Lemonade Internet Draft: Lemonade Server to Client S. H. Maes Notifications Document: draft-ietf-lemonade-server-to-client- C. Wilson notifications-00.txt Expires: January 2005 July 2004 Lemonade Server to Client Notifications Status of this Memo This document is an Internet-Draft and is subject to 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. Abstract Lemonade server to client notifications provides some extensions to the IMAPv4 Rev1 protocol [RFC3501] for optimization in a mobile setting, aimed at delivering extended functionality for mobile devices with limited resources. These notifications support pushing crucial changes actively to a client, rather than requiring the client to initiate contact to ask for state changes. Conventions used in this document In examples, "C:" and "S:" indicate lines sent by the client and server respectively. 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]. Maes [Page 1] July 2004 An implementation is not compliant if it fails to satisfy one or more of the MUST or REQUIRED level requirements for the protocol(s) it implements. An implementation that satisfies all the MUST or REQUIRED level and all the SHOULD level requirements for a protocol is said to be "unconditionally compliant" to that protocol; one that satisfies all the MUST level requirements but not all the SHOULD level requirements is said to be "conditionally compliant." When describing the general syntax, some definitions are omitted as they are defined in [RFC3501]. Table of Contents Status of this Memo...............................................1 Abstract..........................................................1 Conventions used in this document.................................1 Table of Contents.................................................2 1. Introduction...................................................3 1.1. The Poll Model vs. the Push Model.........................3 1.2. The Server-Side Filtering in Lemonade.....................4 1.3. Synchronization Techniques................................5 1.3.1. State-Comparison-Based Synchronization...............5 1.3.2. Event-based Synchronization..........................6 2. The Lemonade Server to Client Notification Design..............7 2.1. Implementing Filters......................................7 2.1.1. The View Filter......................................8 2.1.2. The Priority/Notification Filter.....................8 2.1.3. The Syntax to define Priority/Notification Filters...8 2.2. Connectivity Models.......................................9 2.2.1. In-Response Connectivity.............................9 2.2.2. Inband Connectivity..................................9 2.2.3. Outband Connectivity................................10 2.3. Keeping the Client In Sync with the Mobile Repository....10 3. Events........................................................11 3.1. Message Events Sent During Inband and Inresponse Mode....11 3.2. Folder Events............................................12 3.3. PIM Events...............................................12 4. Interactions between the Lemonade Client and Lemonade Server..12 4.1. Revisions to IMAPv4 Rev1 Behavior........................12 4.1.1. UID.................................................12 4.1.2. Mobile Repository...................................12 4.1.3. IDLE................................................13 4.1.4. LEMONADESETPREF & LEMONADEGETPPREFS.................13 4.1.5. LEMONADEFILTER......................................13 Security Considerations..........................................15 References.......................................................15 Normative Appendices.............................................16 A. Event Payload..............................................16 Maes Expires - January 2005 [Page 2] July 2004 A.1. Event Payload in Clear Text for Lemonade Sessions.....16 A.2. Outband Channel Event Payload.........................16 Non-Normative Appendices.........................................17 B. Use Cases..................................................17 B.1. State Comparison-Based Sync...........................17 B.2. Event-Based Sync......................................18 Authors Addresses................................................19 Intellectual Property Statement..................................19 Full Copyright Statement.........................................19 1. Introduction The Lemonade Server to Client Notifications extends IMAPv4 Rev1 [RFC3501]. The client devices in this document are assumed to be wireless with limited resources. However, this should not be seen as constraining. The Lemonade Server to Client Notifications can be bound to any transport protocol for inband and outband connectivity. These notifications inform the client of changes in an end user's mailbox. This document will define what events and conditions generate notifications, as well as how the server will inform the client of these notifications. In addition, it covers how the client will process these notifications to maintain email synchrony. The organization of this document is as follows. The rest of this section introduces the concepts of Lemonade Server to Client Notifications so the reader can gain an understanding of the concepts that drive this design. Section 2 discusses actual design decisions for Lemonade Server to Client Notifications. Section 3 defines the bindings for expressing events, while Section 4 is the main body of the protocol, which describes the interactions between the Lemonade server and client. Next are sections concerning security considerations, and references. Finally, there are normative and non-normative appendices, which provide useful information for those who wish to implement the Lemonade Server to Client Notifications. 1.1. The Poll Model vs. the Push Model This section discusses two different models for exchanging notifications from the server to the client. Today, most of the existing email clients implement a polling model, where the end user is notified of changes to an email account only after the email client polls the server for changes. How long it takes a client to learn of a change on the server is thus dependent on how often the client polls for changes. Many clients can poll at high rates so that the client can quickly learn of changes and reflect them on the client display to achieve a quasi-real time synchronization experience for the end user. Because the client must continuously Maes Expires - January 2005 [Page 3] July 2004 poll the server for changes, the bandwidth requirements can be quite high and the connection quality must be good in order to provide a quasi-real time experience to the user. The periodic poll model is used on conventional email clients and is illustrated in Figure 1. +--------------------+ Poll +--------------+ | | <------------ | | | Mail Server | | Email Client | | | ------------> | | +--------------------+ Response +--------------+ Figure 1: Periodic Poll Model Another way to achieve synchronization is for the email server to initiate a session with the client when a crucial change to an email occurs, which is the push model. When important events happen to a userĘs email account, the server informs the client device about the event, and then the client can respond to that event as necessary. In this case, the client device does not need to periodically poll the mail server, so the push model is particularly effective in the mobile computing environment when the cost of constant polling is high. The Lemonade Server to Client Notification Specifications define the semantics for pushing events to a client. The push model is seen in Figure 2. Event +----------------+ Push +--------------+ --------> | Mail Server | ---------> | Email Client | +----------------+ +--------------+ Figure 2: Push Model 1.2. The Server-Side Filtering in Lemonade The Lemonade profile and Lemonade Server to Client Notification protocol is meant to support mobile client devices with memory and connectivity constraints. Due to these constraints, an end user may want to specify filters to limit the number of notifications sent. These filters separate their emails into different sets that the server should handle differently. All end users have a complete repository, which includes all their email messages that are stored on a server. The end user may want to receive a small subset of these messages on their client device, which are to be included on the mobile device. The messages on the device are split further into two categories, lower priority messages that the user chooses to wait for until it can poll the server and higher priority messages that the user would like to be notified of as soon as possible by the server. All three repositories have the same set of folders. +----------------+ +--------------+ +------------+ Maes Expires - January 2005 [Page 4] July 2004 | COMPLETE | | MOBILE | | MOBILE | | | POLL | Priority / | PUSH | | REPOSITORY | View | REPOSITORY |Notification | REPOSITORY | | all the emails |Filters | emails to be | Filters | important | |in an end user's|=======>|on the mobile |============>| emails of | | email account | | device | | end user | +----------------+ +--------------+ +------------+ Figure 3: Filters and Repositories Formally, a repository consists of a set of folders, and each folder has both a name and a set of messages associated with it. While the three repositories all have folders with the same name, there may be different messages in them. The complete repository consists of all folders of an end user and all the associated emails for each of those folders. Messages in the complete repository that pass the view filter make up the poll repository. An end user can specify exactly one view filter per folder per device. In addition, there is a second layer of filtering, called priority or notification filters, and there is exactly one priority filter per folder per device. The push repository is the set of all the messages in the complete repository that pass both the view and the priority filters. From this point forth, it can be assumed that an event in this document refers to only and all changes to messages in the mobile repositories. When the client connects to the server and polls for messages, it can determine what changes have occurred to messages that passed the view filters. Whenever an event occurs to a message that passes the view and priority filters, the server actively pushes a notification to the client. 1.3. Synchronization Techniques After a client receives a notification that informs it that changes have occurred to a mailbox, it needs to employ a synchronization technique to reflect the server side changes onto the client device. There are many techniques for determining what the changes between a server and client are. In this section, two techniques are presented that aim to keep a client device in sync with a given email account, meaning the set of emails on the client device is the same as that in the given email account. 1.3.1. State-Comparison-Based Synchronization IMAPv4Rev1 clients use a state-comparison-based synchronization technique to be in sync with an email account. This technique requires the client to ask the server for information regarding all the folders and all the messages in each folder stored on the server. The client must then compute the difference between the server state Maes Expires - January 2005 [Page 5] July 2004 and the client device state, and make all necessary changes so that the client device state matches the server state. An example of the interaction between the client and server in the IMAPv4 Rev1 protocol for performing a state-comparison-based sync follows. First, the client must retrieve the folders from the server. C: A002 LSUB "" "*" S: * LSUB () "/" "Drafts" S: * LSUB () "/" "Friends" S: * LSUB () "/" "INBOX" S: A002 OK LSUB completed The client must compare its folders with the responses of the command above. If it does not have a folder, it must create that folder on the client device. If there is a folder on the device that is not in any of these responses, then the client must delete that folder. Next, the client needs to make sure that the emails in each of its folders match the server. It performs a SELECT and then a FETCH command for each folder. A sample of a SELECT and FETCH command for the inbox is as follows: C: A003 SELECT ~/INBOX S: * 60 EXISTS S: ... more untagged responses with information about the folder S: A003 OK SELECT completed C: A004 FETCH 1:* (FLAGS UID) S: * 1 FETCH (FLAGS (\Answered) UID 120) S: * 2 FETCH (FLAGS (\Seen) UID 121) S: ... flags for messages with message sequence numbers 3-59 S: * 60 FETCH (FLAGS () UID 250) S: A004 OK FETCH completed The client must go through the full list of email messages in each folder. It must add an email in this list if it is not already on the client. It must modify any email in this list on the client device to reflect any changes to the mutable flags of that message. Also, it should remove any emails on the client device not in this list. After performing these operations, the client is in sync with the server. 1.3.2. Event-based Synchronization Another technique is event-based synchronization. Event-based synchronization is used to keep the client device in sync with the server. This method requires that the client has been fully synchronized with the server at some earlier point. In the IMAPv4 Rev1 protocol, the client must perform a state-comparison-based sync when it selects a folder, but then it can use event-based synchronization to keep itself in sync after that. Although event- Maes Expires - January 2005 [Page 6] July 2004 based synchronization cannot totally replace state-comparison-based synchronization, it is a faster alternative for the client to maintain synchrony when the server is capable of change tracking for a client. In event-based synchronization, the server keeps track of what changes have occurred that are not yet reflected on the client device. Such a change is called an event. When the client finishes processing all events since the last time it was in sync with the server, it is again in sync with the server. Event-based synchronization is particularly effective when the server can push events to the client for immediate processing. In this case, there are likely to be only a small number of events the client needs to process at one time. When a Lemonade client drops a connection or accidentally disconnects the server can retain the session and cache all events during the time the client is disconnected. When the client reconnects it does not need to perform a state-comparison-based synchronization again, instead the server sends the list of pending events to the client. 2. The Lemonade Server to Client Notification Design Lemonade Server to Client Notification assumes extensions of IMAP with the same basic model, where the client connects to the server to open a session to access its email account. A Lemonade client may fetch the contents of the email account or make changes to it just as in IMAP. 2.1. Implementing Filters A Lemonade server should support multiple mobile devices for each email user, and should allow each device to have one unique event filter and a set of view filters and priority/notification filters. The server only needs to support one connection per mobile device for each email user. A mobile client connects to the Lemonade server by supplying its LOGIN information, and then must inform the server of this mobile clientĘs device ID, which is some unique identifier for the client device. The server and client should agree on what convention to use for this ID, and it could be a hash of IMEI. If no device ID is given, then a regular IMAP session is initiated. The LOGIN information is used to specify a user, while the device ID is needed to specify the mobile client. Associated with the user and device ID is exactly one view filter and exactly one priority/notification filter for each folder. These filters are saved and thus persist across Lemonade sessions. Filters can be modified when a Lemonade session is open. Maes Expires - January 2005 [Page 7] July 2004 2.1.1. The View Filter View filters and priority/notification filters are used to filter out email messages which match certain criteria. If an email passes through the view filter, it is stored in the mobile repository. The syntax for defining a view filter or notification filter includes any combination of most of the search criteria as defined for the SEARCH command of IMAP, in Section 6.4.4 and 7.2.5 of RFC 3501, or a days filter. The days filter filters messages received starting a certain number of days before the current day. The ALL search criteria, when used alone, means that every email event satisfies the criteria. By default, view filters are set to ALL. Whenever a view filter is modified, the client needs to perform a state-comparison-based sync to keep in sync with the mobile repository since the messages in the mobile repository may have changed. 2.1.2. The Priority/Notification Filter Priority/Notification filters are used to select emails in the mobile repository which match certain criteria. If an email passes through the notification filter, it is stored in the push repository. The syntax for defining a priority/notification filter is discussed below. By default, priority/notification filters are set to NOT ALL to reduce default traffic at the cost of some delays. Because the view filter defaults to ALL and the priority/notification filter to NOT ALL, the mobile repository will mirror the complete repository, but none of the messages are added to the push repository. This implies that the default behavior is equal to the IMAPv4 Rev1 model. The client does not need to do anything after it resets a priority/notification filter or event filter, instead the server should then only send out notifications that correspond to the most up-to-date filters. 2.1.3. The Syntax to define Priority/Notification Filters The syntax for defining a priority/notification filter is ALL, NONE, or NEW. A priority/notification filter applies for all folders in a push repository. ALL -- All message events concerning messages of the push repository will be sent to the client, such as if the message becomes seen or deleted. NONE -- No events should be pushed to the client. NEW -- Only events that concern new messages arriving to the push repository should be pushed to the client. Maes Expires - January 2005 [Page 8] July 2004 This one event filter applies for all folders. 2.2. Connectivity Models There are three connectivity models for Lemonade Server to Client Notifications, depending on the capabilities of the Lemonade server, the client, and the connection available between them. These models include in-response, inband, and outband. It is explicitly stated in what situations these three connectivity models arise. 2.2.1. In-Response Connectivity The in-response binding scenario is the most basic one and implements the poll model. In this case the client initiates the commands to the Lemonade server and the server responds to client commands with events. In this case there is no need for a persistent connection between the client and the server. The client opens a connection only when it needs to send commands to the Lemonade server, and that is the only time it is notified of new events. +--------+ +++ HTTP, etc. +--------+ | | Command +++ | | | Client |--------------------+++--------------->|Lemonade| | Device | +++ | Server | | | Response + Event +++ | | | |<-------------------+++----------------| | +--------+ +++ +--------+ Figure 4: In-Response connection An in-response connection can occur in several situations: [1] HTTP/HTTPS binding - Server Requires: HTTP/HTTPS listener for IMAPv4 - Client Requires: HTTP/HTTPS client with IMAPv4 processing [2] TCP Binding - Server Requires: IMAPv4 - Client Requires: IMAPv4 + no IDLE 2.2.2. Inband Connectivity The inband binding scenario corresponds to a reliable push model. In this case the server pushes events to the client whenever they occur. To do so, it must have a reliable means of communication with the client, and the client should be ready to accept such notifications. In this case, there needs to be a persistent connection between the client and the server so that the server can push an event at any time. The client may optionally issue a request to retrieve more information concerning an event. +--------+ OOO TCP, Persistent +--------+ | | Push Event OOO HTTP, etc. | | Maes Expires - January 2005 [Page 9] July 2004 | Client |<------------------OOO-----------------|Lemonade| | Device | OOO | Server | | | Optional Request OOO | | | |...................OOO................>| | +--------+ OOO +--------+ Figure 5: Inband Connection An inband connection can occur in the following situations: [1] TCP Binding, Always connected, IDLE - Server Requires: IMAPv4 + IDLE - Client Requires: IMAPv4 + IDLE, constant TCP connection [2] Any other persistent two-way connection - Server Requires: IMAPv4 + IDLE - Client Requires: IMAPv4 + IDLE, constant connection 2.2.3. Outband Connectivity The outband binding scenario corresponds to an unreliable push model. In this case the server pushes events to the client whenever they occur, to the best of its ability. To do so, it should be able to send messages to the client without the need for a persistent connection. However, the outband channel can possibly lose and reorder messages, and there are no timing guarantees. Examples of out-band channels include SMS, JMS, WAP Push, and UDP. As in the inband scenario, the client may optionally open a Lemonade session over an inband or in-response connection and send a command as a result of receiving an event. +--------+ Push Event XXX SMS +--------+ | |<--------------XXX---------------------| | | Client | XXX |Lemonade| | Device | Inband or | Server | | | Request +O+ In-response | | | |---------------O+O-------------------->| | +--------+ +O+ +--------+ Figure 6: Outband Connection Outband connectivity occurs in the following situations: [1] A notification service from the server to the client - Server Requires: A notification generator. - Client Requires: A notification processor. 2.3. Keeping the Client In Sync with the Mobile Repository Whenever a client device opens a new session, it must perform a state-comparison-based sync with the email server so that its state is the same as the mobile repository. Since the client has no way of Maes Expires - January 2005 [Page 10] July 2004 directly detecting only changes to the repository since the last login, it needs to retrieve information about every message in the mobile repository and calculate the changes itself. After that point, the client can use event-based synchronization to keep the device in sync. The Lemonade server can issue a session and track changes to a selected folder for the duration of a session. Until the session is expired, the server must log all events that occur while a client is offline. This way, if the client temporarily loses a connection, it does not have to worry about missing any events and needing to perform another state-comparison-based sync. A client does have the option though to prematurely end a session by issuing a LOGOUT command. Additionally, Lemonade clients can remain inactive for at least twenty four hours without being logged off the server and without the session expiring. 3. Events This section contains the syntax that the server uses to send events to the client. 3.1. Message Events Sent During Inband and Inresponse Mode The client can receive the following untagged responses from the server: [1] The client receives an EXISTS/RECENT event from the server indicating a new message. S: * 501 EXISTS S: * 1 RECENT Next, the client retrieves this new message using a FETCH command. C: A02 FETCH 501 (ALL BODY[]) S: * 501 FETCH ... S: A02 OK FETCH completed [2] The client receives an EXPUNGE event from the server from a message has been permanently removed from a folder. S: * 25 EXPUNGE The client deletes this message from the client device, as it has been removed permanently from the folder. The client does not need to send any command back to the server. [3] The client receives an untagged FETCH event from the server, which can contain just FLAG information if the event is regarding an old message or possibly other information if the event is regarding a new message. This event is received if a message's flags are Maes Expires - January 2005 [Page 11] July 2004 changed, or in response to a new message if the user's preferences are set to do so. S: * 101 FETCH (FLAGS (\Seen \Deleted)) The client saves the information contained in this response accurately in the client device. 3.2. Folder Events This section will contain syntax for indicating folder events. 3.3. PIM Events This section will contain syntax for indicating PIM events. 4. Interactions between the Lemonade Client and Lemonade Server Interactions between Lemonade clients and servers are described in [LEMONADEPROFILE]. The Lemonade Server to Client Notifications also define events to be sent by the server to the client. These events notify the client when there are changes to messages that match an end userĘs view filters and notification filters, as well as any changes to a clientĘs email folders. The syntax defined in this section is an abstract syntax, and payloads may vary according to the communication mechanism used. The normative appendix of this document describes some specific payloads. 4.1. Revisions to IMAPv4 Rev1 Behavior 4.1.1. UID The UID of email messages MUST not change across sessions. Changing the UID of email messages requires a heavy computational burden on the mobile client, so the server should avoid doing so. The UID of email messages MUST not change for the duration of a session. 4.1.2. Mobile Repository In a Lemonade session, the client can only access messages in the mobile repository. This affects the messages returned by FETCH, UID FETCH, etc. Message sequence numbers reflect the relative position of messages within the given folders of the mobile repository, so the message sequence number of an email while logged in to Lemonade may Maes Expires - January 2005 [Page 12] July 2004 also differ from IMAP. When returning information about the email account, only messages in the mobile repository are taken into account. 4.1.3. IDLE The server should implement the IDLE command from RFC 2177. When the client issues this command, the server can push changes to a folder to the client. The server may replace the EXISTS/RECENT message with an untagged FETCH command as specified in [EXTENSIONS] (Section on 2.2.2. ” See LEMONADESETPREF & LEMONADEGETPPREFS). The client should fire this command while in-session to enter inband mode, where the server will actively push notifications to the client. 4.1.4. LEMONADESETPREF & LEMONADEGETPPREFS The LEMONADESETPREF command is described in [EXTENSIONS]. It allows a user to define certain configuration parameters, while the LEMONADEGETPREFS command allows a user to retrieve the configuration values. Any server that implements these commands must respond with LEMONADEPREF as one of the capabilities in response to a CAPABILITY command. It must also announce the values these parameters can be set to in the LEMONADEPROVISION command (See [EXTENSIONS]). These parameters affect how outband notifications are sent to the client, as well as the format for sending new event notifications. If the server supports LEMONADEPREF they are required to support all of the following preferences with at least one value to set each preference to. They are described in [EXTENSIONS]. 4.1.5. LEMONADEFILTER The LEMONADEFILTER command allows users to set up view filters and priority/notification filters. LEMONADEFILTER can be fired when the state is AUTHENTICATED or SELECTED. The first argument to this command is the folder that that filter should be applied to, or "ALL" for all folders. Next the user specifies "V", "N", or "B" to set either a view filter or a priority/notification filter, or both. Following this, it must specify the filter criteria using a combination of search criteria as defined for the SEARCH command of IMAP, in Section 6.4.4 and 7.2.5 of RFC 3501, or the days filter. The ALL search criteria, when used alone, means that every email message satisfies the criteria. Or it can specify "V" or "N" to get a view filter or priority/notification filter. In this case, the last argument is "GET" to retrieve the filter. By default, view filters are set to ALL, while priority/notification filters are set to NOT ALL. This means that the mobile repository includes all the messages in the complete repository, but none are pushed to the client, which is the IMAPv4 Rev1 model. Maes Expires - January 2005 [Page 13] July 2004 Exactly one view filter and one priority/notification filter is associated with each folder for each device. When a new view filter or priority/notification filter is created, it replaces the previous filter for that folder. When a view filter is modified, the client needs to perform a state-comparison-based sync on the client in order for the device to be in sync with the mobile repository. The server always sends only notifications that correspond to the most up-to- date view filters and priority/notification filters. All filters persist across Lemonade sessions; once set, a filter on a folder applies until the user changes it. Lemonade introduces a filter, the days filter, which allows a user to specify from how many days before today it would like to see emails. To see only today's email, a 0 should be used for the int. lemonadefilter_cmd = tag SP "LEMONADEFILTER" SP ("ALL" / folder) SP (("V" / "N" / "B") SP lemonadefilter_criteria) / (("V" / "N") "GET") lemonadefilter_criteria = (IMAPv4Rev1_searching_criteria / days_filter) [SP lemonadefilter_criteria] days_filter = "DAYSBEFORETODAY" SP int Valid States: AUTHENTICATED or SELECTED Responses: untagged responses: lemonadefilterGet_resp lemonadefilterGet_resp = "*" SP "LEMONADEFILTER" SP folder SP ("V"/"N") lemonadefilter_criteria Result: OK - filter created NO - can't create the filter BAD - invalid arguments Example: The client creates a priority/notification filter for all messages in the Inbox from "John" since Jun. 1st, 2003. C: A001 LEMONADEFILTER INBOX P SINCE 1-Jun-2003 FROM "John" S: A001 OK LEMONADEFILTER completed Example: The client asks for the view filter for all the folders. C: A001 LEMONADEFILTER ALL V GET S: * LEMONADEFILTER ~/INBOX V ALL S: * LEMONADEFILTER ~/TRASH V NOT ALL S: A001 OK LEMONADEFILTER completed Example: Stop notifications on a particular device, fired while in AUTHENTICATED mode. C: A001 LEMONADEFILTER ALL P NOT ALL S: A001 OK LEMONADEFILTER ALL P NOT ALL completed Maes Expires - January 2005 [Page 14] July 2004 Security Considerations The protocol calls for the same security requirements for an in- response and inband connectivity mode as IMAP. For the outband connectivity mode, servers should use encryption methods for notifications if sensitive information is included in the payload of that notification. When an implementation of Lemonade is proxy-based, this may create new security issues. These issues are discussed in detail in Appendix C, because the issues are dependent on the implementation of this protocol rather than inherent to the protocol itself. References [OMA-EN] Open Mobile Alliance Email Notification Version 1.0, August 2002. http://www.openmobilealliance.org/tech/docs/EmailNot/OMA- Push-EMN-V1_0-20020830-C.pdf [IMAP-DISC] Austein, R. "Synchronization Operations For Disconnected Imap4 Clients", IMAP-DISC, November 1994. http://asg.web.cmu.edu/cyrus/rfc/draft-ietf-imap-disc-01.html [RFC2119] Brader, S. "Keywords for use in RFCs to Indicate Requirement Levels", RFC 2119, March 1997. http://www.ietf.org/rfc/rfc2119 [RFC2180] Gahrns, M. "IMAP4 Multi-Accessed Mailbox Practice", RFC 2180, July 1997. http://www.ietf.org/rfc/rfc2180 [RFC2234] Crocker, D. and Overell, P. "Augmented BNF for Syntax Specifications", RFC 2234, Nov 1997. http://www.ietf.org/rfc/rfc2234 [RFC2420] Kummert, H. "The PPP Triple-DES Encryption Protocol (3DESE)", RFC 2420, September 1998. http://www.ietf.org/rfc/rfc2420 [RFC2616] Fielding, R. et al. "Hypertext Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999. http://www.ietf.org/rfc/rfc2616 [RFC2617] Franks, J. et al. "HTTP Authentication: Basic and Digest Access Authentication", RFC 2617, June 1999. http://www.ietf.org/rfc/rfc2617 Maes Expires - January 2005 [Page 15] July 2004 [RFC2683] Leiba, B. "IMAP4 Implementation Recommendations", RFC 2683 Sep 1999. http://www.ietf.org/rfc/rfc2683 [RFC2177] Leiba, B. "IMAP4 IDLE Command", RFC 2177, June 1997. http://www.ietf.org/rfc/rfc2177 [RFC2818] Rescorla, E. "HTTP over TLS", RFC 2818, May 2000. http://www.ietf.org/rfc/rfc2818 [RFC2822] Resnick, P. "Internet Message Format", RFC 2822, April 2001. http://www.ietf.org/rfc/rfc2822 [RFC3501] Crispin, M. "IMAP4, Internet Message Access Protocol Version 4 rev1", RFC 3501, March 2003. http://www.ietf.org/rfc/rfc3501 [LEMONADEPROFILE] Maes, S.H. and Melnikov A., "Lemonade Profile", draft-ietf-lemonade-profile-00.txt, (work in progress), July 2004. [EXTENSIONS] Maes, S.H., Lima R., Kuang, C., Cromwell, R., Ha, V. and Chiu, E., "Lemonade Command Extensions", draft-maes-lemonade- command-extensions-00.txt, (work in progress), July 2004. Normative Appendices A. Event Payload A.1. Event Payload in Clear Text for Lemonade Sessions The event payload for a Lemonade session follows the general format explained in Section 1.3.2, and is in clear text. A.2. Outband Channel Event Payload The suggested payload for notifications is that suggested by the OMA, see [OMA-EN]. This notification informs the client that some push event has happened on the server, so it must connect to fetch the information. When the client finally connects, the Lemonade server has opportunity to send other pending events for this client. Example: new message arrives on the server and this is notified via outband. S: pushes SMS with the following text: Maes Expires - January 2005 [Page 16] July 2004 C: needs to connect and send any command to get the pending events and act upon them. C: A00 Login joe password S: * SESSION SELECTED S: * FOLDER INBOX S: * 100 EXITS S: * 87 EXPUNGE S: * 90 FETCH (FLAGS \Seen) S: A00 OK LOGIN completed C: must now act on the events on the order they are received, meaning, first perform a FETCH to get new message, then expunge message 87 and change flags of message 90. Non-Normative Appendices B. Use Cases In this section some use cases on Lemonade are presented so that it is possible to correctly understand concepts and message flow. B.1. State Comparison-Based Sync Each time a client logs into a new Lemonade session, it must perform a state comparison-based sync. To synchronize with the server, the client needs to fetch all the new messages, and all the flags of the old messages. The client has N messages in a given folder with highest UID = X and is disconnected from the Lemonade server. It connects to the server and performs the following command: First, it retrieves all the new messages. C: A01 UID FETCH X+1:* ALL S: * m FETCH ... S: ... S: A01 OK FETCH completed The client stores all this information on the device and displays it. Next, it wishes to sync up the old messages. C: A02 FETCH 1:m-1 (UID FLAGS) S: * 1 FETCH (UID 3242 FLAGS (\Seen ...)) S: ... S: * n FETCH (UID 3589 FLAGS (\Seen ...)) S: A02 OK FETCH completed Maes Expires - January 2005 [Page 17] July 2004 B.2. Event-Based Sync During a Lemonade session, the client will receive events in the form of untagged EXISTS, RECENT, EXPUNGE, or FETCH responses. The client must respond to these events. Sometimes, it will receive these events by polling, by issuing a Lemonade command, such as NOOP. It can also use IDLE so that the server can push events to the client. The example following shows how the client acts during an IDLE command, but it should also take the same actions (minus firing and exiting IDLE mode) when it receives these events through polling. A client can choose to issue an IDLE command to get events pushed to it, or it can receive events from polling using NOOP or any other IMAP command. First the client issues the IDLE command: C: A02 IDLE S: + Ready for argument Now the client can receive any of the three following untagged responses from the server. When the client receives an EXISTS/RECENT response from the server: S: * 501 EXISTS First, the client must exit from this IDLE command. C: DONE S: A02 OK IDLE completed Next, the client retrieves this new message using a FETCH command. C: A02 FETCH 501 ALL S: * 501 FETCH ... S: A02 OK FETCH completed The client returns to IDLE mode by issuing another IDLE command. C: A03 IDLE S: + Ready for argument When the client receives an EXPUNGE response from the server: S: * 25 EXPUNGE The client deletes this message from the client device, as it has been removed permanently from the folder. The client can remain in IDLE mode. When the client receives an untagged FETCH response from the server, either signally a flag change to an old message or a new message: S: * 101 FETCH (FLAGS (\Seen \Deleted)) The client updates the information on the device for this message appropriately. Maes Expires - January 2005 [Page 18] July 2004 Authors Addresses Stephane H. Maes Oracle Corporation 500 Oracle Parkway M/S 4op634 Redwood Shores, CA 94065 USA Phone: +1-650-607-6296 Email: stephane.maes@oracle.com Corby Wilson Enterprise Mobility Systems Nokia 503 Martindale Street Suite 610 Pittsburgh, PA 15212 USA Phone: +1-412-576-5402 Email: Corby.Wilson@nokia.com Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. 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