Ascend Archive
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(ASCEND) GigaRouter/GRF experiences

Hi,

I started to monitor this mailing list one week ago, 
so please don't flame me if something of this is "old stuff".

We at RUS run two GigaRouters and one GRF400 with
a variety of HiPPI, ATM OC3c, FDDI, and Ethernet.

Here is a very nasty thing we found on the GigaRouter:
(software is 4.7.18)

1. Fragmentation from HiPPI to ATM (HiPPI IP routing)
 When 65280 bytes HiPPI packets get fragmented to
 fit ATM MTU, data is (randomly?) corrupted. We proved inserted
 zero's with an ATM tester. This ruins TCP performance
 and makes NFS almost unusable. The only workaround we
 know is to let HiPPI send with ATM MTU.
 This again ruins HiPPI performance and puts additional 
 workload on the supercomputers.
 (reported to Ascend support)

We also found some funny things on the GRF400 
you may be interested in: (software is 1.3.8)

1. Fragmentation from HiPPI to ATM (HiPPI IP routing)
 Behaves the same as the GigaRouter BUT we found that
 it runs well if you set the ATM MTU to a value
 slightly less than 9180 bytes - say 9179 bytes.
 Then we saw no bad checksums on the participating hosts.
 (reported to Ascend support)

2. Filter daemon doesn't load new configuration sometimes
 We observed that the filter daemon sometime (don't know why)
 refuses to load its configuration when doing the kill -HUP. 
 The entry in the gr.console only does not show the
 filter activation then. We found that letting the deamon
 reload an empty filter configuration (all commented out)
 and then the configuration we originally intended again, 
 it works without rebooting the box.

3. "locked" interfaces - well configured but dead
 If you configure two interfaces with identical IP addresses
 (one taken down), the newly configured one wins and the old
 one gets what I name "locked". If you then configure the
 new interface with another IP address, the old one remaines
 locked. It shows up, well configured, but is dead.
 We found that you have to give it an IP address of a different
 subnet - say from some spare subnet or so - to unlock it.
 Then you can again assign the original IP address.
 We did this on the GigaRouter and the GRF400.

Please comment on my points and allow some questions too:

1. Does anyone have experiences with filtering and what
   impact it has on the performance ?
2. Does anyone already have a GRF1600 and/or the restricted
   version of the OC12c interface ?
3. Anyone using HiPPI and ATM on the GigaRouter/GRF ?
   (IP-Routing vs. HiPPI over ATM tunnel, etc.)

I would be very interested, if you could let me know.

Thanks in advance,
Best Regards

Tassilo Erlewein


-- 
Tassilo Erlewein
Computing Center University of Stuttgart
Communication Systems & BelWue Development          
Allmandring 30, D-70550 Stuttgart

tel ++49 711 685 5871
fax ++49 711 678 7626
e-mail: erlewein@rus.uni-stuttgart.de
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