Re: [Sigtran] Number of links towards a DPC (ITU)

["Brian F. G. Bidulock" <[e-mail]>]

Arvind,

ITU has a 4-bit SLS and a 4 bit SLC.  The SLS and SLC is shared under
ITU and ITU does not do SLS rotation.  Therefore, because 1 bit is used
for link-set selection, there can only be 8 links in a linkset (16 links
in a combined linkset).

ANSI has an 8-bit SLS and a 5-bit SLC.  The SLS and SLC are not shared
and ANSI does SLS rotation.  Therefore, it is possible to have 32 links
in a linkset (64 links in a combined linkset).  Using the old 5-bit SLS
it was only possible to have 16 links in a linkset and 32 links in a
combined linkset because 1 of the 5 bits was used for linkset selection
within a combined linkset.

So, there are two considerations: SLS and SLC size.  The most links in a
link set is restricted by the size of the SLC (the number of signalling
links that can be identified between two signalling point  codes);
however, the combined linkset is also restricted by the SLS size (over
how many distinct signalling links can the traffic be distributed).

That said, signalling links are identified by the 3-tuple PC-PC-SLC.
Just because you have multiple PCs on a signalling point does not
necessarily increase the number of signalling links that it can support.
So, if you have 4 PCs, it does not necessarily mean that you can support
4 times as many signalling links.  It is common, for example on a class
5 switch, to provide 1 primary PC that is used in management messages on
signalling links and 3 additional ones (in our example) that are only
aliases (that is, messages can be routed to them but they do not
participate in signalling link management messages).

Some stacks; however, are also capable of supporting multiple signalling
points.  In which case, each primary PC can act as a completely
independent signalling point with its own set of signalling links.  SS7
network operators do no like connecting to systems where multiple
independent signalling points are implemented on the same hardware.

If you need a lot of signalling links for capacity, broadband (or
better, M2PA) signalling links can be used.  In the case of M2PA, the
signalling capacity is not dependent on the number of signalling links
and only a pair of signalling links is required (and recommended).

--brian

Arvind Kumar wrote:                        (Fri, 14 Jun 2013 14:09:27)
>    Hi All,
>    Would appreciate if somebody help me,
>    I have SS7 Stack with multiple OPC, I would like to create multiple
>    linksets towards a single destination (suppose 2000).
>    How many links are possible in all the link-sets. I know there is no
>    limitation of number of link-sets, but as I  understood, towards a
>    given destination the maximum number of links depends upon maximum
>    value of SLS.
>    For ITU it could be 16.
>    But my doubt is I have mutiple OPCs for my SS7 Stack, could number of
>    links  be possible
>    = number of OPCs * 16
>    Please comment.

-- 
Brian F. G. Bidulock
[e-mail]
http://www.openss7.org/