Subject: RFC 1323 performance pitfalls?

From: Bob Braden <[email-masked]>
Date: Fri, 19 Jan 2001 16:51:58 GMT

----------
X-Sun-Data-Type: text
X-Sun-Data-Description: text
X-Sun-Data-Name: text
X-Sun-Charset: us-ascii
X-Sun-Content-Lines: 67

----- Begin Included Message -----

---

From: "David L. Nicol" <[email-masked]>
Date: Fri, 19 Jan 2001 15:35:30 -0600

Bob Braden wrote:

> as long as a TCP implementation correctly
> negotiates use of

Ah, that's the problem.  Recalcitrant and non-compliant.

-- 
                      David Nicol 816.235.1187 [email-masked]
               "Live fast, die young, and leave a beautiful corpse"

---

From: [email-masked]
Date: Sat, 20 Jan 2001 20:46:20 +0300 (MSK)

Hello!

> >			now it seems that some versions of Linux also add
> >lots of delay when processing TCP packets with options in them.

I am sorry, such bugs never were noticed with either of versions of linux.

If you see some problems, please, prepare tcpdumps and send report
to linux-kernel or to me.

Alexey

---

From: Mike Schwartz <[email-masked]>
Date: Sat, 20 Jan 2001 12:56:05 -0800

I exchanged some mail with the guy who wrote that original note (saying 
that Linux's RFC 1323 implementation was adding delay).  He said the issue 
as he recalled it was when a Linux box was acting as a router, and slowing 
down when handling RFC 1323 timestamps sent with every packet.  I'm not 
sure why that would matter since from the router's perspective the 
timestamps are just payload.  Anyway,  I just ran a few ttcp tests between 
two hosts connected by switched 100bt through a router (all 3 machines 
running RedHat 7) and I got 85-90 Mbps...

thanks,
  - Mike

---

From: Andi Kleen <[email-masked]>
Date: Sun, 21 Jan 2001 00:45:13 +0100

> running RedHat 7) and I got 85-90 Mbps...

PPP/SLIP routers tend to slow down a bit with timestamps because they
cannot use VJ compression anymore and the header is transmitted fully.
Of course not the router really slows down, the latency of the link
just increases a bit because more bytes need to be transfered.
It is usually only noticeable with small packets and very slow links. 

-Andi

---

From: Bill Sommerfeld <[email-masked]>
Date: Sat, 20 Jan 2001 21:58:49 -0500

> It is usually only noticeable with small packets and very slow links. 

As recently as this past december, I've run into (well, dialed into)
PPP implementations "in the wild" which miscompressed (or, perhaps,
misuncompressed) packets with RFC1323 timestamps... got horribly laggy
performance until I turned them off on the laptop and then *poof* it
started working as expected.

					- Bill

---

From: "Oleg Vishnepolsky" <[email-masked]>
Date: Tue, 23 Jan 2001 13:25:34 -0500

Is it true that Cisco Arrowpoints rearrange order of packets that flow through them and hence negatively 
affect the transport protocols performance ?
Oleg Vishnepolsky