Cell Relay Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] UBR over ATM
Various sources seem to be giving me seemingly conflicting information about how UBR is implemented. Can someone straighten me out by telling which of the following statements are false (or true)? (My primary concern is IP traffic implemented across different ATM interface rates - how does the UNI/NNI negotiate the rate if at all?): · PC based LANE or Classical IP implementations today use UBR (or proprietary ABR). · In most implementations there is no CAC for UBR traffic. · If there is a CAC for UBR, the CAC function knows the entire network topology (how did it get to know the topology?). · If the CAC function doesn't know the entire network topology, it asks at connection setup (what signaling message is that?). · UBR specifies a PCR and CDVT, but in almost all implementations that's just set to the constraints of the physical interface for any VCC. · Barring any large buffers or packet discard schemes, UBR traffic from a high bit-rate source will suffer a high cell loss, if sent to a low bit-rate destination. Any controls on the bit-rate are from the upper layer protocols/application at the ends of the connection. Thanks in advance. -- ---------------------------------------------------------------------- Richard S. Tsumaki Systems & Information Technologies Group TRW Data Technologies Division DH6/2728AC Phone: (310)764-3690 1800 Glenn Curtiss Street Fax: (310)764-7059 Carson, CA 90746 Email: richard.tsumaki@trw.com ---------------------------------------------------------------------- |
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