This MIB is for managing information required to 
route messages transported over Signalling System 
No. 7 (SS7) Network via Cisco IP Transfer
Point.  

The Cisco IP Transfer Point (ITP) is a hardware 
and software solution that transports SS7 traffic 
using IP.  Each ITP node provides the functions
necessary to act as a SS7 signalling point.  Each 
signalling point is connected to other signalling 
point using IP based or traditional TDM links.

The relevant ITU documents describing this technology 
are the ITU Q series, including ITU Q.700: Introduction
to CCITT Signalling System No. 7 and ITU Q.701 
Functional description of the message transfer part
(MTP) of Signalling System No. 7.


Definitions and overview:

Route:
A route consists of one or more linksets used to transport
MTP3 Message Signal Units(MSU) between signalling points.  
A route is an association between a destination point 
code(DPC) and a linkset, i.e., a linkset that can be used
to send an MSU to the given DPC.

Routeset:
A routeset is a set of routes to a given DPC.  Each route
within a routeset is on a possible path toward the DPC.
Each route within the routeset has associated with it a
route priority.

In the following simple configuration, two routes exist
that can be used to transport MSUs from STP1 to STP4.

  ---------         STP1-STP2         --------- 
  - STP1  ----------------------------- STP2  - 
  ---------                           --------- 
      |                                   |
      | STP1-STP3               STP2-STP4 |
      |                                   |
  ---------         STP3-STP4         --------- 
  - STP3  ----------------------------- STP4  - 
  ---------                           --------- 

Routeset on STP1 for DPC = STP4:
    STP1-STP2,
    STP1-STP3


Linkset:
A linkset is a set of signalling links connecting
two signalling points.

Combined Linkset: 
Two linksets with equal number of links and capacity
that form routes of equal priority to a given DPC are
called Combined Linksets.  It is primarily used for
load sharing and redundancy.  In the following, example,
linksets 'SSP1-STP1' and 'SSP1-STP2' form a combined 
linsket.
  
   
        SSP1-STP1             ---------
     |------------------------- STP1  -
     |                        ---------
    - - 
  -     -
 -  SSP1 -  
  -     -
    - - 
     |  SSP1-STP2            ---------
     |------------------------ STP2  -
                             ---------

Routing:  
The routing of SS7 Message signalling Units(MSU) is based 
on the DPC.  Message Signalling Units are sent from an
originating point code(OPC) to DPC.  Each MSU will 
traverse one or more linksets as it is routed to its 
final destination.  When an MSU arrives at a signalling
point and the DPC does not match the signalling point's
point code the MSU must be directed toward the DPC.  Each
signalling point has enough routing information to 
determine which linkset should be used to transmit the
MSU toward its final destination.

Route statement:  
Each ITP Signalling Point has route statements needed to
determine which linkset should be used to transmit 
message signalling units to destinations.  Each route
statement consists of a destination, a priority and a
linkset name.  The destination is specified as a 
combination of DPC and mask.  The priority, also know
as cost, is used to define the order in which the routes
are selected.  The linkset name specifies which linkset
to use to reach the destination.

Route table:  
Each ITP Signalling Point has a table of routes.  
These route entries are used to determine which linkset
should be selected to transmit message signalling units 
to a given destination.  

There are two basic type of routing.  The first type
is fully-qualified and uses all bits of the target DPC.  
The other type is summary routing that uses a subset
of the bits in the target DPC and is used to represent 
groups of point codes rather than a single point code.

Example of route table entries.

Example 1: variant = ITU

DPC/MASK  Priority  Linkset-name
--------  --------  -----------------------
5.5.5/14  3         STP1-STP2
5.5.5/14  7         STP1-STP3

Description: Two route table entries that define a
primary route using linkset 'STP1-STP2' and an alternate
route using linkset 'STP1-STP3' to point-code 5.5.5.

Example 2: variant = ITU

DPC/MASK  Priority  Linkset-name
--------  --------  -----------------------
5.5.5/14  3         STP1-STP2
5.5.5/14  3         STP1-STP3
5.5.5/14  7         STP1-STP4

Description: Two route table entrys that define a
combined linkset consisting of linkset 'STP1-STP2' and
'STP1-STP3' to point code 5.5.5.  An alternate route is
also defined using linkset 'STP1-STP4'.

Example 3: variant = ANSI

DPC/MASK  Priority  Linkset-name
--------  --------  -----------------------
5.5.0/16  3         STP1-STP2

Description: A route table entry that defines routing
to a cluster.  The cluster represents all point codes
in the range from 5.5.0-5.5.255.

Example 4: variant = ANSI

DPC/MASK  Priority  Linkset-name
--------  --------  -----------------------
5.5.0/16  3         STP1-STP3
5.5.5/24  3         STP1-STP2


Description: The mixing of fully-qualified and summary
route table entrys allow for different routes to be
defined for certain DPC in a cluster.  In this 
configuration, the fully-qualified route will be the 
primary and the summary route will act as a backup.
                 
Route table:  
A group of route table entrys used to route MSU for a 
particular instance of a signalling point.

A sample route table.

DPC/MASK  Priority  Linkset-name
--------  --------  -----------------------
0.0.0/0   7         STP1-STP4
5.5.0/16  3         STP1-STP3
5.5.5/24  3         STP1-STP2
.
.
122.5.5   5         STP1-STP2
.
.
243.200.1 6         STP1-STP3