Subject: Re: [Megaco] what is the meaning of Reserve Value and Reserve Gro up

From: Christian Groves <[email-masked]>
Date: Thu, 12 May 2005 13:43:38 +1000

Hello Raphael,

If the groups were identical eg. same o=,s=,c= etc apart from the codec then I 
believe it would be equivalent to Tom's case 2 from 2 years ago.
The use of ReserveGroup and multiple SDPs would simply result in a larger 
message. The ReserveValue would be a more compact form.
I see the use of ReserveGroup where you need to tie multiple capabilities together.

Regards, Christian

Raphael Tryster wrote:

> I understand that Tom's Case 1 below must use multiple SDP sessions, and
> hence ReserveGroup, because different transport protocols are involved.
> My question is whether Case 2 could be rewritten as two SDP sessions,
> using ReserveGroup instead of ReserveValue, as follows:
> 
> Case 2: 
> 
> Local={ 
> v=0 
> o=... 
> s=... 
> c=ATM ... 
> m=audio ? AAL1/ATMF 96 
> a=atmmap: 96 AMR 
> v=0 
> o=... 
> s=... 
> c=ATM ... 
> m=audio ? AAL1/ATMF 97 
>  a=atmmap: 97 PCMU 
> etc. 
> } 
> 
> ReserveGroup=true would cause resources to be reserved to support both
> AMR 
> and PCM mu-law over AAL1.  ReserveGroup=false would cause resources to
> be 
> reserved for just one of these possibilities, with AMR preferred. 
> 
> Is the above equivalent in functionality to Case 2 as Tom wrote it 3
> years ago?  If so, what additional considerations would influence which
> format to prefer?
> 
> Raphael Tryster 
> 
> 
> -----Original Message----- 
> From: Tom-PT Taylor [mailto:[email-masked]
> <mailto:[email-masked]> ] 
> Sent: Saturday, March 16, 2002 12:48 AM 
> To: 'Zhang, Yuyong'; 'Christian Groves'; John Joseph Chooracken 
> Cc: [email-masked]' 
> Subject: RE: [Megaco] what is the meaning of Reserve Value and Reserve
> Gro up 
> 
> A group is equivalent to a session description (i.e. the v=0 line and
> what 
> follows).  So ReserveGroup indicates whether to choose and reserve
> resources 
> for one of a set of session descriptions, or to reserve resources for
> all of 
> them.  Within each, ReserveValue indicates whether to choose and reserve
> one 
> of a set of alternative values (particularly codecs) or to be prepared
> to 
> handle all of the presented values.  Christian's examples below
> translate 
> into 
> 
> Case 1: 
> 
> Local={ 
> v=0 
> o=... 
> s=... 
> c=IP IP4 ... 
> m=audio ? rtp/avp 96 
> a=rtpmap: 96 AMR 
> [see draft-ietf-avt-rtp-amr-13.txt] 
> v=0 
> o=... 
> s=... 
> c=ATM ... 
> m=audio ? AAL1/ATMF 0 
> [see RFC 3108] 
> etc. 
> } 
> 
> ReserveGroup=true would cause resources to be reserved for both AMR over
> IP 
> and PCM mu-law over AAL1.  ReserveGroup=false would cause the MG to
> choose 
> one of these two possibilities, with the first being preferred. 
> 
> Case 2: 
> 
> Local={ 
> v=0 
> o=... 
> s=... 
> c=ATM ... 
> m=audio ? AAL1/ATMF 96 97 
> a=atmmap: 96 AMR 
> a=atmmap: 97 PCMU 
> [references as above] 
> etc. 
> } 
> 
> ReserveValue=true would cause resources to be reserved to support both
> AMR 
> and PCM mu-law over AAL1.  ReserveValue=false would cause resources to
> be 
> reserved for just one of these possibilities, with AMR preferred. 
> 
> 
> 
> -----Original Message----- 
> From: Zhang, Yuyong [mailto:[email-masked]
> <mailto:[email-masked]> ] 
> Sent: Friday, March 15, 2002 2:38 PM 
> To: 'Christian Groves'; John Joseph Chooracken 
> Cc: [email-masked]' 
> Subject: RE: [Megaco] what is the meaning of Reserve Value and Reserve 
> Gro up 
> 
> 
> Hi Christian, all 
> 
> How the Group information are represented in the SDP? Please give a
> example 
> in SDP syntax about the usage of Group (the c-line, m-line, a-line 
> combination. 
> 
> Regards, 
> 
> Yuyong 
> 
> -----Original Message----- 
> From: Christian Groves [mailto:[email-masked]
> <mailto:[email-masked]> ] 
> Sent: Tuesday, March 12, 2002 4:22 PM 
> To: John Joseph Chooracken 
> Cc: [email-masked]' 
> Subject: Re: [Megaco] what is the meaning of Reserve Value and Reserve 
> Group 
> 
> 
> Hello John, 
> 
> Reserve Group allows you to reserve resources for different sets of a 
> number of properties/SDP lines. eg. 
> Group ID 1 
>         pkg1/codec = AMR 
>         pkg2/transport = IP 
> Group ID 2 
>         pkg1/codec = G711 
>         pkg2/transport = ATM 
> 
> Whereas reserve value only reserves values for single properties. eg. 
>         pkg1/codec = AMR, G711 
>         pkg2/transport = ATM 
> 
> Regards, Christian 
> 
> John Joseph Chooracken wrote: 
> 
>>Hi , 
>>
>>   Please tell me  what is the difference between Reserve Value and 
> 
> Reserve 
> 
>>Group in Local Control Descriptor. 
>>
>>Thanx in advance. 
>>
>>Regards, 
>>John 
>>"Scientists study the world as it is, engineers create the world that 
> 
> never 
> 
>>has been. " 
>>-- Theodore Von Karman 
>>
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