It’s Time for Internet QoS To Become Reality

Posted: 04/1999

It’s Time for Internet QoS To Become Reality
By Ashley Stephenson

Everyone agrees that business use of the Internet is a rapidly growing phenomenon. With
its lower cost and global availability, the Internet is emerging as a truly viable
alternative to private wide area networks (WANs), but it will rise to supremacy only if
Internet protocol (IP) can provide the quality of service (QoS) that new commercial
applications require. The challenge for Internet service providers (ISPs) is to be able to
fully leverage the Internet’s already enormous and growing infrastructure without
compromising performance and reliability. Today’s "best effort" IP is enough to
support casual web browsing, e-mail and early e-commerce applications but customers are
beginning to require more predictable QoS for applications such as mainstream e-commerce,
corporate intranets, virtual private networks (VPNs) and extranets.

It all starts with the ability for customers to classify and prioritize the QoS
requirements of their networking traffic. Service providers then must be able to map these
requirements into service levels that are guaranteed within their networks and also across
the public network backbone. With an emphasis on service level guarantees, this
increasingly dependable QoS will allow customers to grow beyond traditional wide area
services by using more robust Internet connections. This translates to new business
customers and higher revenues for providers that can deliver such improved services. QoS
for IP can be delivered over the Internet using current standards and technologies; the
reality is that service providers are starting to build services that support guaranteed,
end-to-end Internet QoS today using a combination of access controls and backbone
provisioning by:

* Defining QoS. Customers, service providers and the network itself must share a
common vocabulary that defines what QoS means, and must adhere to a means of moderating
QoS levels across the Internet.

* Implementing access QoS. Band-width control and traffic policing are critical
at the point where customer traffic enters the network. End-to-end QoS begins at the
customer premises and must be granular enough to differentiate the service requirements of
multiple traffic streams.

* Implementing backbone QoS. The network backbone administers QoS differently
than the access point of the network does. Instead of individual traffic streams, backbone
QoS works on aggregates of customer traffic. To support end-to-end service guarantees, the
backbone must provide enough transport and control to satisfy the overall service levels
promised to customers.

Two Internet Engineering Task Force (IETF) standards emerging for addressing IP QoS are
differentiated services (DiffServ) and multiprotocol label switching (MPLS). Although the
two are intended to help solve the same overall set of problems, they approach the QoS
challenge from different network perspectives.

DiffServ is a Layer 3 solution that addresses QoS requirements in a connectionless
environment. Its main purpose is to standardize a set of QoS building blocks from which
network providers can develop QoS-enhanced IP services. DiffServ QoS is implemented at the
network edge by access devices and then supported across the backbone by DiffServ-capable
routers. Because it operates purely at Layer 3, DiffServ can be deployed on any Layer 2
infrastructure. DiffServ and non-DiffServ routers and services can be mixed in the same
environment.

MPLS is a strategy for streamlining the backbone transport of IP packets across a Layer
3/Layer 2 network. Although it does involve QoS issues, that is not its main purpose. MPLS
currently is focused on improving Internet scalability through better traffic engineering.
MPLS will help service providers build backbone networks that better support QoS specific
traffic. It typically entails significant changes in the existing network architecture.
MPLS essentially is a hybrid of the network (Layer 3) and transport (Layer 2) structure,
and represents an entirely new way of building IP backbone networks.

DiffServ and MPLS are separate developments that can function independently. Neither
specification requires the other, but MPLS networks should be able to derive QoS status
from DiffServ traffic. The goal is that they can be used together as access (DiffServ) and
backbone (MPLS) counterparts.

In the near term, DiffServ may have more relevance. It tackles IP QoS head on, and it
provides mechanisms for interfacing access QoS and backbone QoS support in the network.
The specification is drafted, early implementations of the technology have proven stable
for more than half a year and standards-based products now are available. MPLS is not
expected to reach request for comment (RFC) status until sometime later this year, but
should become a major element of Internet backbone growth in 2000.

All indications point to 1999 as being the year QoS will become a reality on the
Internet. The market demand is growing, standards are progressing and technologies are
becoming more readily available every day. The time is now for service providers to offer
QoS services to enable customers to access the true power of the Internet.

Ashley Stephenson is chairman of Xedia Corp., Littleton, Mass. He can be reached at +1 978 952 6000.