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INTERNET DRAFT R Briscoe Large-scale Multicast Applications Working Group P Bagnall Expiration: 29 January 1998 BT 29 July 1997 Taxonomy of Communication Requirements for Large-scale Multicast Applications draft-ietf-lsma-requirements-00.txt Status of this Memo This document is an Internet-Draft. 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.'' To learn the current status of any Internet-Draft, please check the ``1id-abstracts.txt'' listing contained in the Internet- Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Abstract The intention of this draft is to define a classification system for the communication requirements of any large-scale multicast application (LSMA). It is very unlikely one protocol can achieve a compromise between the diverse requirements of all the parties involved in any LSMA. It is therefore necessary to understand the worst-case scenarios in order to minimise the range of protocols needed. Dynamic protocol adaptation is likely to be necessary which will require logic to map particular combinations of requirements to particular mechanisms. Standardising the way that applications define their requirements is a necessary step towards this. Classification is a first step towards standardisation. 1. Introduction =============== This taxonomy consists of a large number of parameters that are considered useful for description of communication requirements of LSMAs. To describe a particular application, each parameter would be assigned a value. Typical ranges of values are given wherever possible. Failing this, the type of any possible values is given. The parameters are collected into ten or so higher level categories, but this is purely for convenience. The parameters are pitched at a level considered meaningful to application programmers. However, they describe communications not applications - the terms "3D virtual world", or "shared TV" might imply communications requirements, but they don't accurately describe them. Assumptions about the likely mechanism to achieve each requirement are avoided where possible. The exception to this is that receiver initiated join to multicast address groups [refmcast] on an open access Internet is assumed. While the parameters describe communications, it will be noticed that few requirements concerning routing etc. are apparent. This is because applications have few direct requirements on these second order aspects of communications. Requirements in these areas will have to be inferred from application requirements (e.g. latency). The taxonomy is likely to be useful in a number of ways: - most simply, it can be used as a checklist to create a requirements statement for a particular LSMA. Example applications will be classified [bagnall97] using the taxonomy in order to exercise (and improve) it - because strictest requirement have been defined for many parameters, it will be possible to identify worst case scenarios for the design of protocols - because the scope of each parameter has been defined (per session, per receiver etc.), it will be possible to highlight where heterogeneity is going to be most marked - a step towards standardisation of the way LSMAs define their communications requirements. This could lead to standard APIs between applications and protocol adaptation middleware - identification of limitations in current Internet technology for LSMAs to be added to the LSMA limitations draft [limitations] - identification of gaps in Internet Engineering Task Force (IETF) working group coverage This approach is intended to complement that used where application scenarios for Distributed Interactive Simulation (DIS) are proposed [scenarios] in order to generate network design metrics (values of communications parameters). Instead of creating the communications parameters from the applications, we try to imagine applications that might be enabled by stretching communications parameters. The above introduction assumes all the items under the "Further Work" section (near the end) have been completed. As they haven't, the reader is advised to read that section next! 2. Definitions ============== The following terms have no agreed definition, so they will be defined for this document. Session a happening or gathering consisting of flows of information related by a common description that persists for a non-trivial time (more than a few seconds) such that the participants (be they humans or applications) are involved and interested at intermediate times may be defined recursively as a super-set of other sessions Secure session a session with restricted access A session or secure session may be a sub and/or super set of a multicast group. A session can simultaneously be both a sub and a super-set of a multicast group by spanning a number of groups while time-sharing each group with other sessions. 2.1. Definitions of Roles ========================= Below is an attempt to list all the possible roles in an LSMA. In any particular LSMA, many of these roles will merge and many will not be necessary. In order to model the information flows in an LSMA (the comms parameters) it is generally essential to have a model of the roles. This would require the linkages between the roles to be defined for the specific application in question. This approach is standardised in the Open Distributed Processing Reference Model [rmodp] where these are called the Information Model and the Enterprise Model respectively. Security policy owner defines policy within which sessions can be created for a security domain (e.g. corporate security policy) Party liable (to some degree) for information accuracy a role that may be established to oversee the self-regulation of information providers, e.g. Stock Exchange, IEEE conference, Compuserve, Internet Watch Foundation Session owner has original idea to set up session and sets Terms and Conditions within constraints of above parties Session creator e.g. assistant of session owner, or some session creation service Session secretary advertises or negotiates timing etc Membership rule creator Rules may be different for different roles (e.g. senders v. receivers) List controller(s) maintain membership list based on membership rule and control and negotiate inclusion in list Access manager(s) trusted by list controller to manage access to session, e.g. handing out keys Security session members potential participants, e.g. those that hold keys Participants active senders and receivers Senders Receivers Disallowed participants actively black-listed as opposed to just not invited Media distributors more formal role than just senders in an interactive application Billable parties pay for participants, e.g. participant's company Payment Brokers banking services - per participant Clearing system connects payment brokers Certification authorities (CAs) Authenticate parties - per participant Certification hierarchy connects CAs 3. Taxonomy =========== 3.1 Summary of Communications Parameters ======================================== Before the communications parameters are defined, typed and given worst- case values, they are simply listed for convenience. Also for convenience they are collected under classification headings. Reliability packet loss Transactional Guaranteed Tolerable loss Semantic loss component reliability fail-over time mean time between failures Ordering Ordering type Timeliness Hard/soft real-time Synchronicity Burstiness Jitter expiry latency optimum bandwidth tolerable bandwidth required by time and tolerance host performance fair delay frame size content size Session Control initiation start time end time duration active time burstiness atomic join late join allowed ? temporary leave allowed ? late join with catch-up allowed ? potential streams per session active streams per sessions sessions per super-session session semantics session list rule (see Security: membership criteria) terms and conditions Session Topology # of senders # of receivers density of senders/host density of receivers/host density of senders/router density of receivers/router shape session heterogeneity heterogeneity (of almost all other params) bandwidth along path hops/path rate of join/leave between sub-sets rate of join/leave from whole super-session time-zone dependent? burstiness of join/leave rate admin domains/path admin domains/group Directory latency of lookups (see Timeliness: latency) fail-over timeout (see Reliability: fail-over time) registration churn mobility Security strength authentication purpose tamper-proofing non-repudiation strength type denial of service membership admission control action restriction (privacy) membership privacy retransmit detection strength membership criteria membership principals collusion prevention fairness action on compromise security dynamics mean time between compromises compromise detection time limit compromise recovery time limit Payment & Charging for what charge basis content services when who pays whom prevention of onward re-sale costing of communications see also topology cost elements cost epochs quotations charging costs 3.2 Definitions, types and strictest requirements ================================================= The terms used in the above table are now defined for the context of this document. Under each definition, the type of their value is given and where possible worst-case values and example applications that would exhibit this requirement. There is no mention of whether a communication is a stream or a discrete interaction. An attempt to use this distinction as a way of characterising communications proved to be remarkably unhelpful and was dropped. 3.2.1 Reliability ================= 3.2.1.1 Reliability - Packet loss ================================= Transactional ------------- When multiple operations must occur atomically, transactional communications guarantee that either all occur or none occur and a failure is flagged. Type: Boolean - on/off Strictest requirement - on Example application: bank credit transfer, debit and credit must be atomic. NB: Transactions are potentially much more complex, but it is believed this is an application layer problem. Guaranteed ---------- Guarantees communications will succeed in certain cases. Type: enumerated Deferrable û if communication fails it will be deferred until a time when it will be successful. Guaranteed û the communication will succeed so long as all necessary components are working. No guarantee - failure will not be reported. Strictest requirement - deferred Example application: stock quote feed û guaranteed NB: the application will need to set parameters to more fully define Guarantees, which the middleware may translate into, for example, queue lengths. Tolerated loss -------------- This specifies the proportion of data from a communication that can be lost before the application becomes completely unusable. Type: fixed point fraction of data Strictest requirement: 0% Example application: video û 40% Semantic loss ------------- The application specifies how many and which parts of the communication can be discarded if necessary. type: identifiers - names disposable app level frames strictest requirement - no loss allowed example application: video feed - P frames may be lost, I frames not. 3.2.1.2. Component Reliability ============================== Fail-over time -------------- The time before a failure is detected and a replacement component is invoked. This is not directly an application requirement. Type: time (milliseconds) Strictest Requirement: application dependent Example application: Name lookup - 5 seconds Mean time between failures -------------------------- Type: time (days) Strictest requirement: indefinite Example application: xxx 3.2.2. Ordering =============== Ordering type ------------- Specifies what ordering must be preserved for the application Type: boolean û true=idempotent false=> enumeration timing values: global per sender none sequenced values: global per sender none causal values: global per sender none Strictest requirement - global timed, sequenced & causal Example application : Game - global causal (to make sure being hit by bullet occurs after shot is fired!) 3.2.3. Timeliness ================= There is a ômeta-requirementö on timeliness. If hard real-time is required then the interpretation of all the other requirements changes. Failures to achieve the required timeliness must be reported before the communication is made. By contrast soft real-time means that there is no guarantee that an event will occur in time. However statistical measures can be used to indicate the probability of completion in the required time, and policies such as making sure the probability is 95% or better could be used. Hard-real time: Boolean - hard/soft Synchronicity ------------- To make sure that separate elements of a session are correctly synchronised with respect to each other Type: milliseconds - allowable sync error Strictest requirement û 80ms Example application: TV lip-sync value 80ms Burstiness ---------- This is a measure of the variance of bandwidth requirements over time. Type: fixed point - variation in b/w as fraction of b/w for variable b/w communications Fixed point - duty cycle (fraction of time at peak b/w) for intermittent b/w communications. Strictest requirement: variation -> max b/w, duty cycle -> 0 Example application: sharing video clips, with chat channel - sudden bursts as clips are swapped. Compressed Audio - difference between silence and talking NB: More detailed analysis of communication flow (eg max rate of b/w change or Fourier Transform of the b/w requirement) is possible but as complexity increases usefulness and computability decrease. Jitter ------ Jitter is a measure of variance in the time taken for communications to traverse from the sender (application) to the receiver, as seen from the application layer. Type: milliseconds - maximum acceptable time error Strictest requirement - <1ms Example application: audio streaming - <1ms NB: A jitter requirement implies that the communication is a real-time stream. Expiry ------ This specifies how long the information being transferred remains valid for. Type: date (seconds since...) Strictest requirement - for ever Example application: key distribution - 3600 seconds (valid for at least one hour) Latency ------- Time between initiation and occurrence of an action from application perspective. Type: time (milliseconds) Strictest requirement û application dependent Example application - audio conference 20ms NB: where an action consists of several distinct sequential parts the latency ôbudgetö must be split over those parts. For process control the requirement may take any value. Optimum Bandwidth ----------------- Bandwidth required to complete communication in time Type: bandwidth (kb/s) Strictest requirement - xxx Example application - I phone 8kb/s Tolerable Bandwidth ------------------- Minimum bandwidth that application can tolerate Type: bandwidth (kb/s) Strictest requirement - xxx Example application - I phone 4kb/s Required by time and tolerance ------------------------------ Time communication should complete by and time when failure to complete renders communication useless (therefore abort). Type: time - preferred complete time time - essential complete time Strictest requirement û application dependent Example application: email - 1min & 1 day NB: bandwidth * duration = size; only two of these parameters may be specified. An API though could allow application authors to think in terms of any two. Host performance ---------------- Ability of host to create/consume communication Type: application benchmark Strictest requirement: full consumption Example application: video - consume 15 frames a second NB: host performance is complex since load, media type, media quality, h/w assistance, and encoding scheme all affect the processing load. These are difficult to predict prior to a communication starting. To some extent these will need to be measured and modified as the communication proceeds. Fair delay ---------- Time between receipt of communication and response by the client should determine winner of race conditions, not the first response at the server. Type: acceptable unfairness (milliseconds) Strictest requirement: 10ms Example application: auction room - <10ms Frame size ---------- Size of logical data packets from application perspective Type: data size (bytes) Strictest requirement: 6bytes (gaming) Example application: video = data size of single frame update Content size ------------ The total size of the content (not relevant for continuous media) Type: data size (kB) Strictest requirement: N/A Example application: xxx 3.2.4. Session Control ====================== initiation ---------- which initiation mechanism will be used type: enumeration values : announcement invitation directive example application: corporate s/w update - directive start time ---------- time sender start sending! type: date (milliseconds since ...) strictest requirement: now example app: FTP - at 3am end time -------- type: date (milliseconds since ...) strictest requirement: now example app: FTP - now+30mins duration -------- (end time) - (start time) = (duration), therefore only two of three should be specified. type: time (milliseconds) strictest requirement: -> 0ms for discrete, indefinite for streams example app: audio feed - 60mins active time ------------ total time session is active, not including breaks type: time (milliseconds) example app: spectator sport transmission burstiness ---------- expected level of burstiness of the session type: fixed point. variance as fraction of max bandwidth strictest requirement: =bandwidth example app: commentary & slide show: 90% of max atomic join ----------- session fails unless a certain proportion of the potential participants accept an invitation to join. Alternatively, may be specified as a specific numeric quorum. type: fixed point (proportion required) or int (quorum) strictest requirement: 1.0 (proportion) example app: price list update, committee meeting Note: whether certain participants are essential is application dependent. late join allowed ? ------------------- does joining a session after it starts make sense type: Boolean & indirection strictest requirement: allowed example application: game - not allowed, indirect to spectator channel temporary leave allowed ? ------------------------- does leaving and then coming back make sense for session type: Boolean strictest requirement: allowed example application: FTP - not allowed late join with catch-up allowed ? --------------------------------- is there a mechanism for a late joiner to see what they've missed type: Boolean & indirection strictest requirement: allowed example app: sports event broadcast, allowed, indirect to highlights channel potential streams per session ----------------------------- total number of streams that are part of session, whether being consumed or not type: int strictest requirement: indefinite example app: football match mcast - multiple camera's, commentary, 15 streams active streams per sessions (ie max app can handle) --------------------------- maximum number of streams that an application can consume simultaneously type: int strictest requirements: indefinite example app: football match mcast - 6, one main video, four user selected, one audio commentary sessions per super-session -------------------------- number of sessions that a single super-session consists of type: int strictest requirement: indefinite example app: parallel and serial meetings in a conference session semantics ----------------- description of which streams are redundant alternate formats, etc. type: session hierarchy description object (dependent on session description packet def) example app: movie with dubbing in several languages session list rule (see Security: membership criteria) ----------------- terms and conditions -------------------- expiry agreement records 3.2.5. Session Topology ======================= Note: topology may be dynamic. One of the challenges in designing adaptive protocol frameworks is to predict the topology before the first join. # of senders ------------ the number of senders is a result the middleware may pass up to the application type: int strictest requirement: indefinite example app: network MUD - 100 # of receivers -------------- the number of receivers is a results the middleware may pass up to the application type: int strictest requirement: indefinite example app: video mcast - 100,000 density of senders/host ----------------------- The total number of senders / total number of hosts 1 hop from the multicast tree (in the shadow). This may be required by the middleware, the network should support. type: fixed point strictest requirement: < 1 example app: international audio conference - 0.2 density of receivers/host ------------------------- as above density of senders/router ------------------------- A measure of the utilisation of routers in the tree. This may be required by the middleware. The network should support it. type: fixed point example app: TV broadcast - 0.001 density of receivers/router --------------------------- A measure of the utilisation of routers in the tree. This may be required by the middleware. The network should support it. type: fixed point example app: TV broadcast - 0.6 shape ----- the shape of the multicast tree. The middleware may need to know this. The network should support it. type: enumeration values: star, ring, mesh, multi-level, hybrid multi-level etc. example app: xxx session heterogeneity --------------------- number of distinct groups of participants where within each group the requirements of all members are identical. type: fixed point (# of sub-sets / # of participants) strictest requirement: none example app: movie, subset of English-speaking consumers with slow terminals as against French-speaking with slow terminals etc. heterogeneity (of almost all other params) ------------------------------------------ See Further Work bandwidth along path -------------------- an indication of the rate limiting hop in the path, and it's bandwidth. Needed by the middleware hops/path --------- measure of the distance to the core/sender of a communication rate of join/leave between sub-sets -------------------------------- the rate at which participants change from one sub-set to another type: events per time per user strictest requirement: xxx example application: TV sports event - camera switching - 0.2/s rate of join/leave from whole super-session ------------------------------------------- a measure of participant churn in the super-session (application). type: events per time strictest requirement: 100 per second example app: internet shop - shoppers entering & leaving shop 0.2/min NB: 10% per minute may join/leave once application stable. [NSA] time-zone dependent? -------------------- Is membership likely to be linked to time-zones (i.e. are members humans, teenagers or computers?) type: Boolean example app: email - relevant burstiness of join/leave rate ------------------------------ measure of variance of join/leave rate. Needed by middleware, from application (prediction) and network (measurement). type: standard deviation of events per second strictest requirement: xxx example app: football match - high variance between duration of match and start and end chat forum: low variance - people joining and leaving continuously without a start or end. admin domains/path ------------------ number of admin domains traversed by traffic along a path in the multicast group. type: int strictest requirement: example app: admin domains/group ------------------- number of admin domains which are carrying the communication. type: int strictest requirement: example app: 3.2.6. Directory ================ latency of lookups (see Timeliness: latency) ------------------ fail-over timeout (see Reliability: fail-over time) ----------------- registration churn ------------------ rate at which name/value mappings are changed type: probability/time (%/second) strictest requirement: example app: mobility -------- defines restrictions on when directory entries may be changed type: enumeration values: while entry is in use while entry in unused never strictest requirement: while entry is in use example app: voice over mobile phone, while entry is in use (as phone gets new address when changing cell). 3.2.7. Security =============== Strength -------- The level to which a system or any sub-system is capable of providing information security. Stated as the cost of mounting a successful attack. In practice this typically reduces to key length comparisons, but these continually need updating as processing speeds improve. Key length measures are also specific to encryption attacks, whereas cost can be applied to physical attacks for example. Strength applies to every security-related parameter as well as to whole systems. Type: currency at a set date (to inflation-proof), e.g. 1970 US$ Strictest requirement: a) $300M in 1995 (estimated budget of major intelligence agency)[Blaze95] b) an international use requirement restricts key length to {TBA} bits Authentication purpose ---------------------- The purpose of ensuring that a principal is who they claim to be. Authentication also has a strength, or level of certainty that a positive result is correct (see strength) and a time span over which authentication is valid (for legal follow-up). Type: Boolean: for admission (see action restriction)? Boolean: data from each sender authenticated? Strictest requirement: authentication of admission to all types of session and of all senders within sessions Example application: inter-governmental conference Tamper-proofing --------------- Assurance that various aspects of information including its quality is not violated during communication Type: Boolean: data is unchanged and complete? Boolean: data timeliness is assured (no malicious packet delay)? Boolean: no replay of transmission is possible? Strictest requirement: All true Example application: stock price feed Non-repudiation strength ------------------------ The probability of being able to prove that various aspects of a communication must have occurred. Type: fixed point Strictest requirement: 1.0 (full audit trail) Example application: Full audit trail: billing based on usage logs. Random partial records: to deter users from fraud with the threat of the possibility of being able to detect it. Non-repudiation type -------------------- Prove that various aspects of a communication must have occurred. Logical time is defined as a value in a sequence of events with no regard to the actual time between the events (e.g. proving a message was sent before or after sending or receiving another message). Type: Boolean: sender proving reception enumeration: by whom values: {>1 rcvr, certain rcvrs, random rcvrs, all rcvrs } Boolean: what Boolean: when Boolean: logical time Boolean: sender proving send (redundant if proves reception) Boolean: what Boolean: when Boolean: logical time Boolean: delta time (since previous rcv) Boolean: proving membership Boolean: when Boolean: logical time Boolean: rcvr proving received Boolean: when Boolean: logical time Strictest requirement: All true Example application: Quality audits, auctions, voting, patent disputes Denial of service ----------------- TBA - difficult to say anything about this without a particular system design or mechanism. See also sender exclusion under privacy. Membership admission control ---------------------------- Whether admission to membership of a session is controlled. Type: binary enumeration (Boolean?) Strictest requirement Example application: Action restriction (privacy) ---------------------------- The different types of activity listed below may be private to different secure sessions within an application. These could be considered as the ACTION field of an access control list, but this doesn't imply an ACL is a good method to use. Indeed, access to nearly all the actions below can be separately controlled by distributing data related to each action in a separate secure session. Type: membership list/rule for each of the actions below that requires a distinct one from the others: - sending data - receiving data - forwarding on data - sending metadata (headers) - receiving metadata (headers) - forwarding on metadata - sending keys - receiving keys - forwarding on keys - session announcement (includes identity of key controller) - listing members (see also membership detection) - forwarding on list - admitting members Strictest requirement: all required, but all different lists. Excluding senders of unsolicited traffic into a session and deterring retransmission (see also retransmission detection) are the most difficult ones. Example application: banking work-flow where no one person may have access to sufficient information to allow fraud. Membership privacy ------------------ How hidden the fact that a particular participant has joined a session is (see also Privacy; listing members). Type: enumeration values: openly identified anonymously identified (only size of membership is known) unadvertised (but traffic could be traced) undetectable Strictest requirement: undetectable - involves randomising traffic patterns Example application: news feed where customers wish their interests to be private. Retransmit detection strength ----------------------------- How strong is the requirement to monitor receivers to detect onward transmission. This is one case where the real requirement - retransmit prevention - has not been stated, because it is assumed to be impossible.(see also Privacy; forwarding on data, list, keys etc.) all rcvrs certain rcvrs random rcvrs Type: Strictest requirement Example application: Membership Criteria ------------------- The type of criterion used to limit the scope of membership Type: enumeration values: session bounded by topology (e.g. fire-wall, TTL) session bounded by administrative scope Internet-wide membership based on a rule Strictest requirement: Internet-wide membership based on a rule Example application: limited by topology: corporate video-conference; Rule-based: support forum open to all parties with paid-up support contracts. Membership rules may be: - simple lists of all members - address rule (e.g. a.b.c.*) - based on knowledge of a secret (token, username-password, challenge-response, customer id) - based on payment Membership Principals --------------------- Entities that may join a rule-based secure session atomically. That is, a group of individuals is a principal if they can only all join or leave together. Principals can be considered as the SUBJECT field of an access control list, but this is not intended to imply ACL is a good method to use. Type: enumeration values: certified individual ids certified group ids (corporations, organisations) login accounts lists (i.e. lists of lists, such as multicast groups, secure sessions) addresses decryption proxies (decrypt and re-multicast for a secondary group such as everyone in a corporation) Strictest requirement: mixture of all types. Example application: N/A Collusion prevention -------------------- Which aspects of collusion it is required to prevent. Collusion is defined as malicious co-operation between members of a secure session. Superficially, it would appear that collusion is not a relevant threat in a multicast, because everyone has the same information, however, wherever there is differentiation, it can be exploited. Type: Boolean: time race collusion (true if needs preventing) Boolean: key encryption key (KEK) sharing Boolean: sharing of differential QoS (not strictly collusion as across sessions not within one) Strictest requirement: All true. Time race collusion is the most difficult one to prevent. Example application: A race where delay of the start signal may be allowed for, but one participant may fake packet delay while receiving the start signal from another participant. Fairness -------- see timeliness for tolerance between delay differences see reliability for tolerance between different reliabilities Action on compromise -------------------- The action to take on detection of compromise (until security reassured). Not sure this has anything to do with communications, really. Type: binary enumeration (Boolean?) values: warn but continue pause Strictest requirement: pause Example application: Secure video conference - if intruder alert, everyone is warned, but they can continue while knowing not to discuss sensitive matters (cf. catering staff during a meeting). 3.2.7.1. Security Dynamics -------------------------- Security dynamics are the delays that security operations insert into a system's operation. The delays under normal operation (e.g. key processing, certification of authenticity etc.) need to be taken into account when designing to meet other requirements like latency. This parameter is therefore concerned with delays in abnormal security circumstances (e.g. system compromise): mean time between compromises ----------------------------- This is not the same as the strength of a system. A fairly weak system may have a very long time between compromises because it is not worth breaking in to, or it is only worth it for very few people. Mean time between compromises is a combination of strength, incentive and scale. Type: hours Strictest requirement: xxx Example application: xxx Compromise detection time limit ------------------------------- The average time it must take to detect a compromise (one predicted in the design of the detection system, that is). Type: seconds Strictest requirement: xxx Example application: xxx Compromise recovery time limit ------------------------------ The maximum time it must take to re-seal the security after a breach. Type: hours Strictest requirement: 1 second [NSA] Example application: xxx 3.2.8. Payment & Charging ========================= This whole section is probably too far outside the scope of the LSMA working group and is unfinished anyway. charging for what? ------------------ content services content distribution service QoS transmission security services directory services Type: Strictest requirement Example application: Charge basis: content --------------------- (often different granularity to ownership basis) ownership of content own use/consumption unlimited limited (e.g. n copies or n "views") royalty-based (pay per "view") resale unlimited limited (e.g. n copies) royalty-based (could hit multicast enabled routers hard!) own use and resale own use and not resale resale and not own use Type: Strictest requirement Example application: Charge basis: services ---------------------- subscription time expired in perpetuity pay per consumption time pay per "object" hybrids of all these Type: Strictest requirement Example application: Payment: When? --------------- pre-paid deposit pre-pay (before any of each charge basis listed above) post-pay (before any of each charge basis listed above) periodically billed by usage free for introductory period credit and debit decoupled within tolerance time limited money limited time/money hybrid (formula, e.g. 30days if <ú50) Type: Strictest requirement Example application: Who pays whom? -------------- (directly as opposed to one collecting for another - every role player could charge directly, but these are the more likely ones to do so) This bit would be easier to read in two dimensions - who charges and who pays Media distributor (typically pays media owner (typically pays media advertiser)) Session owner (typically pays session advertiser (and might well pay media distributor)) Network providers (may be paid by session owner, but difficult as diff. receivers use diff.networks) Terminal owners (e.g. library, kiosk, arcade, pub etc) Matchmaker (in auctions, session directories etc.) advertising (to partially allay costs, or cover totally) sender pays (e.g. propaganda that receivers are paid to read!) pay to receive, paid to send (e.g. to encourage contribution of home videos - yuk!) Type: Strictest requirement Example application: prevention of onward re-sale ---------------------------- Type: Strictest requirement Example application: 3.2.8.1. Costing of communications ================================== See also topology Elements of cost ---------------- terminal resources & QoS network resources & QoS server resources & QoS Type: Strictest requirement Example application: Cost epochs ----------- up front investment fixed running costs independent of use variable (use-dependent) costs Type: Strictest requirement Example application: quotations ---------- response time off-line "well known" pricing expiry spot pricing Type: Strictest requirement Example application: Costs of charging ----------------- communications storage processing debt recovery fraud detection customer service (proving charges are valid) Type: Strictest requirement Example application: 4. Mapping of Requirements to IETF Working Groups ================================================= TBA 5. Further Work =============== Attempt to simplify! Refine definitions and types. In particular clarify where enumerations aren't intended to be "one of" types. Complete specifying worst case values & example apps. Identification of scope of each parameter (per session, per receiver, per sender etc.) to highlight potential heterogeneity problems Mapping between requirements and IETF Working Groups Exercising the taxonomy with some scenarios Exercising the taxonomy with some media-types which represent large sub- sets of application capabilities so can potentially be "macros" or shorthand to set values (or ranges) for a large number of parameters at once. 6. Security Considerations ========================== See comprehensive security section of taxonomy. References ============= [Bagnall97] Bagnall Peter, Example LSMA classifications [TBA] [refmcast] IP multicast ref [limitations] Pullen M, Myjak M, Bouwens C, Limitations of Internet Protocol Suite for Distributed Simulation in the Large Multicast Environment, Internet Draft, 26 Mar 1997, draft-ietf-lsma-limitations- 01.txt [scenarios] Seidensticker S, Smith W, Myjak W, Scenarios and Appropriate Protocols for Distributed Interactive Simulation, Internet Draft, 21 Jul 1997, draft-ietf-lsma-scenarios-01.txt [rmodp] Open Distributed Processing Reference Model (RM-ODP), ISO/IEC 10746-1 to 10746-4 or ITU-T (formerly CCITT) X.901 to X.904. Jan 1995. Catalogue entries: <URL:http://www.iso.ch/isob/switch-engine- cate.pl?searchtype=refnumber&KEYWORDS=10746> [blaze95] Blaze, Diffie, Rivest, Schneier, Shimomura, Thompson and Wiener, Paper on minimal key lengths for security in secret key ciphers? late 1995 [NSA] Wallner D, Harder E, Agee R, Key Management for Multicast: Issues and Architectures, National Security Agency, 1 July '97. Internet Draft draft-wallner-key-arch-00.txt 8. Authors' Addresses ===================== Bob Briscoe B54/74 BT Labs Martlesham Heath Ipswich, IP5 3RE England Phone: +44 1473 645196 Fax: +44 1473 640929 EMail: briscorj@boat.bt.com Home page: http://www.labs.bt.com/people/briscorj/ Peter Bagnall B54/74 BT Labs Martlesham Heath Ipswich, IP5 3RE England Phone: +44 1473 647372 Fax: +44 1473 640929 EMail: pbagnall@jungle.bt.co.uk Home page: http://www.labs.bt.com/people/bagnalpm/