Nicolas' Blog

For some of the latest projects I’m working on, it is required that I quite frequently access various machines that are located behing a corporate firewall, on a privately adressed subnet inside a company.

One option I had but got fed up with quite fast was :

 outside$ ssh nicolas@gateway 
 gateway$ ssh root@box1 
 box1# 
or  
 ssh -t nicolas@gateway ssh root@box1

Once again, SSH came in handy and I found that everything was there for me to have that first hop and re-ssh done automatically. Just added the following to my ~/.ssh/config

 Host gateway       
 Hostname gateway.example.org       
 User nicolas 

 Host box1       
 Hostname 192.168.0.1       
 User root       
 ProxyCommand ssh gateway nc -w 1 %h 22

This, coupled to ssh’s passwordless authentication made my day a lot easier ;)

Some of the software projects I’m involved in require access to a CVS repository which is behind a corporate firewall that will drop all incoming traffic which is not directed to a specific machine (the SSH server) on port 22. This situation made it hard to code from outside the organization’s network.

Some geekery would be to setup an SSH tunnel from the eclipse machine that would encrypt pserver while outside of the organization and forward it from the SSH server to the CVS server. This could be done by executing the following command:

ssh -L2401:cvs.example.org:2401 ssh.example.org

One would then configure eclipse to access the CVS repository located at localhost using pserver, ssh would do the rest.

This method is now “integrated” into eclipse. When going to File->New->Project->CVS->Project from CVS, you can now choose the pserverssh2 connection method.

You then have to fill the “Host” field using this syntax:

sshlogin@ssh.example.org#sshPort@cvs.example.org

or

sshlogin@ssh.example.org@cvs.example.org

if the ssh server listens on the default port 22.

You then fill in the username and password with your pserver CVS’ credentials and you’re all set!

Enjoy!

Almost a month ago, I started my Internship at the Laboratory for Analysis and Architecture Systems.

I’ve finished the first part of the Interniship which consisted in the study of currently implemented techniques for coding multimedia contents and transmitting them on a packet switching network.
Among the documents produced (hopefully soon to be on the website) are a report on the different coding techniques used aswell as a detailed analysis of the flow ADU’s structure oriented towards optimization of a selective repeat mechanism that a QoS aware transport protocol could use.
I also contributed to an ongoing study for characterization of multimedia flows on a packet switch network lead by a friend whose report should (if I get his authorization) also be posted here soon.

The second part of the Internship consists in protocol modeling following the work on dynamically adaptative and composable transport protocols. I’m discovering the different uses of the TAU Generation2 modeling tool aswell as the “ETP framework” in which my work should take place.. More to come on that soon… I hope.