From: Jim Brown (Jim.Brown@xxxxxxxxxxxxx)
Date: Wed Jul 17 2002 - 17:44:33 GMT-3
I think the solution to the requirement is to limit the amount of broadcast
traffic on the switch port.
Take a look at the set port broadcast command in the command reference. This
is for broadcast suppression.
-----Original Message-----
From: Kelly Cobean [mailto:kcobean@earthlink.net]
Sent: Monday, July 15, 2002 6:37 AM
To: ccielab
Subject: RE: Packets vs Bytes
Joseph,
These two units of measure are for different layers of the OSI model.
Remember that at the physical layer, we typically measure things in bits in
networking, and a byte is just 8 bits. This lets you know the RAW
throughput of your interface, regardless of packet size, data rate, etc.
It's just how many bits (divided by 8 to get bytes) have come or gone from
your interface. Now, since a router is considered a Layer3 device (in the
traditional sense of the word router), it deals with units called packets
(Layer2 uses frames and Layer4 uses segments). Counting the number of
packets a router or interface is processing helps to determine how hard the
router is working.
>From a bandwidth standpoint, processing 1000 packets at 100 bytes each is no
different than processing 100 packets at 1000 bytes each. 100x1000 is the
same as 1000x100, 100,000. From a CPU standpoint however, there's a big
difference. In the first scenario, the router has to inspect 1000 layer 2
headers, 1000 layer 3 headers, calculate 1000 checksums, and rewrite 1000
layer 2 headers. In the second scenario, to pass the same amount of data,
the router only has to inspect 100 L2 headers, 100 L3 headers, calculate 100
checksums, and rewrite 100 layer 2 headers. So, from a CPU standpoint, the
router did ten times less work in scenario 2 (and yes, I'm assuming process
switching here, for example's sake). Setting queue depth allows you to
specify how much data the router is going to attempt to queue before it
finally cries uncle and starts dropping packets.
You can see how the combination of bytes for bandwidth control, packets for
CPU control, and queue depth for a combination of both gives you a very
flexible policing (if that's the right word for it) ability.
Any of the Masters have anything to add, or corrections?
HTH,
Kelly Cobean, CCNP, CCSA, ACSA, MCSE, MCP+I
Network Engineer
AT&T Government Solutions, Inc.
Disclaimer:
The opinions expressed herein are those of the author alone, and do not
necessarily relfect those of AT&T Government Solutions, Inc., it's
management, or it's affiliates.
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
Joseph Kimmer
Sent: Saturday, July 13, 2002 5:48 PM
To: ccielab@groupstudy.com
Subject: Packets vs Bytes
What is the difference between a packet and a byte?
I was looking at an ASET lab that wants to limit broadcast traffic on a
VLAN that a router is attached to with various parameters provided in
bytes, packets, and queue depth requirements.
Would this type of solution be referring to a combination of broadcast
control on a switch port and hold-queue limits on the router interface???
I'm really not sure how to tackle this one...
Any thoughts?
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