stateful proxy nodes

[nahid]

Hi all,
I am trying to simulate a network consist of a server, n clients and m proxy servers. my clients can only see proxies and connect them. proxies are my clients sink application. I want my proxies to forward the exact traffic to  server( server is sink for my proxies) and return back the servers response to clients. How can I achieve this? can anybody help me with that?

[Tommaso Pecorella]

Hi,

it shouldn't be hard. Just modify one of the applications in the src/applications/model directory to receive and forward your traffic.

T.

[nahid]

Thanks for your reply.
I have tried to change packetSink in the src/applications to send the receiving packets to my server. but I have a problem. Proxies send packets to server correctly but they send acks for clients. I want to return server's answer to clients not the proxies answer. How can I prevent tcp default behavior to answer the receiving packet?

thanks.

[nahid]

I mean proxies have to wait for server response and then return that response to clients.

[Tommaso Pecorella]

Well, that's all in the application logic:

- receive a request

- forward to the server

- wait for the reply

- forward to the client

Considering that you'll have 2 sockets (one from/to the client and one from/to the server) you can couple them. However the coupling will have to be done in the HandleAccept callback.

Every TCP socket will fire a HandleAccept callback (if set) when a new connection is made.

I'd expect that fo every new connection from a client you'll open a new connection to the server - in the HandleAccept is the best option.

Afterwards, you can just check where a request (or reply) comes from just by checking the socket, and forward it to the other one.

Hope it is clear,

T.

[nahid]

Thanks. I have  tried that. I start connection to server when clients connect to proxy. and I call my own method , "SendPacket" at the end of HandleRead method to send receiving packets to server. but the problem is that still proxy sned packet ack to clients before receiving server's answer. how can I say proxy to wait for the reply??

thanks.

[Tommaso Pecorella]

Hi,

the ACK is unavoidable.

T.

[nahid]

So, What can I do to keep session alive? because when the Ack is received the client application calls dodispose method and I lose the socket and consequently I can't return server's response to client. how can I solve this?

[Tommaso Pecorella]

If your client closes the connection when it receives an ACK, then there's a bug in your application (or you didn't fully understood how it works).

T.

[nahid]

Sorry I am new to ns3. How can I get the event of ack received by client? Or event of ack sent by server?

[nahid]

And Another thing is that I am using http client and server introduced here. for the proxy server I have changed the server code to implement new proxy application for forwarding requests and answers.

[Tommaso Pecorella]

You should study TCP, not ns-3. ACKs are at TCP-level.

T.