Frame Relay is a link level data networking service that is particularly
well-suited to handling "bursty" traffic. It was designed primarily to
provide efficient LAN-to-LAN interconnection, but is also highly effective at
supporting other types of data such as SNA, and more recently, voice, video and
complete multimedia traffic.
Structurally, frame relay packets transmit data in much the same way as X.25,
but because of the widespread digital facilities and smarter end-devices, there
is no necessity for X.25 facilities such as error correction and flow control,
with the overheads that these incur. This means that frame relay technology
utilizes the robustness of today’s digital transmission media to obviate
transmission overheads, and still maintains the quality of the transmission by
relying on the smartness and intelligence of devices at the network ‘end-points’
Frame relay, by operating at Level 2 rather than Level 3, does not rely on
the wide area network to provide error correction. The intelligent CPE and
application software which use higher level protocols provide this error
correction at the end points. Consequently, the protocol requires much less
processing in the network switches and offers higher throughput rates than is
typically supportable with public X.25 services.
Step1: Frame Relay Technology
The frame relay protocol provides increased efficiency by allowing multiple
logical connections to take place over one physical access line into the
network. This provides significant savings over private lines by:
The frame relay links mentioned above are referred to as
Permanent Virtual Circuits (PVCs). Each PVC is a logically defined path through
the network that interconnects two end-points just as a private (leased) line
would, except that network bandwidth is not dedicated solely for the use of that
PVC. Bandwidth can be allocated dynamically "on demand", allowing a
user to increase its bandwidth, as needed. Because of this, it is necessary to
define a service parameter for data throughput to ensure that all users can both
take advantage of additional bandwidth when this is available, but also have a
set amount of throughput on which they can depend. This parameter is known as
the Committed Information Rate (CIR), and represents the minimum throughput
which the network will deliver on a PVC regardless of how busy the network is.
Data sent in excess of this rate is known as "excess data" or burst,
and the ability to deliver this will be determined by the overall network
traffic at the same instant.
The way a network handles excess data is as important as how
it handles committed data. If a network rejects significant proportions of
excess data, the overall performance on a PVC can be greatly reduced.
While most global service providers worldwide support traffic
burst for predefined slice of time (a few mili seconds or so), a few carriers
have designed their network to carry traffic bursts for much longer periods of
time depending on the network utilization during those times. Notable amongst
these is Global One, which has branded its committed throughput as Enhanced CIR
(E-CIR). E-CIR remains available to the user/customer for as long as the
bursting demands, depending on the network availability. The network doesn’t
automatically withdraw the burst support after pre-determined periods of time.
Step 2: Frame Relay Providers in India
It was in early 1998 that international frame relay services
were launched in India. Global One was the first international carrier to launch
international frame relay services in India. However, there are other players
besides Global One today, including Equent,Concert,TMI and C&W.
To comply with the regulatory framework, all these carriers
have partnered with VSNL to provide the services in India. All the international
frame relay service providers have commercial sharing arrangements on the port
at India end and PVC/CIR.
Step 3: Frame Relay Components
The individual components that comprise frame relay services
include the access line, the port and PVC. It is important to understand the
functionality of these components as they are the basis for implementing frame
relay service. The figure entitled "Frame Relay Components",
illustrates how these components fit into a frame relay network.
Access line: The access line is the physical connection
(leased line) between the frame relay service providers Point-of-Presence (PoP)
and the customer location. The access line speed must be equal to, or greater
than, the port speed.
Port: The port is the physical connection to a frame relay
switch. Each port is capable of supporting multiple PVCs. Proper sizing
(determining the speed) of the port is therefore, very important. In most of the
networks, each site only needs one port connection, even though many different
users, applications and protocol, may need network access.
In addition to taking into account the number of PVCs and CIR
speeds, service provider will advise customers on the speed ports that are
recommended for certain locations.
Permanent Virtual Circuit (PVC): PVC is the logical
connection between two frame relay ports. Each end of the PVC is defined by the
port address and a Data Link Connection Identifier (DLCI).
Frames are routed through the network via each PVC. The DLCI
is an address which is carried in the frame header. The DLCI identifies a
logical connection between the user and the local network access node. The DLCI
has local significance only and may change as the PVC is routed through the
network. Overall, DLCI addresses ensure that the integrity of the PVC is
maintained.
The service provider needs to assign each PVC a Committed
Information Rate (CIR). The CIR is the speed of transmission for a particular
logical connection.
Customer Premise Equipment (CPE): Frame relay service
requires that every customer location connected to the network, has two types of
equipment on its premise:
In India, DoT provides only leased line connectivity to the
PoP of the service provides, so the customer has to buy router and CSU/DSU from
the service providers or the local market. Mostly, VSNL provides the CSU/DSU for
international frame relay services, which has a partnership with all the
international service providers in India like Global One.
Step 4: Implementation of Frame Relay Services
Frame relay can be used for connecting the offices of an
organization for running any business.
Applications, like ERP, LAN-to-LAN connectivity for messaging
and other data transfer or for any specific customized application that an
organization is already using, which needs to talk to the mail/central server at
the HO or vice a versa.
Depending on the kind of application and the amount of data
transfer requirement, customers can decide on the CIR options like 16 K to 1 MB
and port speed up to 2 MB. For customers wanting to connect their HO to multiple
locations, they can go for a port with higher speed at HO, and then multiple PVC
between all the locations to the HO server.
Future of FR services
In future we can see a major development happening in Frame
Relay technology like:
-
Higher Access Speed: Looking at
the improvement in the telecom infrastructure and the fiber optic cable
deployment, in future, service providers will be able to offer higher access
speed of E1 and more as there will not be any last mile problem.
-
Shadow PVC: Major FR services
providers like Global One, have started offering shadow PVC as a part of the
product for companies running mission critical business applications. In
case the main PVC that you are working on is down due to international cable
fault or any other reason, the Shadow PVC (an alternate PVC is defined,
which is used when the main PVC is down) is used, and so, your operations
are not disturbed.
-
Classes of Services: Prioritize
your traffic internationally based on application needs, like Priority
class( High transfer priority for time-sensitive applications like SAP, SNA),
LAN class ( Normal transfer priority for volume-sensitive applications like
email) and Multimedia class ( highest transfer priority for real time
applications, high disgard priority, CIR 8k to 384k).
-
Lower Cost: As the infrastructure
is getting ready for higher bandwidth requirement, the cost per unit will go
down and so, the rates for Frame Relay services will also be reduced.
-
Improved SLAs: With a better
infrastructure, customers can expect improvement in the quality of services,
like last mile, and will thus, be able to sign an improved SLA (Service
Level Agreement).
-
Provide end to end Solution: For
customer convenience, major plays like Global One have already started
offering end-to-end transport solutions (router, loop, infrastructure etc).
Kamlesh Raval
marketing manager Global One India Pvt Ltd.
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