Clarification required regarding the ECN_USED control filed in TCP Profile

Anil Maguluri <[email protected]> Wed, 31 Mar 2010 10:12:57 +0530
Newsgroups	gmane.ietf.rohc
Message-ID	<C7232BDB534C6241BE85C96D129205D002F41D1E10@BLRINMSMBX01.bglrodc.lntinfotech.com>
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Hi All,

Please clarify me whether my understanding is right or not.

As per my understanding, the ecn_used flag is enable whenever the TCP SYN =
packet
has ECE and CWR bits are set (ENC-SETUP SYN). This information is going to=

send using TCP dynamic chain (tcp_ecn_flags) and set ecn_used flag in the =
TCP Dynamic chain
in the IR packet.

Decompressor receives the IR packet with ecn_used flag is set, update the =
ecn_used
flag in the context.

Whenever ecn_used flag is enable, compressor has to send TCP/IP ECN flags =
in the
irregular chain of the compressed packets and decompressor has to decode i=
t from the
irregular chain to reconstruct the packet.

Please clarify the below queries.

=E8 If the TCP flow started with ECN enable/supported, is it static the li=
fe time of the flow?

=E8 If not, is TCP is going to send SYN packet again with disabling the EC=
E and CWR flags?

=E8 How frequently TCP flow can change from ECN enable to non-ECN?

=E8 If the TCP flow is changed from ECN capable to non-ECN, compressor has=
 to inform

to decompressor while setting the ecn_used as zero. Right? So that, compre=
ssor no

need to sending TCP/IP ECN flags in the irregular chain.


Thanks for your support.

Regards,
Anil Kumar Maguluri

________________________________
This Email may contain confidential or privileged information for the inte=
nded recipient (s) If you are not the intended recipient, please do not us=
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<p class=3D"MsoNormal">Hi All,<o:p></o:p></p>
<p class=3D"MsoNormal"><o:p>&nbsp;</o:p></p>
<p class=3D"MsoNormal">Please clarify me whether my understanding is right=
 or not.<o:p></o:p></p>
<p class=3D"MsoNormal"><o:p>&nbsp;</o:p></p>
<p class=3D"MsoNormal">As per my understanding, the ecn_used flag is enabl=
e whenever the TCP SYN packet<o:p></o:p></p>
<p class=3D"MsoNormal">has ECE and CWR bits are set (ENC-SETUP SYN). This =
information is going to<o:p></o:p></p>
<p class=3D"MsoNormal">send using TCP dynamic chain (tcp_ecn_flags) and se=
t ecn_used flag in the TCP Dynamic chain<o:p></o:p></p>
<p class=3D"MsoNormal">in the IR packet.<o:p></o:p></p>
<p class=3D"MsoNormal"><o:p>&nbsp;</o:p></p>
<p class=3D"MsoNormal">Decompressor receives the IR packet with ecn_used f=
lag is set, update the ecn_used
<o:p></o:p></p>
<p class=3D"MsoNormal">flag in the context. <o:p></o:p></p>
<p class=3D"MsoNormal"><o:p>&nbsp;</o:p></p>
<p class=3D"MsoNormal">Whenever ecn_used flag is enable, compressor has to=
 send TCP/IP ECN flags in the<o:p></o:p></p>
<p class=3D"MsoNormal">irregular chain of the compressed packets and decom=
pressor has to decode it from the<o:p></o:p></p>
<p class=3D"MsoNormal">irregular chain to reconstruct the packet.<o:p></o:=
p></p>
<p class=3D"MsoNormal"><o:p>&nbsp;</o:p></p>
<p class=3D"MsoNormal">Please clarify the below queries.<o:p></o:p></p>
<p class=3D"MsoListParagraph" style=3D"margin-left:.25in;text-indent:-.25i=
n;
mso-list:l0 level1 lfo1">
<![if !supportLists]><span style=3D"font-family:Wingdings"><span style=3D"=
mso-list:Ignore">=E8<span style=3D"font:7.0pt &quot;Times New Roman&quot;"=
>
</span></span></span><![endif]>If the TCP flow started with ECN enable/sup=
ported, is it static the life time of the flow?<o:p></o:p></p>
<p class=3D"MsoListParagraph" style=3D"margin-left:.25in;text-indent:-.25i=
n;
mso-list:l0 level1 lfo1">
<![if !supportLists]><span style=3D"font-family:Wingdings"><span style=3D"=
mso-list:Ignore">=E8<span style=3D"font:7.0pt &quot;Times New Roman&quot;"=
>
</span></span></span><![endif]>If not, is TCP is going to send SYN packet =
again with disabling the ECE and CWR flags?<o:p></o:p></p>
<p class=3D"MsoListParagraph" style=3D"margin-left:.25in;text-indent:-.25i=
n;
mso-list:l0 level1 lfo1">
<![if !supportLists]><span style=3D"font-family:Wingdings"><span style=3D"=
mso-list:Ignore">=E8<span style=3D"font:7.0pt &quot;Times New Roman&quot;"=
>
</span></span></span><![endif]>How frequently TCP flow can change from ECN=
 enable to non-ECN?<o:p></o:p></p>
<p class=3D"MsoListParagraph" style=3D"margin-left:.25in;text-indent:-.25i=
n;
mso-list:l0 level1 lfo1">
<![if !supportLists]><span style=3D"font-family:Wingdings"><span style=3D"=
mso-list:Ignore">=E8<span style=3D"font:7.0pt &quot;Times New Roman&quot;"=
>
</span></span></span><![endif]>If the TCP flow is changed from ECN capable=
 to non-ECN, compressor has to inform<o:p></o:p></p>
<p class=3D"MsoListParagraph" style=3D"margin-left:.25in">to decompressor =
while setting the ecn_used as zero. Right? So that, compressor no<o:p></o:=
p></p>
<p class=3D"MsoListParagraph" style=3D"margin-left:.25in">need to sending =
TCP/IP ECN flags in the irregular chain.<o:p></o:p></p>
<p class=3D"MsoListParagraph" style=3D"margin-left:.25in"><o:p>&nbsp;</o:p=
></p>
<p class=3D"MsoNormal">Thanks for your support.<o:p></o:p></p>
<p class=3D"MsoNormal"><o:p>&nbsp;</o:p></p>
<p class=3D"MsoNormal">Regards,<o:p></o:p></p>
<p class=3D"MsoNormal">Anil Kumar Maguluri<o:p></o:p></p>
</div>
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