[c-nsp] Cisco Selective Packet Discard and ISR 3825 Router running IOS 12.4 mainline

[Bruce Pinsky]

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

William Chu wrote:
> Hi:
> 
> Has anyone have any experience on Selective Packet Discard (SPD) and how to 
> tune the queues?
> 
> I am seeing flushes on the Ge0/0 interface, but no drops on the input queue. 
> When I issued the show ip spd command on the router I saw that the SPD queue 
> depth was set at 73/74 for min and max, respectively.  The IP SPD commands 
> are hidden on the router, but yet they are enabled by  default.
> 
> The reason I am asking is because I have a Cisco 3825 on our network and we 
> send out a series of ping packets through this router to ping up to a 
> thousand devices over the WAN. Due to network addressing issue we must PAT 
> our ping server's IP before it hits the WAN. Our server sends out a series 
> of ping on batches, but each batch consisted of a few hundred ping requests 
> at the same time so it kind of overrun the SPD queue and thus causing 
> premature ping failures randomly.
> 
> Does anyone know how SPD work?  Because ICMP is kind of a low priority 
> packet type so I wonder if SPD drops ICMP packets first before it drops 
> other (such as SNMP).
> 

Although written primarily from the perspective of the 7500 and 12K, this
is fairly good explanation of SPD:

http://www.cisco.com/en/US/products/hw/routers/ps167/products_tech_note09186a008012fb87.shtml

- --
=========
bep

-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.4 (MingW32)
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org

iD8DBQFFLA+8E1XcgMgrtyYRAsbYAKDMCpAQhMHn/KCmToUefIwVAVYUuwCgrSYJ
j0SCRkCbUYTT4d0CTK040yE=
=417r
-----END PGP SIGNATURE-----