Some troubleshooting books (like CIT) make a big deal about the reliability and connection-oriented nature of ISDN which got me thinking...
Q.921 is definitely reliable and connection-oriented (looks just like LLC2, in fact), but it only runs on the D channel, right? (It's also known as LAPD.) How about Q.931? Does it only run on the D channel? It seems to deal with signalling issues, such as call setup. (Does it have a LAP designation, by the way?) For end-user data, my theory is that ISDN doesn't provide any reliability. Is that right? Data on the B channel would typically be encapsulated in PPP which does not offer reliability (ACKs and retransmissions). I'm trying to synthesize an answer to the silly question about who retransmits when a bit is changed or dropped on a WAN network. Here's my summarization. Does it look OK? Technology Provides Reliability? (ACKs and retransmissions) ATM No BISYNC Yes Cisco's HDLC No ISDN No, except on the D Channel which uses LAPD Frame Relay No LAPB Yes LAPD, Q.921 Yes PPP No SDLC Yes X.25 Uses LAPB, so Yes Thanks! Priscilla ________________________ Priscilla Oppenheimer http://www.priscilla.com Message Posted at: http://www.groupstudy.com/form/read.php?f=7&i=27568&t=27568 -------------------------------------------------- FAQ, list archives, and subscription info: http://www.groupstudy.com/list/cisco.html Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
