[LARTC] Linha fale a vontede todos os dias (11)6839-0277

[RH Equipe Teleinfor]

Linha fale a vontade todos os dias, aquela que você só paga a assinatura
www.telefonevesper.com.br


----- Original Message -----
From: "Jonathan Lynch" <jlynch at frink.nuigalway.ie>
To: <lartc at mailman.ds9a.nl>
Sent: Tuesday, October 11, 2005 6:04 PM
Subject: [LARTC] The effects of queueing on delay


>
> I have a router with 3 network interfaces like in the following ASCII
> diagram below. All interfaces are 100mbit. There is tcp traffic being
> sent from net1 to net3 and from net2 to net3 and the tcp connections
> consume as much bandwidth as possible. There is a pfifo queue on the
> egress interface eth0 of the core router with a limit of 10 packets.
>
>
> net1 --> (eth1) router (eth0) -> net3
>                 (eth2)
>                   ^
>                   |
>                 net 2
>
> I police traffic on the edge of net1 to 48.4375 Mbit and shape the
> traffic on exit of net 2 to 48.4375 Mbit. There are no packets in the
> queue of the egress interface eth0 of the router at any stage. (every
> packet is enqueued by pfifo_enqueue() to an empty queue. I have
> confirmed this by adding adding a counter in sch_fifo.c that is
> incremented every time there is a packet in the queue when a new packet
> is enqueued.) The delay is at a maximum of 2ms.
>
> When I increase the policing rate and shaping rates to 48.4687. The
> combined increase is 31.2 kbit which is very small. there are some
> packets queued for a short period and some dropped which clears the
> queue. The maximum number of packets dropped was 20 per second. But the
> delay goes up to 30ms.
>
> check out the graphs at
> http://frink.nuigalway.ie/~jlynch/queue/
>
>
> I cant seem to explain this. Even if the queue was full all the time and
> each packet was of maximum size, the delay imposed by queueing should be
> a maximum of 10 * 1500 * 8 /100,000,000 which equals 1ms.
>
> How can so much delay be added by such a small increase in the
> throughput coming from net1 and net2 ?
>
> I would appreciate if someone could explain it to me.
>
> Btw im using a stratum 1 NTP server on the same LAN to ensure
> measurement accuracy.
>
>
> Jonathan
>
> _______________________________________________
> LARTC mailing list
> LARTC at mailman.ds9a.nl
> http://mailman.ds9a.nl/cgi-bin/mailman/listinfo/lartc