From: Kemal YILDIRIM (kemalhy@gmail.com)
Date: Fri Oct 13 2006 - 14:02:12 ART
Do not let this kind of typos confuse you, just clear out why you need
fragmentation on WAN links.
- you need lower delay, because voice quality would suffer if you haven't
lower delay.
- you don't need to fragment small packages, it would introduce unneccessary
L2 overhead, and undesired
- max. one way delay for voice must be less than 150ms.
- codecs has fixed compression and decompression delay.
for example if you you G729r8 codec with 20 bytes payload,
it would produce 10ms delay for compression, and 10 ms for decompression
you have left 130ms delay advance,
you need to account serialization and packatization delays as well.
to obtain a lower serialization delay such as 10ms, how many bits must be
send in one interval, this depends on circuit speed, you need to convert
bits to bytes.
HTH
Kemal
_____
From: RalF ... [mailto:routeflap@gmail.com]
Sent: Friday, October 13, 2006 2:59 PM
To: Kemal YILDIRIM; gsinapov@telelink.bg
Cc: Cisco certification
Subject: Re: 160 instead of 40
Hi Kemal and Georgi, I'm still confused..
At the link you can read the following:
"The fragment payload size is set to 40 bytes. The "frag" map class is
associated with DLCI 100 on serial interface 1."
and they just configure something else:
router(config-map-class)# frame-relay fragment 160
now if you look at the routers the help in line shows:
R1(config-map-class)#frame-relay fragment ?
<16-1600> Define fragment size, Bytes
Many Thanks for talking a look a this
On 10/13/06, Kemal YILDIRIM <kemalhy@gmail.com> wrote:
Hi there,
Most of the routing protocols hello packages are about 50 bytes long ( ospf
hellos are 48bytes, can fit in an ATM cell, is this a coincidence?).
we don't want to slice them when sending through frame relay cloud.
This is why you need to choose a value greater than most of the small
packages size. Also this value must be small enough for real time
applications such as voice and video. In your example, if the line speed
128K, we will spend 10ms to send 1280bits(160 bytes). Look at the table1 in
the document which you sent.
HTH
Kemal
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of RalF
...
Sent: Thursday, October 12, 2006 6:46 PM
To: Cisco certification
Subject: 160 instead of 40
Hi,
http://www.cisco.com/en/US/products/sw/iosswrel/ps1834/products_feature_guid
<http://www.cisco.com/en/US/products/sw/iosswrel/ps1834/products_feature_gui
d>
e09186a008008003f.html#wp1015437
Wondering why they used 160 instead of 40?
--Thanks RalF
This archive was generated by hypermail 2.1.4 : Wed Nov 01 2006 - 07:29:05 ART