Answer:
SUBJECT D4-3)
Question: What are the differences between Q.93B, Q.931, and Q.2931?
Answer:
Essentially, Q.93B is an enhanced signalling protocol for call
control at the Broadband-ISDN user-network interface, using the ATM
transfer mode. The most important difference is that unlike Q.931
which manages fixed bandwidth circuit switched channels, Q.93B has
to manage variable bandwidth virtual channels. So, it has to deal
with new parameters such as ATM cell rate, AAL parameters (for
layer 2), broadband bearer capability, etc. In addition, the ATM
Forum has defined new functionality such as point-to-multipoint
calls. The ITU-T Recommendation will specify interworking
procedures for narrowband ISDN.
Note that as of Spring 1994, Q.93B has reached a state of maturity
sufficient to justify a new name, Q.2931 for its published official
designation.
SUBJECT D4-4)
Question: Information about B-ISDN and B-ICI
Answer:
B-ISUP provides the signalling requirements to support basic bearer services and
supplementary services (for Capability Set 1 and Capability Set 2 B-ISDN) for
B-ISDN applications.
In the ATM scenario, the introduction of this protocol meets the needs to
support the Switched Virtual Connections (SVCs), whereas initial ATM service
supported only the Permanent Virtual Connections (PVCs).
This protocol is conceptually the natural evolution of the ISDN User Part
(ISUP) in the Broadband field, but many important
changes have been introduced:
B-ICI stands for Broadband Inter Carrier Interface and is
the broad term for the interface and B-ISUP stack as described and documented
by ATM Forum.
This is a standard interface (based on the ITU-T B-ISUP) which has been chosen
by both ITU-T and ATM Forum for interconnecting *public* ATM networks (whereas
P-NNI is the standard non-SS7 non-ITU-T based interface for interconnecting
*private* ATM networks).
This protocol takes many features from ANSI B-ISUP (T1.648.1-4), especially
those needed for routing signalling messages through different vendor networks
(like the Exit Message and the Carrier Identification Code, Charge Number,
Carrier Selection Information, Outgoing Facility Identifier, Originating Line
Information parameters).
For an introduction to both ISUP and B-ISUP see
SUBJECT D4-5)
Question:
Signalling messages defined in Q.2931 and ATM Forum UNI v3.1
seems to establish VCCs only. How to establish VPCs by signalling?
Answer:
ATM Forum UNI 4.0 provides for switched VPs. This is done by:
Overall, the protocol is designed for source routing, where
the first switch in the network has enough information about
the topology of the network to determine a route, and then the
path information is added to the signaling message (SETUP)
and routed along the path. The overall protocol is considerably
more complex than this, as its necessary to minimise the
view of the topology of a network from the sources point of view
(a topological hierarchy is used, among other things), but thats
basically the approach.
SUBJECT D4-6)
Question: With regard to a carrier ATM network, I recently heard
the topic of an "M4" management interface.
Answer: The ATM Forum Management WG defines "management information flows" M1
to M5. A management information flow exchanges information between an
ATM management system and a part of a prototypical ATM network. For
instance, the M2 interface defines the information flow between a
private ATM switch and the local private network management system. The
management information flow includes a conceptual view (requirements)
and a MIB. Ideally the MIB can be used by SNMP or CMIP.
The protypical ATM network looks something like this:
The prototypical ATM management system is made up of local private
management systems and public management systems. This combination of
management systems, management flows and MIB's is the start of end to
end ATM network management.
So the MIB's and information flows of M4 allow a management system
within your ATM carrier to manage the central office and other carrier
ATM switches of their ATM network.
If you are using their services, you wouldn't have direct access to
this informtion. You would have indirect access to parts of it (read
only) via the M3 interface. For instance, your private management
system could query their public management system to read circuit/path
status or counters for your paths traversing their public network
service.
If you were a developer of public-type ATM switches, you would
implement the MIB's associated with M4; plus private MIB extensions. If
you were a management system vendor you might implement M1-3 if you
were only interest
ed in private network management; M3-5 if you were interested in the
management of public networks; M1-5 if you managed both.
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B-ISUP runs over this protocol stack:
SS7 MTP-Level 3
Q.2140
Q.SAAL
ATM
and contains a specific module, called "Compatibility Process", for managing
both unrecognized signalling informations and interworking issues with a
N-ISUP (Narrowband ISUP, i.e. ISUP).
"Signalling System #7",
Travis Russel,
McGraw-Hill
For more references surf the Trillium WEB site at
http://www.trillium.com
The ATM Forum also has a Private-NNI SWG. Currently they have worked on a protocol
(called PNNI) for
distributing link and node state information, and a call
setup procedure, to support intra-network routing and
switching. The spec itself was completed in 1996.
ATM Device----Private ATM Net----Public ATM Net----Public ATM Net
Note: it may be more clear to mentally replace the word "public" with "carrier"
in all of this discussion.
M3 M5
_ Private Mgt Sys<-->Public Mgt Sys<-->Public Mgt Sys
/ ^ ^ ^
M1/ M2| M4| M4|
/ v v v
ATM Device----Private ATM Net----Public ATM Net----Public ATM Net
The management information flows relate to the above network:
Last Changed 24 November 2002