IDR Z. Li Internet-Draft China Mobile Intended status: Standards Track J. Dong Expires: September 16, 2016 Huawei Technologies March 15, 2016 Carry congestion status in BGP extended community draft-li-idr-congestion-status-extended-community-00 Abstract A new extended community is introduced in this document to carry the link congestion status, especially for the exit link of one AS. We call this extended community congestion status community, which can be used by the BGP routers to steer the Internet-access traffic among the exit links by deploying policy routing. 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 [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 http://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 16, 2016. 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 Li & Dong Expires September 16, 2016 [Page 1] Internet-Draft CS extended community March 2016 (http://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. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Congestion Status Extended Community . . . . . . . . . . . . 4 2.1. Congestion Status Extended Community for Two-Octet AS . . 4 2.2. Congestion Status Extended Community for Four-Octet AS . 5 3. Security Considerations . . . . . . . . . . . . . . . . . . . 6 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 5. Normative References . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction typically the architecture of a large scale ISP's network is multi- layered, as illustrated in Figure 1. The national backbone network has its own AS, and each of the province or state network has a specific AS. Backbone network connects all the province or state networks together and has several exit links to access the Internet. In some circumstances, the province or state network may have direct exit links to the Internet. The total bandwidth of the backbone exit links is usually much bigger than that of the direct exit links in the province or state networks. Thus, the Internet-access traffic is mainly transported through the backbone exit links by deploying route policies on the ASBR routers in the province or state networks. The ASBR routers in the province or state networks, for example, prefer the routes learned from the backbone by setting higher local preference for those routes. However, when the backbone exit links are congested due to traffic increasing or delay of the capacity expansion, the ASBR routers in the province or state networks do not know this, and still delivery Internet-access traffic to the backbone. The customer experience deteriorates, the operator, in turn, will receive more and more complaints for its bad network performance. Then, the operator has to steer some Internet-access traffic to the direct exit links in the province or state networks by deploying route policy on the ASBR routers. This kind of policy should be removed when the capacity expansion of the backbone exit links is done. The ASBR routers do not konw this again. Li & Dong Expires September 16, 2016 [Page 2] Internet-Draft CS extended community March 2016 +---------------------------------------------------------+ | | | Internet | | +----------+ +----------+ +----------+ | +-| Router a |----------| Router b |---------| Router c |-+ +----------+ +----------+ +----------+ / \ \ / ---/-----\-------------------\------------------/---------- | \ \ /ISP Network | +----------+ +----------+ +----------+ | +-| Router 1 |----| Router 2 |----| Router 3 |-+ | | +----------+ +----------+ +----------+ | | | | | | BACKBONE | | | AS B | | | +----------+ +----------+ +----------+ | | +-| Router L |----| Router M |----| Router N |-+ | +----------+ +----------+ +----------+ | / | \ | / | \ +----------+ +----------+ +----------+ +-| Router X |-+ +-| Router Y |-+ +-| Router Z |-+ | +----------+ | | +----------+ | | +----------+ | | province X | | province Y | | province Z | | AS X | | AS Y | | AS Z | +--------------+ +--------------+ +--------------+ Figure 1 This document introduces a new extended community [RFC4360] to delivery the congestion status of the exit link to other BGP peers. The BGP receiver can then use this community to deploy route policy, thus steer Internet-access traffic according to the congestion status of the exit link. Router X in the above figure, for example, can steer some Internet-access traffic to the direct exit link when it knows the backbone exit link is congested. The introduced community is called congestion status extended community. Congestion status extended community is good not only to the ASBRs in other AS, but also to the BGP peers within one AS. For instance, Router M in backbone AS chooses Router 2 to transport the Internet- access traffic by default. When Router M receives congestion status extended communities from Router 1,2,3, which indicate the utilization of the exit link of Router 1,2,3 is 90%, 70%, and 50% respectively, it can choose Router 3 to transport some Internet- access traffic using route policy. Li & Dong Expires September 16, 2016 [Page 3] Internet-Draft CS extended community March 2016 2. Congestion Status Extended Community As described in [RFC4360], the extended community attribute is an 8-octet value with the first one or two octets to indicate the type of this attribute. Since congestion status extended community needs to be delivered from on AS to other ASes, and used by the BGP speakers both in other ASes and within the same AS as the sender, it MUST be a transitive extended community, i.e. the T bit in the first octet MUST be zero. Congestion status extended community has two encoding formats, one is for two-octet AS, the other is for four-octet AS. 2.1. Congestion Status Extended Community for Two-Octet AS Congestion status extended community for two-octet AS is a sub-type allocated from Transitive Two-Octet AS-Specific Extended Community Sub-Types defined in section 5.2.2 of [RFC7153]. Its format is as Figure 2. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x00 | Sub-Type | Sender AS Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | Bandwidth | Utilization | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2 The "Type" field MUST be 0x00, which indicate this is a Transitive Two-Octet AS-Specific Extended Community. The "Sub-Type" field is used to indicate this is a Congestion Status Extended Community. Its value is to be assigned by IANA. 0x06 is suggested. The "Sender AS Number" field is 2 octets. Its value is the AS number of the BGP speaker who generates this congestion status extended community. The generator MUST have 2-octct AS number. The "Reserved" field is 2 octets. This field is used to align with the Congestion Status Extended Community for Four-Octet AS defined in the next section of this document. Its value SHOULD be zero. The BGP peers who receive this community MUST ignore this field. Li & Dong Expires September 16, 2016 [Page 4] Internet-Draft CS extended community March 2016 The "Bandwidth" field is 1 octet. Its value is the bandwidth of the exit link in unit of gbps (gigabits per second). The "Utilization" field is 1 octet. Its value is the utilization of the exit link in unit of percent. We can use the "Utilization" field together with the "Bandwidth" field to calculate the traffic load that we can further steer to this exit link. 2.2. Congestion Status Extended Community for Four-Octet AS Congestion status extended community for four-octet AS is a sub-type allocated from Transitive Four-Octet AS-Specific Extended Community Sub-Types defined in section 5.2.4 of [RFC7153]. Its format is as Figure 3. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x02 | Sub-Type | Sender AS Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sender AS Number (cont.) | Bandwidth | Utilization | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3 The "Type" field MUST be 0x02, which indicate this is a Transitive Four-Octet AS-Specific Extended Community. The "Sub-Type" field is used to indicate this is a Congestion Status Extended Community. Its value is to be assigned by IANA. 0x06 is suggested. The "Sender AS Number" field is 4 octets. Its value is the AS number of the BGP speaker who generates this congestion status extended community. The generator MUST have 4-octct AS number. The "Bandwidth" field is 1 octet. Its value is the bandwidth of the exit link in unit of gbps (gigabits per second). The "Utilization" field is 1 octet. Its value is the utilization of the exit link in unit of percent. We can use the "Utilization" field together with the "Bandwidth" field to calculate the traffic load that we can further steer to this exit link. Li & Dong Expires September 16, 2016 [Page 5] Internet-Draft CS extended community March 2016 3. Security Considerations Malicious router may use the congestion status extended community to interfere the traffic steering decision of the BGP receiver. BGP peers SHOULD use MD5 for authentication [RFC4360]. BGP receiver SHOULD only accept the congestion status community or extended community delivered from BGP peers with MD5 authentication. 4. IANA Considerations One sub-type is solicited to be assigned from Transitive Two-Octet AS-Specific Extended Community Sub-Types registry to indicate the extended community with Type 0x00 is a Congestion Status Extended Community for Two-Octet AS. 0x06 is suggested. One sub-type is solicited to be assigned from Transitive Four-Octet AS-Specific Extended Community Sub-Types registry to indicate the extended community with Type 0x02 is a Congestion Status Extended Community for Four-Octet AS. 0x06 is suggested. 5. 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, . [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended Communities Attribute", RFC 4360, DOI 10.17487/RFC4360, February 2006, . [RFC7153] Rosen, E. and Y. Rekhter, "IANA Registries for BGP Extended Communities", RFC 7153, DOI 10.17487/RFC7153, March 2014, . Authors' Addresses Zhenqiang Li China Mobile No.32 Xuanwumenxi Ave., Xicheng District Beijing 100032 P.R. China Email: li_zhenqiang@hotmail.com Li & Dong Expires September 16, 2016 [Page 6] Internet-Draft CS extended community March 2016 Jie Dong Huawei Technologies Huawei Campus, No.156 Beiqing Rd. Beijing 100095 P.R. China Email: jie.dong@huawei.com Li & Dong Expires September 16, 2016 [Page 7]