INTERNET-DRAFT Linda Dunbar Intended status: Proposed Standard Donald Eastlake Huawei Radia Perlman Intel Igor Gashinsky Yahoo Yizhou Li Huawei Expires: January 14, 2014 July 15, 2013 TRILL: Directory Assistance Mechanisms Abstract This document describes mechanisms for using directory server(s) to assist TRILL (Transparent Interconnection of Lots of Links) edge switches in reducing multi-destination traffic, particularly ARP/ND and unknown unicast flooding. Status of This Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Distribution of this document is unlimited. Comments should be sent to the TRILL working group mailing list. 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. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. L. Dunbar, et al [Page 1] INTERNET-DRAFT TRILL: Directory Assist Mechanisms Table of Contents 1. Introduction............................................3 1.1 Terminology............................................3 1.2 Circumstances Causing Directory Use....................4 2. Push Model Directory Assistance Mechanisms..............5 2.1 Requesting Push Service................................5 2.2 Push Directory Servers.................................5 2.3 Multiple Push Directory Servers........................5 2.3 Additional Push Details................................7 3. Pull Model Directory Assistance Mechanisms..............8 3.1 Pull Directory Request Format..........................8 3.2 Pull Directory Response Format........................11 3.3 Pull Directory Hosted on an End Station...............13 3.4 Pull Directory Request Errors.........................15 3.5 Cache Consistency.....................................16 3.6 Additional Pull Details...............................18 4. Directory Use Strategies and Push-Pull Hybrids.........19 4.1 Strategy Configuration................................19 5. Security Considerations................................22 6. IANA Considerations....................................23 6.1 ESADI-Parameter Data..................................23 6.2 RBridge Channel Protocol Number.......................24 6.3 Pull Directory and No Data Bits.......................24 Acknowledgments...........................................25 Normative References......................................25 Informational References..................................26 Authors' Addresses........................................27 L. Dunbar, et al [Page 2] INTERNET-DRAFT TRILL: Directory Assist Mechanisms 1. Introduction [DirectoryFramework] describes a high level framework for using directory servers to assist TRILL [RFC6325] edge nodes to reduce multi-destination ARP/ND and unknown unicast flooding traffic and to potentially improve security aginst address spoofing within a TRILL comapus. Because multi-destination traffic becomes an increasing burden as a network scales, reducing ARP/ND and unknown unicast flooding improves TRILL network scalability. This document describes specific mechanisms for directory servers to assist TRILL edge nodes. These mechanims are optional to implement. The information held by the directories is address mapping information. Most commonly, what MAC address [RFC5342bis] corresponds to an IP address within a Data Label (VLAN or FGL (Fine Grained Label [RFCfgl])) and what egress TRILL switch (RBridge) that MAC address is attached to. But it could be what IP address corresponds to a MAC address or possibly other mappings. In the data center environment, it is common for orchestration software to know and control where all the IP addresses, MAC address, and VLANs/tenants are. Thus such orchestration software is appropriate for providing the directory function or for supplying the Directory(s) with information they need. Directory services can be offered in a Push or Pull mode. Push mode, in which a directory server pushes information to RBridges indicating interest, is specified in Section 2. Pull mode, in which an RBridge queries a server for the information it wants, is specified in Section 3. Modes of operation including hybrid Push/Pull are discussed in Section 4. The mechanisms used to keep the mappings held by different Directories synchronized is beyond the scope of this document. 1.1 Terminology 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]. The terminology and acronyms of [RFC6325] are used herein along with the following additional acronyms and terms: Data Label: VLAN or FGL. FGL: Fine Grained Label [RFCfgl]. Host: Application running on a physical server or a virtual machine. L. Dunbar, et al [Page 3] INTERNET-DRAFT TRILL: Directory Assist Mechanisms A host must have a MAC address and usually has at least one IP address. IP: Internet Protocol. In this document, IP includes both IPv4 and IPv6. RBridge: An alternative name for a TRILL switch. TRILL switch: An alternative name for an RBridge. 1.2 Circumstances Causing Directory Use An RBridge can consult Directory information whenever it wants, by searching through information it has because that information has been pushed to it or pulled by it and retained or by requesting information from a pull directory. However, the following are expected to be the most common circumstances leading to directory use. All of these are cases of ingressing a native frame. o Ingressing a native frame with an unknown unicast destination MAC. The mapping from the destination MAC and Data Label to its egress RBridge of attachment is needed to ingress the frame as unicast. If the egress RBridge is unknown, the frame must be dropped or ingressed as a multi-destination frame and flooded to all edge RBridges for its Data Label. o Ingressing an ARP [RFC826]. ARP is a very flexible protocol but is primarily used on a link to query for the MAC address corresponding to an IPv4 address, test if an IPv4 address is in use, or to announce a change in any of IPv4 address, MAC address, and point of attachment. ... more TBD ... o Ingressing a ND [RFC903]. ...TBD... Secure Neighbor Discovery messages [RFC3971] will, in general, have to be sent to the neighbor intended so that neighbor can sign the answer; however, directory information can be used to unicast a Secure Neighbor Discovery packet rather than multicasting it. o Ingressing a RARP [RFC4861]. ...TBD... Any of the above could be cause for an ingress RBridge to consult Directory information that has been pushed to it, to send a pull request to a Pull Directory, or both. L. Dunbar, et al [Page 4] INTERNET-DRAFT TRILL: Directory Assist Mechanisms 2. Push Model Directory Assistance Mechanisms In the Push Model, Push Directory servers push down the mapping information for the various addresses of end stations in some Data Label. A Push Directory advertises whether or not it believes it is pushing complete mapping information for a Data Label. The Push Model uses the [ESADI] protocol. With this model, it is RECOMMENDED that complete address mapping information for a Data Label be pushed and that a participating RBridge simply drop a data packet, instead of flooding the packet, if the destination unicast MAC address is in a Data Label being pushed and can't be found in the address mapping information available. This will minimize flooding of packets due to errors or inconsistencies but is not practical if directories have incomplete information. 2.1 Requesting Push Service In the Push Model, it is necessary to have a way for an RBridge to request information from the directory server(s). RBridges simply use the ESADI protocol mechanism to announce, in the IS-IS link state database, all the Data Labels for which they are participating in [ESADI]. They are then pushed the mapping information for all such Data Labels being served by a Push Directory server. 2.2 Push Directory Servers Push Directory servers advertise their availability to push the mapping information for a particular Data Label to ESADI participants for that Data Label by turning on a flag bit in their ESADI Parameter APPsub-TLV [ESADI] (see Section 7.1) for athat ESADI instance. Each Push Directory server MUST participate in ESADI for the Data Labels for which it can push mappings and set the PD bit in their ESADI-Parameters APPsub-TLV for that Data Label. 2.3 Multiple Push Directory Servers For robustness, it is useful to have more than one copy of the data being pushed. Each RBridge that is a Push Directory server is configured with a number in the range 1 to 8, which defaults to 2 for each Data Label for which it can push directory information. This is the number of copies of the directory it believes should be pushed. L. Dunbar, et al [Page 5] INTERNET-DRAFT TRILL: Directory Assist Mechanisms Each Push Directory server also has an 8-bit priority to be active (see Section 6.1 of this document). This priority is treated as an unsigned integer where larger mangitude means higher priority and is in its ESADI Parameter APPsub-TLV. In cases of equal priority, the 6-byte IS-IS System ID is used as a tie breaker and treated as an unsigned integer where larger magnitude means higher priority. For each Data Label it can serve, each Push Directory RBridge server orders the Push Directory servers that it can see as data reachable [RFCclear] in the ESADI link state database for that Data Label and determines its position in that order. If a Push Directory server believes that N copies of the mappings for a Data Label should be pushed and finds that it is first in priority or, more generally, equal to or higher than Nth in priority, it is Active. If it finds that it is N+1st or lower in priority, it is Passive. For example, assume four Push Directory servers for Data Label X: server A with priority 123 configured to believe there should be 2 copies pushed; server B, priority 88, 1 copy; server C, priority 40, 3 copies; and server D, priority 7, 2 copies. Server A, seeing that is highest priority, is Active. Server B, seeing that it is 2nd highest priority and believing that only 1 copy should be pushed, is Passive. Server C sees that it is 3rd highest priority and believes 3 copies should be pushed, so it is Active. And server D sees it is 4th highest priority and, believing that only 2 copies should be pushed, is Passive. If a Push Directory server is Active for Data Label X, it includes the Data Label X directory mappings it has in its ESADI-LSP for Data Label X and updates that information as the mappings it knows change. If the Push Directory server is configured to believe it has complete mapping information for Data Label X then, after it first actually transmits all of its ESADI-LSPs for X it then waits its CSNP time (see Section 6.1 of [ESADI]), and then updates its ESADI-Parameters APPsub-TLV to set the Complete Push (CP) bit to one. This change will cause its EASDI fragment zero to be flooded. It then maintains the CP bit as one as long as it is Active. If a Push Directory server is Passive for Data Label X, it removes or continues to leave out all Data Label X directory mappings it holds from its ESADI-LSP for Data Label X. However, if it was Active and was advertising the CP bit as one in its ESADI-Parameters APPsub-TLV, it first updates the CP bit to zero and floods its updated ESADI-LSP fragment zero. Its then waits its CSNP time before withdrawing all its directory mapping information. L. Dunbar, et al [Page 6] INTERNET-DRAFT TRILL: Directory Assist Mechanisms 2.3 Additional Push Details Push Directory mappings can be distinguished for any other data distributed through ESADI because mappings are distributed only with the Interface Addresses APPsub-TLV [IA] and are flagged as being Push Directory data. RBridges, whether or not they are a Push Directory server, MAY continue to advertise any locally learned MAC attachment information in [ESADI] using the Reachable MAC Addresses TLV [RFC6165]. However, if a Data Label is being served by complete Push Directory servers, advertising such locally learned MAC attachment would generally not be done as it should not add anything and would just waste bandwidth and ESADI link state space. An exception would be when an RBridge learns local MAC connectivity and that information appears to be missing from the directory mapping. Because a Push Directory server may need to advertise interest in Data Labels even though it does not want to receive user data in those Data Labels, the No Data flag bit is provided as discussed in Section 6.3. If an RBridge notices that a Push Directory server is no longer data reachable [RFCclear], it MUST ignore any Push Directory data from that server because it is no longer being updated and may be stale. There may be transient conflicts between mapping information from different Push Directory servers or conflicts between locally learned information and information received from a Push Directory server. In case of such conflicts, information with a higher confidence value is preferred over information with a lower confidence. In case of equal confidence, Push Directory information is preferred to locally learned information and if information from Push Directory servers conflicts, the information from the higher priority Push Directory server is preferred. L. Dunbar, et al [Page 7] INTERNET-DRAFT TRILL: Directory Assist Mechanisms 3. Pull Model Directory Assistance Mechanisms In the Pull Model, an RBridge pulls mapping information from an appropriate Directory Server when needed. Pull Directory servers for a particular Data Label X are located by looking in the main TRILL IS-IS link state database for RBridges that advertise themselves by having the Pull Directory flag on in their Interested VLANs or Interested Labels sub-TLV [RFC6326bis] for X. If multiple RBridges indicate that they are Pull Directory Servers for a particular Data Label, a pull request can be sent to any of them that is data reachable but it is RECOMMENDED that pull requests be sent to server that is least cost from the requesting RBridge. Pull Directory requests are sent by enclosing them in an RBridge Channel [Channel] message using the Pull Directory channel protocol number (see Section 6.2). Responses are returned in an RBridge Channel message using the same channel protocol number. The requests to Pull Directory Servers are derived from normal ARP [RFC826], ND [RFC4861], RARP [RFC903] messages or data frames with unknown unicast destination MAC addresses intercepted by the RBridge when they would otherwise be ingressed. Pull Directory responses include an amount of time for which the response should be considered valid. This includes negative responses that indicate no data is available. Thus both positive responses with data and negative responses can be cached and used for immediate response to ARP, ND, RARP, or unknown destination MAC frames, until they expire. If information previously pulled is about to expire, an RBridge MAY try to refresh it by issued a new pull request but, to avoid unnecessary requests, SHOULD NOT do so if it has not been recently used. 3.1 Pull Directory Request Format A Pull Directory request is sent as the Channel Protocol specific content of an inter-RBridge Channel message TRILL Data packet. The Data Label in the packet is the Data Label in which the query is being made. The priority of the channel message is a mapping of the priority of the frame being ingressed that caused the request with the default mapping depending, per Data Label, on the strategy (see Section 4). The Channel Protocol specific data is formatted as follows: L. Dunbar, et al [Page 8] INTERNET-DRAFT TRILL: Directory Assist Mechanisms 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | V | T | RESV | Count | RESV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | QUERY 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... | QUERY 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... | ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... | QUERY K +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... V: Version of the Pull Directory protocol as an unsigned integer. Version zero is specified in this document. T: Type. 0 => Response, 1=> Query, 2=> Unsolicited Update, 3=> Reserved. An unsolicited update is formated as a response except there was no corresponding query. Messages received with type = 3 are discarded. RESV: Reserved bits. MUST be sent as zero and ignored on receipt. Count: Number of queries present. Sequence Number: An opaque 32-bit quantity set by the sending RBridge, returned in any responses, and used to match up responses with queries. QUERY: Each Query record within a Pull Directory request message is formatted as follows: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | SIZE | RESV | TYPE | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ If TYPE = 1 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | AFN | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | Query address ... +--+--+--+--+--+--+--+--+--+--+--... If TYPE = 2, 3, 4, or 5 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | Query frame ... +--+--+--+--+--+--+--+--+--+--+--... L. Dunbar, et al [Page 9] INTERNET-DRAFT TRILL: Directory Assist Mechanisms SIZE: Size of the query data in bytes as an unsigned byt starting with and including the SIZE fiel itself. Thus the minimium legal value is 2. A value of SIZE less than indicates a malformed message. The "QUERY" with the illegal SIZE value and all subsequent QUERYs MUST be ignored and the entire query message MAY be ignored. RESV: A block of reserved bits. MUST be sent as zero and ignored on receipt. TYPE: There are two types of queries currently defines, (1) a query that provides an explicit address and asks for other addresses for the interface specified by the query address and (2) a query frame. The fields of each are specified below. Values of TYPE are as follows TYPE Description ---- ----------- 0 reserved 1 query address 2 ARP query frame 3 ND query frame 4 RARP query frame 5 Unknown unicast MAC query frame 6-14 assignable by IETF Review 15 reserved AFN: Address Family Number of the query address. Address: This is the query address. The query is asking for any other addresses that correspond to the same interface within the data label of the query and the RBridge from which they are reachable. Typically that would be either (1) a MAC address, in which case the querying RBridge is interested in the RBridge by which that MAC address is reachable, or (2) an IP address, in which case the querying RBridge is interested in the corresponding MAC address and the RBridge by which that MAC address is reachable. Query Frame: Where a Pull Directroy query is the result of an ARP, ND, RARP, or unkown unicast MAC destination address, the ingress RBridge MAY send the frame to a Pull Directory Server if the frame is small enough to fit into a query message. This avoids the requirement that the ingress RBridge hold the frame pending a Pull Directory response. A query count of zero is explicitly allowed, for the purpose of pinging a Pull Directory server to see if it is responding to L. Dunbar, et al [Page 10] INTERNET-DRAFT TRILL: Directory Assist Mechanisms requests. On receipt of such an empty query messgea, a response message that also has a count of zero MUST be sent. If no response is received to a Pull Directory request within a configurable timeout, the request should be re-transmitted with the same Sequence Number up to a configurable number of times that defaults to three. If there are multiple queries in a request, responses can be received to various subsets of these queries by the timeout. In that case, the remaining unanswered queries should be re- sent in a new query with a new sequence number. If an RBridge is not capable of handling partial responses to requests with multiple queries, it MUST NOT sent a request with more than one query in it. 3.2 Pull Directory Response Format Pull Directory responses are sent as the Channel Protocol specific content of inter-RBridge Channel message TRILL Data packets. Responses are sent with the same Data Label and priority as the request to which they correspond except that the response priority is limited. This priority limit is configurable at a per RBridge level and defaults to priority 6. The Channel protocol specific data format is as follows: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | V | T |F|P|N| RESV| Count | ERR | subERR | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RESPONSE 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... | RESPONSE 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... | ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... | RESPONSE K +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... V: Version of the Pull Directory protocol. Version zero is specified in this document. T: Type. 0 => Response, 1=> Query, 2=> Unsolicited Update, 3=> Reserved. An unsolicited update is formated as a response except there was no corresponding query. Unsolicited responses are sent to maintain cache consistency (see Section 3.5). Messages received with type = 3 are discarded. L. Dunbar, et al [Page 11] INTERNET-DRAFT TRILL: Directory Assist Mechanisms F: The Flood bit. If zero, the reply is to be unicast to the provided Nickname. If T=2, F=1 is used to flood messages for certain unsolicited cache consistency maintenance messages from an end station Pull Directory server as discussed in Section 3.5. If T is not 2, F is ignored. P, N: Flags used in connection with certain flooded unsolicited cache consistency maintenance messages. Ignored if T is not 2. If the P bit is a one, the solicited response message relates to cached positive response information. If the N bit is a one, the unsolicited messages related to cached negative information. See Section 3.5. RESV: Reserved bits. MUST be sent as zero and ignored on receipt. Count: Count is the number of responses present in the particular reponse message. ERR, subERR: A two part error code. See Section 3.4. Sequence Number: An opaque 32-bit quantity set by the requesting RBridge and copied by the Pull Directory into all responses to the query. For an unsolicited "response", the contents are unspecified. RESPONSE: Each response record within a Pull Directory response message is formatted as follows: 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | SIZE | RESV | Index | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | Lifetime | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | Response Data ... +--+--+--+--+--+--+--+--+--+--+--... SIZE: Size of the response data in bytes starting with and including the SIZE field itself. RESV: Four reserved bits that MUST be sent as zero and ignored on receipt. Index: The relative index of the query in the request message to which this response corresponds. The index will always be one for request messages containing a single query. The index will always be zero for unsolicited "response" messages. Lifetime: The length of time for which the response should be L. Dunbar, et al [Page 12] INTERNET-DRAFT TRILL: Directory Assist Mechanisms considered valid in seconds. Response Data: There are two types of response data. If the ERR field is non-zero, the response data is a copy of the query data, that is, an AFN followed by an address. If the ERR field is zero, the response data is the contents of an Interface Addresses APPsub-TLV (see Section 5) without the usual TRILL GENINFO TLV type and length and without the usual IA APPsub-TLV type and length before it. Multiple response records can appear in a response message with the same index if the answer to a query consists of multiple Interface Address APPsub-TLV contents. This would be necessary if, for example, a MAC address within a Data Label appears to be reachable by multiple RBridges. All response records to any particular query record MUST occur in the same response message. If a Pull Directory holds more mappings for a queried address than will fit into one response message, it selects which to include by some method outside the scope of this document. See Section 3.4 for a discussion of how errors are handled. 3.3 Pull Directory Hosted on an End Station Optionally, a Pull Directory actually hosted on an end station MAY be supported. In that case, when the RBridge advertising itself as a Pull Directory server receives a query, it modifies the inter-RBridge Channel message received into a native RBridge Channel message and forwards it to that end station. Later, when it receives one or more responses from that end station by native RBridge Channel messages, it modifies them into inter-RBridge Channel messages and forwards them to the source RBridge of the query. The native RBridge Channel Pull Directory messages use the same Channel protocol number as do the inter-RBridge Pull Directory Channel messages. The native messages MUST be sent with an Outer.VLAN tag which gives the priority of each message which is the priority of the original inter-RBridge request packet. The Outer.VLAN ID used is the Designated VLAN on the link. The native RBridge Channel message protocol dependent data for a Pull Directory query is formatted as follows: L. Dunbar, et al [Page 13] INTERNET-DRAFT TRILL: Directory Assist Mechanisms 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | V | T | RESV | Count | Nickname | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Label ... (4 or 8 bytes) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | QUERY 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... | QUERY 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... | ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... | QUERY K +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... Data Label: The Data Label of the original inter-RBridge Pull Directory Channel protocol messages that was mapped to this native channel message. The format is the same as it appears right after the Inner.MacSA of the original Channel message. Nickname: The nickname of the requesting RBridge. All other fields are as specified in Section 3.1. The native RBridge Channel message protocol specific content for a Pull Directory response is formatted as follows: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | V | T |F|P|N| RESV| Count | ERR | subERR | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Nickname | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data Label ... (4 or 8 bytes) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | RESPONSE 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... | RESPONSE 2 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... | ... +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... | RESPONSE K +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... L. Dunbar, et al [Page 14] INTERNET-DRAFT TRILL: Directory Assist Mechanisms Data Label: The Data Label to which the response applies. The format is the same as it appears right after the Inner.MacSA in TRILL Data messages. Nickname: The nickname of the destination RBridge or, if F=1, ignored. All other fields are as specified in Section 3.2. 3.4 Pull Directory Request Errors An error response message is indicated by a non-zero ERR field. If there is an error that applies to the entire request message or its header, as indicated by the range of the value of the ERR field, then the query records in the request are just expanded with a zero Lifetime and the insertion of the Index field echoed back in the response records. If errors occur at the query level, they MUST be reported in a response message separate from the results of any successful queries. If multiple queries in a request have different errors, they MUST be reported in separate response messages. If multiple queries in a request have the same error, this error response MAY be reported in one response message. In an error response message, the query or queries being responded to appear, expanded by the Lifetime for which the server thinks the error might persist and with their Index inserted, as the response record. ERR values 1 through 63 are available for encoding request message level errors. ERR values 64 through 255 are available for encoding query level errors. the SubErr field is available for providing more detail on errors. The meaning of a SubErr field value depends on the value of the ERR field. L. Dunbar, et al [Page 15] INTERNET-DRAFT TRILL: Directory Assist Mechanisms ERR Meaning --- ------- 0 (no error) 1 Unknown V field value 2 Request data too short 3 Administratively prohibited 4-31 (Available for allocation by Standards Action) 32 Unknown AFN 33 No mapping found 34 Administratively prohibited 35-255 (Available for allocation by Standards Action) More TBD...? 3.5 Cache Consistency Pull Directories MUST take action to minimize the amount of time that an RBridge will continue to use stale information from the Pull Directory. A Pull Directory server MUST maintain one of the following, in order of increasing specificity. 1. An overall record per Data Label of when the last returned query data will expire at a requestor and when the last query record specific negative response will expire. 2. For each unit of data (IA APPsub-TLV Address Set) held by the server and each address about which a negative response was sent, when the last expected response with that unit or negative response will expire at a requester. 3. For each unit of data held by the server and each address about which a negative response was sent, a list of RBridges that were sent that unit as the response or sent a negative response to the address, with the expected time to expiration at each of them. A Pull Directory server may have a limit as to how many RBridges it can maintain expiry information for by method 3 above or how many data units or addresses it can maintain expiry information for by method 2. If such limits are exceeded, it MUST transition to a lower numbered strategy but, in all cases, MUST support, at a minimum, method 1. When data at a Pull Directory changes or is deleted or data is added L. Dunbar, et al [Page 16] INTERNET-DRAFT TRILL: Directory Assist Mechanisms and there may be unexpired stale information at a querying RBridge, the Pull Directory MUST send an unsolicited message as discussed below. If method 1, the most crude method, is being followed, then when any information in a Data Label is changed or deleted or an additional administrative Pull Directory access restriction imposed, and there are outstanding cached positive query data response(s), an all- addresses flush positive message is flooded (multicast) within that Data Label. And if data is added or an administrative restriction is removed and there are outstanding cached negative responses, an all- addresses flush negative message is flooded. "All-addresses" is indicated by the Count in an unsolicited response being zero. On receiving an all-addresses flooded flush positive message from a Pull Directory server it has used, indicated by the U, F, and P bits being one, an RBridge discards all cached data responses it has for that Data Label. Similarly, on receiving an all addresses flush negative message, indicated by the U, F, and N bits being one, it discards all cached negative responses for that Data Label. A combined flush positive and negative can be flooded by having all of the U, F, P, and N bits set to one resulting in the discard of all positive and negative cached information for the Data Label. If method 2 is being followed, then an RBridge floods address specific update positive unsolicited responses when data which is cached by a querying RBridge is changed or deleted or an administrative restriction is added to such data and floods an address specific update negative unsolicited responses when such information is deleted or an administrative restriction is removed from such data. Such messages are similar to the method 1 flooded unsolicited flush messages. The U and F bits will be one and the message will be multicast. However that Count field will be non-zero and either the P or N bit, but not both, will be one. On receiving such as address specific message, if it is positive the addresses in the response records in the unsolicited response are compared to the addresses about which the recipient RBridge is holding cached positive information and, if they match, the cached information is updated and its remaining cache life set to the minimum of its previous value in the cache and the Lifetime value in the unsolicited response. In the case of a newly imposed administrative restriction, the Lifetime in the unsolicited response is set to zero so the cached information immediately expired. On receiving an address specific unsolicited negative response, the addresses in the response records in the unsolicited response are compared to the addresses about which the recipient RBridge is holding cached negative information and, if they match, the cached negative information is discarded. If method 3 is being followed, the same sort of messages are sent as with method 2 except they are not flooded but unicast only to the specific RBridges the server believes may be holding the cached L. Dunbar, et al [Page 17] INTERNET-DRAFT TRILL: Directory Assist Mechanisms positive or negative information that may need updating. 3.6 Additional Pull Details If an RBridge notices that a Pull Directory server is no longer data reachable [RFCclear], it MUST discard all responses it is retaining from that server within one second as the RBridge can no longer receive cache consistency messages from the server. Because a Pull Directory server may need to advertise interest in Data Labels even though it does not want to received user data in those Data Labels, the No Data flag bit is provided as discussed in Section 7.3. L. Dunbar, et al [Page 18] INTERNET-DRAFT TRILL: Directory Assist Mechanisms 4. Directory Use Strategies and Push-Pull Hybrids For some edge nodes which have great number of Data Labels enabled, managing the MAC&Label <-> RBridgeEdge mapping for hosts under all those Data Labels can be a challenge. This is especially true for Data Center gateway nodes, which need to communicate with a majority of Data Labels if not all. For those RBridge Edge nodes, a hybrid model should be considered. That is the Push Model is used for some Data Labels, and the Pull Model is used for other Data Labels. It is the network operator's decision by configuration as to which Data Labels' mapping entries are pushed down from directories and which Data Labels' mapping entries are pulled. For example, assume a data center when hosts in specific Data Labels, say VLANs 1 through 100, communicate regularly with external peers, the mapping entries for those 100 VLANs should be pushed down to the data center gateway routers. For hosts in other Data Labels which only communicate with external peers occasionally for management interface, the mapping entries for those VLANs should be pulled down from directory when the need comes up. The mechanisms described above for Push and Pull Directory services make it easy to use Push for some Data Labels and Pull for others. In fact, different RBridges can even be configured so that some use Push Directory services and some use Pull Directory services for the same Data Label if both Push and Pull Directory services are available for that Data Label. And there can be Data Labels for which directory services are not used at all. 4.1 Strategy Configuration Each RBridge that has the ability to use directory assistance has, for each Data Label X in which it is might ingress native frames, one of four major modes: 0. No directory use. The RBridge does not subscribe to Push Directory data or make Pull Directory requests for Data Label X and directory data is not consulted on ingressed frames in Data Label X that might have used directory data. This includes ARP, ND, RARP, and unknown MAC destination addresses, which are flooded. 1. Use Push only. The RBridge subscribes to Push Directory data for Data Label X. 2. Use Pull only. When the RBridge ingresses a frame in Data Label L. Dunbar, et al [Page 19] INTERNET-DRAFT TRILL: Directory Assist Mechanisms X that can use Directory information, if it has cached information for the address it uses it. If it does not have either cached positive or negative information for the address, it sends a Pull Directory query. 3. Use Push and Pull. The RBridge subscribes to Push Directory data for Data Label X. When it ingresses a frame in Data Label X that can use Directory information and it does not find that information in its link state database of Push Directory information, it makes a Pull Directory query. The above major Directory use mode is per Data Label. In addition, there is a per Data Label per priority minor mode as listed below that indicates what should be done if Directory Data is not available for the ingressed frame. In all cases, if you are holding Push Directory or Pull Directory information to handle the frame given the major mode, the directory information is simply used and, in that instance, the minor modes does not matter. A. Flood immediate. Flood the frame immediately (even if you are also sending a Pull Directory) request. B. Flood. Flood the frame immediately unless you are going to do a Pull Directory request, in which case you wait for the response or for the request to time out after retries and flood the frame if the request times out. C. Discard if complete or Flood immediate. If you have complete Push Directory information and the address is not in that information, discard the frame. If you do not have complete Push Directory information, the same as A above. D. Discard if complete or Flood. If you have complete Push Directory information and the address is not in that information, discard the frame. If you do not have complete Push Directory information, the same as B above. In addition, the query message priority for Pull Directory requests sent can be configured on a per Data Label, per ingressed frame priority basis. The default mappings are as follows where Ingress Priority is the priority of the native frame that provoked the Pull Directory query: L. Dunbar, et al [Page 20] INTERNET-DRAFT TRILL: Directory Assist Mechanisms Ingress If Flood If Flood Priority Immediate Delayed -------- --------- -------- 7 5 6 6 5 6 5 4 5 4 3 4 3 2 3 2 0 2 0 1 0 1 1 1 Priority 7 is normally only used for urgent messages critical to network connectivity and so is avoided by default for directory traffic. L. Dunbar, et al [Page 21] INTERNET-DRAFT TRILL: Directory Assist Mechanisms 5. Security Considerations Push Directory data is distributed through ESADI-LSPs [ESADI] which can be authenticated with the same mechanisms as IS-IS LSPs. See [RFC5304] [RFC5310] and the Security Considerations section of [ESADI]. Pull Directory queries and responses are transmitted as RBridge-to- RBridge or native RBridge Channel messages. Such messages can be secured as specified in TBD. For general TRILL security considerations, see [RFC6325]. L. Dunbar, et al [Page 22] INTERNET-DRAFT TRILL: Directory Assist Mechanisms 6. IANA Considerations This section give IANA allocation and registry considerations. 6.1 ESADI-Parameter Data IANA is request to allocate two ESADI-Parameter TRILL APPsub-TLV flag bits for "Push Directory" and "Complete Push" and to create a sub- registry in the TRILL Parameters Registry as follows: Sub-Registry: ESADI-Parameter APPsub-TLV Bits Registration Procedures: IETF Review References: [ESADI], This document Bit Mnemonic Description Reference --- -------- ----------- --------- 0 UN Supports Unicast ESADI [ESADI] 1 PD Push Directory Server This document 2 CP Complete Push This document 3-7 - available for allocation In addition, the ESADI-Parameter APPsub-TLV is optionally extended, as provided in its original specification in [ESADI], by one byte as show below: +-+-+-+-+-+-+-+-+ | Type | (1 byte) +-+-+-+-+-+-+-+-+ | Length | (1 byte) +-+-+-+-+-+-+-+-+ |R| Priority | (1 byte) +-+-+-+-+-+-+-+-+ | CSNP Time | (1 byte) +-+-+-+-+-+-+-+-+ | Flags | (1 byte) +---------------+ |PushDirPriority| (optional, 1 byte) +---------------+ | Reserved for expansion (variable) +-+-+-+-... The meanings of all the fields are as specified in [ESADI] except that the added PushDirPriority is the priority of the advertising ESADI instance to be a Push Directory as described in Section 2.3. If the PushDirPriority field is not present (Length = 3) it is treated as if it were 0x40. 0x40 is also the value used and place here by an L. Dunbar, et al [Page 23] INTERNET-DRAFT TRILL: Directory Assist Mechanisms RBridge for which this field has not been configured. 6.2 RBridge Channel Protocol Number IANA is requested to allocate a new RBridge Channel protocol number for "Pull Directory Services" from the range allocable by Standards Action and update the table of such protocol number in the TRILL Parameters Registry referencing this document. 6.3 Pull Directory and No Data Bits IANA is requested to allocate two currently reserved bits in the Interested VLANs field of the Interested VLANs sub-TLV (suggested bits 3 and 4) and the Interested Labels field of the Interested Labels sub-TLV (suggested bits 5 and 6) [RFC6326bis] to indicate Pull Directory server (PD) and No Data (ND) respectively. These bits are to be added to the subregistry set up in [ESADI]. In the TRILL base protocol [RFC6325] as extended for FGL [rfcFGL], the mere presence of an Interested VLANs or Interested Labels sub- TLVs in the LSP of an RBridge indicates connection to end stations in the VLANs or FGLs listed and thus a desire to receive multi- destination traffic in those Data Labels. But, with Push and Pull Directories, advertising that you are a directory server requires using these sub-TLVs as part for the Data Label you are serving. If such a directory server does not wish to received multi-destination user data for the Data Labels it lists in one of these sub-TLVs, it sets the "No Data" (ND) bit to one. This means that data on a distribution tree may be pruned so as not to reach the "No Data" RBridge as long as there are no RBridges interested in the Data who are beyond the "No Data" RBridge. This bit is backwards compatible as RBridges ignorant of it will simply no prune when it could, which is safe but may cause increased link utilization. L. Dunbar, et al [Page 24] INTERNET-DRAFT TRILL: Directory Assist Mechanisms Acknowledgments The document was prepared in raw nroff. All macros used were defined within the source file. Normative References [RFC826] - Plummer, D., "An Ethernet Address Resolution Protocol", RFC 826, November 1982. [RFC903] - Finlayson, R., Mann, T., Mogul, J., and M. Theimer, "A Reverse Address Resolution Protocol", STD 38, RFC 903, June 1984 [RFC2119] - Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997 [RFC3971] - Arkko, J., Ed., Kempf, J., Zill, B., and P. Nikander, "SEcure Neighbor Discovery (SEND)", RFC 3971, March 2005. [RFC4861] - Narten, T., Nordmark, E., Simpson, W., and H. Soliman, "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, September [RFC5304] Li, T. and R. Atkinson, "IS-IS Cryptographic Authentication", RFC 5304, October 2008. [RFC5310] - Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., and M. Fanto, "IS-IS Generic Cryptographic Authentication", RFC 5310, February 2009. [RFC5342bis] - Eastlake 3rd, D., "IANA Considerations and IETF Protocol Usage for IEEE 802 Parameters", BCP 141, RFC 5342, September 2008. [RFC6165] - Banerjee, A. and D. Ward, "Extensions to IS-IS for Layer-2 Systems", RFC 6165, April 2011. [RFC6325] - Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A. Ghanwani, "Routing Bridges (RBridges): Base Protocol Specification", RFC 6325, July 2011. [RFC6326bis] - Eastlake, D., Banerjee, A., Dutt, D., Perlman, R., and A. Ghanwani, "TRILL Use of IS-IS", draft-ietf-isis-rfc6326bis, work in progress. [RFCclear] - Eastlake, D., M. Zhang, A. Ghanwani, V. Manral, A. Banerjee, draft-ietf-trill-clear-correct-06.txt, in RFC L. Dunbar, et al [Page 25] INTERNET-DRAFT TRILL: Directory Assist Mechanisms Editor's queue. [Channel] - D. Eastlake, V. Manral, Y. Li, S. Aldrin, D. Ward, "TRILL: RBridge Channel Support", draft-ietf-trill-rbridge- channel-08.txt, in RFC Editor's queue. [RFCfgl] - D. Eastlake, M. Zhang, P. Agarwal, R. Perlman, D. Dutt, "TRILL: Fine-Grained Labeling", draft-ietf-trill-fine- labeling-07.txt, in RFC Editor's queue. [ESADI] - Zhai, H., F. Hu, R. Perlman, D. Eastlake, O. Stokes, "TRILL (Transparent Interconnection of Lots of Links): The ESADI (End Station Address Distribution Information) Protocol", draft- ietf-trill-esadi, work in progress. [IA] - Eastlake, D., L. Yizhou, R. Perlman, "TRILL: Interface Addresses APPsub-TLV", draft-eastlake-trill-ia-appsub-tlv, work in progress. Informational References [DirectoryFramework] - Dunbar, L., D. Eastlkae, R. Perlman, I. Gashinsky, "TRILL Edge Directory Assistance Framework", draft- ietf-trill-directory-framework, work in progress. [ARP reduction] - Shah, et. al., "ARP Broadcast Reduction for Large Data Centers", Oct 2010. L. Dunbar, et al [Page 26] INTERNET-DRAFT TRILL: Directory Assist Mechanisms Authors' Addresses Linda Dunbar Huawei Technologies 5430 Legacy Drive, Suite #175 Plano, TX 75024, USA Phone: (469) 277 5840 Email: ldunbar@huawei.com Donald Eastlake Huawei Technologies 155 Beaver Street Milford, MA 01757 USA Phone: 1-508-333-2270 Email: d3e3e3@gmail.com Radia Perlman Intel Labs 2200 Mission College Blvd. Santa Clara, CA 95054-1549 USA Phone: +1-408-765-8080 Email: Radia@alum.mit.edu Igor Gashinsky Yahoo 45 West 18th Street 6th floor New York, NY 10011 Email: igor@yahoo-inc.com Yizhou Li Huawei Technologies 101 Software Avenue, Nanjing 210012 China Phone: +86-25-56622310 Email: liyizhou@huawei.com L. Dunbar, et al [Page 27] INTERNET-DRAFT TRILL: Directory Assist Mechanisms Copyright, Disclaimer, and Additional IPR Provisions Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. 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Versions of these Legal Provisions that are published by third parties, including those that are translated into other languages, should not be considered to be definitive versions of these Legal Provisions. For the avoidance of doubt, each Contributor to the IETF Standards Process licenses each Contribution that he or she makes as part of the IETF Standards Process to the IETF Trust pursuant to the provisions of RFC 5378. No language to the contrary, or terms, conditions or rights that differ from or are inconsistent with the rights and licenses granted under RFC 5378, shall have any effect and shall be null and void, whether published or posted by such Contributor, or included with or in such Contribution. L. Dunbar, et al [Page 28]