Implementing QoS Solutions In Enterprise
BY HENRY DEWING AND
Lately, weï¿½ve heard that voice mail systems from Atlanta to Anchorage
are overloaded with messages from IT and voice vendors offering VoIP
solutions. In todayï¿½s tightened economy, vendors are searching for
additional sales to make their quotas and trying to convince enterprises
that implementing a VoIP offering will help the enterpriseï¿½s bottom line.
Some vendors concentrate on the financial return of implementing the system,
while others emphasize the new features VoIP brings. In fact, new features
may no longer be unique once a solution is carried from planning to
implementation. IT managers must carefully evaluate the offerings,
considering what developments may occur in the short term future, and select
a solution that satisfies the enterpriseï¿½s business models and provides a
return on investment (ROI.) A vendorï¿½s claims will not materialize if the
vendor cannot provide guidance toward implementation of a system that
reliably delivers VoIP service over those spiffy new IP phones.
Network managers must understand that implementing VoIP will affect how
business is done on both the voice and data sides. Legacy equipment,
including routers and switches, must be properly configured to accommodate
voice and QoS. Hubs, which cannot employ packet classification to
discriminate between traffic, should be avoided in a QoS environment. QoS is
as important to VoIP as 911 access is to traditional voice networks and
security is to traditional data networks. For example, an end-to-end (E2E)
QoS strategy sets up each component of the system to deliver the dial tone
that users are accustomed to hearing even when the building loses power.
A company in the IT industry responded to the voice mail messages VoIP
vendors had been leaving them and selected a reputable IP vendor for its
solution. (This software company is located in California but prefers not to
be named.) The organization listened to the vendor about QoS strategies and
implemented them on their routers and policy servers. The companyï¿½s IT
experience made it ideally suited to turn up a cutting edge converged
communications solution. After the implementation, the enterprise network
manager was surprised to find that the system could not achieve reliable
results -- a percentage of the calls had ï¿½bad connectionsï¿½ with
conversations getting clipped regularly. The first word of a sentence was
occasionally lost, which resulted in halting, somewhat stilted conversation
that adversely affected the end users. Management found this level of
functionality unacceptable and decided to question the entire
implementation. After several heated meetings and a second network study,
the vendor realized that the company was not using a loop-free layer 2
topology, which caused temporary Spanning Tree Protocol-induced network
outages. Despite the vendorï¿½s earlier recommendation to the contrary, the
company had not changed this network configuration because the IT staff had
been wedded to it for its fast connections for data traffic and had
mistakenly assumed it would be great for voice, too.
As this example demonstrates, the need to manage traffic intelligently
across the entire infrastructure is especially important in the VoIP
environment. To achieve efficient and effective traffic management, network
managers need to educate themselves about QoS options. Enterprise network
managers in particular need to be proactive in seeking answers to QoS
questions in order to assess vendorsï¿½ offerings. Many of them are highly
complex so network managers may not have time to address all of the
potential solutions, but it is important to understand the basics of the
tools available and what might be appropriate for their network size and
Unfortunately, end users sometimes relegate QoS to the domain of the
carrier. In fact, recent editions of Newtonï¿½s Telecom Dictionary begin the
definition of QoS as ï¿½the measure of the telephone service quality
provided to a subscriber,ï¿½ with measurements such as volume and length of
time until dial tone is achieved. However, QoS has evolved along with the
convergence of networks and now encompasses additional considerations such
as packet loss.
Intel commissioned research of more than 300 organizations and the results
demonstrated that QoS is a most-recognized but least-understood aspect of
network management. The research revealed that users plan to rely on vendors
or consultants to develop a QoS strategy. These relationships will be
helpful to IT managers, but they must secure an understanding of QoS to be
able to select vendors or consultants.
QoS is a system-wide solution involving hardware, software, and network
management that should be viewed from the PSTN to the desktop. It comprises
the mechanisms that give network managers the ability to control the mix of
bandwidth, delay, variances in delay (jitter), and packet loss in the
network. Consistency in how the various switches and routers define
parameters and service level agreements is required. Running QoS over only
the WAN segment or only the LAN segment of a network will not ensure E2E
coverage and will not eliminate all potential congestion.
Adopt A System-Wide, E2E Plan
Enterprises have evolved their network architectures from separate networks to consolidated and tiered network designs, thereby creating
multiple points of convergence and speed mismatches. For example, a speed
mismatch will occur in a LAN-to-WAN gateway where 100 Mbps Fast Ethernet
feeds into a slower T1 or E1 trunk. QoS should entail a method of allocating
resources in the network at multiple points of convergence so that data gets to its
destination quickly and consistently.
A QoS strategy must be conceived before the first IP phone or gateway is
installed. A rigorous planning and design process to ensure feasibility up
front will avoid headaches and expenses down the road. Network managers
should take into account the size and number of sites and the expected VoIP
traffic (and other delay sensitive streams like video and audio). They
should also consider whether IP phones are powered directly over the LAN
from the Ethernet switch, and whether or not the gateway allows for
automatic fallback to PSTN circuits in the event of quality degradation.
This strategy must be collaboratively determined, followed during the
implementation and tracked with on-going surveillance and fine tuning.
Whether IT professionals maintain their own infrastructure or pay someone
else to do it, they must ensure that on-going performance is monitored and
that the network is tuned and optimized based on the current traffic
Screen For Inherent Bias
Of course, implementations will vary in scope. The size of the
implementation is important; however, research reveals that understanding
whether staff is more proficient with voice or data applications and systems
could become the key success factor when blending both types of traffic into
one system. Staff background is important because their area of
specialization will influence their implementation strategies. The Spanning
Tree Protocol that nearly killed the VoIP implementation discussed earlier
was the legacy of an IT professional more experienced in data networks.
Generally speaking, voice-centric managers will understand and design an
infrastructure that is highly reliable and capable of handling VoIP without
issue, avoiding topologies that drop packets or provide all packets equal
access to network bandwidth. On the other hand, it is generally the
data-centric managers who are comfortable controlling and tuning the
parameters on the servers, routers, and other network elements that
implement the QoS strategy. The goal for implementing QoS must be a single,
ubiquitous strategy that considers the topology and each of the systems
within the network E2E. Both a strategy designed for your particular
environment and a highly available transport network are necessary to
deliver reliable VoIP, but neither is sufficient by itself.
To aid network managers, we provide some observations below regarding QoS
implementation. To ensure success, IT professionals will want to consider
all aspects of the project -- planning, design, implementation, and
operation (known as PDIO) -- and seek out expertise where needed.
Begin With Packet Classification
Even modestly sized networks can have multiple network devices, such as
Ethernet switches, Frame Relay switches, routers, ATM switches, and Ethernet
hubs (which should be avoided in VoIP implementations) between the client
and the server. Network managers may be tempted to just ï¿½throw more
bandwidthï¿½ at their problems, but increasing bandwidth wonï¿½t guarantee
that traffic will always flow smoothly.
A more proactive tactic to implementing QoS is necessary to reliably deliver
the level of service your VoIP clients will expect. A simple IP packet
prioritization scheme is the place to start. This requires, of course,
enterprise switches that include packet marking -- capabilities that may
not be available on low end, less expensive switches. Frame headers can be
marked with a Class of Service (CoS) at layer 2 using IEEE 802.1q and 802.1p
specifications. At layer 3, packet headers can be marked with a Type of
Service (ToS) using the IP Precedence or Differentiated Service Code Points
In dealing with the vendors that will inevitably come knocking, network
managers should bear in mind that each vendor adds enhancements and
optimizations that may not be interoperable, and if the QoS strategy you
implement is not interoperable across all network elements, then it may not
deliver reliable, deterministic VoIP service.
IT managers also need to know that adding classification will introduce
delays in routing traffic. This additional function imposes a penalty on the
routerï¿½s performance in terms of latency and administrative overload.
Wire-speed devices are required to deliver the performance characteristics
required by voice and video traffic, in terms of delay, jitter, and packet
Simplify With A Policy Server
Companies today are working hard to get more from existing resources. QoS
can assist them in achieving the desired performance for business-critical
applications while avoiding expensive link upgrades. QoS will certainly ease
the burden of managing a network if the enterprise is adopting widespread
VoIP or streaming video, and it will also assist with managing data security
and ensuring employeesï¿½ appropriate use of network resources.
Thereï¿½s no such thing as infinite bandwidth; therefore, network managers
must control which applications get bandwidth first. Unused bandwidth is a
true shame. If one application is inactive, the device should reallocate the
bandwidth for other applications. To achieve reallocation, there must be
consistency in how various switches and routers define parameters. Ideally,
10-12 policies should manage the entire network. IT managers should take
advantage of the trend toward simple implementation and ï¿½push-button QoSï¿½
and be certain to select an option that will scale with network needs.
As mentioned earlier, the QoS strategy should entail the PDIO methodology of
planning, designing, implementing, and operating a ubiquitous scheme. To
begin executing this type of strategy, network managers will want to examine
several areas of importance.
Here are a few to consider:
Traffic Discovery: Analyze which applications are using bandwidth,
considering both inbound and outbound flows. Keep in mind that the service
quality is only as strong as the weakest link. Here is an example
illustrating the impact on data traffic going over the Internet. One
enterprise of about 250 users, many of them young and Web-savvy, undertook a
one-week study of its traffic using an outside vendor. This organization
found that non-critical applications, such as Napster, Real, and Winmedia,
were using over 25 percent of the available bandwidth and crowding out
mission-critical traffic such as hosted Web sites and e-mail. As a result,
on the WAN, application response deteriorated at critical work times and
network efficiency degraded during peak traffic times. The organization
decided to move forward with a QoS strategy.
Prioritization: Determine which applications are business critical and
require protection, considering all applications that are competing for
network resources. Interdepartmental collaboration is required to determine
configurations that provide the proper resources to the proper applications
without harming others. The cooperation of both voice and data teams in
concert with end user requirements will be required to achieve the
ubiquitous strategy that is so essential to successful management of QoS.
The organization mentioned above determined a plan to throttle back on
Napster, Real and Winmedia to create more space for hosted Web sites and
e-mail. It also reminded employees that the ï¿½entertainmentï¿½ use of the
network needed to be curtailed in favor of the business critical
Analysis: Understand the characteristic of the applications to be protected
with an understanding of whether they are sensitive to latency or packet
loss or are ï¿½aggressiveï¿½ bandwidth hogs.
Class Creation: Create a policy to mark each class of traffic using
differentiated services control point of IP precedence as it comes into the
router on the ingress interface.
Progression: Work from the network element closest to the traffic toward the
core, applying markings on the ingress interface of the router.
Policy: Use the markings to build a policy and classify traffic on the rest
of the network segments, keeping it simple by using no more than four
Application: Decide if the policy needs to be applied in one or both
directions -- applying in both directions is recommended.
Monitor Effects: Revisit the issues to ensure that the desired effects were
achieved. The organization described earlier found that it improved
performance of hosted Web sites (over three times faster), e-mail (not
peaking as much, improved efficiency) and outbound FTP performance. Overall,
the results showed more predictable response times for Web sites and
improved overall network efficiency.
Include The Carrier For E2E
Network managers should keep in mind that controlling the outbound traffic
from an enterprise solves half the problem. Prioritization back into the
network is also needed. Traffic prioritization across public networks is
also needed to ensure true E2E quality of service -- which should be every
enterprise network managerï¿½s goal.
Carriers and ISPs are evolving toward providing corporate customers with
better service quality, at a premium. Although upgrade plans may have slowed
after the disappearance of so many CLECs, some carriers and ISPs are
investing to make QoS available as a service enterprise IT managers can buy.
Given trends such as application service providers (ASPs) and e-commerce,
enterprises are conducting more business over the public network, and thus
becoming more closely tied to its performance. Enterprises are looking for
high reliability, like the voice dial tone they are accustomed to with
voice, from ISPs. Service providers offering quality assurances for E2E
traffic will gain more business for the enterprise going forward.
With the advent of VoIP, many service providers that traditionally offer
data-only services (such as frame relay) can now compete with local exchange
carriers in offering VoIP-enabled enterprise customers access to the PSTN.
Convergence in the service provider and enterprise spaces has created a
market for integrated services that compete with traditional voice-only and
New offerings based on the multiprotocol label switching standard (MPLS) are
emerging that will recognize, label, and prioritize IP traffic. MPLS enables
network managers to control the packetsï¿½ journey to ensure they reach
their destinations quickly and successfully. The MPLS Forum recently
estimated that as many as 50 service providers either use MPLS in their core
networks or are offering multiple classes of bandwidth service (e.g.,
silver, gold, platinum) to customers. Eventually, IT managers will purchase
these services from their carriers or ISPs.
Choose A Solid Team
IT professionals should consider a solid planning and design partner during
the QoS process. Experience shows that successful implementations begin
there. In-house staff may need the support of consultants and partners who
have expertise in VoIP and QoS and wonï¿½t be bogged down with technical
details. Network managers should look to consultancies or certified
resellers of VoIP whose staff has achieved various certifications. Regional
certified resellers and national consultancies would be qualified partners.
IT managers who understand QoS will be well positioned to manage an
outsourced project. Competent people designing and tending to QoS will make
the difference in the success and quality of the converged network.
Network managers who employ the PDIO strategy and understand the effort to
deploy QoS will be well positioned to work with partners and vendors,
helping contribute to a healthy bottom line for the enterprise.
Henry Dewing is director of enterprise market development at Intel
Corporation. Stan Potter is business development manager with Cisco Systems,
Inc. TIA is a leading trade association serving the communications and
information technology industry, with proven strengths in market
development, trade shows, domestic and international advocacy, standards
development and enabling e-business. Through its worldwide activities, the
association facilitates business development opportunities and a competitive
market environment. Visit them online at www.tiaonline.org.
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