David Greaves, Derek McAuley et. al.
Olivetti Research Ltd.,
Cambridge CB2 1QA,
Cambridge University Computer Laboratory,
Corn Exchange Street,
Cambridge CB2 3QG,
- Such matters are described in more detail
in a previous article in IEEE Network .
- This adaptation layer, called UDL, places
8 bits of sequencing information in the header of each cell, and is
the one used in the performance example presented in
December 1991 CCITT draft I.361 extended the payload type to three
bits and defined this end-to-end user data bit. It is termed
the `ATM layer user-user indication'.
- Our links are
currently 100 Mbit/s and of course full duplex.
- In MSSAR (and AAL-5), MIDs are not used. Further in MSNL
there is no a priori division of the header into separate VCI
and VPI fields (c.f. Section 4).
- Adaptation protocols
based on a header flag, such as the one described in
Section 4 do not require adaptation layer headers
in every cell payload.
- To avoid this duplication in practice,
the transport protocol must be able to accept a `data-ok' indication
from the lower layers.
- Although CCITT has defined that B-ISDN
should not reorder cells, we are considering all types of ATM system.
- Assuming a 32 bit CRC, there are twelve 32 bit words
in each cell payload.
- The major between the two machines is that the
/200 has an 800 Mbit/s Turbochannel while the /25 has a 400 Mbit/s
- The B-ISDN switch manufacturers are faced with the
same VCI/VPI look-up problem, so are probably able easily to control
VCI space. The question is whether they will make VCI non-sparseness
guarantees to the customer.