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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (January 19, 2015) is 3357 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group X. Xu 3 Internet-Draft Huawei 4 Intended status: Informational S. Hares 5 Expires: July 23, 2015 Individual 6 Y. Fan 7 China Telecom 8 C. Jacquenet 9 Orange 10 B. Fee 11 Extreme Networks 12 W. Henderickx 13 Alcatel-Lucent 14 January 19, 2015 16 FIB Reduction in Virtual Subnet 17 draft-xu-l3vpn-virtual-subnet-fib-reduction-02 19 Abstract 21 Virtual Subnet is a BGP/MPLS IP VPN-based subnet extension solution 22 which is intended for building Layer3 network virtualization overlays 23 within and/or across data centers. This document describes a 24 mechanism for reducing the FIB size of PE routers in the Virtual 25 Subnet context. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on July 23, 2015. 44 Copyright Notice 46 Copyright (c) 2015 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 62 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 63 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 64 3. Solution Description . . . . . . . . . . . . . . . . . . . . 3 65 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 66 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 67 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 68 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 69 7.1. Normative References . . . . . . . . . . . . . . . . . . 5 70 7.2. Informative References . . . . . . . . . . . . . . . . . 5 71 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 73 1. Introduction 75 Virtual Subnet [I-D.ietf-l3vpn-virtual-subnet] is a BGP/MPLS IP VPN 76 [RFC4364] -based subnet extension solution which is intended for 77 building Layer3 network virtualization overlays within and/or across 78 data centers. In the Virtual Subnet context, since CE host routes of 79 a given VPN instance need to be exchanged among PE routers 80 participating in that VPN instance, the resulting forwarding table 81 (a.k.a. FIB) size of PE routers may become a big concern in large- 82 scale data center environment where they may need to install a huge 83 amount of host routes into their forwarding tables. In some cases 84 where host routes need to be maintained on the control plane, it 85 needs a method to reduce the FIB size of PE routers without any 86 change to the RIB and the routing table. Therefore, this document 87 proposes a very simple mechanism for reducing the FIB size of PE 88 routers. The basic idea of this mechanism is: Those host routes 89 learnt from remote PE routers are selectively installed into the FIB 90 while the remaining routes including local CE host routes are 91 installed into the FIB by default as before. 93 1.1. Requirements Language 95 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 96 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 97 document are to be interpreted as described in RFC 2119 [RFC2119]. 99 2. Terminology 101 This memo makes use of the terms defined in [RFC4364]. 103 3. Solution Description 105 +----------+ 106 +----+PE/RR(APR)+----+ 107 +-----------------+ | +----------+ | +-----------------+ 108 |VPN_A:1.1.1.1/24 | | | |VPN_A:1.1.1.1/24 | 109 | \ | | | | / | 110 | +------+ \++---+-+ +-+---++/ +------+ | 111 | |Host A+------+ PE-1 | | PE-2 +------+Host B| | 112 | +------+\ ++-+-+-+ +-+-+-++ /+------+ | 113 | 1.1.1.2/24 | | | | | | 1.1.1.3/24 | 114 | | | | | | | | 115 | DC West | | | IP/MPLS Backbone | | | DC East | 116 +-----------------+ | | | | +-----------------+ 117 | +--------------------+ | 118 | | 119 VRF: V VRF:V 120 +------------+---------+--------+------+ +------------+---------+--------+------+ 121 | Prefix | Nexthop |Protocol|In_FIB| | Prefix | Nexthop |Protocol|In_FIB| 122 +------------+---------+--------+------+ +------------+---------+--------+------+ 123 | 1.1.1.1/32 |127.0.0.1| Direct | Yes | | 1.1.1.1/32 |127.0.0.1| Direct | Yes | 124 +------------+---------+--------+------+ +------------+---------+--------+------+ 125 | 1.1.1.2/32 | 1.1.1.2 | Direct | Yes | | 1.1.1.2/32 | PE-1 | IBGP | No | 126 +------------+---------+--------+------+ +------------+---------+--------+------+ 127 | 1.1.1.3/32 | PE-2 | IBGP | No | | 1.1.1.3/32 | 1.1.1.3 | Direct | Yes | 128 +------------+---------+--------+------+ +------------+---------+--------+------+ 129 | 1.1.1.0/25 | APR | IBGP | Yes | | 1.1.1.0/25 | APR | IBGP | Yes | 130 +------------+---------+--------+------+ +------------+---------+--------+------+ 131 |1.1.1.128/25| APR | IBGP | Yes | |1.1.1.128/25| APR | IBGP | Yes | 132 +------------+---------+--------+------+ +------------+---------+--------+------+ 133 | 1.1.1.0/24 | 1.1.1.1 | Direct | Yes | | 1.1.1.0/24 | 1.1.1.1 | Direct | Yes | 134 +------------+---------+--------+------+ +------------+---------+--------+------+ 136 Figure 1: Selective FIB Installation Example 138 To reduce the FIB size of PE routers, the selective FIB installation 139 concept as described in [I-D.ietf-grow-va] can be leveraged in the 140 Virtual Subnet context. Take the VPN instance demonstrated in 141 Figure 1 as an example, the FIB reduction procedures are described as 142 follows: 144 1. Multiple more specific prefixes (e.g., 1.1.1.0/25 and 145 1.1.1.128/25) corresponding to an extended subnet (i.e., 146 1.1.1.0/24) are specified as Virtual Prefixes (VPs). Meanwhile, 147 one or more PE routers (or route reflectors) are configured as 148 Aggregation Point Routers (APR) for each VP. The APRs for a 149 given VP would install a null route to that VP while propagating 150 a route to that VP via the L3VPN signaling. 152 2. For a given host route in the routing table which is learnt from 153 any remote PE router, PE routers which are non-APRs for any VP 154 covering this host route would not install it into the FIB by 155 default. In contrast, PE routers (or route reflectors) which are 156 APRs for any VP covering that host route would install it into 157 the FIB. If one or more particular remote host routes need to be 158 installed by non-APR PE routers by default as well for whatever 159 reasons, the best way to realize such goal is to attach a special 160 extended communities attribute to those particular host routes 161 either by originating PE routers or by route reflectors. Upon 162 receiving any host routes attached with the above extended 163 communities attribute, non-APR PE routers SHOULD install them by 164 default. 166 3. Upon receiving a packet destined for a given remote CE host, if 167 no host route for that CE host is found in the FIB, the ingress 168 PE router would forward the packet to a given APR according to 169 the longest-matching VP route, which in turn forwards the packet 170 to the final egress PE router. In this way, the FIB size of 171 those non-APR PE routers can be greatly reduced at the potential 172 cost of path stretch. 174 In order to forward packets destined for remote CE hosts directly to 175 the final egress PE routers without the potential path stretch 176 penalty, non-APR PE routers could perform on-demand FIB installation 177 for remote host routes which are available in the routing table. For 178 example, upon receiving an ARP request or Neighbor Solicitation (NS) 179 message from a local CE host, the non-APR PE router would perform a 180 lookup in the routing table. If a corresponding host route for the 181 target host is found but not yet installed into the FIB, it would be 182 installed into the FIB. Another possible way to trigger on-demand 183 FIB installation is as follows: when receiving a packet whose 184 longest-matching FIB entry is a particular VP route learnt from any 185 APR, a copy of this packet would be sent to the control plane while 186 this original packet is forwarded as normal. The above copy sent to 187 the control plane would trigger a lookup in the routing table. If a 188 corresponding host route is found but not yet installed into the FIB, 189 it would be installed into the FIB. To provide robust protection 190 against DoS attacks on the control plane, rate-limiting of the above 191 packets sent to the control plane MUST be enabled. Those FIB entries 192 for remote CE host routes which are on-demand installed on non-APR PE 193 routers would expire if not used for a certain period of time. 195 4. Acknowledgements 197 The authors would like to thank Truman Boyes,Brendan Fee, Robert 198 Raszuk and Bruno Decraene for their valuable suggestions on this 199 document. 201 5. IANA Considerations 203 The type value for the Extended Communities Attributes as described 204 in this doc is required to be allocated by the IANA. 206 6. Security Considerations 208 This document does not introduce any new security risk. 210 7. References 212 7.1. Normative References 214 [I-D.ietf-l3vpn-virtual-subnet] 215 Xu, X., Raszuk, R., Hares, S., Yongbing, F., Jacquenet, 216 C., Boyes, T., and B. Fee, "Virtual Subnet: A L3VPN-based 217 Subnet Extension Solution", draft-ietf-l3vpn-virtual- 218 subnet-03 (work in progress), December 2014. 220 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 221 Requirement Levels", BCP 14, RFC 2119, March 1997. 223 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 224 Networks (VPNs)", RFC 4364, February 2006. 226 7.2. Informative References 228 [I-D.ietf-grow-va] 229 Francis, P., Xu, X., Ballani, H., Jen, D., Raszuk, R., and 230 L. Zhang, "FIB Suppression with Virtual Aggregation", 231 draft-ietf-grow-va-06 (work in progress), December 2011. 233 Authors' Addresses 235 Xiaohu Xu 236 Huawei 238 Email: xuxiaohu@huawei.com 240 Susan Hares 241 Individual 243 Email: shares@ndzh.com 245 Yongbing Fan 246 China Telecom 248 Email: fanyb@gsta.com 250 Christian Jacquenet 251 Orange 253 Email: christian.jacquenet@orange.com 255 Brendan Fee 256 Extreme Networks 258 Email: bfee@enterasys.com 260 Wim Henderickx 261 Alcatel-Lucent 263 Email: wim.henderickx@alcatel-lucent.com