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| Title: | Digital Brouters Conference |
| Notice: | New common-code brouter family: RouteAbout, DECswitch 900 |
| Moderator: | MARVIN::HART LL |
|
| Created: | Mon Jul 17 1995 |
| Last Modified: | Fri Jun 06 1997 |
| Last Successful Update: | Fri Jun 06 1997 |
| Number of topics: | 929 |
| Total number of notes: | 3736 |
888.0. "high Multicast Drop Rate from FDDI to VNbus" by BERN02::DEY (Walter Dey, Berne Switzerland) Mon May 05 1997 11:46
Status Test FDDI-ATM (DEChub900 Multiswitch 5.1, VNswitch 900EF (1.51),
VNswitch900EA (1.50) :
VNswitch 900EF and EA are installed in Hub900 chassis .
VNswitch900 module were selectively connected to VNbus 1 or
VNbus 2.
FDDI Switch is connected to Novartis shared FDDI IS-Core
(22 FDDI Attached Routers, average load > 6000 Frames/sec).
VNswitch900EA is configured in a ATM VLAN (emulated Ethernet),
which has 4 ATM-attached Routers (Ciba, Sandoz Link).
Results:
Ping from FDDI Router connected to IS Core to ATM attached
Sandoz Router on VLAN over VNswitch EF-EA works ok (ARP request./reply,
ICMP).
Telnet Connection possible.
However ATM attached Sandoz Routers doesn't see any OSPF Neighbours on the
FDDI IS-Core.
Counter on VNswitch900 EF shows high Multicast Drop Rate from FDDI to
VNbus
Traces were done at the FDDI and ATM side:
At ATM Port, we see only a moderate Multicast Rate (only 802.3 Frames),
but no OSPF Hellos (V2 Frames from IS Core Router over VNswitch connection).
On the FDDI side, ARP Requests/Reply of Sandoz Routers were visible.
Tests were repeated, replacing VNswitch900EA/EF link over VNbus
by a internal Ethernet segment.
Everything works ok:
FDDI-ATM link over VNswitch 900 (internal 10M Link). Die
OSPF Hellos are visible, OSPF Router Exchange ok.
On the ATM side, 802.3 Frames (SNA, Netbios) and DIX Ethernet Frames (IP, IPX)
are seen.
| T.R | Title | User | Personal
Name | Date | Lines |
|---|
| 888.1 | BUS? | FORBIN::WILKINSON | | Wed May 07 1997 20:45 | 20 |
| I am not sure which counter you are refering to in your statement:
"Counter on VNswitch900 EF shows high Multicast Drop Rate from FDDI to
VNbus"
I suspect that you might be refering to the translation queue drops.
The packets would not be translated for transmit on the VNbus. The
VNbus support both FDDI and Ethernet frames.
I suspect that the drop problem may be occurring with the BUS of the
LANE. Your might want to compare the rx multicast frames on the FDDI
port of the EF and the VNbus port of the AE. If they are similar,
then the droppage is further downstream. If it is further down stream,
you may want to enable multicast ratelimiting to ease the load on the
BUS. Some BUS implementations in our switches cannot support 6000
multicast packets/sec. You can use a separate workstation/pc as the
BUS to increase the performance.
Hugh
|
| 888.2 | Not BUS, VNbus | BERN02::DEY | Walter Dey, Berne Switzerland | Thu May 08 1997 13:56 | 5 |
| I have to contact the customer to findout the counter he is referring
to.
however, this has nothing to do with bus (they use mss from IBM who has
much better performance); it is VNbus related, because the problem
disappears, once you connect EA and EF externally.
|
| 888.3 | fragmentation? | FORBIN::WILKINSON | | Fri May 09 1997 23:54 | 11 |
| We have seen a packet fragmentation problem in the EF<->AE configuration
where LANE is involved. This problem appeared to go away when the
VNbus was taken out of the configuration. The last 4 bytes in each of
the packet fragments are being replaced by a CRC. The actual problem
is being fixed in a software update and involves the AE software.
So, if those routing update packets exceed 1500 bytes in size, they
would be subject to fragmentation. Upon re-assembly, the IP packet
checksum would fail.
Hugh
|