Medianet Reference Guide - Cisco

Chapter 6
Medianet Management and Visibility Design Considerations
Cisco Network Analysis Module
single queue. This can provide a higher level of granularity into the visibility of various video
applications, if separate applications are mapped to separate service classes. The traffic rate and drop
rate, as well as counts of total packets and bytes outbound, and also counts of total drops for each queue
can be seen from the show policy-map interface command when such a policy map is applied to the
interface.
Simple Network Management Protocol
The Simple Network Management Protocol (SNMP) refers both to a specific protocol used to collect
information and configure devices over an IP network, as well as an overall Internet-standard network
management framework. The SNMP network management framework consists of the following
components:
• Network management stations (NMSs)—Typically a server that runs network management
applications, which in turn uses the SNMP protocol to monitor and control network elements.
• Network elements—The actual managed devices (routers, switches, TelePresence codecs, and so
on) on the IP network.
• Agents—Software components running within network elements that collect and store management
information.
• Managed objects—Specific characteristics of network elements that can be managed. Objects can
be single entities or entire tables. Specific instances of managed objects are often referred to as
variables.
• Management information bases (MIBs)—Collections of related management objects. MIBs define
the structure of the management data through a hierarchical namespace using object identifiers
(OIDs). Each OID describes a particular variable that can either be read from a managed object or
set on a managed object. MIBs can be standards-based or proprietary. Because SNMP management
information uses a hierarchical namespace, individual vendors can extend the management
capabilities of their products through proprietary MIBs, which are typically published.
Currently, three versions of SNMP are commonly deployed:
• SNMPv1—The initial version introduced in the late 1980s. The security model used by SNMPv1
consists of authentication only, using community strings (read-only and read/write) that are sent in
clear text within SNMP messages. Because of this, SNMPv1 is considered inherently insecure, and
read/write capability should be used with caution, even over private networks.
• SNMPv2c—Proposed in the mid 1990s. The “c” in SNMPv2c indicates a simplified version of
SNMPv2 that also uses a security model based on community strings. SNMPv2 improved the
performance of SNMPv1 by introducing features such as the get-bulk-request protocol data unit
(PDU) and notifications, both listed in Table 6-3. However, because SNMPv2c still uses the same
security model as SNMPv1, read/write capability should be used with caution.
• SNMPv3—Introduced in the early 2000s, and is currently defined primarily under IETF
RFCs 3411-3418. A primary benefit of SNMPv3 is its security model, which eliminates the
community strings of SNMPv1 and SNMPv2. SNMPv3 supports message integrity, authentication,
and encryption of messages; allowing both read and read/write operation over both public and
private networks.
As mentioned above, the SNMP protocol defines a number of PDUs, some of which are shown in
Table 6-3, along with the particular version of SNMP that supports them. These PDUs are essentially the
commands for managing objects through SNMP.
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Medianet Reference Guide
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