I am ordering T1-PRI service from local service provider and have a few questions. Is there framing and coding considerations (or is it all one standard), if so what is best? How are calls routed based on DIDs - are these just dtmf tones passed after the call is picked up and treated as normal exten=> definitions? John This e-mail was scanned and found clean by Monroe-Woodbury CSD Antivirus.
B8ZS/ESF I believe is the usual for a PRI DID calls in asterisk are routed just like dtmf dialed extensions, but there are not DTMF tones passed. -----Original Message----- From: asterisk-users-admin@lists.digium.com [mailto:asterisk-users-admin@lists.digium.com] On Behalf Of John Harragin Sent: Thursday, May 29, 2003 11:05 AM To: Asterisk Subject: [Asterisk-Users] T1-PRI deployment questions... I am ordering T1-PRI service from local service provider and have a few questions. Is there framing and coding considerations (or is it all one standard), if so what is best? How are calls routed based on DIDs - are these just dtmf tones passed after the call is picked up and treated as normal exten=> definitions? John This e-mail was scanned and found clean by Monroe-Woodbury CSD Antivirus. _______________________________________________ Asterisk-Users mailing list Asterisk-Users@lists.digium.com http://lists.digium.com/mailman/listinfo/asterisk-users
On Thu, 2003-05-29 at 10:04, John Harragin wrote:> I am ordering T1-PRI service from local service provider and have a few > questions. > > Is there framing and coding considerations (or is it all one standard), if > so what is best? > > How are calls routed based on DIDs - are these just dtmf tones passed after > the call is picked up and treated as normal exten=> definitions?I'll answer this since I just had mine installed and went through this. Signalling comes in just a few options at the base level and is specific to the T1 transport. Your options are ESF or D4 for framing, and AMI or B8ZS for error detection. Your PRI rides on top of the T1 transport. In the PRI your DIDs are passed as part of the call setup in Q.931 packets on the D channel. Specifically you will place all your incoming PRI lines into a context in extentions.conf and then you will make extensions with the incoming phone numbers or part there of if your telco provider isn't sending the whole called number. In these extension deffinitions you can redirect the calls to either the appropriate IVR menu, or an internal extention. -- Steven Critchfield <critch@basesys.com>
I have been on vacation so didn't jump in earlier. Some of what I say here has been gone over earlier in this thread but I will repeat the results as a summery. AMI is not lossy, but it is almost always used in conjunction with a ones density technique called bit7. Bit7 will change bit 7 to a 1 when a word (8 bits) are all zeros. In North America when someone says AMI they really mean AMI with bit7. PRI ISDN will not work on an AMI (with bit7) T1. When validating ones density B8ZS does introduce errors but in such a way that the far end will know that they are errors and remove them. The only reasonable choice for PRI ISDN is B8ZS Robbed bit signaling uses bit 8 of each word of every 6th frame for signaling. This does not introduce errors on the line but it does make those bits unavailable for data. Usually data services assumes that the 8th bit of every work of every frame are not available so that you have 7 of each 8 bit word. That makes 56Kbit/s of 64Kbit/s of bandwidth available. PRI ISDN does not use Robbed bit signaling. Instead it uses the D channel. Slips are caused by a timing problem and have nothing to do with AMI or B8ZS. Framing of either SF (D4) or ESF can be used on a T1 regardless of the line coding. (some mistakenly believe that B8ZS must be used with ESF and AMI must be used with SF) ESF is preferred because more robust performance monitoring is possible while the T1 is in service. Don Pobanz Ps. For a while the group I worked with back at the phone company was known as 'T1s are us' so I should be familiar with this stuff. ;)