ADSM-L

Re: Why does ADSM use 536-byte data packets?

1995-11-20 15:01:41
Subject: Re: Why does ADSM use 536-byte data packets?
From: Howard Heitner <CCHH AT MUSICA.MCGILL DOT CA>
Date: Mon, 20 Nov 1995 15:01:41 EST
I mentioned this to one of our network people and he seemed to
think that this was the size of an IPX packet.  He also
said that indeed the packet size is determined by the media
(ethernet, etc.).


Howard Heitner                       Phone: (514) 398-3721
Associate Director                     Fax: (514) 398-6876
McGill University
Computing Centre
805 Sherbrooke St. W.
Montreal, Que.  H3A 2K6

>Using a Sniffer, we've noticed that ADSM sends out packets, typically 598 or
>604 bytes in size. When we look at the packet in greater detail, the actual
>data portion is 536 bytes, with the remainder being protocol headers (LLC,
>DLC, IP, SNAP, etc.). This strikes me as a major bottleneck; that if I could
>send a smaller number of larger packets, I could improve performance by quite
>a bit (potentially). Oh, BTW I'm using TCP/IP for connectivity to an ADSM/MVS
>server.
>
>I use TCPBUFFSIZE 32 and TCPWINDOWSIZE 24, which are the only tuning options
>available in ADSM itself (for TCP/IP). IBM Level 2 tells me that the sizes
>must be set somewhere in the network or network card.
>
>Has anyone noticed this, and if so, can anything be done about it? I've seen
>this for NetWare and AIX. I haven't sniffed my other client types yet, but
>I believe I'd probably find something similar.
>
>Any help would be appreciated.
>
>Thanks,
>
>Andy Raibeck
>Connecticut Mutual
>203-987-3521