FIB Reduction in Virtual Subnet
draft-ietf-bess-virtual-subnet-fib-reduction-03
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Expired".
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|
|---|---|---|---|
| Authors | Xiaohu Xu , Christian Jacquenet , Truman Boyes , Brendan Fee , Wim Henderickx | ||
| Last updated | 2016-08-03 | ||
| Replaces | draft-xu-l3vpn-virtual-subnet-fib-reduction | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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| Additional resources | Mailing list discussion | ||
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draft-ietf-bess-virtual-subnet-fib-reduction-03
Network Working Group X. Xu
Internet-Draft Huawei
Intended status: Informational C. Jacquenet
Expires: February 4, 2017 Orange
T. Boyes
Bloomberg LP
B. Fee
Extreme Networks
W. Henderickx
Alcatel-Lucent
August 3, 2016
FIB Reduction in Virtual Subnet
draft-ietf-bess-virtual-subnet-fib-reduction-03
Abstract
Virtual Subnet is a BGP/MPLS IP VPN-based subnet extension solution
which is intended for building Layer3 network virtualization overlays
within and/or between data centers. This document describes a
mechanism for reducing the FIB size of PE routers in the Virtual
Subnet context.
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 February 4, 2017.
Copyright Notice
Copyright (c) 2016 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
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Solution Description . . . . . . . . . . . . . . . . . . . . 3
4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
Virtual Subnet [RFC7814] is a BGP/MPLS IP VPN [RFC4364] -based subnet
extension solution which is intended for building Layer3 network
virtualization overlays within and/or across data centers. In the
Virtual Subnet context, since CE host routes of a given VPN instance
need to be exchanged among PE routers participating in that VPN
instance, the resulting forwarding table (a.k.a. FIB) size of PE
routers may become a big concern in large-scale data center
environment where they may need to install a huge amount of host
routes into their forwarding tables. In some cases where host routes
need to be maintained on the control plane, it needs a method to
reduce the FIB size of PE routers without any change to the RIB and
the routing table. Therefore, this document proposes a very simple
mechanism for reducing the FIB size of PE routers. The basic idea of
this mechanism is: Those host routes learnt from remote PE routers
are selectively installed into the FIB while the remaining routes
including local CE host routes are installed into the FIB by default
as before.
1.1. 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].
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2. Terminology
This memo makes use of the terms defined in [RFC4364].
3. Solution Description
+----------+
+----+PE/RR(APR)+----+
+------------------+ | +----------+ | +------------------+
|VPN_A:192.0.2.1/24| | | |VPN_A:192.0.2.1/24|
| \ | | | | / |
| +------+ \ ++---+-+ +-+---++/ +------+ |
| |Host A+------_+ PE-1 | | PE-2 +------+Host B| |
| +------+\ ++-+-+-+ +-+-+-++ /+------+ |
| 192.0.2.2/24 | | | | | | 192.0.2.3/24 |
| | | | | | | |
| DC West | | | IP/MPLS Backbone | | | DC East |
+------------------+ | | | | +------------------+
| +--------------------+ |
| |
VRF: V VRF:V
+--------------+---------+--------+------+ +--------------+---------+--------+------+
| Prefix | Nexthop |Protocol|In_FIB| | Prefix | Nexthop |Protocol|In_FIB|
+--------------+---------+--------+------+ +--------------+---------+--------+------+
|192.0.2.1/32 |127.0.0.1| Direct | Yes | |192.0.2.1/32 |127.0.0.1| Direct | Yes |
+--------------+---------+--------+------+ +--------------+---------+--------+------+
|192.0.2.2/32 |192.0.2.2| Direct | Yes | |192.0.2.2/32 | PE-1 | IBGP | No |
+--------------+---------+--------+------+ +--------------+---------+--------+------+
|192.0.2.3/32 | PE-2 | IBGP | No | |192.0.2.3/32 |192.0.2.3| Direct | Yes |
+--------------+---------+--------+------+ +--------------+---------+--------+------+
|192.0.2.0/25 | APR | IBGP | Yes | |192.0.2.0/25 | APR | IBGP | Yes |
+--------------+---------+--------+------+ +--------------+---------+--------+------+
|192.0.2.128/25| APR | IBGP | Yes | |192.0.2.128/25| APR | IBGP | Yes |
+--------------+---------+--------+------+ +--------------+---------+--------+------+
|192.0.2.0/24 |192.0.2.1| Direct | Yes | |192.0.2.0/24 |192.0.2.1| Direct | Yes |
+--------------+---------+--------+------+ +--------------+---------+--------+------+
Figure 1: Selective IPv4 FIB Installation Example
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+----------+
+----+PE/RR(APR)+----+
+--------------------+ | +----------+ | +----------------+
|VPN_A: | | | |VPN_A: |
|2001:db8::1/64 | | | |2001:db8::1/64 |
| \ | | | | / |
| +------+ \ ++---+-+ +-+---++/ +------+ |
| |Host A+------_+ PE-1 | | PE-2 +------+Host B| |
| +------+\ ++-+-+-+ +-+-+-++ /+------+ |
| 2001:db8::2/64 | | | | | | 2001:db8::3/64 |
| | | | | | | |
| DC West | | | IP/MPLS Backbone | | | DC East |
+------------------+ | | | | +------------------+
| +--------------------+ |
| |
VRF: V VRF:V
+----------------+-----------+--------+------+ +----------------+-----------+--------+------+
| Prefix | Nexthop |Protocol|In_FIB| | Prefix | Nexthop |Protocol|In_FIB|
+----------------+-----------+--------+------+ +----------------+-----------+--------+------+
|2001:db8::1/64 | ::1 | Direct | Yes | |2001:db8::1/64 | ::1 | Direct | Yes |
+----------------+-----------+--------+------+ +----------------+-----------+--------+------+
|2001:db8::2/64 |2001:db8::2| Direct | Yes | |2001:db8::2/64 | PE-1 | IBGP | No |
+----------------+-----------+--------+------+ +----------------+-----------+--------+------+
|2001:db8::3/64 | PE-2 | IBGP | No | |2001:db8::3/64 |2001:db8::3| Direct | Yes |
+----------------+-----------+--------+------+ +----------------+-----------+--------+------+
|2001:db8::0/63 | APR | IBGP | Yes | |2001:db8::0/63 | APR | IBGP | Yes |
+----------------+-----------+--------+------+ +----------------+-----------+--------+------+
|2001:db8::128/63| APR | IBGP | Yes | |2001:db8::128/63| APR | IBGP | Yes |
+----------------+-----------+--------+------+ +----------------+-----------+--------+------+
|2001:db8::0/64 |2001:db8::1| Direct | Yes | |2001:db8::0/64 |2001:db8::1| Direct | Yes |
+----------------+-----------+--------+------+ +----------------+-----------+--------+------+
Figure 2: Selective IPv6 FIB Installation Example
To reduce the FIB size of PE routers, the selective FIB installation
concept as described in [I-D.ietf-grow-va] can be leveraged in the
Virtual Subnet context. Take the VPN instance demonstrated in
Figure 1 or Figure 2 as an example, the FIB reduction procedures are
described as follows:
1. Multiple more specific prefixes (e.g., 192.0.2.0/25 and
192.0.2.128/25 in IPv4 example, or 2001:db8::0/63 and
2001:db8::128/63 in IPv6 example ) corresponding to an extended
subnet (i.e., 192.0.2.0/24 in IPv4 example, or 2001:db8::0/64 in
IPv6 example) are specified as Virtual Prefixes (VPs).
Meanwhile, one or more PE routers (or route reflectors) are
configured as Aggregation Point Routers (APR) for each VP. The
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APRs for a given VP would install a null route to that VP while
propagating a route to that VP via the L3VPN signaling.
2. For a given host route in the routing table which is learnt from
any remote PE router, PE routers which are non-APRs for any VP
covering this host route would not install it into the FIB by
default. In contrast, PE routers (or route reflectors) which are
APRs for any VP covering that host route would install it into
the FIB. If one or more particular remote host routes need to be
installed by non-APR PE routers by default as well for whatever
reasons, the best way to realize such goal is to attach a special
extended communities attribute to those particular host routes
either by originating PE routers or by route reflectors. Upon
receiving any host routes attached with the above extended
communities attribute, non-APR PE routers SHOULD install them by
default.
3. Upon receiving a packet destined for a given remote CE host, if
no host route for that CE host is found in the FIB, the ingress
PE router would forward the packet to a given APR according to
the longest-matching VP route, which in turn forwards the packet
to the final egress PE router. In this way, the FIB size of
those non-APR PE routers can be greatly reduced at the potential
cost of path stretch.
In order to forward packets destined for remote CE hosts directly to
the final egress PE routers without the potential path stretch
penalty, non-APR PE routers could perform on-demand FIB installation
for remote host routes which are available in the routing table. For
example, upon receiving an ARP request or Neighbor Solicitation (NS)
message from a local CE host, the non-APR PE router would perform a
lookup in the routing table. If a corresponding host route for the
target host is found but not yet installed into the FIB, it would be
installed into the FIB. Another possible way to trigger on-demand
FIB installation is as follows: when receiving a packet whose
longest-matching FIB entry is a particular VP route learnt from any
APR, a copy of this packet would be sent to the control plane while
this original packet is forwarded as normal. The above copy sent to
the control plane would trigger a lookup in the routing table. If a
corresponding host route is found but not yet installed into the FIB,
it would be installed into the FIB. To provide robust protection
against DoS attacks on the control plane, rate-limiting of the above
packets sent to the control plane MUST be enabled. Those FIB entries
for remote CE host routes which are on-demand installed on non-APR PE
routers would expire if not used for a certain period of time.
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4. Acknowledgements
The authors would like to thank Susan Hares, Yongbing Fan, Robert
Raszuk, Bruno Decraene and Fred Baker for their valuable suggestions
on this document.
5. IANA Considerations
The type value for the Extended Communities Attributes as described
in this doc is required to be allocated by the IANA.
6. Security Considerations
Those security considerations as described in [RFC7814] are
applicable to this document. This document does not introduce any
new security risk.
7. References
7.1. 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>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <http://www.rfc-editor.org/info/rfc4364>.
[RFC7814] Xu, X., Jacquenet, C., Raszuk, R., Boyes, T., and B. Fee,
"Virtual Subnet: A BGP/MPLS IP VPN-Based Subnet Extension
Solution", RFC 7814, DOI 10.17487/RFC7814, March 2016,
<http://www.rfc-editor.org/info/rfc7814>.
7.2. Informative References
[I-D.ietf-grow-va]
Francis, P., Xu, X., Ballani, H., Jen, D., Raszuk, R., and
L. Zhang, "FIB Suppression with Virtual Aggregation",
draft-ietf-grow-va-06 (work in progress), December 2011.
Authors' Addresses
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.com
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Christian Jacquenet
Orange
Email: christian.jacquenet@orange.com
Truman Boyes
Bloomberg LP
Email: tboyes@bloomberg.net
Brendan Fee
Extreme Networks
Email: bfee@enterasys.com
Wim Henderickx
Alcatel-Lucent
Email: wim.henderickx@alcatel-lucent.com
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