October 11, 2010 at 11:14GPRS from the inside out. Part 4.1
This is the final part of a series of articles on GPRS / EDGE technologies that we started in the previous three stories: 1 , 2 , 3 . This time we look behind the doors of the mash. halls and see what actually provides the ability to transmit and receive data over the air using a mobile phone - we will talk about hardware for SGSNs and GGSNs.
As we already know from previous articles on packet technologies in mobile networks, 2G networks are still the most widely distributed with the prospect of moving to the next generation of architectures and of course SGSN 's and GGSN ' are the main network elements for such networks . s.
I’ll say right away that the article is not an advertisement for a particular vendor, I’m just an opportunity to share the experience of implementing a packet network (PS Core Network) based on this vendor, in particular, we will talk about NSN products : Flexi ISN , which is an implementation of GGSN and CombiSGSN , which is naturally an SGSN implementation for the PS Core Network.
In almost any packet network there is a division into the so-called subscriber data transfer area (User plane) and the transmission area of service information necessary for establishing communication, its correct interruption, tracking subscriber movements over the network, etc. Moreover, in implementations of more and more modern core network technologies (GPRS / EDGE -> UMTS -> HSDPA -> LTE), this separation is becoming more pronounced, separate network elements are allocated for servicing each of the planes, while in previous technologies both functions are managed planes could be "occupied" by the same network element, for example, SGSN.
In a 2G packet network, the separation of the service of the above planes can be arbitrarily applied to SGSN and GGSN (see the figure below).
We will begin our acquaintance with the implementation of GGSN in a packet network - Flexi ISN [Intelligent Service Node], and in the second part of this article we will take a closer look at the implementations of one of the most basic network elements - SGSN .
Naturally, to the needs of various mobile operators, providing the opportunity to take advantage of services and services based on packet networks, vendors create implementations of various network elements. The packet network is no exception, almost all major telecommunication vendors provide their solutions in the “segment” of GGSNs, and since Since GGSN is a multifunctional router / gateway, monsters such as Cisco , Juniper Networks , not to mention NSN , Huawei and Ericsson , as well as the recently purchased Motorola division, are coming onto the scene .
In order to freshen up a little knowledge of the main network interfaces, with which we were introduced in 3 parts , I recall the key interfaces that NSN's GGSN implementation works with - Flexi ISN, presented in the figure above:
A detailed description and purpose of each of the interfaces can be found in the articles above, and we will begin to consider the capabilities of Flexi ISN.
In fact, Flexi ISN is a GGSN server, the main tasks of which are to establish and maintain subscriber traffic, maintain APN on the operator’s packet network, provide access to various packet networks - internet, intranet. The main characteristics of GGSNs are usually the number of simultaneously raised PDP Contexts and the maximum bandwidth for accessing external channels.
In this regard, Flexi ISN has the following performance characteristics :
Naturally, Flexi ISN supports the basic functionality for providing service in a packet network via the APN requested by the subscriber:
The main features include: Peer-to-Peer Detection & Control, Per Service Access Control, QoS, Charging, Bandwidth Management, as well as:
Based on Flexi ISNs, you can also implement the so-called Multiple Charging Models , i.e. carry out charging based on various events committed by the subscriber.
One of the useful features provided by Flexi ISN is the so-called. Advice of Charge (AoC), which allows you to familiarize yourself with the price for future use of the service, before starting to charge it, i.e. Before opening a certain HTTP / WAP session, the subscriber is redirected to the AoC server, which notifies him of the cost of the requested service and the subscriber can either accept the price conditions for using the service or refuse. In the case of using the so-called non-HTTP / WAP traffic; notifications using WAP Push are used . This functionality can be widely used in conjunction with subscription services.
Another rather convenient functionality that Flexi ISN can provide and which is simply necessary for the realities of mobile operators in the CIS, in my opinion, is the ability to notify a subscriber about the excess of his money balance for using packet services. Such notifications are also possible together with a Push message, which will redirect the subscriber to the operator’s website / portal.
Operators consider transmission of data through peer-to-peer networks to be one of many of their “troubles,” and they try to oppress the presence of all kinds of services based on such networks in order not to lose their precious profit. In particular, this also applies to mobile telephony based on peer-to-peer technology, the same Skype, various instant messengers: ICQ, Jabber, etc., not to mention the transfer of files through various trackers.
And in this case, Flexi ISN is a rather significant " assistant " for operators, as provides fairly extensive capabilities in terms of monitoring and blocking Peer-To-Peer traffic, in particular:
At the same time, it is possible not only to block the selected type of Peer-To-Peer traffic, but to significantly reduce its quality. Traffic blocking can be based on the following criteria:
But peer-to-peer traffic service options are also possible as an additional service that can be provided separately to subscribers for a separate fee. For example, you can provide access to peer-to-peer networks by subscription, the same Skype, Bittorrent, etc.
Or form tariff plans based on the time of day, for example, provide access to the ability to transfer data through peer-to-peer networks only at night, because At this time, the overall load on the operator’s network is reduced.
Quite significant attention is paid to the QoS profiles used to service various services.
Moreover, the influence of QoS profiles can be expanded both to subscribers using PoC services, and so-called services. Streaming services (VoIP, Video broadcasting, etc.), as well as corporate users.
Flexi ISN has quite flexible approaches to organizing access to corporate networks through mobile packet services:
Flexi ISN itself mounted in a rack is as follows:
In the photo above, it is clear that only two Flexi ISN modules were mounted, but it is possible to expand up to 4 such modules to realize the maximum configuration.
This concludes our acquaintance with the structure and basic implementation capabilities of GGSN from NSN. In the second part of this article we will get acquainted with SGSN from the same vendor ...
Small assistant:
APN - Access Point Name
CDR - Call-Data Record
EDGE - Enhanced Data Rates for GSM Evolution
GGSN - Gateway GPRS Support Node
GPRS - General Packet Radio Service
GRE - Generic Routing Encapsulation
GTP - GPRS Tunnelling Protocol
HSDPA - High-Speed Downlink Packet Access
HSUPA - High-Speed Uplink Packet Access
IMS - IP Multimedia System
LTE - Long Term Evolution
NSN - Nokia Siemens Networks
PDP - Packet Data Protocol
PS - Packet Switched
QoS - Quality of Service
SGSN - Serving GPRS Support Node
SIP - Session Initiation Protocol
UMTS - Universal Mobile Telecommunications System
WAP - Wireless Application Protocol
As we already know from previous articles on packet technologies in mobile networks, 2G networks are still the most widely distributed with the prospect of moving to the next generation of architectures and of course SGSN 's and GGSN ' are the main network elements for such networks . s.
I’ll say right away that the article is not an advertisement for a particular vendor, I’m just an opportunity to share the experience of implementing a packet network (PS Core Network) based on this vendor, in particular, we will talk about NSN products : Flexi ISN , which is an implementation of GGSN and CombiSGSN , which is naturally an SGSN implementation for the PS Core Network.
In almost any packet network there is a division into the so-called subscriber data transfer area (User plane) and the transmission area of service information necessary for establishing communication, its correct interruption, tracking subscriber movements over the network, etc. Moreover, in implementations of more and more modern core network technologies (GPRS / EDGE -> UMTS -> HSDPA -> LTE), this separation is becoming more pronounced, separate network elements are allocated for servicing each of the planes, while in previous technologies both functions are managed planes could be "occupied" by the same network element, for example, SGSN.
In a 2G packet network, the separation of the service of the above planes can be arbitrarily applied to SGSN and GGSN (see the figure below).
We will begin our acquaintance with the implementation of GGSN in a packet network - Flexi ISN [Intelligent Service Node], and in the second part of this article we will take a closer look at the implementations of one of the most basic network elements - SGSN .
NSN Flexi ISN
Naturally, to the needs of various mobile operators, providing the opportunity to take advantage of services and services based on packet networks, vendors create implementations of various network elements. The packet network is no exception, almost all major telecommunication vendors provide their solutions in the “segment” of GGSNs, and since Since GGSN is a multifunctional router / gateway, monsters such as Cisco , Juniper Networks , not to mention NSN , Huawei and Ericsson , as well as the recently purchased Motorola division, are coming onto the scene .
In order to freshen up a little knowledge of the main network interfaces, with which we were introduced in 3 parts , I recall the key interfaces that NSN's GGSN implementation works with - Flexi ISN, presented in the figure above:
A detailed description and purpose of each of the interfaces can be found in the articles above, and we will begin to consider the capabilities of Flexi ISN.
In fact, Flexi ISN is a GGSN server, the main tasks of which are to establish and maintain subscriber traffic, maintain APN on the operator’s packet network, provide access to various packet networks - internet, intranet. The main characteristics of GGSNs are usually the number of simultaneously raised PDP Contexts and the maximum bandwidth for accessing external channels.
In this regard, Flexi ISN has the following performance characteristics :
- Capasity:
- about 1M simultaneous PDP Contexts in the basic configuration, with the possibility of expanding to 4M simultaneous PDP Contexts.
- 1Gbps channel bandwidth in the basic configuration, with the ability to expand to 5Gbps channel bandwidth from one rack.
- Up to 5500 PDP Contexts per second.
- Serving up to 1000 different APNs.
- Multi-Access level supports:
- Different Alias APN i.e. the ability to combine various APNs under a specific service.
- Wildcard APN - the ability to support any existing APN operator in the network for subscribers who have * indicated instead of APN in the HLR (More details in the article It Doesn’t matter who you are ... it’s important what APN you have! ).
- Support HSDPA (16Mbps).
- Support HSUPA (8Mbps).
- GGSN’s network capabilities allow you to provide the following features:
- IP address allocation according to the following schemes: Static, Radius, DHCP, Internal Pool
- Overlapping IP Addresses Support “Overlapping networks” for VPN access.
- Policy Based Routing
- Multiple Routing Instances
- L2TP (LAC), GRE, IP-in-IP
- VLAN With QoS Mapping
- IPv6 User Layer
- IPv6 Routing
- WAP GW Redirection (WAP 1.x)
- Traffic redirection
- Load balancing
- Header Modification (HTTP) Feature
- Service options for the following services:
- L3 / L4 Analyses
- L7 Inspection For: HTTP, WAP1.x, WAP2.0, RTSP, MMS (WAP 1.x), P2P
- Personal firewall
- Charging:
- Real-Time DCCA Based Charging
- Offline Charging GTP` (TLV, XML) (one of the varieties of the GTP protocol).
- Radius Online Charging
- Temporary storage of CDR files
- Volume, Time & Hit Charging
- Time step charging
- Redundant CG Connection
- PoC Prepaid Charging Support (see article: Walkie Talkie - PTT )
- MMS Transaction Based Charging
- Self-Contained CDR Format
- End User Notifications (the ability to notify the subscriber using various Push messages, for example, through the Gc interface).
- Compliance with the following requirements for various security policies:
- 3GPP QoS, IMS Support
- User Profile Downloading With: Radius or LDAP
- Radius Disconnect Support
- Service Authorization Based On: Roaming, Location, Access Type
- Service Based QoS, which can significantly increase the level of services provided, see GPRS QoS article - myth or reality?
- IPv4 / IPv6 traffic controlled over Go interface
Naturally, Flexi ISN supports the basic functionality for providing service in a packet network via the APN requested by the subscriber:
The main features include: Peer-to-Peer Detection & Control, Per Service Access Control, QoS, Charging, Bandwidth Management, as well as:
- Lawful Interception (with IPSec), which, by the way, is a strict requirement from law enforcement agencies when introducing this kind of equipment on the operator’s network.
- RoHS Compliance
- Command Line Interface (CLI)
- Service Level Statistics
- Multiple Deployment Options (NAS)
Based on Flexi ISNs, you can also implement the so-called Multiple Charging Models , i.e. carry out charging based on various events committed by the subscriber.
- Deep Packet Inspection [ DPI ] allows you to define and monitor various types of traffic (see article)
- Different services can be charged differently even within the same PDP session.
- Tariff plans based on various protocols, services and levels: FTP, HTTP, WAPv1 / v2, MMS, L3 / L4, P2P, etc.
One of the useful features provided by Flexi ISN is the so-called. Advice of Charge (AoC), which allows you to familiarize yourself with the price for future use of the service, before starting to charge it, i.e. Before opening a certain HTTP / WAP session, the subscriber is redirected to the AoC server, which notifies him of the cost of the requested service and the subscriber can either accept the price conditions for using the service or refuse. In the case of using the so-called non-HTTP / WAP traffic; notifications using WAP Push are used . This functionality can be widely used in conjunction with subscription services.
Another rather convenient functionality that Flexi ISN can provide and which is simply necessary for the realities of mobile operators in the CIS, in my opinion, is the ability to notify a subscriber about the excess of his money balance for using packet services. Such notifications are also possible together with a Push message, which will redirect the subscriber to the operator’s website / portal.
Peer-to-peer networks
Operators consider transmission of data through peer-to-peer networks to be one of many of their “troubles,” and they try to oppress the presence of all kinds of services based on such networks in order not to lose their precious profit. In particular, this also applies to mobile telephony based on peer-to-peer technology, the same Skype, various instant messengers: ICQ, Jabber, etc., not to mention the transfer of files through various trackers.
And in this case, Flexi ISN is a rather significant " assistant " for operators, as provides fairly extensive capabilities in terms of monitoring and blocking Peer-To-Peer traffic, in particular:
- the ability to analyze the following protocols and services:
- The ability to analyze P2P tracking protocols:
At the same time, it is possible not only to block the selected type of Peer-To-Peer traffic, but to significantly reduce its quality. Traffic blocking can be based on the following criteria:
- Peer-to-Peer service type
- type of network access or subscriber location
- subscription to certain services
But peer-to-peer traffic service options are also possible as an additional service that can be provided separately to subscribers for a separate fee. For example, you can provide access to peer-to-peer networks by subscription, the same Skype, Bittorrent, etc.
Or form tariff plans based on the time of day, for example, provide access to the ability to transfer data through peer-to-peer networks only at night, because At this time, the overall load on the operator’s network is reduced.
Service Based QoS
Quite significant attention is paid to the QoS profiles used to service various services.
Moreover, the influence of QoS profiles can be expanded both to subscribers using PoC services, and so-called services. Streaming services (VoIP, Video broadcasting, etc.), as well as corporate users.
Corporate Access Points
Flexi ISN has quite flexible approaches to organizing access to corporate networks through mobile packet services:
- The ability to allocate a separate APN for corporate access.
- Providing virtual networks (VLAN, Separate Routing Instances).
- Allocation of IP addresses from the address space of the corporate network.
- Using Overlapping IP Addresses, the so-called "Overlapping networks."
- Additional authentication mechanisms in corporate networks (Radius)
- Support for IP tunnels (IP-in-IP, GRE, L2TP).
- Using the same APN for access to the corporate segment, as well as for other packet services from the operator.
Ggsn rack
Flexi ISN itself mounted in a rack is as follows:
In the photo above, it is clear that only two Flexi ISN modules were mounted, but it is possible to expand up to 4 such modules to realize the maximum configuration.
This concludes our acquaintance with the structure and basic implementation capabilities of GGSN from NSN. In the second part of this article we will get acquainted with SGSN from the same vendor ...
Small assistant:
APN - Access Point Name
CDR - Call-Data Record
EDGE - Enhanced Data Rates for GSM Evolution
GGSN - Gateway GPRS Support Node
GPRS - General Packet Radio Service
GRE - Generic Routing Encapsulation
GTP - GPRS Tunnelling Protocol
HSDPA - High-Speed Downlink Packet Access
HSUPA - High-Speed Uplink Packet Access
IMS - IP Multimedia System
LTE - Long Term Evolution
NSN - Nokia Siemens Networks
PDP - Packet Data Protocol
PS - Packet Switched
QoS - Quality of Service
SGSN - Serving GPRS Support Node
SIP - Session Initiation Protocol
UMTS - Universal Mobile Telecommunications System
WAP - Wireless Application Protocol