* Question about the hash used in XOR mode
@ 2003-09-21 13:37 Shmulik Hen
2003-09-23 20:31 ` Jay Vosburgh
0 siblings, 1 reply; 2+ messages in thread
From: Shmulik Hen @ 2003-09-21 13:37 UTC (permalink / raw)
To: bonding-devel, netdev
In bond_xmit_xor(), we have the following:
slave = bond->prev;
.
.
.
slave_no = (data->h_dest[5]^slave->dev->dev_addr[5]) % bond->slave_cnt;
Which should give us a number between 0 and slave_cnt-1 which is constant
per destination address, hence acts as a hash function. But, the fact is
slave->dev->dev_addr[5] is the same the whole time, and is actually the
same as bond->device->dev_addr[5].
Is there a special meaning for XORing with a constant ?
Wouldn't it be the same is we did just:
slave_no = data->h_dest[5] % bond->slave_cnt;
--
| Shmulik Hen Advanced Network Services |
| Israel Design Center, Jerusalem |
| LAN Access Division, Platform Networking |
| Intel Communications Group, Intel corp. |
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: Question about the hash used in XOR mode
2003-09-21 13:37 Question about the hash used in XOR mode Shmulik Hen
@ 2003-09-23 20:31 ` Jay Vosburgh
0 siblings, 0 replies; 2+ messages in thread
From: Jay Vosburgh @ 2003-09-23 20:31 UTC (permalink / raw)
To: shmulik.hen; +Cc: bonding-devel, netdev
>slave_no = (data->h_dest[5]^slave->dev->dev_addr[5]) % bond->slave_cnt;
[...]
>Is there a special meaning for XORing with a constant ?
>Wouldn't it be the same is we did just:
> slave_no = data->h_dest[5] % bond->slave_cnt;
I asked Janice Girouard about this... The theory is to mimic
the way Cisco etherchannel load balancing modes operate (in particular
I think the "src-dst-mac" mode).
The Cisco 6000 series switch (and maybe others) documentation
shows the algorithm (in an example; it doesn't go into detail).
-J
---
-Jay Vosburgh, IBM Linux Technology Center, fubar@us.ibm.com
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2003-09-21 13:37 Question about the hash used in XOR mode Shmulik Hen
2003-09-23 20:31 ` Jay Vosburgh
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