INTERNET-DRAFT Kesava Vijaya Krupakaran Intended Status: Proposed Standard Janardhanan Pathangi Narasimhan Expires: March 2, 2013 Dell-Force10 August 29, 2012 Fair Share AF Load Share draft-kvk-trill-fair-share-af-load-share-00 Abstract In an access LAN of a TRILL campus, the DRB can choose to load share the AF responsibility among other RBridges in the LAN. This document throws light on one such approach where the AF appointment is fair share scheduled among the RBridges. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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. 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Table of Contents 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 2 Shares . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3 AF Affinity VLAN Set . . . . . . . . . . . . . . . . . . . . . 4 4 AF and VLAN Mapping . . . . . . . . . . . . . . . . . . . . . . 5 5 AF and Multiple ports on a link . . . . . . . . . . . . . . . . 5 6 Multi-Topology-Aware Port Capability Sub-TLVs . . . . . . . . . 5 6.1 Fair Share Sub-TLV . . . . . . . . . . . . . . . . . . . . 5 6.2 AF Affinity VLAN Set Sub-TLV . . . . . . . . . . . . . . . 6 6.3 Partial VLANs Appointing Sub-TLV . . . . . . . . . . . . . 6 7 Security Considerations . . . . . . . . . . . . . . . . . . . . 7 8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7 9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 9.1 Normative References . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 kvk, et al Expires March 2, 2013 [Page 2] INTERNET DRAFT Fair Share AF Load Share August 29, 2012 1 Introduction In a shared access LAN, the appointed forwarder for a VLAN is responsible for encapsulating and decapsulating native traffic on that VLAN. Other non-AF RBridges in the LAN discard the native traffic for that VLAN. The DRB can choose to be the AF for all VLANs or load share the AF responsibility among other RBRidges in the LAN. This ensures better utilization of resources like hardware tables and buffers. The VLAN partitioning scheme suggested in [RFC6439] section 2.2.1 is static and requires careful configuration. Another simple protocol would be to allocate VLANs in a round-robin fashion among all RBridges in the LAN. However this doesn't leave scope for schemes like retaining 50% of VLANs with the DRB and distribute only the rest among others. Fair share scheduling of AF allows for the flexibility of assigning certain RBridges (say with higher switching capability) AF for higher proportion of VLANs than others. 1.1 Terminology This document uses the acronyms defined in [RFC6439]. 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]. 2 Shares Each RBridge is configured with certain quantity of shares. A share is the proportion of VLANs which would be allocated to the RBridge in comparison with other RBridges. The face value of the shares is a relative quantity and makes sense only when taken in conjunction with total shares allocated in the LAN. These shares are advertised by each RBridge in its hello. The DRB load shares the AF among RBridges based on the relative value of shares. For instance, let A, B and C be three RBridges with S(A) = 2, S(B) = 1 and S(C) = 1. Then A is assigned the AF for 1/2 of the VLANs while B and C the AF for 1/4th of the VLANs each. Even when the number of VLANs for which the RBridge is to be AF calculates to a non integer value, it should be made sure that there kvk, et al Expires March 2, 2013 [Page 3] INTERNET DRAFT Fair Share AF Load Share August 29, 2012 is only one AF for a VLAN in a multi-access LAN. 3 AF Affinity VLAN Set Fair share scheduling distributes VLANs among RBridges according to proportion of shares allocated. This allows allocation of higher proportion of VLANs to certain RBridges (with higher switching capability). However, this does not guarantee that these RBridges would handle larger share of the native traffic. Following the previous example, even though A is appointed AF for 50% of the VLANs while B only 25% of the VLANs, the traffic load of VLANs for which B is AF could be considerably higher that those in A. In order to overcome this conundrum, each RBriged in access LAN is configured with an AF Affinity VLAN Set apart form the share proportion. This RBridge has AF affinity to the set of configured VLANs. Thus when the DRB appoints an RBridge AF for a set of VLANs, the members of the set are chosen from the AF Affinity VLAN Set advertised. Expanding on the previous example, if X denotes an RBridge, let S(X) be the shares assigned to X, V(X) be the AF Affinity VLAN Set and AF(X) denote the set of VLANs for which X is assigned AF. Let the access LAN encompass ten shared VLANs [11, 20]. In this case the AF assignment with just the shares configured could be as in Table 1. If RBridge A has higher switching capability and VLANs [16, 20] are heavily loaded, this AF appointment defeats the purpose. +----------------------------------------------------+ |Table 1: AF appointment using fair share scheduling | +--------+-------------+-----------------------------+ | X | S(X) | AF(X) | +--------+-------------+-----------------------------+ | A | 2 | {11, 12, 13, 14, 15} | +--------+-------------+-----------------------------+ | B | 1 | {16, 17, 18} | +--------+-------------+-----------------------------+ | C | 1 | {19, 20} | +--------+-------------+-----------------------------+ By configuring AF Affinity VLAN set in each RBridge, this difficulty can be overcome. Such a configuration is shown in Table 2. How the AF Affinity VLAN set is arrived at is beyond the scope of this document. Long term traffic planning tools could be helpful in extrapolating a decent configuration. kvk, et al Expires March 2, 2013 [Page 4] INTERNET DRAFT Fair Share AF Load Share August 29, 2012 +----------------------------------------------------------+ |Table 2: Fair share scheduling with AF Affinity VLAN set | +--+-------+-----------------------+-----------------------+ |X | S(X) | V(X) | AF(X) | +--+-------+-----------------------+-----------------------+ |A | 2 | {16, 17, 18, 19, 20} | {16, 17, 18, 19, 20} | +--+-------+-----------------------+-----------------------+ |B | 1 | {11, 12, 13, 14} | {11, 12, 13} | +--+-------+-----------------------+-----------------------+ |C | 1 | {12, 13, 14} | {14, 15} | +--+-------+-----------------------+-----------------------+ 4 AF and VLAN Mapping If the DRB detects VLAN mapping, it appoints one RBridge (possibly itself) as the AF for all VLANs as suggested in [RFC6439] section 2.4 to prevent loops. 5 AF and Multiple ports on a link The shares configured represents the whole RBridge's proportion of AF sought. Further load sharing of AF among multiple ports on same link in an RBridge is a local decision. 6 Multi-Topology-Aware Port Capability Sub-TLVs Two new Multi-Topology-Aware Port Capability Sub-TLVs are required for the purpose of fair share AF appointment - Fair Share Sub-TLV and AF Affinity VLAN Set Sub-TLV. 6.1 Fair Share Sub-TLV Fair Share Sub-TLV is used to advertise the number of shares configured in the RBridge. Number of shares is a two octet value. When an RBridge advertises zero shares, it is not assigned any AF. +-+-+-+-+-+-+-+-+ | Type | (1 byte) +-+-+-+-+-+-+-+-+ | Length | (1 byte) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Number of Shares | (2 bytes) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ kvk, et al Expires March 2, 2013 [Page 5] INTERNET DRAFT Fair Share AF Load Share August 29, 2012 6.2 AF Affinity VLAN Set Sub-TLV AF Affinity VLAN Set Sub-TLV is used to advertise the AF Affinity VLAN set configured in an RBridge. It is a facsimile of the Enabled- VLANs sub-TLV. +-+-+-+-+-+-+-+-+ | Type | (1 byte) +-+-+-+-+-+-+-+-+ | Length | (1 byte) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RESV | Start VLAN ID | (2 bytes) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | VLAN bit-map.... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 6.3 Partial VLANs Appointing Sub-TLV As discussed in [RFC6439] section 2.2.3, the size of hello imposes a limit on the distribution of AF info in AF Sub-TLV by the DRB. The nature of the algorithm means that the AF appointment information could be disjoint. If the number of VLANs on a shared link is too high, all AF appointments cannot be accommodated in a single hello using the start end mechanism of AF Sub-TLV. In such case, the DRB should appoint one RBridge (possibly itself) as AF for all VLANs. Alternatively, the AF information can be sent in a bitmap rather than start-end mechanism as suggested in AF Sub-TLV. For this purpose the Partial VLANs Appointing Sub-TLV suggested in Adaptive VLAN Assignment draft [VlanAsn] can be used. kvk, et al Expires March 2, 2013 [Page 6] INTERNET DRAFT Fair Share AF Load Share August 29, 2012 7 Security Considerations This document raises no new security issues for IS-IS. 8 IANA Considerations This document suggests two additional Sub-TLV to Multi-Topology-Aware Port Capability TLV apart from the reuse of Partial VLANs Appointing Sub-TLV from Adaptive VLAN Assignment draft. o Fair Share Sub-TLV o AF Affinity VLAN Set Sub-TLV 9 References 9.1 Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC6325] R. Perlman, D. Eastlake, et al, "RBridges: Base Protocol Specification", RFC 6325, July 2011. [RFC6326] D. Eastlake, A. Banerjee, et al, "Transparent Interconnection of Lots of Links (TRILL) Use of IS-IS", RFC 6326, July 2011. [RFC6439] D. Eastlake, R. Perlman, et al, "Routing Bridges (RBridges): Appointed Forwarders", RFC 6439, November 2011. [RBisisb] D. Eastlake, A. Banerjee, et al, "Transparent Interconnection of Lots of Links (TRILL) Use of IS-IS", draft-eastlake-isis-rfc6326bis-09.txt, work in progress. [VlanAsn] M.Zhang and D.Zhang, "Adaptive VLAN Assignment for Data Center RBridges", draft-zhang-trill-vlan-assign-03.txt, work in progress. kvk, et al Expires March 2, 2013 [Page 7] INTERNET DRAFT Fair Share AF Load Share August 29, 2012 Authors' Addresses Kesava Vijaya Krupakaran Dell Olympia Technology Park, Guindy Chennai 600 032 Phone: +91 44 4220 8496 Email: Kesava_Vijaya_Krupak@Dell.com Janardhanan Pathangi Dell Olympia Technology Park, Guindy Chennai 600 032 Phone: +91 44 4220 8459 Email: Pathangi_Janardhanan@Dell.com kvk, et al Expires March 2, 2013 [Page 8]