Many companies conduct
most of their business online and any loss of service can affect the
profitability of the company. Internet service providers (ISPs) and even
internal IT departments now offer a defined level of service--a service level
agreement--to provide their customers with a degree of predictability.
performance requirements for business-critical applications, voice over IP
(VoIP) networks, audio and visual conferencing, Multiprotocol Label Switching
(MPLS), and Virtual Private Networks (VPNs) are creating internal pressures on
converged IP networks to become optimized for performance levels. Network
administrators are increasingly required to support service level agreements
that support application solutions. IP Service Level Agreements (SLAs) allow
you to manage IP service levels for IP applications and services.
The Cisco NX-OS IP
SLAs use active traffic monitoring--the generation of traffic in a continuous,
reliable, and predictable manner--for measuring network performance. Cisco
NX-OS IP SLAs send data across the network to measure performance between
multiple network locations or across multiple network paths. It simulates
network data and IP services and collects network performance information in
real time. The information collected includes data about the response time,
one-way latency, jitter (interpacket delay variance), packet loss, voice
quality scoring, network resource availability, application performance, and
server response time. Cisco NX-OS IP SLAs performs active monitoring by
generating and analyzing traffic to measure performance either between Cisco
NX-OS devices or from a Cisco NX-OS device to a remote IP device such as a
network application server. Measurement statistics provided by the various
Cisco NX-OS IP SLAs operations can be used for troubleshooting, problem
analysis, and designing network topologies.
IPSLA do not
support rollback. The rollback is related to IPSLA configuration via CLI.
Cisco NX-OS IP SLAs
provides the following improvements over a traditional service level agreement:
- End-to-end measurements—The
ability to measure performance from one end of the network to the other allows
a broader reach and more accurate representation of the end-user experience.
such as delay, jitter, packet sequence, Layer 3 connectivity, and path and
download time that are broken down into bidirectional and round-trip numbers
provide more data than just the bandwidth of a Layer 2 link.
- Ease of
deployment--Leveraging the existing Cisco devices in a large network makes
Cisco NX-OS IP SLAs easier and cheaper to implement than the physical probes
often required with traditional service level agreements.
monitoring--Cisco NX-OS IP SLAs can simulate and measure performance statistics
generated by applications running over Layer 3 through Layer 7. Traditional
service level agreements can only measure Layer 2 performance.
- Pervasiveness--Cisco NX-OS
IP SLAs support exists in Cisco networking devices that range from low-end to
high-end switches. This wide range of deployment gives Cisco NX-OS IP SLAs more
flexibility over traditional service level agreements.
The following figure
shows how Cisco NX-OS IP SLAs have taken the traditional concept of Layer 2
service level agreements and applied a broader scope to support end-to-end
performance measurement, including support of applications.
Figure 1. Scope of
Traditional Service Level Agreement Versus Cisco NX-OS IP SLAs
Using Cisco NX-OS IP
SLAs, you can measure, provide, and verify service level agreements. You can
also analyze and troubleshoot network performance for IP services and
applications. Depending on the specific Cisco NX-OS IP SLAs operation,
statistics of delay, packet loss, jitter, packet sequence, connectivity, path,
server response time, and download time can be monitored within the Cisco
device and stored in both CLI and SNMP MIBs. The packets have configurable IP
and application layer options such as a source and destination IP address, User
Datagram Protocol (UDP)/TCP port numbers, a type of service (ToS) byte
(including Differentiated Services Code Point [DSCP] and IP prefix bits), a
Virtual Private Network (VPN) routing/forwarding instance (VRF), and a URL web
Because Cisco NX-OS
IP SLAs are accessible using SNMP, it also can be used by performance
monitoring applications such as CiscoWorks Internetwork Performance Monitor
(IPM) and other third-party, Cisco partner performance management products.
based on the data gathered by a Cisco NX-OS IP SLAs operation allow the switch
to receive alerts when performance drops below a specified level and when
problems are corrected. Cisco NX-OS IP SLAs use the Cisco RTTMON MIB for
interaction between external Network Management System (NMS) applications and
the Cisco NX-OS IP SLAs operations running on the Cisco devices. For a complete
description of the object variables referenced by the Cisco NX-OS IP SLAs
feature, see the text of the CISCO-RTTMON-MIB.my file, available from the Cisco