The main purpose of this MIB is to define the SNMP
notifications and alarms generated by Session Border Controller
application and used to send these notifications to SNMP
manager application. Each of these event/notification is
explained in detail in the MIB file.

The SBC service is implemented on a service card on CISCO
routers. SBC application offer functionalities like
firewall/NAT traversal, media bridging, policy-based call
routing, signaling protocol inter-working, call billing and
some degree of Call Admission Control. SBC looks to play an
essential role in full-scale commercial deployment of VoIP and
integration into the existing PSTN. 
The Session Border Controller (SBC) enables direct IP-to-IP
interconnect between multiple administrative domains for
session-based services providing protocol inter-working,
security, and admission control and management. The SBC is a
voice over IP (VoIP) device that sits on the border
of a network and controls call admission to that network.

The primary purpose of an SBC is to protect the interior of 
the network from excessive call load and malicious traffic.
Additional functions provided by the SBC include media 
bridging and billing services. 

Various types of notifications required for SBC applications
are
as follows:
1. When SIP/H2.48 calls are established and SBC application
receives traffic (RTP/RTCP packets) from a source whose IP
address or port is ambiguous, a source alert event is generated
for the unwanted data packets received by SBC application.

2. Blacklisting is the process of matching inbound packets based
on some simple parameters (for example source IP address) and
preventing packets that match those parameters from being
processed. SBC detects an attempt to disrupt traffic flowing
through it. When a source is blacklisted in SBC application, an
event is generated to provide information of the blacklisted
source like its IP address, port, VPN address etc.

3. When there is a change in the state of any SBC service
configured like a new SBC service is configured or the SBC card
goes to standby state, reboot or offline state, a service is
removed from SBC card, an event is generated by SBC.

4. When a large number of SIP/H.248 calls are ongoing and 
system is congested i.e. high CPU usage or high use of memory
utilization, congestion event is generated at this point and
when congestion is cleared means CPU usage comes to normal
another event for congestion clear is generated.

5. When a service is configured on SBC application, its call
policies are defined during the configuration like maximum
number of calls, maximum call rates etc. If any of these
policies is violated, an event for violation of service level
agreement is generated.

6. When a radius server is attached/detached with SBC, a
notification is generated to provide information of radius
server type, IP address, port etc.

7. When an adjacency is attached/detached with SBC, a
notification is generated to provide its information like the
adjacency type and state.

8. When a H.248 controller is attached/detached with SBC to
establish H.248 calls with SBC, a notification is generated to
provide the information regarding the attached/detached H.248
controller like controller index, IP address, port, state etc.

GLOSSARY
SBC: Session Border Controller

CSB: CISCO Session Border Controller

CAC: Call Admission Control - protects voice traffic from the
negative effects of other voice traffic and to keep excess voice
traffic off the network. It is used to prevent congestion in
Voice traffic. It is used in the Call Setup phase.

RTP: Real Time Transport Protocol - defines a standardized
packet format for delivering audio and video over the Internet.

RTCP: Real Time Control Protocol - It is a sister protocol of
the Real-time Transport Protocol (RTP). RTCP provides
out-of-band control information for an RTP flow. It partners RTP
in the delivery and packaging of multimedia data, but does not
transport any data itself. It is used periodically to transmit
control packets to participants in a streaming multimedia
session.

VMG: Virtual Media Gateway - introduced to bridge between
different transmission technologies and to add service to
end-user connections. Its architecture separates control and
connectivity functions into physically separate network layers.
VPN: Virtual Private Network - It is a communications network
tunneled through another network, and dedicated for a specific
network.

Gate Id - Context Identifiers assigned uniquely to a SIP/H.248
call flows.

Flow Pair Id: Stream Identifiers assigned uniquely to a
SIP/H.248 call flows.

Adjacency: An adjacency contains the system information to be
transmitted to next HOP.

SLA: Service Level Agreement - Service level agreement includes
some call admission control policies which are defined during
the SBC configurations like maximum number of calls, maximum
call rates etc.

Diameter Server: A Diameter Server is one that handles
authentication, authorization and accounting requests for a
particular realm.

REFERENCES
1. CISCO Session Border Controller Documents and FAQ
http://zed.cisco.com/confluence/display/SBC/SBC