LTE Broadcast (eMBMS) enables a Single Frequency
Network (SFN) broadcast capability within LTE, so that the same content
can be sent to a large number of users at the same time, resulting in a
more efficient use of network resources than each user requesting the
same content and then having the content unicast to each user. eMBMS uses HTTP protocol , so wanted to know if it is a REStfull api?
Simple answer is no - eMBMS is more than just an interface, as Makoto says, it is a set of specifications that make up a Mobile Multicast solution.
There is a good overview which should illustrate this here:
http://www.slideshare.net/zahidtg/lte-embms-technology-overview
Related
The realization of high data rates in LTE technology over an all IP network means an ever increasing load on packet data networks. 3GPP has defined data offloading as a key solution to cope with this challenge. Data offloading has been a critical area of study in 3GPP Release-10.
Two important traffic offload techniques namely LIPA and SIPTO have been introduced.
However along with data is it possible to offload voice and SMS traffic as well using LIPA and SIPTO?
It is possible to offload voice and SMS traffic using a local gateway extension tunnel.
The tunnel is shown in pink on the attached picture as given:
Please refer to Link for more information ----> TD S2-096015.
I am investigating the SIP signaling and RTP media in VoLTE traffic. I can see RTP header but was told that the RTP payload and the SIP packets are all encrypted in IPsec. Is this true? If yes, at what interface I can see the decrypted packets?
Thanks.
LTE is based on IMS (IP Multimedia Subsystem) which is a very broad and encompassing set of specifications for an architectural framework that enables multimedia communication between IP connected end points.
Because it is so broad and all encompassing there are actually many different security points and interfaces - for example there are security specs for communication between an access network connected device (such as a mobile phone) and the core, for communication between different nodes within a single core network, for communication between different operator's or organisation's core networks etc.
3GPP and LTE build on the IMS specs and include specific security specs for the Mobile world also. There is a 3GPP spec which looks at access security for IMS (3GPP TS 33.203) and it includes the following diagram:
Each of the numbers in the diagram above is a different security 'association' and the above standard references one or more specifications for each one.
The result of all this security complexity and these many security layers is that the answer to your question depends on the point in the network you are looking at. For example, if you intercept the traffic between the phone and the base station you will not be able to see anything as it will all be encrypted at a lower layer (notwithstanding the latest GSM/3G security hacks etc). Similarly if you are looking at the traffic between the core network nodes or between different networks this may be over IPSEC tunnels etc and again you will not be able to see it.
If your aim is to intercept and eavesdrop on VoLTE voice calls then you are going to find this very hard as many of the above mechanisms are designed to prevent this - I won't say it is impossible as I'm sure someone will reference a hack or a 'government backdoor' example for similar technology etc.
If your interest is academic, or in profiling the performance of the network etc then you may be able to achieve what you want using one of the open source IMS solutions - e.g. http://www.openimscore.org.
Or, if you are working for, or with, one of the network equipment vendors then you may be in a position to insert or leverage network management and/or OSS 'hooks' or mechanisms which allow you gather info from some unencrypted data at certain points in the end to end flow.
I need to make TCP based decentralised chat app for local network. By decentralised I mean there is no central server. Each entity on a network should have server/client architecture. When app starts it should check which user is online ( already running the app ). My question is how can i check that? Can i do it by trying to connect via connect() function from socket library? I'm new to programming, especially socket programing, so if it's a dumb question sorry in advance.
You should definitely study how other decentralized applications do this. There are lots of techniques.
Each instance of the application should, as part of its server functionality, track the addresses of other instances of the application. Each instance should, as part of its client functionality, keep track of a few instances it can connect to. Prefer instances that have been around for a long time.
The software should include a list of servers that have been running for a long time and are expected to typically be available. You may wish to include a fallback method such DNS, maintained by anyone willing to keep a list of well-known servers offering access through a well-known port. The fallback method can also be IRC or HTTP.
If you want to stay decentralized, you might want to try multicasting or broadcasting a request packet to all hosts on the network to discover other instances of your chat application.
Something similar has been implemented in Pidgin, named Bonjour. It works quite nicely and provides chatting capabilities on a local network. More specifically, it is defined as a Serverless Messaging part of XMPP.
If you are looking for code examples, have a look at one of my projects where I use multicast to discover hosts on the local network that provide a specific service: Headers and implementation.
At the bottom, it's all about socket communications. If there is some way to get the ip of the both users, why can't the connection be directly setup between the users instead of having to go thru a server in the middle?
My 2 cents:
No one out there forces us to have a server based real-time communication model. Infact XMPP have an extension called "Serverless Messaging" which defines how to communicate over local or wide-area networks using the principles of zero-configuration networking for endpoint discovery and the syntax of XML streams and XMPP messaging for real-time communication. This method uses DNS-based Service Discovery and Multicast DNS to discover entities that support the protocol, including their IP addresses and preferred ports.
P2P chat applications have been for over a decade now. Having a server in the middle is purely a decision dependent upon your application needs. If your application can live with chats getting lost while the user was transitioning between online/offline status, then you can very well have a direct P2P model going. Similarly, there are a loads and loads of advantages (contact list management, avatars, entity discovery, presence authorization, offline messages, ....) when it comes to choosing a server based messaging model. If you try to have all this right inside your P2P based clients, they might die or under-perform because of all the work they will need to perform by themselves.
"WebSockets" were not designed for P2P/Serverless communication, rather they were designed to provide a standardized PUSH semantic over stateless HTTP protocol. In short, "WebSockets" is a standardized way replacing hacky comet, long-polling, chunked-encoding, jsonp, iframe-based and various other technique developers have been using to simulate server push over HTTP.
Named WebSockets (if someday it is fully and widely supported) could be the solution.
http://namedwebsockets.github.io/spec/
Named WebSockets are useful in a variety of collaborative local device
and local network scenarios: Discover matching peer services on the
local device and/or the local network.
Direct communication between users is possible in Peer To Peer (P2P) networks. In P2P each participant can act as client as well as server. But for P2P networks you need to write a separate program to make the communication possible.
Web Sockets let you leverage existing common browsers as clients. All depends on what is the purpose of your application and how you want to deploy it.
If there is some way to get the ip of the both users
You nailed the answer right in your question.
Most machines I use have IP address of 192.168.0.10 (or similar from 192.168. private network) and are deep, deep behind several layers of NAT. With the end of free IPv4 address pool and IPv6 nowhere near sight, this is the reality most users live. Having a stable intermediary of known, routable address helps a ton working around this issue.
WebSockets don't allow the socket to listen for connections, only to connect as a client to a server (not reverse). Technically they could make it allow this, but as far as I understand the spec doesn't currently (nor is it expected to) allow listen functionality for WebSockets.
The new WebRTC (http://www.webrtc.org/) spec looks like it might support peer-to-peer connections. I have not played with WebRTC at all so I'm not in a position to comment on it. I think it would be a bit more involved than WebSocket stuff. Maybe someone who knows WebRTC better can chime in. (Also apart from the latest version of Chrome I'm not sure if any of the other browsers really support WebRTC yet).
By looking at current Google wave APIs, I can't find a way to create an alternative client.
It's not a robot or gadget, and the embed API is very slim.
Nevertheless, I do see some clients out there - such as Waver and Waveboard.
How do they do it ? is it based on XMPP ?
Note that Waver and Waveboard aren't actual clients, rather single-application web-browsers wrapped around the official https://wave.google.com/wave/ URL.
The Wave Federation protocol comes with a Protocol Buffers based experimental client/server protocol. Some people are using that to make a client, but it's not yet interoperable with the existing wave infrastructure unless you set up your own server (it won't work with #googlewave.com users, you must set up your own wave federation server and have it communicate to that).
During Google I/O they announced the Google Wave Data API which allows a program to read and write to wave on behalf of a user using OAuth. I'm using it to create a true mobile client, but at the current state, it's still very limited and restricted to the actions of fetchWave, search and folderAction (markAsRead/Unread, mute and archive).
http://code.google.com/apis/wave/extensions/wavedataapi/index.html
Lars Rasmussen did mention the beginning of a public client/server protocol, but I can't yet find anything about it.