[Sip-implementors] <Session-Version> in SDP

[NK]

Dear All,

I have query regarding the Session version in SDP. I know if we are making
any changes in SDP then from 183 to 200OK with SDP then there will be
increment in session version from 183 <session version = 1> to 200 OK
<session-version=2>. However i have 2 doubt as below. Can you please help
me on this.

1) Is that Value should be increment by 1 only? I mean suppose in 183
w/SDP we have Session Version =1 , then is that mandatory that we should
have "session-version=2" or it can be 3 directly. OR

2) if in 183 w/SDP and 200 Ok we had the same value but when "re-invite
happened then SDP was same but "session-version" value incremented from 1
==>3 directly. I feel it should be 2 (i mean increment by 1 only). Please
advise if my understanding is correct.

Regards,
Nitin Kapoor

[Paul Kyzivat]

Post by NK
Dear All,
I have query regarding the Session version in SDP. I know if we are making
any changes in SDP then from 183 to 200OK with SDP then there will be
increment in session version from 183 <session version = 1> to 200 OK
<session-version=2>. However i have 2 doubt as below. Can you please help
me on this.
1) Is that Value should be increment by 1 only? I mean suppose in 183
w/SDP we have Session Version =1 , then is that mandatory that we should
have "session-version=2" or it can be 3 directly. OR
2) if in 183 w/SDP and 200 Ok we had the same value but when "re-invite
happened then SDP was same but "session-version" value incremented from 1
==>3 directly. I feel it should be 2 (i mean increment by 1 only). Please
advise if my understanding is correct.

RFC 3264 requires that it be incremented by 1. But if you are on the
receiving side I suggest you be lenient about this.

Thanks,
Paul

[NK]

Hi Paul,

Thanks!!. Yes i checked 3264 and it says it should be increment by 1.

However i am more concerned that if there is re invite and in 200 OK SDP(in
the correspondence of re-invite) there is no change as compare to previous
SDP then also <session-version> should increment by 1?

Regards,
Nitin Kapoor

Post by Paul Kyzivat

Post by NK
Dear All,
I have query regarding the Session version in SDP. I know if we are making
any changes in SDP then from 183 to 200OK with SDP then there will be
increment in session version from 183 <session version = 1> to 200 OK
<session-version=2>. However i have 2 doubt as below. Can you please help
me on this.
1) Is that Value should be increment by 1 only? I mean suppose in 183
w/SDP we have Session Version =1 , then is that mandatory that we should
have "session-version=2" or it can be 3 directly. OR
2) if in 183 w/SDP and 200 Ok we had the same value but when "re-invite
happened then SDP was same but "session-version" value incremented from 1
==>3 directly. I feel it should be 2 (i mean increment by 1 only). Please
advise if my understanding is correct.

RFC 3264 requires that it be incremented by 1. But if you are on the
receiving side I suggest you be lenient about this.
Thanks,
Paul
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[Paul Kyzivat]

Post by NK
Hi Paul,
Thanks!!. Yes i checked 3264 and it says it should be increment by 1.
However i am more concerned that if there is re invite and in 200 OK
SDP(in the correspondence of re-invite) there is no change as compare to
previous SDP then also <session-version> should increment by 1?

In this case you certainly may use the same version.

It is less clear if it is valid to increase the version number when the
SDP is not changed. If you MUST NOT increment in this case then you are
obligated to keep track whether it is changed or not, and that may not
always be convenient.

IMO it is not an error to increment when there has been no change. But
others may not agree.

Frankly I think having version number indicate there has been no change
is silly. No experienced programmer will trust this to be correct.

Thanks,
Paul

Post by NK
Regards,
Nitin Kapoor
On Mon, Jul 14, 2014 at 7:02 PM, Paul Kyzivat <pkyzivat at alum.mit.edu
Dear All,
I have query regarding the Session version in SDP. I know if we are making
any changes in SDP then from 183 to 200OK with SDP then there will be
increment in session version from 183 <session version = 1> to 200 OK
<session-version=2>. However i have 2 doubt as below. Can you please help
me on this.
1) Is that Value should be increment by 1 only? I mean suppose in 183
w/SDP we have Session Version =1 , then is that mandatory that we should
have "session-version=2" or it can be 3 directly. OR
2) if in 183 w/SDP and 200 Ok we had the same value but when "re-invite
happened then SDP was same but "session-version" value
incremented from 1
==>3 directly. I feel it should be 2 (i mean increment by 1 only). Please
advise if my understanding is correct.
RFC 3264 requires that it be incremented by 1. But if you are on the
receiving side I suggest you be lenient about this.
Thanks,
Paul
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[sampat patnaik]

Hi Nitin,


Please find the explanation below which states that the increament is always done by 1 as per RFC.

RFC 4566:
?



5.2.?
Origin ("o=")

????? o=<username>
<sess-id> <sess-version> <nettype> <addrtype>
??????? <unicast-address>

???? <sess-version> is a version number for this
session description.? Its? usage is up to the creating tool, so long
as <sess-version> is
????? increased when a modification is made to the
session data.? Again,? it is RECOMMENDED that an NTP format timestamp
is used.

According to another spec RFC 3264, this incrementing of version
implies new offer:
RFC 3264:
When
issuing an offer that modifies the session,??? the
"o=" line of the new SDP MUST be identical to that in
the??? previous SDP, except that the version in the origin field
MUST
increment by one from the previous SDP.? If the version in the
origin?line does not increment, the SDP MUST be identical to the SDP
with?that version number. ??

Regards
Sampat


On Tuesday, 15 July 2014 4:36 AM, NK <nitinkapoorr at gmail.com> wrote:



Hi Paul,

Thanks!!. Yes i checked 3264 and it says it should be increment by 1.

However i am more concerned that if there is re invite and in 200 OK SDP(in
the correspondence of re-invite) there is no change as compare to previous
SDP then also <session-version> should increment by 1?

Regards,
Nitin Kapoor

Post by Paul Kyzivat

Post by NK
Dear All,
I have query regarding the Session version in SDP. I know if we are making
any changes in SDP then from 183 to 200OK with SDP then there will be
increment in session version from 183 <session version = 1> to 200 OK
<session-version=2>.? However i have 2 doubt as below. Can you please help
me on this.
1) Is that Value should be increment by 1? only? I mean suppose in 183
w/SDP we have Session Version =1 , then is that mandatory that we should
have "session-version=2" or it can be 3 directly. OR
2) if in 183 w/SDP and 200 Ok we had the same value but when "re-invite
happened then SDP was same but "session-version" value incremented from 1
==>3 directly. I feel it should be 2 (i mean increment by 1 only). Please
advise if my understanding is correct.

RFC 3264 requires that it be incremented by 1. But if you are on the
receiving side I suggest you be lenient about this.
? ? ? ? Thanks,
? ? ? ? Paul
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