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Frame
relay
Frame
your data
There
are numerous technology options like leased lines, VSAT
links or VPNs that offer high-speed, reliable and secure
connectivity between multiple geographically distinct locations.
Ivano Rondelli, Country Director, Tele Media International
(TMI), suggests you use Frame Relay technology and have
the service provider sweat it out, managing the backbone.
He also tells us how the technology enables your enterprise
to make use of its cost-effectiveness, reduce overheads,
and increase ease-of-use. by Soutiman Das Gupta
What
are the limitations of VSATs (Very Small Aperture Terminals),
leased lines and VPNs (Virtual Private Networks)?
VSATs are characterized by very high latency due to a long
path that the signal has to cross to reach its destination.
The VSAT service provider may have promised high bandwidth
with reliable connectivity, but the actual performance depends
on transponder space and weather conditions. Leased lines
have its fair share of downtime and bottlenecks. In case
of IPLCs (International Private Leased Circuit), when data
passes from one provider to another provider's gateway,
there're chances of signal loss and outage. Each provider
will ping-pong responsibilities delaying the network recovery.
VPNs do not provide any guarantee of throughput amounts.
And since there's strong encryption on both sides, transmission
is slow. It requires very expensive equipment which also
needs well-trained technical staff to manage the service.
In that case, what wide-area connectivity option does
an enterprise have?
You can consider the option of using Frame Relay technology
backbone to transmit your data and voice. Frame Relay is
a popular service and technology used to link distant LANs
and networks (see box for a detailed explanation). The Frame
Relay WAN (Wide Area Network) backbone connects LAN switches,
bridges, and routers to nodes that function as Frame Relay
end points or PoPs (Point of Presence). Data can be transferred
at usual speeds of 64 to 128 Kbps, and one can go for a
maximum throughput of 2 Mbps.
Enterprises that have LANs scattered globally can be interconnected
using PVCs. A PVC (Permanent Virtual Circuit) is a point-to-point
connection established and defined during the start of the
service. These also operate at speeds between 64 Kbps and
2 Mbps.
What are the advantages of a Frame Relay-based WAN backbone?
Frame Relay technology offers many inherent advantages
to an enterprise user and is a strong contender among competing
technologies for connecting corporate LANs. It scores over
other technologies like IPLCs, VSATs and VPNs on counts
of lower cost of ownership, well established standards and
easy interfaces that allow plug-and-play service implementation,
interoperability with a large variety of protocols, network
scalability and disaster recovery.
At the time of signing up for services with a service provider,
a user can decide on a CIR (Committed Information Rate)
and port speed. The CIR is a pledge on the part of the service
provider to provide a certain amount of transmission capacity.
And if the company needs more bandwidth, it can simply call
the service provider and request allocation of additional
bandwidth or ports.
Frame Relay transmission is simple because it operates on
the thumb rule, 'If a frame has a problem, discard it!’
This makes the job to control traffic congestion and handle
corrupt frames very efficient and admirable. In such cases
the faulty frames will be discarded and normal data transmission
can resume. Do note that different service providers implement
signaling mechanisms in different ways.
How does the customer connect to a service provider at
his end?
The service provider will have its PoPs (Point of Presence)
scattered worldwide, which has backbone switches and routers.
Each PoP is connected to one or more PoPs in order to build
a redundant network.
A hardware device called FRAD (Frame Relay Access Device)
is required at the customer's location to access the network.
A router can act as a FRAD, and actually it is the most
widely used customer access device. The FRAD connects to
a port on a Frame Relay switch in the PoP using an interface
called UNI (User-to-Network Interface). This line or port
can typically provide bandwidth in multiples of 64 Kbps.
The entire traffic for each customer generally travels through
the same port.
Why will an enterprise prefer this service to other options?
A big advantage of Frame Relay is its cost-effectiveness
compared to leased lines and IPLCs. Frame Relay service
providers take care and manage the entire service end-to-end.
Maintenance of the backbone, backing up data, and disaster
recovery can sometimes also be looked after by the provider.
Leased line service providers can't do this.
The performance standards are generally high and connectivity
more reliable than other options. PoPs are connected in
a mesh, and if one breaks down; the geographically nearest
PoP can take over. The network can introduce a number of
features like congestion management, change management,
and bandwidth scalability. It can support multiple protocols
and allow a smooth migration to ATM services in future.
A customer can use VoFR (Voice over Frame Relay) to transport
voice between its locations. It also allows Web-based traffic
and performance reports and the service provider can offer
easier billing options.
Bandwidth on a single connection is limited to 2 Mbps.
What happens when the enterprise needs more?
When an organization needs more than 2 Mbps, it can
use second PVC and more that will branch out from within
the access line. PVCs in their full capacity can handle
peak hour demands, traffic bursts, and bandwidth-intensive
applications like video conferencing. Each customer's CIR
can be guaranteed and spare bandwidth made available to
prevent any congestion on the network.
TMI
TMI (Tele Media International) Limited is a wholly
owned subsidiary of Telecom Italia Group. It's the sixth
largest telecommunications operator in the world. It started
operations in 1982 and has been in India since 1994 in partnership
with VSNL. It has 130 PoPs in 44 countries and is one of
the largest private digital networks in the world.
The company's backbone connects the 44 countries uses Cisco/Stratacom
for ATM, Frame Relay, IP and messaging services, Newbridge
for the transport layer and Ericsson for Intelligent Voice
services. In India, the company only provides Frame Relay
services. Other services are expected to be launched soon.
You can contact Ivano Rondelli at: TMI India, 909-912, Maker
Chambers V, Nariman Point, Mumbai - 400 021,
Tel. 022-282 4606, Fax 022-282 4590, Web: www.tminet.net
Frame
Relay all the way
Frame
Relay is a high-speed packet switching protocol used in
WANs that can provide bandwidth up to 45 Mbps. It operates
at the physical and data link layers of the OSI reference
model and is popular for connecting LANs across large distances.
Frame Relay transmission is much faster than a X.25 network
which was the first packet-switching WAN standard. It's
mostly used to route LAN protocols like IPX or TCP/IP and
can also carry asynchronous traffic, voice, and SNA (Systems
Network Architecture IBM's mainframe network standards).
Frame Relay provides permanent and switched logical connections,
known as PVCs (Permanent Virtual Circuits) and SVC (Switched
Virtual Circuits). These are logical connections provisioned
ahead of time. The connections are identified by a DLCI
(Data Link Connection Identifier) number that is significant
to the local Frame Relay switch.
Frame Relay is cost effective mostly because the network
buffering requirements are carefully optimized. It’s
also much faster than X.25.
The last 2 bytes of the frame are always generated by a
CRC (Cyclic Redundancy Check) of the rest of bytes between
the flags. CRC is an error checking technique that can ensure
the accuracy of transmitting digital data. The remaining
components of the frame contain the user data.
Soutiman
Das Gupta can be reached at soutimand@networkmagazineindia.co
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