IP FUNDAMENTALS FOR GPRS

SUMIT SINGH

What is GPRS?

General Packet Radio Service is a radio technology for GSM networks that adds packet-switching protocols, shorter set-up time for ISP connections, and offer the possibility to charge by amount of data sent rather than connect time.

GPRS promises to support flexible data transmission rates typically up to 20 or 30 Kbps (with a theoretical maximum of 171.2 Kbps), as well as continuous connection to the network.

A 2.5G enhancement to GSM, GPRS is the most significant step towards 3G, needing similar business model, and service and network architectures.

Why not GSM for Packet Switching?

Inefficient use of the radio interface resources.

The call establishment time is too long

Download takes too long.

Only text SMS is supported

GSM is too expensive for serving in the Internet and sometimes the user had to pay for a connection for which he didn’t get any data at all (data losses).

Why GPRS?

Efficient utilization of radio resources where in a channel can be shared by multiple user.

User pays for the volume of data transmitted.

GPRS Architecture

GPRS Architecture

Network Elements in GPRS

Packet Control Unit (PCU) Serving GPRS Support Node (SGSN): The MSC of

the GPRS network Gateway GPRS Support Node (GGSN): Gateway to

external networks Border Gateway (BG): Gateway to other PLMN

Network Elements in GPRS

Intra-PLMN backbone: an IP based network inter-connecting all the GPRS elements

Charging Gateway (CG) Legal Interception Gateway (LIG) Domain Name System (DNS) Firewalls: Used for security reasons wherever a

connection to an external network is required.

GPRS Architecture

What is IP?

IP stands for Internet Protocol. It specifies the format of packets, also called

datagrams, and the addressing scheme. IP by itself is something like the postal system. It

allows you to address a package and drop it in the system, but there’s no direct link between you and the recipient.

What is TCP/IP?

IP when combined with a higher- level protocol called Transport Control Protocol (TCP) enables to establishes a virtual connection between a destination and a source.

The virtual connection so formed with the combination of TCP and IP ( and hence TCP/IP), enables the two hosts to send messages back and forth for a period of time.

IP Address

Identifies host uniquely on a TCP/IP network. Consist of 32 bits arranged in 4 octets. Can be represented in decimal notation as A.B.C.D

where A,B,C,D can be any decimal number between 0 to 255.

Overall 232 = 4295 million IP addresses IP address consist of two parts:

Network Id and Host Id Subnet Mask identifies the Net Id and Host Id. Internet Assigned Number Authority (IANA) assigns

IP Addresses to companies

Public & Private IP Address

Public IP addresses are range of IP addresses recognised by Internet for routing data traffic.

Private IP addresses are range of IP addresses used to create separate islands of network following same IP schema.

The pool of Private IP addresses are:From 10.0.0.0 to 10.255.255.255From 172.16.0.0 to 172.31.255.255From 192.168.0.0 to 192.168.255.255

Static & Dynamic IP Addressing

Static IP Host configuration means that the IP address remains with the host forever until manually changed.

Dynamic IP Host Configuration means same or different IP address allocated to the host every time it logs on to the network.

What is DHCP?

DHCP stands for Dynamic Host Configuration Protocol

Dynamic IP Host Configuration is done with the help of DHCP protocol and the server running this service is called DHCP Server.

What is Ethernet Switch?

Used to provide connectivity between different host with in a same network.

The same network means the Network Id of all the host must be same.

What is Router?

Used to provide connectivity between hosts which are part of different network.

Host belonging to different network are identified by different Net Id.

Port Numbers

Once a packet is delivered to a host, the question arises to which application process should the transport layer deliver it.

TCP and UDP provide an addressing method to separate different application processes inside the IP capable devices, and this is referred to as Port Numbers.

Each application running on the IP capable device is allotted one port number.

Port number runs from 0 to 65536.

Socket

A socket is simply a combination of IP address and Port number.

What is NAT?

NAT stands for Network Address Translation. It is a way of translating a range of IP addresses to

different range of IP address(es). Often used for saving public IP address and is

implemented in routers/ firewall connected to the external network.

How NAT is Implemented?

How NAT is Implemented?

NAT Table

SourceComputer

SourceComputer'sIP Address

SourceComputer's

Port

NAT Router'sIP Address

NAT Router'sAssigned

Port Number

A 192.168.32.10 400 215.37.32.203 1

B 192.168.32.13 50 215.37.32.203 2

C 192.168.32.15 3750 215.37.32.203 3

D 192.168.32.18 206 215.37.32.203 4

What is DNS?

Domain name system is an application layer protocol which is used to convert difficult to remember 32 bit IP address to more easily remembered symbolic names.

example www.google.com <-> 64.233.161.104 The DNS in GPRS network helps to find the correct

GGSN IP address based on the Access Point Name (APN) supplied by the MS.

What is Firewall?

A firewall is simply a program or hardware device that filters the information coming through the Internet connection into your private network or computer system. If an incoming packet of information is flagged by the filters, it is not allowed through.

Firewalls use one or more of three methods to control traffic flowing in and out of the network: - Packet filtering - Proxy service

Packet Filtering

Packets (small chunks of data) are analysed against a set of filters.

Packets that make it through the filters are sent to the requesting system and all others are discarded.

Proxy service

Information from the Internet is retrieved by the firewall and then sent to the requesting system and vice versa.

Use of IP In GPRS

THANKS!

SUMIT SINGH