larry@pdn.UUCP (Larry Swift) (08/08/88)
So, is anyone out there involved with ISDN Layer 3? I'm trying to study
the docs (Q.930, Q.931, Q.932), but with everything else I've got to do,
it's slow going. Any references to summaries, etc., would be appreciated.
Larry Swift UUCP: {peora,uunet}!pdn!larry
Paradyne Corp., LF-207 Phone: (813) 530-8605
P. O. Box 2826
Largo, FL, 34649-9981 She's old and she's creaky, but she holds!stanwyck@druco.ATT.COM (D. Stanwyck) (08/22/88)
in article <4091@pdn.UUCP>, larry@pdn.UUCP (Larry Swift) says: > 1) I'm having difficulty understanding the term "user-to-user signalling" > which seems to be used in opposition to circuit-switching and packet > switching. These three service type seem to make up the Layer 3 offering, > but the difference between the first two escapes me. User-user signalling is a service where the two "users" (hint- user <> end-system) may send information between themselves in the call control messages. This comes is several varieties - some associated with a circuit-switched call, and at least one not associated with any other communication path. This latter is the type you mention above. For this connection type, the network is told that all you want is to relay messages between the users without establishing a related communication path for e.g., a voice call. You could (correctly) call this using the CCS7 network or whatever the network's internal common channel signalling fabric is based on as a packet-switching network. As a result, not all network providers are jumping eagerly into this service, as the user data flows could potentially (and likely) block call-related signalling information. > 2) Where and how is leased circuit support accomplished? I see an > occasional reference to it, but no clear descriptions. Leased circuits are not dealt with in the Recommendations. At this time (though not necessarily in the future) they are strictly administrative items between you and the networks involved. No signalling related to them is defined. > 3) What is the difference between "Release Request" and "Disconnect > Request" in the call control states described in Section 2 of Q.931? This is a specific technical point - probably better dealt with by mail or phone. The brief answer is that Disconnect Request does not require the termination of all communication - i.e., you could potentially keep some type of user-user signalling up, while release request occurs some messages later and implies a total release of communications. > 4) What is "Suspend" used for (same section)? Nothing in the US. Suspend/Resume is used in some (one) European network for an desired ability for you to take your ISDN set, tell the other party to hang on, unplug your phone, walk down the street a few houses, plug it in there, and resume the conversation that was in progress at the other location. Of course, if you happen to walk across the boundary between exchanges, or take longer than <network defined timer>, the call will collapse and you won't be able to resume. > 5) What are the terms "overlap sending/receiving" and "overlap mode" > descriptive of (same section)? Overlap sending/receiving and overlap modes relate to whether the address information is all carried in one message or is sent piecemeal to/from the exchange. Both are possibilities. > Larry Swift UUCP: {peora,uunet}!pdn!larry > Paradyne Corp., LF-207 Phone: (813) 530-8605 You really should get a copy of the current draft proposed American National Standard (DpANS) based on Q.931. It should be out for ballot by the end of this year. Otherwise, join T1S1 and attend T1S1.2 or see your company representative who does attend (Paradyne's mailing list member is Wayne Moore at MS LF104, 813-530-8262). -- AT&T o o 303-538-5004 Don Stanwyck || druco!stanwyck Denver, CO USA \__/ Telecom Standards
larry@pdn.UUCP (Larry Swift) (08/26/88)
Don, thanks for the info. Some additional questions: In article <3080@druco.ATT.COM> stanwyck@druco.ATT.COM (D. Stanwyck) writes: >User-user signalling is a service where the two "users" (hint- user <> >end-system) may send information between themselves in the call control >messages. This comes is several varieties - some associated with a >circuit-switched call, and at least one not associated with any other >communication path. This latter is the type you mention above. > >For this connection type, the network is told that all you want is to relay >messages between the users without establishing a related communication >path for e.g., a voice call. You could (correctly) call this using the >CCS7 network or whatever the network's internal common channel signalling >fabric is based on as a packet-switching network. As a result, not all >network providers are jumping eagerly into this service, as the user data >flows could potentially (and likely) block call-related signalling >information. This discription almost sounds synonymous with OSI's "connectionless" service, which isn't flow-controlled. Is that a reasonable association? >.... The brief answer is that Disconnect Request does not require the >termination of all communication - i.e., you could potentially keep some >type of user-user signalling up, while release request occurs some messages >later and implies a total release of communications. Can you give some idea of application? >Overlap sending/receiving and overlap modes relate to whether the address >information is all carried in one message or is sent piecemeal to/from the >exchange. Both are possibilities. Just curious here. Do you have an idea as to how the term "overlap" came to be used? >You really should get a copy of the current draft proposed American National >Standard (DpANS) based on Q.931. It should be out for ballot by the end of >this year. I have Q.931; is the ANSI draft substantially different? more readable? I'll try to get a copy. Larry Swift UUCP: {peora,uunet}!pdn!larry Paradyne Corp., LF-207 Phone: (813) 530-8605 P. O. Box 2826 Largo, FL, 34649-9981 She's old and she's creaky, but she holds!
stanwyck@druco.ATT.COM (D. Stanwyck) (09/01/88)
in article <4183@pdn.UUCP>, larry@pdn.UUCP (Larry Swift) says: > In article <3080@druco.ATT.COM> stanwyck@druco.ATT.COM (D. Stanwyck) writes: >>User-user signalling is a service where the two "users" (hint- user <> >>end-system) may send information between themselves in the call control >>messages. This comes is several varieties - some associated with a >>circuit-switched call, and at least one not associated with any other >>communication path. This latter is the type you mention above. >> >>For this connection type, the network is told that all you want is to relay >>messages between the users without establishing a related communication >>path for e.g., a voice call. You could (correctly) call this using the >>CCS7 network or whatever the network's internal common channel signalling >>fabric is based on as a packet-switching network. > > This discription almost sounds synonymous with OSI's "connectionless" > service, which isn't flow-controlled. Is that a reasonable association? Not quite. There are several characteristics which are similar to the connectionless service - yet the user-user service is connection oriented. By definition, all connection data units are self-routing - that is, they contain the complete address of the destination. User-User messages flow over a connection which has been requested by a SETUP message, and is broken by a RELEASE message. While the individual data units are neither ordered, error protected, or acknowledged, they are still associated with a connection. >>.... The brief answer is that Disconnect Request does not require the >>termination of all communication - i.e., you could potentially keep some >>type of user-user signalling up, while release request occurs some messages >>later and implies a total release of communications. > > Can you give some idea of application? Let me explain a little more. Suppose I have a voice call controlled by the out-of-band signalling mechanism. Suppose I want to release the connection with the other user (i.e., drop the voice circuit) but retain the signalling connection to the network for further use. An example of the further use that was used at the time the message set was selected (though the service is not yet defined) was the ability to have a service that would have the network deliver billing information (e.g., time and charges) after the call was dropped. The signalling order would be as follows: user sends DISCONNECT to the network, with a Facility information element requesting the time and charges facility. The network drops the voice circuit (clears toward the other end) but retains the call reference. Later, using that call reference, the network delivers the time and charges information to the user, either in the RELEASE message (terminating further signalling) or in a separate message. If the latter, then the user responds with the RELEASE message, etc. Does this help? >>Overlap sending/receiving and overlap modes relate to whether the address >>information is all carried in one message or is sent piecemeal to/from the >>exchange. Both are possibilities. > > Just curious here. Do you have an idea as to how the term "overlap" came > to be used? Overlap was used to indicate that (in the old days) the control and signalling overlapped each other. For instance, the user dial pulses a number toward the network. Let's say that number is 303-987-6543 (fictional number). As the local exchange receives the pulses, it would process the 303, determine the trunk to connect to, and start outpulsing on that trunk overlapping with the incoming pulses. Today most switches collect the entire number most of the time prior to trunk selection, but some networks (e.g., the Fed. Rep. of Germany) still have many that operate the other way. >>You really should get a copy of the current draft proposed American National >>Standard (DpANS) based on Q.931. It should be out for ballot by the end of >>this year. > > I have Q.931; is the ANSI draft substantially different? more readable? > I'll try to get a copy. Substantially different? Well, not much has been added, but some things have been deleted (e.g., suspend/resume). A few things have been changed, but overall, it is similar. Readablility - much better, as it is set as a single document (actually, two documents) by modern american word processing systems with laser printers. Not that the "american" makes it better, but the uniformity and print quality does. > Larry Swift UUCP: {peora,uunet}!pdn!larry -- AT&T o o 303-538-5004 Don Stanwyck || druco!stanwyck Denver, CO USA \__/ Telecom Standards