Subject: [Sigtran] Query on stream mapping in V5UA

From: Pavan Puri <[email-masked]>
Date: Tue, 7 Jun 2005 20:06:48 +0530

Hi, 

We have the following doubt about Interface Identifier and stream mapping 
in V5UA stack. 

According to V5.2 standard, a maximum of 6 channels can be reserved for 
signalling(C - channel) on all  
links(max 3 on each link) in a V5.2 Interface. 
V5UA rfc says that One single stream SHOULD NOT be used to carry data of 
more than one C-channel 
Does this mean that there should be separate stream for each C-channel(i.e 
1 stream for 1 C-Channel) ? 

Our further concern is that, If more than one Interface identifiers are 
added in one Application Server(AS)  
then the number of streams required in a SCTP association handling the 
traffic for this AS, would be  
proportional to Interface Identifiers added (going by the format of 
interface id in V5UA is a combination 
of Link + channel id as against V5.2 specifications  which state that an 
interface  is a  collection of  upto 
 16 links and each of the first two links could have a maximum of  three 
C-channels each ). 
So for example if we add 50 Interface Identifiers(combination of Link id + 
channel id) in an AS, is it required  
to have more than 50 streams in the ASP-SGP association handling the 
traffic of this AS ? 

Following text has been described in rfc3807 for SCTP Stream Management  
  
" A single SCTP stream SHOULD be used for grouping all of the following 
   protocols together: BCC, Link Control, Control and PSTN protocol on a 
   specific C-channel.  A separate SCTP stream SHOULD be used for the 
   Protection protocol on a specific C-channel.  One SCTP stream SHOULD
   be used for all ISDN user ports on a specific C-channel.  One single
   stream SHOULD NOT be used to carry data of more than one C-channel. 

   In addition, one separate SCTP stream SHOULD be used for all MPH 
   (link related) messages."

and following have been defined for description of Interface Identifier -: 

"The format of the integer formatted Interface Identifier is shown 
   below: 

    0                   1                   2                   3 
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |        Link Identifier                              | Chnl ID | 
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   Link Identifier - Identifier for an E1 link on the SG (27 bits).
      MUST be unique on the SG.  This Link Identifier MUST match the 
      Link Identifier used in the Link Management Messages defined later 
      in this document. 

   Chnl ID - Channel Identifier (5 bits).  This is equal to the time- 
      slot number of the addressed time slot.  Possible values are 15, 
      16 and 31 representing the possible time slots for C-channels on a 
      V5 interface.  For Link Management Messages, the Chnl ID MUST be 
      set to 0.  All other values are reserved for future use." 

Regards 
Pavan 

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