Networking

System.Net related postings

Mike Flasko — Fri, 10 Mar 2006 01:06:00 GMT

I'm excited to see the recent postings relating to the System.Net.Mail namespace. If the area of managed networking interests you, please see these blogs kept by my peers on the System.Net team:

http://blogs.msdn.com/wndp - Windows Network Developer Platform team blog

http://blogs.msdn.com/dgorti - System.Net Dev Lead

http://blogs.msdn.com/joncole

http://blogs.msdn.com/malarch

me :) : http://blogs.msdn.com/mflasko

System.Net wants to hear from you!

Mike Flasko — Wed, 21 Sep 2005 18:03:00 GMT

I have recently taken on the role of PM for the System.Net team. Now that Whidbey is winding down, we are starting Orcas (aka the next version of the .Net Framework) planning and want to hear what you think. What needs to be changed/improved/added? Want to put in your 2 cents and describe the scenarios in which you use or would like to use the System.Net namespace? If so, navigate here:

http://blogs.msdn.com/wndp/archive/2005/09/06/461533.aspx

Help make the .Net Framework better - link to the above post !

SSL and TLS Essentials

Mike Flasko — Fri, 20 May 2005 17:05:00 GMT

I was on a good blogging pace this month until a very nasty flu got ahold of me. Needless to say I have had a lot of couch and movie time over the past week and a half which, when I had the energy, allowed me to do some reading. If you read the title of this post you will know my latest book of choice was “SSL and TLS Essentials - Securing the Web” by Stephen Thomas. I think (maybe I just never noticed) this is one of the first books I have read that was published by Wiley Computer Publishing and it was definitely my first go at a book written by Stephen Thomas.

The verdict is.... it is a great read. In tune with what my friend Jason Kemp wrote, this book is highly focused on one subject, which is what makes it great. Those catch-all programming books are generally trash and never really answer your burning questions on the subject at hand. This book, just short of 200 pages, starts out light by introducing public/private key technology (with cartoons :) ), then moves into describing SSL from version 2.0 to 3.0 and finally its migration to TLS (Transport layer security). The book then concludes with a look at X.509 certificates, including a walk through (byte-by-byte) of an actual certificate and an overview of the theoretical weaknesses of SSL and known exploits of various algorithms with given key lengths.

If you are completely new to SSL/TLS or want to get a solid understanding (message layouts, certificate fields, etc) of the protocol and its surrounding technologies this is the book for you.

The technology formerly known as Rendezvous

Mike Flasko — Sun, 08 May 2005 17:01:00 GMT

Bonjour, formerly known as Rendezvous, is a networking technology from Apple that is designed to make zero-configuration simple. The Apple website says it “enables automatic discovery of computers, devices, and services on IP networks”. In a previous article I dumped on OS X quite a bit and ruffled some peoples feathers :), but I have to say this is one area that is quite interesting and they are releasing an SDK for Windows as well. For more information check it out here.

I have seen the technology in action in a classroom setting where students were doing collaborative note taking using SubEthaEdit. I have to admit, it is pretty cool.

Writing an IP Independent Client using Winsock

Mike Flasko — Mon, 02 May 2005 17:20:00 GMT

Winsock is the socket-based API on the Windows platform. Winsock (on Windows) provides more functionality than a standard BSD socket interface and also has additional MS only functions above what is defined in the WinSock spec (WinSock is not a strictly MS thing). Maybe in a future post I will talk about how Winsock is really just a layer on top of a much more general API allowing Windows to easily move to the next API of the decade. Ok lets get back on track and start talking about IP independent client apps.

When writing a client today we must be thinking of both IPv4 and IPv6 as a possible network layer. Yes, I know v6 has been “just around the corner” for quite some time now, but we are finally seeing signs it is starting to take real flight. For example, Longhorn will choose to use a IPv6 address over an IPv4 one if both are available.

The following is a list of DOs and DO NOTs when writing IP independent apps:

Avoid making reference to an address family anywhere in your code (AF_INET, AF_INET6)
Do not allocate protocol specific structures (SOCKADDR_IN, SOCKADDR_IN6), but instead use SOCKADDR_STORAGE, which is as large as the largest protocol specific address structure and provides padding for 64-bit alignment issues
Avoid hard-coded addresses. Winsock provides constants for any that you will need (Loopback, wildcard for binding, etc)
When passing address information around in your functions, pass the entire address structure (SOCKADDR) and not just the protocol specific one.
Avoid the legacy IPv4 only name resolution API calls and use getaddrinfo and getnameinfo instead as they work with both v4 and v6.

The following is a small piece of sample code demonstrating an IP independent client:

struct addrinfo hints, *result=NULL;                
char *remoteAddr, *portNum;
SOCKADDR dest;
int res;

// set remoteAddr and portNum to some values via user input, config file, etc
// remoteAddr = "foobar.com"  portNum="5000";

memset(&hints,0,sizeof(hints));
hints.ai_flags = AI_CANONNAME;
hints.ai_family = AF_UNSPEC;    // resolution could return v4 or v6 address
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;

res = getaddrinfo(remoteAddr, portNum,&hints,&result);
if(res == WSANO_DATA){
  //resolution failed - return error
}

s = SOCKET(result->ai_family, result->socktype, result->ai_protocol);
if(s == INVALID_SOCKET){
   //failure when creating the socket - return error
}

res = connect(s, result->ai_addr, result->ai_addrlen);
if(res == SOCKET_ERROR){
   //error connecting to foobar.com - return error
}

//must be freed because it is dynamically allocated by the getaddrinfo call
freeaddrinfo(result);  

// you are connected ....send and receive data 

//graceful TCP socket closure
shutdown(s, SD_BOTH);
closesocket(s);

Upcoming Longhorn Networking Chat

Mike Flasko — Fri, 11 Mar 2005 19:15:00 GMT

To quote the web transports team blog:

“There is an upcoming online chat with Jawad Khaki (corporate VP of Windows Networking and Devices) regarding Longhorn Networking features on March 22 at 11:30. Want to be the first to know what is changing (and there are years worth of work here) in the networking stack? This is the place to be. Or maybe that you have a favorite issues regarding the tcp/ip stack, winsock, firewall, UPNP, wireless, NDIS, home networking, Peer-to-Peer, IPV6? Here's your chance to tell the man in charge.”

Jawad will be joined in the chat by some of his GM's like Henry Sanders (Transports General manager where, among others, the web transports, HTTP.SYS, winsock, net device drivers and the TCP/IP stack live). I had to present my work for Henry a few times when I interned at MS - a very sharp guy. This talk should be more than worth your time.

Whats next for bluetooth?

Mike Flasko — Tue, 09 Nov 2004 05:05:00 GMT

The Bluetooth Special Interest Group (SIG) published a road map for the technology that spans through 2006 that lets peripherals, cell phones and other devices communicate wirelessly over short distances. Bluetooth has been widely adopted in Europe thanks to cell phone integration, however, this has yet to be the case for the majority of the devices in Canada or the USA. The Bluetooth SIG is hoping that their new road map will further adoption of their technology in cell phones distributed in North America as they believe such devices will be the train bluetooth will ride into the American market. The highlights of the road map are:

For 2004, the SIG points to today's Bluetooth Version 2.0 + EDR (Enhanced Data Rate), which promises to increase data rates to 3 megabits per second (mbps) from 1mbps and decrease power consumption
Next year, the group will continue to tackle security and privacy, the number of devices that can communicate at the same time, and power consumption--a key problem for battery-powered mobile devices
In 2006, the specification is scheduled to support multicasting, or the ability to send a single message to several devices and to increase Bluetooth's range to about 100 metres.

Chip makers CSR, Broadcom and RF Micro have adopted version 2.0 + EDR and the SIG expects products with these chips to hit the market in about 8-9 months from now.

What do you think - does bluetooth have a strong future in North America?

Network settings the easy way

Mike Flasko — Sun, 31 Oct 2004 22:52:00 GMT

If you are like me, you constantly play around with your home network. I find first handle knowledge is the best way to learn :). The point of this post is:

I wanted a way to store my network interface settings and then easily restore them all after I had played around with my machine to the point where nothing worked anymore. I came across this little hack that I thought is pretty cool:

To save your interface settings:

netsh -c interface dump > settings.txt

To restore the settings when you are done:

netsh -f settings.txt

Yes, I know the GUI in the control panel allows me to do all that. I love a good GUI as much as the next guy, but I suggest every tinker happy user (this is me) should start looking around the contexts of netsh - you will be amazed at how much you can tuck away in a .cmd file to make administration that much faster.

The Twenty Most Critical Internet Security Vulnerabilities

Mike Flasko — Wed, 13 Oct 2004 03:42:00 GMT

SANS has posted their Top 20 most critical internet security vulnerabilities. The list is really two seperate lists, one for Windows and one for UNIX/Linux. Topping the list on the Windows side are web servers and BIND's DNS Server takes the cake for UNIX/Linux. The list is quite extensive and provides some interesting links to CVE (Common Vulnerabilities and Exposures) reports. The top 20 list can be found here.

Do any of the items on the lists surprise anyone?

Job Offer

Mike Flasko — Fri, 27 Aug 2004 19:22:00 GMT

Today I received a job offer from Microsoft in Redmond for a full time position as a Program Manager when I graduate on their Transports and Connectivity team (core networking in Windows) - HORRAY!!!! I don't know any specifics nor have I accepted the offer yet, but I'm really stoked!