| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 3631.1 | ATM MAX PDU Size is 4510 | GALVIA::thebe.ilo.dec.com::rawlings | | Mon May 12 1997 08:44 | 27 |
|
Andreas,
The maximum PDU Size support by DECNIS over the W631
card is 4510 octets.
It is invalid to specify 9180.
The script compiler may well not complain, since the
check against supported sizes is only performed on
the DECNIS.
It is not possible, without major effort, to get DECNIS to
use larger PDU sizes.
The maximum sizes you can set are:
Routing circuit:
4500
ATM PVC:
4510
There is no Max PDU size parameter for the ATM CON MAN LINE
Regards,
Mark.
|
| 3631.2 | two more questions | TAGAUS::AURAND | | Mon May 12 1997 10:03 | 20 |
| Hi Mark,
many thanks for your answer.
>> The maximum PDU Size support by DECNIS over the W631
>> card is 4510 octets.
According to RFC1577 this will result in changing the MTU Size to 4500
on other nodes in the LIS or will Classical IP still work if some nodes
have a MTU of 9180 and the DECnis uses 4500 ?
>> There is no Max PDU size parameter for the ATM CON MAN LINE
What I meant was the MAXIMUM PDU SIZE for the ATM MULTIPROTOCOL
ENCAPSULATION LINK. Is this the ATM PVC (4510) - LLC Header (8 Bytes ?)
Many thanks for your help
Andreas
|
| 3631.3 | You *may* be able to run the DECNIS at 4500, whilst the LIS uses 9180 | GALVIA::thebe.ilo.dec.com::rawlings | | Mon May 12 1997 11:07 | 34 |
|
Sorry,
My misunderstanding.
The max size at ATM MUL PROT ENC link is 4500.
The requirement for all members of the LIS to use
the same PDU size comes from the dynamic nature of
SVC connections and the lack of PDU size negotiation.
When one member of a LIS needs to talk to another, it
'looks-up' the ATM address of the required system; creates
and SVC; and starts transmitting.
There is no negotiation of Max PDU size, so the Max PDU
must be assumed to be OK.
This 'assumption' leads to the statement in the RFC specifying
all LIS members should use the same Max PDU Size.
Now, DECNIS doesn't implement SVCs and participates as
a member of a LIS by attaching to a partner LIS system via a PVC.
This means that only the attached system needs to be using the
lower size of 4500 on the Links to the DECNIS.
If you can be sure that the system the DECNIS is attached to
will fragment frames for the DECNIS larger than 4500 you
should be OK.
However, if not, the full LIS will need to be brought down to
4500.
Regards,
Mark
|
| 3631.4 | | TAGAUS::AURAND | | Tue May 13 1997 05:10 | 5 |
| Hi Mark,
many thanks for the explanation.
Best regards - Andreas
|