
Copyright (c) 2019 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
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. VPN TE Using BMP . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Common Header . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Per Peer Header . . . . . . . . . . . . . . . . . . . . . 4
2.3. Label Message . . . . . . . . . . . . . . . . . . . . . . 4
3. Implementation Examples . . . . . . . . . . . . . . . . . . . 6
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. Normative References . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
The Border Gateway Protocol (BGP) [RFC4271], as an inter-Autonomous
(AS) routing protocol, is used to exchange network reachability
information between BGP systems. Later on, RFC4760 [RFC4760] extends
BGP to carry not only the routing information for BGP, but also for
multiple Network Layer protocols (e.g., IPv6, Multicast, etc.), known
as the MP-BGP (Multiprotocol BGP). The MP-BGP is currently widely
deployed in case of MPLS L3VPN, to exchange VPN labels learned for
the routes from the customer sites over the MPLS network. BGP routes
are needed for both intra-domain and inter-domain route optimization.
Before BGP Monitoring Protocol (BMP) [RFC7854] was introduced, BGP
routes could be only obtained through manual query, such as screen
scraping. The introduction of BMP greatly improves the BGP route
monitoring efficiency and accuracy.Currently, it provides the
monitoring of BGP adj-rib-in [RFC7854], BGP local-rib
[I-D.ietf-grow-bmp-local-rib] and BGP adj-rib-out
[I-D.ietf-grow-bmp-adj-rib-out].
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In the MPLS (Multiprotocol Label Switching) VPN traffic egnieering
scenario, the controller distributes optimized route entries with
MPLS VPN labels (inner labels) to the target devices. The target
devices use the inner MPLS VPN labels to find the corresponding VRF
(Virtual routing and forwarding) instance, and then add the optimized
route entries into the target VRF table. Techically, it's workable
to extract the labels from VPNv4 routes by monitoring the VPNv4
routes exchanged between two PE (provider edge) devices, i.e., by
monitoring the adj-rib-out of and adj-rib-in of both PEs. However,
unlike the public BGP routes and IGP routes, VPNv4 routes are not
usually used for either the inter-domain or intra-domain traffic
optmization. Thus, it's not very cost efficient, from the
perspective of CPU and network bandwidth consumption, to monitor the
VPNv4 routes only for the purpose of label extraction.
Depending on the implementation scenarios, there are typically
different ways of allocating the VPN route labels: per route per
label, per VRF per label, per next hop per label, and so on. For
example, in the Multi-AS VPN case, the redistribution of labeled
VPNv4 routes from one AS to another can be realized through setting
up the EBGP peering between ASBRs (Autonomous System Border Routers).
In this case, the per route per label allocation method is preferred.
However, per route per label allocation can be very consuming as for
the label space, thus, in many cases the per VRF/next hop per label
assignment modes are adopted.
This document descrbes a method using BMP to collect the MPLS VPN
label information. A new BMP message type is proposed to carry the
label information. More specifically, in the per route per label
case, the VRF nformation, route prefix and label are included in the
newly defined BMP Label Message. In the per instance per label case,
the VRF information and label are included in the newly defined BMP
Label Message, while in the per next hop per label case, the VRF
information, next hop and label are included in the newly defined BMP
Label Message. The report of BMP Label Message is triggered by the
label assignment chnage.
There are several merits of using the BMP Label Message type to
collect the MPLS VPN labels compared with extracting labels from the
monitored VPNv4 routes:
o It saves work of extracting the label information from the VPNv4
routes, and saves network bandwidth considering that VPNv4 routes
includes all route attributes that are not necessary in this case.
o In the per instance/next hop per label assignment cases, the same
VPN label is used for multiple VPNv4 routes. The BMP Label
Message only report the label information once (if no change), and
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thus saves network resources compared with the repeated label
report by monitoring VPNv4 routes.
o The label assignments are typically less dynamic compared with the
VPNv4 routes. Thus, acquiring the label information through the
real-time monitoring of VPNv4 routes is not quite necessary.
All in all, it's more efficient to collect the MPLS VPN label
independently than extracting it from VPNv4 routes. In Section 2,
the BMP Label Message format is defined, and in Section 3, two
specific implementation examples are provided to show case the usage
of BMP Label Message.
2. VPN TE Using BMP
This document defines a new BMP message type called the Label Message
to carry the VPN label.
2.1. Common Header
This document defines a new BMP message type to carry the VPN label
data.
o Type = TBD: Label Message
The new defined message type is indicated in the Message Type field
of the BMP common header.
2.2. Per Peer Header
The Label Message is not per peer based, thus it does not require the
Per Peer Header.
2.3. Label Message
+--------------------------------+------------------------------+
| Label Assignment Mode | Reserved |
+--------------------------------+------------------------------+
| Label Mapping Information |
+---------------------------------------------------------------+
| Label |
+---------------------------------------------------------------+
Figure 1: BMP Label Message
o Label Assignment Mode (4 Bits): indicates how label is assigned.
Curerntly, 3 types of label assignment mode are defined: "0000"
indicating the per instance per label assignment mode, "0001"
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indicating the per next hop per label assignment mode, "0010"
indicating the per instance per label assignment mode. More modes
can be defined per requirement.
o Reserved (1 Byte): reserved for future use.
o Label Mapping Information (Variable): is interpreted in
combination with the Label Assignment Mode field. If the Label
Assignment Mode field is set to "0000", meaning per instance per
label assignment mode, then this field is set to VRF Route
Distinguisher; If the Label Assignment Mode field is set to
"0001", meaning per next hop per label assignment mode, then this
field is set to the next hop address; If the Label Assignment Mode
field is set to "0010", meaning per route per label assignment
mode, then this field is set to the route prefix.
o Label (3 Bytes): indicates the label value with 20 bits label and
4 bits zero padding.
More specifically, the Label Mapping Information field is defined as
follows. Regarding different values indicated in the Label
Assignment Mode field,
+---------------------------------------------------------------+
| Length |
+---------------------------------------------------------------+
| VRF RD |
+---------------------------------------------------------------+
| Next Hop/Prefix |
+---------------------------------------------------------------+
Figure 2: Label Mapping Information
o Length (2 Bytes): indicates the length of the following Label
Mapping Information value fields. The Length field value SHALL be
set in accordance with the Label Assignment Mode field. If the
Label Assignment Mode is set to "0000", the Length field is set to
the length of the VRF RD field (i.e., 8 Bytes); If the Label
Assignment Mode is set to "0001", the Length field is set to the
length of the VRF RD field (8 Bytes) + the length of the Next Hop
field (variable); If the Label Assignment Mode is set to "0010",
the Length field is set to the length of the VRF RD field (8
Bytes) + the length of the Prefix field (variable).
o VRF RD (8 Bytes): indicates the route distinguisher (RD) of the
VRF. In either the "per instance per label" case, or "per next
hop per label" case, or "per route per label" case, the VRF
information (i.e., RD) SHALL be indicated in this field.
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o Next Hop/Prefix (Variable): is interpreted in combination with the
Label Assignment Mode field and the Length field. If the Label
Assignment Mode is set to "0000", this field SHALL be set empty;
If the Label Assignment Mode is set to "0001", this field SHALL be
set to the next hop address (i.e., the CE's address), with length
indicated by the Length field (i.e., Length value - 8 Bytes); If
the Label Assignment Mode is set to "0010", this field SHALL be
set to the prefix of the route, with length indicated by the
Length field (i.e., Length value - 8 Bytes)
3. Implementation Examples
In this section, we use two examples to more specifically explain how
to use BMP for VPN traffic engineering.
+-------------+
Option 1: | BMP server | Option2:
10.2.1.0/24 +------+ + +---------+10.2.1.0/24
NH:CE1 | | Controller | |NH:PE1
Label:100 | +-+----------++ |Label:100
10.2.0.0/24 | VRF1 ^ ^VRF1 | |
10.1.0.0/24 10.1.1.0/24 | R1:100| |R1:500 | |10.1.1.0/24
+++ NH:PE2 | R2:200| |R2:600 | |NH:PE2
| Label:600 | R3:300| |R3:700 | |Label:600
| | R4:400| |R4:800 | |
| | ******|**|*******|******** |
+----+---+ R1:10.2.0.0/16 v * | | + AS0 * |
| CE1 | R2:10.1.0.0/16 ++-----+ | | Option 1: * |
| (ISP1 +--------------->+ PE1 +--+ | 10.2.1.0/24 * |
| AS1) +------------| | VRF1 | | NH:PE1 * |
+--------+ R1,R2 +----->+ | | Label:100 * |
R3:10.2.0.0/17 | | +------+ | 10.1.1.0/24 * v
R4:10.1.0.0/17 | | * | NH:CE1 +-----++ +---+
+ | | * | Label:600 | PE3 +---+AS4|
v | | * | + | VRF1 | +---+
+----+---+ R3,R4 | | +------+-----+ | | |
| CE2 +---------+ +-->+ PE2 | | +------+
| (ISP2 | | VRF1 +<------------+ *
| AS2) +--------------->+ | *
+--------+ R3,R4 +------+ *
**************************
Figure 3: VPN TE using BMP example: per route per label
Two prefixes 10.2.0.0/24 and 10.1.0.0/24 are generated from ISP1
(AS1), advertised to ISP 2 (AS2) in the format of R3: 10.2.0.0/17,
and R4: 10.1.0.0/17, and also advertised to AS0 in the format of R1:
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10.2.0.0/16, and R2: 10.1.0.0/16. R1, R2 are advertised to both PE1
and PE2 in AS0, and so are R3 and R4. By the rule of the longest
prefix match, any traffic, with the destination address within the
subnets of 10.2.0.0/16 or 10.1.0.0/16, coming from AS4 that traverses
AS0 will exit from PE2. This may cause unbalanced traffic loads on
PE2 and PE1. In addition, the costs of traversing through AS1 and
AS2 might be different due to business contracts assigned between
different ISPs. Now suppose for traffic and cost optimization
purposes, the operator wants to: 1) steer the traffic, with the
destination address within the subnets of 10.2.0.0/16, to exit from
PE1 and then traverse AS1 (ISP1) to its destination; 2) steer the
traffic, with the destination address within the subnets of
10.1.0.0/16, to exit from PE2 and then traverse AS1 (ISP1) to its
destination.
In the example shown in Figure 2, the VPN label assignement mode is
per route per label. Thus, PE1 assigns R1, R2, R3, R4 with label
100, 200, 300, 400, respectively, under VRF1. PE2 assigns R1, R2,
R3, R4 with label 600, 700, 800, 900, respectively, under VRF1.
Using the BMP Label Message, PE1 and PE2 reports to the BMP server
with the per-route labels, which also includes the VRF RD
information. Then the TE controller (suppose it's colocated with the
BMP server) combines the label information with routes, and
distribute the optimized routes with label to either the ingress or
egress devices. There are typically two options:
o Option 1: The controller distributes the optimized route to the
Egress devices, i.e., PE1 and PE2. For optimizing 10.2.0.0/16
traffic, controller distributes 10.2.0.0/24 with next hop as CE1,
label as 100, RT as 100:1 to PE1, so that when traffic, with the
destination address within the subnets of 10.2.0.0/16, arrives at
PE1 will exit from PE1 and choose CE1 (ISP1) as its next hop.
Controller also distributes 10.2.0.0/24 with next hop as PE1,
label as 100, RT as 100:1 to PE1, so that when traffic, with the
destination address within the subnets of 10.2.0.0/16, arrives at
PE2 will exit from PE1 and choose CE1 (ISP1) as its next hop. For
optimizing 10.1.0.0/16 traffic, controller distributes 10.1.0.0/24
with next hop as PE2, label as 600, RT as 100:1 to PE1, so that
when traffic, with the destination address within the subnets of
10.1.0.0/16, arrives at PE1 will exit from PE2 and choose CE1
(ISP1) as its next hop. Controller also distributes 10.1.0.0/24
with next hop as CE1, label as 600, RT as 100:1 to PE2, so that
when traffic, with the destination address within the subnets of
10.1.0.0/16, arrives at PE2 will exit from PE2 and choose CE1
(ISP1) as its next hop.
o Option 2: The controller distributes a more specific route to the
Ingress device, i.e., PE3. Controller distributes 10.2.0.0/24
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with next hop as PE1, label as 100, RT as 100:1 to PE3, so that
when traffic, with the destination address within the subnets of
10.2.0.0/16, arrives at PE3 will exit from PE1 and choose CE1
(ISP1) as its next hop. Controller also distributes 10.1.0.0/24
with next hop as PE2, label as 600, RT as 100:1 to PE3, so that
when traffic, with the destination address within the subnets of
10.2.0.0/16, arrives at PE3 will exit from PE2 and choose CE1
(ISP1) as its next hop.
+-------------+
Option 1: | BMP server | Option2:
10.2.1.0/24 +------+ + +-+ +-----+10.2.1.0/24
NH:CE1 | | Controller | |NH:PE1
Label:1000 | +-+----------++ |Label:1000
| VRF1 ^ ^VRF1 + |
10.2.0.0/24 10.1.1.0/24 |CE1:1000| |CE1:3000 |10.1.1.0/24
10.1.0.0/24 NH:PE2 |CE2:2000| |CE2:4000 |NH:PE2
+++ Label:3000 | | | + |Label:3000
| | | | | |
| | ******|**|*******|******** |
+----+---+ R1:10.2.0.0/16 v * | | + AS0 * |
| CE1 | R2:10.1.0.0/16 ++-----+ | | Option 1: * |
| (ISP1 +--------------->+ PE1 +--+ | 10.2.1.0/24 * |
| AS1) +------------| | VRF1 | | NH:PE1 * |
+--------+ R1,R2 +----->+ | | Label:1000 * |
R3:10.2.0.0/17 | | +------+ | 10.1.1.0/24 * v
R4:10.1.0.0/17 | | * | NH:CE1 +-----++ +---+
| | | * | Label:3000| PE3 +---+AS4|
v | | * | + | VRF1 | +---+
+----+---+ R3,R4 | | +------+-----+ | | |
| CE2 +---------+ +-->+ PE2 | | +------+
| (ISP2 | | VRF1 +<------------+ *
| AS2) +--------------->+ | *
+--------+ R3,R4 +------+ *
**************************
Figure 4: VPN TE using BMP example: per next hop per label
In the example shown in Figure 3, he VPN label assignement mode is
per next hop per label. Comparing the two examples in Figure 2 and
Figure 3, less label information are reported though BMP if the label
is allocated per next hop.
4. Acknowledgements
TBD.
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5. IANA Considerations
TBD.
6. Security Considerations
TBD.
7. Normative References
[I-D.ietf-grow-bmp-adj-rib-out]
Evens, T., Bayraktar, S., Lucente, P., Mi, K., and S.
Zhuang, "Support for Adj-RIB-Out in BGP Monitoring
Protocol (BMP)", draft-ietf-grow-bmp-adj-rib-out-03 (work
in progress), December 2018.
[I-D.ietf-grow-bmp-local-rib]
Evens, T., Bayraktar, S., Bhardwaj, M., and P. Lucente,
"Support for Local RIB in BGP Monitoring Protocol (BMP)",
draft-ietf-grow-bmp-local-rib-02 (work in progress),
September 2018.
[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>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
[RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
"Multiprotocol Extensions for BGP-4", RFC 4760,
DOI 10.17487/RFC4760, January 2007,
<https://www.rfc-editor.org/info/rfc4760>.
[RFC7854] Scudder, J., Ed., Fernando, R., and S. Stuart, "BGP
Monitoring Protocol (BMP)", RFC 7854,
DOI 10.17487/RFC7854, June 2016,
<https://www.rfc-editor.org/info/rfc7854>.
Authors' Addresses
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Yunan Gu
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: guyunan@huawei.com
Jie Chen
Tencent
Email: jasonjchen@tencent.com
Penghui Mi
Huawei
Shenzhen, Guangdong
China
Email: mipenghui@huawei.com
Shunwan Zhuang
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: zhuangshunwan@huawei.com
Zhenbin Li
Huawei
Huawei Bld., No.156 Beiqing Rd.
Beijing 100095
China
Email: lizhenbin@huawei.com
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