widespread distribution of manufacturing industry as well as mining industry has led to a demand for Frame Relay services in a wider //broader coverage not limited only in big cities but also in remote areas where telecommunication infrastructure not yet available.
This paper describes how satellite communication in general and VSAT technology in particular will lead to frame Relay wider distribution across Indonesia.
BACKGROUND
Frame Relay by it’s nature was designed to work in an environment where link quality surpass that old telephone line then telecommunication providers sought ways to overcame that draw back.
To enhance network reliability by providing alternate route /diversity to terrestrial using VSAT link in case of failure and link degradation for frame relay nodes have been deployed in certain areas where majority customers asked for high network availability.
VSAT AS TRUNK BETWEEN FRAME RELAY NODE
FIG 1 Fiber Interconnected F Relay Network
This situation will not be available in small city with less business activity so the idea to spread this service for remote areas is by utilizing VSAT solution.
Antenna deployment generally starting with a 2.4-m dish and 10W RF power will be adequate to support Frame Relay node from 64kbps to 512kbps.
Customers who previously subscribe other WAN service will start with CIR 32kbps and access speed 64kbps. This is adequate to handle LAN to LAN traffic with moderate traffic and business expand there will be enough capacity to increase speed and CIR that this trunk can carried. If we look fig 2 its obvious that by selecting a 4.5 m antenna at the main ring site and redundant outdoor configuration will provide ample capacity to anticipate customer growth.
This flexibility in terms of development is one of the key that VSAT offered and eventually that will support the idea of provide service at remote areas with minimal start up capacity and investment. But for areas where market prediction will grow faster based on number of customers using data communication antenna diameter 3.8 m is a good start up to accommodate quick customer growth and also to provide alternate route for 2M fiber link.
For instance for eastern area Indonesia 64kbps using 2.4 antenna is interconnected to main nodes in Java with startup capacity 16 port capacity from 19.2 to 38.4kbps access speed. Antenna reconfiguration as bandwidth increase or customer traffic increase can be easily perform with minimum network downtime. Due to the fact that satellite contribute delay to the network a teleport type Antenna at Frame Relay main nodes was set up minimize inter node traversing/delay time. Teleport using larger antenna size and more RF power to accommodate more VSAT as a point of entry to Frame Relay ‘cloud’.
DOWNSIZING NODE CAPACITY ACCORDING TO USER NEEDS
Initial market prediction for frame relay services has forced the deployment of nodes which has trunk capacity in 2 Mbps . This capacity was predicted with the assumption that customers traffic will be in high speed mode for example 64k and 128kbps.
But the economic downturn has made customers to lower their requirement and instead of using 64k choose 19.2 CIR as they thruput choice. Along with that, number of customers intended to lease the capacity is not as expected and eventually there’ll be idle capacity in some areas with 2 Mbps start up link.
With VSAT solution this 2Mbp link is converted from fiber based link to satellite solution with capacity close to CIR leased by that customers and this will avoid trunk inefficiency in that specific nodes.
This practical solution is applied in many areas where market demand is foreseen to be flat or stay as it is.
VSAT FRAME RELAY TO REACH REMOTE AREAS
For manufacturing and mining business sector where site/location choosed hardly possible to justify the installation of terrestrial frame relay than the only choice is to install VSAT Frame Relay using 1.8 m antenna at remote with 5W RF power. This is possible by having that remote connected to HUB site of 7.2 m antenna .
Baseband section will be interconnected with Frame Relay gateway that is collocated at the HUB site and eventually that specific remote has already connected with Frame Relay ‘cloud’ and available for any PVC connection elsewhere around the fiber ring Frame relay network.
One of the drawbacks though from this configuration that further traffic expansion from this remote site will be hard to justify due to the antenna size which is intended for link up to 64kbps. The possible solution to this case is by deploying small nodes and total earth station reconfiguration from a customer premises solution to exchange type solution.
BACK UP RING TO INCREASE NETWORK AVAILABILITY
New services instead of the new technology offered also must bring with it network reliability to make sure transformation from old services happen smoothly.
Public Frame Relay services as well should cater for this problem and geographic diversity configuration is the most suitable for that purpose.
If we examine configuration below that routing to point B can be either go through totally fiber link or in case of failure the system will automatically routed the traffic through VSAT link. This will guarantee link availability and keep the service to the customer but thing we have to concern in this case that traffic from A to B will experience a delay from 100ms to 560 ms .
Even though on the VSAT side we can upgrade the link up to 2 Mbps chances that the inherit satellite will eventually cause 5 times delay.
For this back up ring solution VSAT configuration will be based on teleport type in which at the central site a 5m or a 7m antenna will be deployed while at the remote Frame Relay node a 2.4 antenna (5-10W )/single system configuration is enough as start up . Again this calculation will depend on number of Frame Relay nodes that this link have to support for any fiber link failure.
Other things we have to concern is application response time such as SNA real time application which is very sensitive to link delay. In this case customer should configure a larger time out ( T1 ) to anticipate network round trip delay due to failure in fiber link and rerouting through VSAT link.
FIG 2 RING TYPE ROUTING
RESPONSE TIME ANALISYS AND APPLICATION REQUIREMENT
PING test is performed either from GB/main node or from collocated node. Provided table of test result and refer to the diagram and pinpoint number of nodes, transmission types used in between nodes.
Figure 3 illustrated response times of fiber based Frame relay network perform in term of round trip delay imposed by network for specific application.It clearly suggest that 20ms is the average response time packet round trip delay if number of nodes it traversed is less than three nodes. This is an ideal condition for application to perform well.
FIG-3 Response time for pure fiber network
In figure 4 further illustrated that additional nodes and less bandwidth deployed will add some delays in the network performance and eventually affect QoS.
FIG 4 Fiber network with extended nodes
The other possible configuration is ring Frame Relay network with regional HUB to accommodate traffic from Frame Relay nodes that have small number of customers.
Especially for regional with less reliable fiber backbone by terminating and distributing traffic from remote nodes will decrease the possibility of total failure compared to terminating with star configuration by using single HUB to terminate traffic.
The other aspect by routing the traffic from other satellite link will give benefit to network reliability. But delay issue emerge from this solution is exist and has to be carefully adjust to customers application timer parameters.
FIG 5 Regional HUB Frame relay
Application critical to network delay such as voice with maximum delay tolerable in an average of 125ms is not suitable if voice frames transported using frame relay with satellite link backbone. Alternative solution by adjusting customer’s router frame size is also not acceptable as well. Customers in remote areas usually start to subscribe frame relay services for data application such as on line and inter-branch application. Eventually as they find that capacity is still available on their circuit, customers ask for voice application and not realizing that traffic to it’s location actually provided by satellite.
CONCLUSION
VSAT as an alternative transmission media to interconnect Frame Relay nodes is a good solution for network expansion especially with its ability to start up in small capacity nodes . Besides that since Frame Relay technology demand low BERT link quality than a shift to VSAT is a good option even though delay which is inherit in satellite link is something that has to overcome by choosing the right application the customers can pass through the network.
Apart from that due to it’s nature of single hop than the consequences of traversing from many nodes in reaching the customers headquarters is a good nature of VSAT or satellite technology.
Further assessment of customer traffic profile will be able to find out either the traffic is symmetric or asymmetric and if that is the case than VSAT solution will be much intended due to its ability to provide asymmetric link.
With frame relay infrastructure deployed in Indonesia and with the support of satellite communication, proliferation of Internet as the way to interconnect worldwide is clearly seen. More than 80 % of dedicated Internet connection using frame relay as it’s backbone and more circuits are expected to use this infrastructure in 2000 for Internet connection due to it is available all over Indonesia and more cost effective compared digital leased line solution.
Considering Telkom-1 satellite launch success whereby it provide much better EIRP ( 3 dB increment compare to Palapa B2 R ) it will offer better link performance and therefore using satellite either as access for Frame Relay cloud network or trunk solution will bring great advantage for network reliability.
Source : The Pacific Telecommunication Council (PTC)
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