Internet Standards/CD2.mdf/ccitt/1992/z/z335.asc

Text File | 1991-12-31 | 17KB | 491 lines

Recommendation Z.335

                     ROUTING ADMINISTRATION


1.     General

       This Recommendation has been developed in accordance to  the  methodology
defined in Recommendations Z.332 and Z.333.

       The main part of this Recommendation deals  with  the  model  of  routing
administration and a glossary of the terms used is also included.

       The list of operator jobs and the list of system functions to be controlled
are contained in Annex A.

       For each system function to be controlled by means of MML, one or more MML
functions can be derived and each of them can be described using the metalanguage
defined in Recommendation Z.333, in order to  detail  the  relevant  information
structure.

       Annex B contains a list of MML functions and information structure diagrams
associated to each of them to be used as guidelines.

2.     Introduction

       The routing functions are those system functions that are  in  charge  of
routing a call attempt toward its destination on the basis of the data associated
with the call attempt (e.g. the dialled digits, etc.) and the data associated to the
network (e.g. identities of the circuit sub-groups serving a certain destination,
etc.). The destination of a call attempt may be inside the switching system as well
as outside the switching system. If the destination is inside the switching systems,
the routing will consist of identifying the termination that corresponds to  the
destination. If the destination is outside  the  switching  system  the  routing
functions shall search for a free circuit, within a given circuit sub-group on which
the call attempt will be routed.

       Routing consists of functions whose parameters may vary with the  network
design and the switching system design to fit the network application. The economics
of a switching system in a network application is, in part, a function of how well
the routing functions match the network design.

       The main activities for creating and maintaining routing administration data
may be summarized by the following items:

       -    analysis of the data provided by the traffic measurement functions;

       -    defining the routing strategies on the basis of the achieved results;

       -    creating new or changing the existing items, related to the routing in
            the switching systems, in order to satisfy the routing strategies.
            Only  the  last  of  these  items  is  within  the  scope  of   this
Recommendation.

       This Recommendation deals with the routing administration functions involved
with the routing towards destinations outside the  switching  system,  whichever
signalling system is used.

3.     Routing administration model












3.1    Introduction

       To service a call in order to make it proceed towards the desired  called
party, two steps are pointed out:

       -    the identification of the destination of the call made by means of the
            analysis of the selection digits and by means of other information;

       -    the selection of a free circuit within a set of suitable circuits on
            which the call may be forwarded.

       The routing functions provided by a system deal mainly with the second step
and the present Recommendation relates to their administration. In this section a
model for the administration of routing functions is  reported,  describing  the
information used.

       Figure 1/Z.335 provides a description of the connections that exist at the
man-machine interface, among the routing items (such as circuit ,  circuit  sub-
groups, routes and route groups) that can be administered by means of MML functions.

       The purpose of this model is to provide an overview of the routing items and
the relevant parameters. No specific association between parameters and  routing
items is intended other than for explanatory  purposes.  Any  parameter  can  be
associated to any routing item depending on the specific needs of an administration
or of the network: for example, the type of signalling system may be determined at
route group, route or circuit sub-group level, without changing its function.

       The collection of combinations of destination and  additional  parameters
forms the routing table, which contains all the possibilities of routing for a given
system. One entry in this table is called routing table element.








                                 FIGURE 1/Z.335

                          Routing administration model

Note - Option A  =The model comprises route groups, routes and circuit sub- groups
       Option B  =The model comprises routes and circuit sub-groups
       Option C  =The model comprises circuit sub-groups only

       These options are to be considered, on an equal footing, as complete models
of equal acceptability. Even though route groups and routes  can  be  implicitly
present in the routing table, they do not necessarily appear explicitly in the man-
machine interface.

3.2    Parameters

       The parameters used in the decision process of routing a call are included
in the following list. In Figure 1/Z.335 they are  represented  by  destination,
additional parameters and supplementary information. This list is open-ended and not
all the parameters are needed for all applications. The list may vary according to
administration needs, telecommunication network levels, etc.







       The methods used to evaluate these parameters within the switching system
should not be constrained by the model.

       1)   Destination;

       2)   Class of incoming circuit sub-group;

       3)   Calling party category;

       4)   Parameters for network management (e.g. time  of  day,  presence  of
            carrier failures, etc.);

       5)   Signalling system (incoming and outgoing);

       6)   Transmission characteristics (incoming and outgoing);

       7)   Circuit type (e.g. two wires, four wires);

       8)   Presence of echo canceller;

       9)   Transmission medium characteristics (i.e. presence of satellite links);

       10)  Selection of specific carrier or specific network.

       The destination is identified by means of the selection digits, on the basis
of the incoming route (origin information) or signalled information.

       The additional parameters are those parameters that allow identification of
the possible choices for routing a call towards a given destination. The following
factors may be used as additional parameters (the list is neither mandatory  nor
complete):

       1)   Class of incoming circuit sub-group;

       2)   Calling party category;

       3)   Parameters for network management.

       A combination of destination and additional parameters identify a routing
table element which contains all the possibilities to set up a call in order  to
forward it.

3.3    Route group

       A route group consists of one or more routes that may be used for a given
destination. A route group may be accessed  by  more  than  one  combination  of
destination and additional parameters.

3.4    Route

       A route consists of one or more circuit sub-groups and of some information
associated with the route describing the use of the route itself.

       Examples of this information may be:

       -    seizure signal to send (terminal, transit);

       -    number of digits to send;












       -    digits to add.

       If the route is not present  in  the  routing  administration  model  the
information should be associated to other routing items.

3.5    Circuit sub-group

       A circuit sub-group is a set of circuits between two exchanges. In options A
and B, circuits within a circuit sub-group have similar characteristics (e.g. type
of signalling, type of transmission path, etc.).

       The selection of a given circuit sub-group inside a route can be made on the
basis of supplementary  information  such  as  signalling  system,  transmission
technique, circuit type (e.g. two wires, four wires), presence of echo canceller,
transmission medium characteristics (e.g. presence of satellite links), etc. Other
information may also be associated  to  circuit  sub-groups;  examples  of  this
information are:

       -    traffic direction;

       -    class of incoming circuit sub-group;

       -    search method to select a circuit inside the sub-group.

3.6    Circuit

       A circuit is characterized by an identity, by  its  hardware  termination
identity and by its sequence number inside the circuit sub-group (this latter is
only used for selection purposes in outgoing circuit sub-groups). If common channel
signalling is used, a label should be assigned to the circuit.

4.     Additional information

4.1    Management of the status of routing items

       In order to change the  routing  capabilities  of  the  telecommunication
systems, facilities are required to alter the operating status of the items involved
(i.e. to put a circuit in service or out of service, etc.).

       This topic is left for further study.

4.2    Reliability mechanisms

       In order to prevent malfunctions and errors when servicing  a  call,  the
routing administration functions used  in  the  telecommunication  systems  must
implement reliability mechanisms.  The  most  critical  functions,  e.g.  change
functions, should not be provided to the operator if reliability mechanisms are not
provided.

       The selection and implementation of reliability mechanisms are not covered
in this Recommendation.

       However, due to the fact that the mechanism used may affect the man- machine
interface, it is highlighted that such aspect should be studied and  taken  into
account when designing the real man-machine interface.

5.     Glossary of used terms







Circuit:         connection between two exchanges for one call at a time, including
                 the junctors that terminate the circuit.

Circuit sub-group:group of circuits between two exchanges having the same traffic
                 direction (incoming, outgoing, bidirectional), the same signalling
                 characteristics and the same transmission medium characteristics.

Route:           collection of circuit sub-groups between two exchanges that are
                 equivalent for routing purposes. The term route is equivalent to
                 the concept of "circuit group" as used in Recommendation Z.337 and
                 in E-Series Recommendations.

Route group:     the set of all the possible routes  on  which  a  call  may  be
                 forwarded to the appropriate destination.


                                    ANNEX A

                           (to Recommendation Z.335)

       List of system functions to be controlled by MML and list of jobs


A.1    List of system functions to be controlled by MML

       1)   Managing the routing data base

       2)   Querying the routing data base

A.2    List of jobs

1)     To create/change items involved in the routing functions or change old ones
       (e.g. circuit sub-groups, routes, etc.)

       -    the purpose of the job is to create and/or change the configuration of
            the switching system regarding the items involved in the routing of a
            call;

       -    the system is supposed to record the new data and to check their static
            correctness;

       -    the operator is supposed to input all needed data;

       -    the complexity of the job may be high depending on the amount of the
            data to be input for the item to be created/changed;

       -    the frequency of the job is medium;

       -    the job is supposed to be performed at exchange and/or OMC level.

2)     To delete items related to the routing

       -    the purpose of the job is to delete items no longer useful;

       -    the system is supposed to delete the specified  items  deleting  the
            related data only if no call is currently routed on the item;

       -    the operator is supposed to introduce the identity of the item to be
            deleted;












       -    the complexity of the job is low (if  the  system  makes  sufficient
            checks);

       -    the frequency of the job is low;

       -    the job is supposed to be performed at exchange and/or OMC level.

3)     To interrogate different kinds of information related to the routing

       -    the purpose of the job is to get information on the current data used
            by the system to perform the routing;

       -    the system is supposed to output the information requested in suitable
            formats and on the selected devices;

       -    the operator is supposed to input the identity of  the  item  to  be
            interrogated and to select the information to be retrieved;

       -    the complexity of the job is low;

       -    the frequency of the job is high;

       -    the job is supposed to be performed at exchange and/or OMC level.

                                    ANNEX B

                           (to Recommendation Z.335)

                  Guidelines for the list of MML functions and
                   associated information structure diagrams


B.1    Introduction

       This annex contains guidelines for the list of MML functions and associated
information structure diagrams related to the routing administration model defined
in Recommendation Z.335, section 3.

B.2    List of MML functions

       This list contains possible MML functions for routing administration.

       This list is not  mandatory  nor  complete,  it  may  vary  according  to
administration needs, telecommunication network levels, regulatory needs, etc.

       These MML functions do not represent the actual command structure of  any
real implementation of the man-machine interface.  Each  of  the  MML  functions
identified can be implemented by providing one or more separate distinctive commands
or several MML functions could be implemented by using a single command.

1)     Creation

       -    create a circuit

       -    create a circuit sub-group

       -    create a route (only options A and B)*







       -    create a route group (only option A)*

       -    create a destination

2)     Deletion

       -    delete a circuit

       -    delete a circuit sub-group

       -    delete a route (only options A and B)*

       -    delete a route group (only option A)*

       -    delete a destination



*  Options A and B are defined in Recommendation Z.335, section 3.

3)     Interrogation

       -    interrogate a circuit

       -    interrogate a circuit sub-group

       -    interrogate a route (only options A and B)*

       -    interrogate a route group (only option A)*

       -    interrogate a destination

4)     Changing

       -    change a circuit

       -    change a circuit sub-group

       -    change a route (only options A and B)*

       -    change a route group (only option A)*

       -    change a destination

B.3    Information structure diagrams

       Only the information entities needed for  the  MML  functions  previously
derived have been identified. They are reported in this section by means of diagrams
representing each MML function information structure.

       These diagrams represent typical routing function requirements. They are not
intended to constrain in any way the enhancement of these functions in the light of
technological advances or specific administration or regulatory requirements.

       The metalanguage used is described in Recommendation Z.333.























*  Options A and B are defined in Recommendation Z.335, section 3.