SEMINAR-GPRS2

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EXTENSION OF GPRSOVER OPTICAL NETWORKS : 

EXTENSION OF GPRSOVER OPTICAL NETWORKS

An Overview of the topics covered : 

An Overview of the topics covered The definition of GPRS Implementation of GPRS in the present scenario The need to extend GPRS over Optical Networks GPRS Architecture GPRS Roaming OVPN Architecture Extension of GPRS over Optical Networks Agent-Based OVPN model towards GPRS roaming

GPRS : 

GPRS General Packet Radio Service (GPRS) is a new service which provides packet radio access for users based on the Global System in Mobile Communications (GSM) technology It is an important step of mobile communications towards packet switching for mobile networks

Its Advantages : 

Its Advantages The development of GPRS enabled GSM operators to meet the growing demand of wireless packet data services over public packet networks, such as the Internet and corporate intranet The integration of GPRS with GSM not only revitalizes many existing wireless applications, such as email, messaging, information services, etc but also creates conditions for many other new applications It also brings continuous packet data connections to mobile users at a reasonable cost

Implementation of GPRS : 

Implementation of GPRS In the present scenario, leased lines or virtual private networks (VPNs) are used to interconnect GPRS support nodes A tendency now is to use the optical technology to transport data over public networks. Here dedicated optical channels or optical VPNs (OVPNs) are used to support GPRS over optical networks.

The problems faced when extending GPRS over optical networks are: : 

The problems faced when extending GPRS over optical networks are: In optical networks, the optical channels or OVPNs are normally stable over time This causes an obstacle in using OVPN to support GPRS because of the roaming of mobile terminals. A mobile user can roam anywhere and its GPRS access points to optical networks can change A model of dynamical OVPNs management is then needed to provide and reconfigure OVPNs when GPRS access points are changed

GPRS Architecture : 

GPRS Architecture GPRS has been designed as an extension of the existing GSM network infrastructure to offer wireless packet data services A number of new functional elements are therefore added to support the end to end transport of IP based packet data The two core network functions required are the Serving GPRS Support Node (SGSN) and the Gateway GPRS Support Node (GGSN). In addition there is a functional node called Packet Control Unit (PCU)

Slide 8: 

PCU MSC HLR SGSN GGSN Packet Data Networks BSS MS Other PLMN Gb Gn Gi Gp GPRS reference model Leased lines or VPNs GGSN Other PLMN

SGSN, GGSN and PCU : 

SGSN, GGSN and PCU The SGSN monitors the state of the mobile stations and track their movements within a given geographical area. It is also responsible for establishing and managing data connections between mobile users and the destination network The GGSN provides the attachment point between the GPRS domain and the external Packet Data Network (PDN), such as the Internet. Each external PDN is given a unique Access Point Name (APN) that is used by the mobile user to establish the connection to the destination network The PCU manages the transmission and reception of data to/from the mobile terminals. In addition it provides radio link layer functions, radio resource management etc

The Interfaces used in GPRS : 

The Interfaces used in GPRS Gn – It is used as a tunnel of data packets between the SGSN and GGSN. In case of handoff during an active session, it is also used for tunneling data packet from the old SGSN to the new SGSN of the mobile terminal Gi – It is added as the link between the GPRS network and the external PDN. All the packets to/from the supported PDN enter or leave the GPRS network through this interface Gb – It is added as the link between SGSN and PCU

GPRS Roaming : 

GPRS Roaming GPRS roaming enables subscribers to access their GPRS services while they are abroad or beyond the reach of their home mobile network It requires that a connection be made between GPRS operators so that subscribers can move from one network to another and yet still access their GPRS services GPRS roaming is based on bilateral relationships between individual GPRS operators. It becomes complex and expensive to maintain as the number of roaming partners increases. The GPRS Roaming Exchange (GRX) therefore is recommended for using GPRS roaming

Slide 12: 

GGSN #2 GGSN #1 Gp Interface Roaming partner #1 Roaming Partner #2 Visited PLMN Home PLMN GRX MS GPRS roaming based on GRX

GRX : 

GRX It is built on a private or public IP backbone and transports GPRS roaming traffic via the GPRS Tunneling Protocol between the visited and home Public Land Mobile Network (PLMN). A Gp interface is added to support roaming when a mobile terminal is traveling in a visited PLMN and its data packets are still handled by a GGSN in its home PLMN. The Gp interface is similar to the Gn interface except that an additional security is provided through external border gateways

GRX (contd) : 

GRX (contd) The GRX acts as a hub There is no need for a GPRS operator to establish a dedicated connection to each roaming partner, instead the GPRS operator establishes a connection with the GRX. This allows a faster implementation of new roaming relations and a rapid deployment time for new operators.

Slide 15: 

CE-3 CE-1 CE-2 PE-1 P PE-2 PE-3 Customer site #1 Customer site #2 Customer site #3 Optical Networks AC-1 AC-2 OC The reference model of OVPN

OVPN ARCHITECTURE : 

OVPN ARCHITECTURE It is composed of three components: Customer edge (CE) devices which are on customer sites and which attach to provider networks Provider edge (PE) devices which belong to provider networks and which connect to customer sites Provider (P) devices, which are in the provider networks and which are connected to PE devices and other P devices The OVPN architecture is based on PE devices, so the OVPN functions are located only on PE and P devices, but transparent with CE devices

Slide 17: 

Access Circuit (AC) is the link between a CE device and a PE device and it can be a optical or non optical link depending on the kinds of its terminals (CE and PE) In the core optical network, the connections between the PE (and/or P) devices are optical channels (OCs) The concatenation of an AC, an OC and another AC forms a CE-CE completed connection called the Virtual Circuit (VC) When passing through optical networks, many VCs can be multiplexed into an OC in such way to exploit its bandwidth at the maximum

Slide 18: 

GGSN-3 GGSN-1 GGSN-2 PE-1 P PE-2 PE-3 GPRS Partner #1 GPRS Partner #2 GPRS Partner #3 Optical Networks AC-1 AC-2 OC The reference model of GPRS over optical networks

Extension of GPRS over Optical Networks : 

Extension of GPRS over Optical Networks Here the GPRS partners play the role of customer sites and the edge GGSNs are CE devices As shown in the reference model, a packet radio channel of GPRS is mapped into a VC in the serving OVPN The role of PE devices are to establish tunnels through the core optical network, multiplex packet radio channels from GGSNs into tunnels, maintain the tunnels, and demultiplex the packet radio channels from the tunnels to GPRS partners

The problems encountered : 

The problems encountered Problems arise on how the GPRS roaming impacts on the management and maintenance of the serving OVPN and how the serving OVPN changes to adapt to the GPRS roaming Changes in the serving OVPN is caused by the changes of the access points of the GPRS that it supports. If changes of the packet radio channel do not make any change on the edge GGSNs, no change is required for the serving OVPN. Where as if some edge GGSNs are replaced by others, the serving OVPN must be reconfigured. The reconfiguration of serving OVPN normally requires a delay, which can cause considerable loss of data. To reduce this loss, predictions about possible changes for a GPRS before providing a serving OVPN are needed.

Prediction of changes of a serving OVPN : 

Prediction of changes of a serving OVPN The radio channels which can be used to transport packet data can be determined in advance. Also the edge GGSNs used as access points (CE devices) of an OVPN can be determined A simple solution to avoid reconfiguration of the serving OVPN is to interconnect all the these edge GGSNs by only one OVPN This solution requires many network resources because it exists on some connections which are never used. But the advantage being the robustness it offers

Slide 22: 

Set of edge GGSNs 6 5 1 2 3 4 6 5 1 4 2 3 Interconnecting all edge GGSNs by one OVPN

Slide 23: 

Another solution is to divide the set of the edge GGSNs into groups based on packet radio channels supported by each edge GGSN. This way, each OVPN is dedicated to support a group of packet radio channels. If switching is established between packet radio channels in a same group, no change is required for the serving OVPN. But if the current GPRS switches its packets from a current channel to another in another group, the OVPN providing system simply switches these packets from the current serving OVPN to another. This method demands a smaller delay to switch the serving OVPN and it saves network resources. This method can fail if the needed resources for establishing the new OVPN are unavailable.

Slide 24: 

Set of edge GGSNs 6 5 1 2 3 4 6 5 1 4 6 4 2 3 Group-1 Channels 1 and 2 Group-2 Channels 3,4 and 5 Classifying edge GGSNs into groups

Reconfiguration of a serving OVPN : 

Reconfiguration of a serving OVPN GPRS roaming can require some changes in topology of its serving OVPN or a new OVPN needs to be established. There are many possible ways to reconfigure a serving OVPN. Lets see this with the help of an example.

Slide 26: 

CE #3 CE #1 CE #2 PE-1 P PE-2 PE-3 GGSN #1 GGSN #2 GGSN #3 OVPN-1 OVPN-2 Public data networks An example of OVPN reconfiguration

Agent based OVPN model towards GPRS Roaming : 

Agent based OVPN model towards GPRS Roaming The efficiency of dynamically providing an OVPN along with GPRS roaming depends on the knowledge exchanging capacity between PE devices and the individual decision making capacity of each node In order to implement these capacities a multi-agent technology has been integrated into the OVPN model Three types of agents have been defined namely controlling agent, grooming agent and the OVPN agent

Slide 28: 

Control agent OVPN Agent-1 OVPN Agent-3 Grooming agent OVPN Agent-2 OVPN Agent-N New- remove Mux- demux Interaction of agents in OVPN component

Controlling Agent : 

Controlling Agent There is one controlling agent on each PE device Its role is to create, maintain and remove OVPN agents A controlling agent has a table of OVPN agents which contains information about the participation of the current PE device in different OVPNs

Slide 30: 

Table of OVPN agents Sensors Has OVPN Agent existed? Has OVPN Agent existed? Control Agent E f f e c t o r s New error remove New OVPN agent Remove an OVPN agent Yes No No Yes Internal structure of the control agent

Grooming Agent : 

Grooming Agent When passing through the core optical network, VCs are groomed into OCs The optimization of the grooming aims to efficiently exploit the bandwidth of OCs and reduce the network cost. The grooming agent is defined for this purpose Based on the status of VCs needed to groom and the status of OCs in the table of available OCs, the grooming agent will choose appropriate strategies to run the grooming. These strategies are also dynamic to adapt to changes of VCs in a serving OVPN

Slide 32: 

Table of Available OCs Groom of VCs Into OCs E f f e c t o r s Sensors Are there Available OCs? Yes No Update Available OCs VCs groomed Position of each VC in OCs Require new OCs Grooming agent Internal structure of grooming agent

OVPN Agent : 

OVPN Agent An OVPN agent establishes, manages and maintains Virtual Circuits (VCs) To perform these operations, internal components are defined namely (1) AC allocation unit (2) The Optical Channel location unit (3) The Virtual Circuit maintenance unit

Slide 34: 

The AC allocation unit finds pairs of appropriate ACs (in terms of QoS and transport technique) for a given VC and reserves them The OC location unit searches and locates an OC corresponding to the allocated pair of ACs The VC maintenance unit checks and maintains the existing VCs Each OVPN agent has a table of OVPN components and it also contains the information about available resources in these OVPN components. The functional units will access to this table for speeding up their operations

Slide 35: 

Table of OVPN components AC allocation unit OC allocation unit VC maintenance unit Sensors E f f e c t o r s Available ACs Required ACs Available OCs VC status OK or Not Available ACs? VC status? OVPN agent Internal structure of the OVPN agent

CONCLUSION : 

CONCLUSION The extension of GPRS over public data networks is therefore needed in order to achieve high bandwidths and greater scalability This seminar thus intends to propose a solution to this extension by using optical VPNs to interconnect GPRS support nodes Since GPRS is used to carry mobile communications, the OVPNs must be dynamic and flexible. The reconfiguration of serving OVPN using intelligent agent technology has been presented High bandwidths are needed on public data networks and hence optical transport technology is deployed and used

Slide 37: 

Thank You