INTERNET DRAFT Weibin Zhao Service Location Group Henning Schulzrinne draft-zhao-slp-da-interaction-07.txt Columbia University Expires: December 30, 2000 Erik Guttman Sun Microsystems June 30, 2000 mSLP - Mesh-enhanced Service Location Protocol draft-zhao-slp-da-interaction-07.txt Status of This Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Copyright Notice Copyright (C) The Internet Society (2000). All Rights Reserved. Abstract This document presents mSLP - Mesh-enhanced Service Location Protocol, which enhances SLPv2 with a scheme for the interaction of Directory Agents (DAs). mSLP proposes to use a fully meshed peering DA architecture. Peer DAs exchange service registration information, and maintain the same consistent data for the shared scopes. mSLP provides a reliable directory service for an SLP system. It also greatly simplifies Service Agent (SA) registrations. mSLP is backward compatible with SLPv2, and incremental deployment is supported. Zhao, et al. Expires: December 30, 2000 [Page 1]
Internet Draft DA Interaction June 30, 2000 1. Introduction In the Service Location Protocol (RFC 2608 [1]), Directory Agents (DAs) are introduced for caching service advertisements from Service Agents (SAs), and answering queries from User Agents (UAs). They exist to enhance the performance and scalability of SLP. When multiple DAs are present, how should they interact with each other? This is an open issue in SLPv2. This document presents mSLP - Mesh-enhanced Service Location Protocol, which enhances SLPv2 with a scheme for the interaction of DAs. mSLP proposes that if DAs are needed in an SLP system, a fully meshed peering DA architecture should be used, i.e., more than one DA should be present for each scope, and they should maintain a fully meshed peer relationship (similar to IBGP [2]). Peer DAs exchange their data for the shared scopes when they set up a peer relationship, and continue to exchange new service registration information during the entire peering period. As a result, they maintain the same consistent data for the shared scopes. mSLP provides a reliable directory service for an SLP system. It also greatly simplifies SA registrations. The scalability of SLP is thereby enhanced. mSLP is backward compatible with SLPv2, and incremental deployment is supported. The rest of this document is organized as follows: Section 2 defines the terminology. Section 3 reviews the current DA message flows in SLPv2. Section 4 defines the mesh-enhancement extension. In Section 5, we describe the DA peer relationship. In Section 6, we present the message forwarding control among DAs. We discuss our design in Section 7, list constants in Section 8, and give security considerations in Section 9. 2. Terminology Peer DAs If two DAs have one or more scopes in common within one administrative domain, they are peers. Peer DAs coordinate with each other and store the same consistent data for the shared scopes. Peering TCP connection A persistent TCP connection that is kept between a pair of peer DAs for the entire peering period. It provides a reliable communication channel for the peer DAs to exchange messages. Therefore, a DA implementation is not burdened by managing message retransmissions. Its closing can be an indication of the termination of the peer relationship. Zhao, et al. Expires: December 30, 2000 [Page 2]
Internet Draft DA Interaction June 30, 2000 Mesh-enhanced DA A DA who maintains a peering TCP connection to each of its peers and forwards messages to its peers according to the rules given in this document. A mesh-enhanced DA MUST carry the "mesh-enhanced" attribute keyword in its DAAdvert messages. Mesh-aware SA An SA who understands the "mesh-enhanced" attribute in a DAAdvert message and uses the mesh-enhanced DA capability accordingly. 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 [5]. 3. DA Message Flows in SLPv2 This section reviews the DA message flows defined in SLPv2. Figure 1 illustrates SA registrations with DAs. For each service registration (SrvReg) and deregistration (SrvDeReg) message, a DA replies with a service acknowledgment (SrvAck) message. +----+ +----+ | | --- SrvReg/SrvDeReg --> | | | SA | | DA | | | <------- SrvAck ------- | | +----+ +----+ Figure 1. SA Registrations Figure 2 shows UA queries with DAs. A DA replies with a service reply (SrvRply) message to a service request (SrvRqst) message, a service type reply (SrvTypeRply) message to a service type request (SrvTypeRqst) message, and an attribute reply (AttrRply) message to an attribute request (AttrRqst) message. +----+ +----+ | | ----- SrvTypeRqst/SrvRqst/AttrRqst ----> | | | UA | | DA | | | <---- SrvTypeRply/SrvRply/AttrRply ----- | | +----+ +----+ Figure 2. UA Queries Figure 3 depicts DA discovery. A DA replies with a unicast DA advertisement (DAAdvert) message to a multicast SrvRqst message which Zhao, et al. Expires: December 30, 2000 [Page 3]
Internet Draft DA Interaction June 30, 2000 has "service:directory-agent" as service type. +-------+ Multicast SrvRqst +----+ | | ----- (service:directory-agent) ----> | | | UA/SA | | DA | | | <-------- Unicast DAAdvert ---------- | | +-------+ +----+ Figure 3. DA Discovery Figure 4 shows DA advertisements which are multicast periodically. +----+ +-------+ | | | | | DA | ---- Multicast DAAdvert ---> | UA/SA | | | | | +----+ +-------+ Figure 4. DA Advertisement From Figure 1 to 4, we can see that SLPv2 does not define the message flows among DAs. We will define these flows for the interaction of DAs and refine above flows in the following sections. 4. Mesh-enhancement Extension We define a new SLP extension - "mesh-enhancement extension" for specifying the interaction operations of mesh-enhanced DAs. This extension has a five-byte extension header, a one-byte field denoted as "Action-ID", and an optional part of DA list. Figure 5 illustrates its format. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mesh-Enhancement Extension ID | Next Extension Offset (NEO) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | NEO, contd. | Action-ID | Number of DA URLs | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length of DA URL #1 | DA URL #1 \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ . . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Length of DA URL #N | DA URL #N \ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5. Mesh-Enhancement Extension Zhao, et al. Expires: December 30, 2000 [Page 4]
Internet Draft DA Interaction June 30, 2000 The Action-ID is used to specify the requested operations from the receiving DA or to indicate the status information to the receiving DA. Table 1 lists the defined Action-IDs. Action-ID Abbreviation 0 No_Action 1 Mesh_Forward_Rqst 2 Data_Dump_Rqst 3 Peer_Conn_Indication 4 Peer_DA_Indication 5 Peer_Conn_Keepalive Table 1. Actions in Mesh-Enhancement Extension No_Action: null operation. It is used to turn off other operations. Mesh_Forward_Rqst: mesh forwarding request. It requests that the receiving DA forward the message to all DAs (both mesh-enhanced and non-mesh-enhanced) in the registration scope. Data_Dump_Rqst: data dump request. It requests that the receiving DA dump all the service registration data in the shared scopes to the requesting DA. Peer_Conn_Indication: peer connection indication. It informs the receiving DA that this is a peering TCP connection. Peer_DA_Indication: peer DAs indication. It carries the optional DA list in the form of URLs. The receiving DA SHOULD peer with all DAs in this list. Peer_Conn_Keepalive: peer connection keepalive. It indicates that this peering TCP connection is alive. The receiving DA SHOULD not close it. 5. Peer Relationship We use a set of fully meshed peering TCP connections among peer DAs. A mesh-enhanced DA maintains a peer list. Each entry in this peer list includes peer URL, shared scopes, boot timestamp, peering TCP connection ID, and mesh flag. The boot timestamp is to identify a rebooted peer. The peering TCP connection is used for message forwarding. The mesh flag indicates whether the peer is mesh-enhanced or not. A mesh-enhanced DA adds an entry to its peer list whenever it discovers a new peer, removes an entry from the peer list when it finds the corresponding peer is down, and updates an entry when it detects the corresponding peer is rebooted. Zhao, et al. Expires: December 30, 2000 [Page 5]
Internet Draft DA Interaction June 30, 2000 A peer relationship has three stages: setting up, keeping and tearing down. We describe each stage in detail next. We consider the situation where mesh-enhanced DAs, non-mesh-enhanced DAs, mesh-aware SAs and non-mesh-aware SAs are coexisted. Our scheme works even if multicast is NOT supported or a DA's multicast DAAdvert can not reach all of its peer DAs. 5.1. Setting Up a Peer Relationship In SLP, each DA periodically sends DA Advertisement (DAAdvert) messages to the administratively scoped SLP multicast [3] address (239.255.255.253 is the default address in the IPv4 local scope). All DAs listen to this address. A DAAdvert message from a mesh-enhanced DA MUST carry the "mesh-enhanced" attribute keyword (Figure 6). +-----+ +-----------+ | | | | | DA1 | ------- Multicast DAAdvert ------> | DA2/UA/SA | | | [attr = mesh-enhanced] | | +-----+ +-----------+ Figure 6. Mesh-enhanced DA Advertisement When a mesh-enhanced DA learns about a new peer (either mesh-enhanced or non-mesh-enhanced), it creates a peering TCP connection to the peer if such connection does not yet exist. The mesh-enhanced DA uses this peering TCP connection to forward messages to the peer. The peer, if mesh-enhanced, also uses this peering TCP connection to forward messages in the opposite direction. Therefore, a peering TCP connection can be set up between two mesh-enhanced DAs or between a mesh-enhanced DA and a non-mesh-enhanced DA. In the latter case, the message forwarding only goes in uni-direction from the mesh-enhanced DA to the non-mesh-enhanced DA. For a non-mesh-enhanced peer, the mesh-enhanced DA just sets up a peering TCP connection with it and forwards message to it through the peering TCP connection. But for a mesh-enhanced peer, the mesh- enhanced DA MUST take the following additional steps: (1) Peering Connection Indication: After a peering TCP connection is established, the DA who initiates the connection sends a "Peer_Conn_Indication" DAAdvert message (it has a mesh-enhancement extension with the Action-ID set to "Peer_Conn_Indication"; similar notations are used in the rest of this document) through the connection to mark it as the peering TCP connection (Figure 7). (2) Peer DAs Indication: After sending the "Peer_Conn_Indication" DAAdvert message, the mesh-enhanced DA sends a "Peer_DA_Indication" Zhao, et al. Expires: December 30, 2000 [Page 6]
Internet Draft DA Interaction June 30, 2000 DAAdvert message through the peering TCP connection (Figure 7). This message carries a list of DAs that the receiving DA MUST peer with. This DA list is constructed based on the sending DA's peer information and the receiving DA's service scopes. More precisely, this list includes those DAs in the sending DA's peer list that share some scopes with the receiving DA. (1) "Peer_Conn_Indication" DAAdvert +-----+ (2) "Peer_DA_Indication" DAAdvert +-----+ | | <----------------- (TCP) ----------------- | | | DA1 | | DA2 | | | ------------------ (TCP) ----------------> | | +-----+ "Peer_DA_Indication" DAAdvert +-----+ Figure 7. Peering Connection and Peer DAs Indication How does a mesh-enhanced DA react when it receives the "Peer_Conn_Indication" and "Peer_DA_Indication" DAAdvert messages? When a mesh-enhanced DA receives a "Peer_Conn_Indication" DAAdvert message, it SHOULD use the TCP connection from which the message is received as the peering TCP connection to the sending DA instead of establishing another one (there is a small possibility that a pair of peering TCP connections might be created between the two peer DAs if they try to set up a peering TCP connection to each other almost at the same time), and reply with a "Peer_DA_Indication" DAAdvert message (Figure 7). By exchanging the peer information through "Peer_DA_Indication" DAAdvert messages, the mesh-enhanced DAs can learn about other DAs in the shared scopes even if multicast is not supported (the initial peer relationships can be configured by hand or through DHCP [4]). The interaction sequence in Figure 6 and 7 can be summarized as follows (assume DA2 is mesh-enhanced): DA1 is a mesh-enhanced peer of DA2: <1> DA2 discovers DA1. <2> DA2 creates peering TCP connection to DA1. <3> DA2 sends "Peer_Conn_Indication" DAAdvert to DA1. <4> DA2 sends "Peer_DA_Indication" DAAdvert to DA1. <5> DA1 sends "Peer_DA_Indication" DAAdvert to DA2. DA1 is a non-mesh-enhanced peer of DA2: <1> DA2 discovers DA1. <2> DA2 creates peering TCP connection to DA1. When a mesh-enhanced DA receives a "Peer_DA_Indication" DAAdvert message, it checks the DA list in the message. This DA list can be Zhao, et al. Expires: December 30, 2000 [Page 7]
Internet Draft DA Interaction June 30, 2000 empty in which case the number of DA URLs equals 0. If any URL in the list is NOT in its peer list, the mesh-enhanced DA unicasts an active DA discovery service request (a SrvRqst message with service type = "service:directory-agent") to the DA corresponding to the URL, to obtain a DAAdvert message from it (Figure 8). For example, if DA2 received the URL for DA3 from DA1 in the "Peer_DA_Indication" DAAdvert message (Figure 7), and DA3 is NOT in DA2's peer list, DA2 MUST then acquire a DAAdvert message from DA3 (Figure 8). Upon receiving the DAAdvert message from DA3, DA2 can go through the whole process to set up a peer relationship with DA3. +-----+ Unicast SrvRqst +-----+ | | ----- (service:directory-agent) ----> | | | DA2 | | DA3 | | | <-------- Unicast DAAdvert ---------- | | +-----+ +-----+ Figure 8. Obtaining DAAdvert (3) Getting Data: After sending the "Peer_DA_Indication" DAAdvert message, the mesh-enhanced DA SHOULD decide whether it needs to get the data from the new peer. If it needs, it sends a "Data_Dump_Rqst" DAAdvert message to the peer (Figure 9). +-----+ "Data_Dump_Rqst" DAAdvert +-----+ | | -------------- (TCP) ------------> | | | DA1 | | DA2 | | | <--------- SrvReg (TCP) ---------- | | +-----+ (data of shared scopes) +-----+ Figure 9. Dumping Data Please note that a mesh-enhanced DA does not need to download data from all of its new peers. For example, when a newly booted DA joins a peering DA set of three DAs, it needs to get a copy of the existing registration data from one of these three DAs, but not from all of them, which incurs a lot of redundant transmissions. How to choose a DA to download the data from the peering DA set is implementation dependent. There are a variety of choices for doing this. The new DA can randomly choose one DA from the peering DA set or just use the first DA it found. Other criteria, such as the nearest DA or the most lightly loaded DA, can also be used for the selection. The choice only affects performance. On the other hand, when a mesh-enhanced DA receives a "Data_Dump_Rqst" DAAdvert message, it dumps all the data of the shared scopes to the requesting DA. Each data record is sent as a SrvReg message, with a re-calculated new lifetime (= old lifetime - Zhao, et al. Expires: December 30, 2000 [Page 8]
Internet Draft DA Interaction June 30, 2000 elapsed time). After exchanging their data in both directions, peer DAs have the same consistent data for the shared scopes. 5.2. Keeping a Peer Relationship In SLPv2, a DA could close an idle TCP connection after CONFIG_CLOSE_CONN seconds (5 minutes at least). To keep a peering TCP connection alive, a mesh-enhanced DA SHOULD send a "Peer_Conn_Keepalive" DAAdvert message via the channel every CONFIG_DA_KEEPALIVE (see Section 8) seconds (Figure 10). +-----+ +-----+ | | | | | DA1 | ---------------- (TCP) ----------------> | DA2 | | | "Peer_Conn_Keepalive" DAAdvert | | +-----+ +-----+ Figure 10. DA Keepalive 5.3. Tearing Down a Peer Relationship A mesh-enhanced DA SHOULD tear down a peer relationship when it finds that the peer has closed the peering TCP connection; when it receives a multicast DAAdvert message from the peer with a DA stateless boot timestamp set to 0 meaning the peer is going to shutdown; or when it has not received the keepalive DAAdvert message from the peer for more than CONFIG_DA_KEEPALIVE seconds. In the last case, there may be a network partition and peer DA states get inconsistent. To tear down a peer relationship, a DA stops forwarding messages to this peer, closes TCP connection with this peer, and removes this peer from its peer list. 6. Message Forwarding Control 6.1. Forwarding SrvReg and SrvDeReg Messages A mesh-enhanced DA forwards SrvReg and SrvDeReg messages from mesh- aware SAs. The forwarding rules are as follows: (1) Explicit Forwarding: A SrvReg or SrvDeReg message is forwarded only when it explicitly requests to be forwarded. A mesh-aware SA needs to add the mesh-enhancement extension to a SrvReg or SrvDeReg message and set the Action-ID to "Mesh_Forward_Rqst" if it wants the message to be forwarded by a mesh-enhanced DA. This is for the compatibility with SLPv2, where SAs need to register with all existing DAs. To avoid unnecessary forwarding, the explicit forwarding rule is used. Zhao, et al. Expires: December 30, 2000 [Page 9]
Internet Draft DA Interaction June 30, 2000 (2) One-hop Forwarding: A SrvReg or SrvDeReg message is forwarded only once by a mesh-enhanced DA to all of its peers (both mesh- enhanced and non-mesh-enhanced) in the registration scope. Before forwarding a message, a mesh-enhanced DA sets the Action-ID in the mesh-enhancement extension to "No_Action". In this way, a forwarded message will never be forwarded again. Since the peering DA set is in a fully connected mesh, one-hop forwarding is enough to ensure that a message can reach all peer DAs. Figure 11 shows how a SrvReg/SrvDeReg message is forwarded. +----+ "Mesh_Forward_Rqst" +-----+ "No_Action" +-----+ | | -- SrvReg/SrvDeReg -> | | --- SrvReg/SrvDeReg --> | | | SA | | DA1 | | DA2 | | | <------ SrvAck ------ | | <------- SrvAck ------- | | +----+ +-----+ +-----+ Figure 11. Forwarding Registration (3) Handling SrvAck: Since a DA always replies with a SrvAck message when it receives a SrvReg or SrvDeReg message, a mesh-enhanced DA SHOULD process SrvAck messages from other DAs. In Figure 11, DA1 returns a SrvAck message to SA upon receiving and processing a SrvReg/SrvDeReg message. As DA1 also forwards the message to DA2, it SHOULD properly handle the SrvAck message from DA2. 6.2. Forwarding DAAdvert Messages A mesh-enhanced DA also forwards DAAdvert messages from its non- mesh-enhanced peers. The forwarding rules are as follows: (1) A DAAdvert message is forwarded only when it comes from a new or rebooted non-mesh-enhanced peer. (2) A mesh-enhanced DA forwards a DAAdvert message to all of its mesh-enhanced peers that share some scopes with the advertised DA. (3) A forwarded DAAdvert message SHOULD not be forwarded again. It can be identified easily since the sending DA and the advertised DA are different for a forwarded DAAdvert message. Forwarding the DAAdvert message from a new or rebooted non-mesh- enhanced peer can ensure that the DA is known to all of its mesh- enhanced peers even if multicast is NOT supported or its multicast DAAdvert messages can NOT reach all of its mesh-enhanced peers. With the peer setting up procedure described in Section 5.1 and the forwarding rules given in this section, a DA (mesh-enhanced or non- mesh-enhanced) known to one mesh-enhanced peer can be known to all of its mesh-enhanced peers. Therefore, a mesh-enhanced DA can know all Zhao, et al. Expires: December 30, 2000 [Page 10]
Internet Draft DA Interaction June 30, 2000 of its peers (mesh-enhanced and non-mesh-enhanced), and forward service registration information from mesh-aware SAs to them properly. 7. Design Discussion In this section, we discuss several important design issues. 7.1 Meshed Peering TCP Connections The fully meshed peering DA architecture is built on top of a set of fully meshed peering TCP connections, which greatly facilitates message forwarding control. Any message received by a DA only needs one-hop forwarding to reach all other DAs in the peering DA set. We anticipate a small number of DAs for each service scope, and 2-4 is the recommended value. There is no need to have separate DA for each scope. A DA can serve multiple scopes, and a peering TCP connection is used for all shared scopes between each pair of peer DAs. 7.2 Reliability The fully meshed peering DA architecture provides maximum robustness. It ensures that no single failure point exists in the SLP directory service. All service registrations are kept by at least two DAs. If one DA is down, at least one other peer DA can continue to provide the service information for the scope. Moreover, the peering DA architecture ensures the data consistency among peer DAs automatically. It also enables a DA to recover from crash with much less effort since a rebooted DA can get the existing data from its peering DA set. This is done through DA coordination, no SA involvement is needed. 7.3 Simplifying SA Registrations and Scalability The fully meshed peering DA architecture greatly simplifies SA registrations. A mesh-aware SA only needs to register with one mesh- enhanced DA in the registration scope. The information will be propagated automatically within the peering DA set. Thus, a mesh- aware SA does not need to implement the complicated algorithm to register with all existing DAs and to re-register when new mesh- enhanced DAs are discovered, or old mesh-enhanced DAs are found to have rebooted. With mesh-enhanced DAs and simplified SAs, the overall SLP system scalability can be enhanced. 7.4 Forwarding UA Queries A further extension to the interaction of SLP DAs is to forward UA queries besides SA registrations. It works as follows: When a mesh- Zhao, et al. Expires: December 30, 2000 [Page 11]
Internet Draft DA Interaction June 30, 2000 enhanced DA receives a UA query which is not in its scope, it forwards the query to another DA which supports the scope. This can simplify UA implementation since UAs do not need to keep track of DA scopes. A UA can send its queries to any mesh-enhanced DA. However, this adds much complexity to the mesh-enhanced DA implementation. First, a mesh-enhanced DA needs to keep track of all DAs of all scopes, not only the DAs that share some scopes with it. Second, a mesh-enhanced DA needs to forward the query to another DA, and it also needs to forward the reply from another DA back to the UA. We did not include this extension in our scheme mainly due to its complexity. However, for a thin-client UA implementation, it might deserve further consideration. 7.5 Compatibility mSLP is backward compatible with SLPv2. It only defines a new attribute ("mesh-enhanced") for the DAAdvert message and a new SLP extension (mesh-enhancement extension) which is used by DAAdvert, SrvReg and SrvDeReg messages. In mSLP, DAs are enhanced with very little added complexity, and the changes are almost transparent to UAs and SAs. UAs can be kept unchanged. SAs can be greatly simplified by using the mesh-forwarding capability for the service registrations. mSLP supports incremental deployment of mesh-enhanced DAs. A mesh- enhanced DA MUST set up peer relationships with both mesh-enhanced DAs and non-mesh-enhanced DAs. A mesh-aware SA only needs to register with one mesh-enhanced DA. However, it still needs to take care of newly found non-mesh-enhanced DAs and rebooted non-mesh-enhanced DAs since these non-mesh-enhanced DAs can not get the existing data from other DAs. Therefore, uniformly mesh-enhanced DAs can provide a much easier job for mesh-aware SAs. 7.6 Summary We summarize the operations for UAs, mesh-aware SAs, non-mesh-aware SAs, mesh-enhanced DAs and non-mesh-enhanced DAs as follows: UA A UA MAY prefer to use a mesh-enhanced DA to a non-mesh-enhanced DA since a mesh-enhanced DA is more likely to reliably contain the complete set of current service registration data for the UA's scope. Non-mesh-aware SA It needs to discover all DAs in its scope and register with all Zhao, et al. Expires: December 30, 2000 [Page 12]
Internet Draft DA Interaction June 30, 2000 of them. It does NOT use the mesh-enhancement extension. Mesh-aware SA It identifies mesh-enhanced DAs from the "mesh-enhanced" attribute in the DAAdvert messages. It only needs to discover one mesh-enhanced DA and register with it using a mesh-enhancement extension with the Action-ID set to "Mesh_Forward_Rqst". If there are no mesh-enhanced DAs in its scope, it operates in the same way as a non-mesh-aware SA [1]. Non-mesh-enhanced DA It accepts SrvReg and SrvDeReg messages from SAs and mesh- enhanced DAs normally. It dose NOT forward them. Mesh-enhanced DA (1) It MUST carry the "mesh-enhanced" attribute keyword in its DAAdvert messages (Section 2). (2) It MUST keep a list of peer DAs (mesh-enhanced and non-mesh- enhanced) that share some scopes with it, and maintain a peering TCP connection to each of them. For each mesh-enhanced peer, a "Peer_Conn_Indication" DAAdvert message SHOULD be sent OR processed, a "Peer_DA_Indication" DAAdvert message SHOULD be sent AND processed, a "Data_Dump_Rqst" DAAdvert message MAY be sent OR processed (Section 5). (3) It accepts SrvReg and SrvDeReg messages from SAs and mesh- enhanced DAs. It MUST forward the "Mesh_Forward_Rqst" SrvReg and SrvDeReg to all peer DAs (both mesh-enhanced and non-mesh- enhanced) in the registration scope. It also processes SrvAck messages from mesh-enhanced DAs (Section 6.1). (4) When it receives a DAAdvert messages from a new or rebooted non-mesh-enhanced peer, it MUST forward the message to all of its mesh-enhanced peers that share some scopes with the advertised DA (Section 6.2). 8. Constants Mesh-enhancement Extension ID 0x0006 (Section 4) CONFIG_DA_KEEPALIVE 290 seconds (Section 5.2) Note: CONFIG_DA_KEEPALIVE < CONFIG_CLOSE_CONN, which has a default value of 300 seconds [1]. Zhao, et al. Expires: December 30, 2000 [Page 13]
Internet Draft DA Interaction June 30, 2000 9. Security Considerations DA authentication is more important in mSLP since a mesh-aware SA depends on the mesh-enhanced DA it registers with to forward its SrvReg and SrvDeReg messages. A mesh-enhanced DA SHOULD use standard SLPv2 authentication to authenticate other DAs in the mesh. A mesh- enhanced DA SHOULD also perform authentication before accepting SrvReg and SrvDeReg messages to prevent illegitimate modification or elimination of legitimate service registrations. mSLP is just as secure as SLPv2. 10. References [1] E. Guttman, C. Perkins, J. Veizades, M. Day, "Service Location Protocol Version 2", RFC 2608, June 1999. [2] Y. Rekhter, T. Li, "A Border Gateway Protocol 4 (BGP-4)", RFC 1771, March 1995. [3] D. Meyer, "Administratively Scoped IP Multicast", RFC 2365, July 1998. [4] R. Droms, "Dynamic Host Configuration Protocol", RFC 2131, March 1997. [5] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 11. Authors' Addresses Weibin Zhao Department of Computer Science Columbia University 1214 Amsterdam Avenue, MC 0401 New York, NY 10027-7003 Email: zwb@cs.columbia.edu Henning Schulzrinne Department of Computer Science Columbia University 1214 Amsterdam Avenue, MC 0401 New York, NY 10027-7003 Email: hgs@cs.columbia.edu Erik Guttman Sun Microsystems Eichhoelzelstr. 7 74915 Waibstadt Zhao, et al. Expires: December 30, 2000 [Page 14]
Internet Draft DA Interaction June 30, 2000 Germany Email: Erik.Guttman@sun.com 12. Full Copyright Statement Copyright (C) The Internet Society (2000). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Zhao, et al. Expires: December 30, 2000 [Page 15]