Is there any good book about networks and network protocols? One question I currently have is: How does the operating system determine the IP address of the router in a LAN?
I want to understand those basics. I know that I can look up most of the common protocols by searching for their respective RFC, but I don't even know which protocols are used for which purpose.
The operating system knows the ip address of the first router (default gateway), because someone told it - either manually when configuring the TCP/IP settings or dynamically via DHCP, BOOTP or similar.
There are plenty of good book suggestions in the closed question "What are good books on computer networks"
http://www.pearsonhighered.com/kurose-ross/
http://books.google.co.in/books/about/Computer_Networks.html?id=Pd-z64SJRBAC
Both are good books. Enjoy !!
Related
Here's a link to my network diagram http://i48.tinypic.com/dcev0y.png
I am trying to learn on my own how to setup networks, and on the hybrid network parts I am confused, how does one calculate the amount of minimum datalink needed for a situation like the picture linked above.
English is not my primary language so it is hard for me to search for the proper keywords. Any help is kindly appreciated.
If possible to do so it would be useful to ask the network provider how much bandwidth was available on each route and how much was currently being used.
If there is a network administrator in your organisation you should speak with them first.
This would be the easiest way to aquire an understanding the network topology in the diagram. But you would need to sensitive to the fact network administrators are typically very busy and under pressure so bear that in mind if you are asking for their time.
If you need to figure this out yourself you need to research and learn about basic network monitoring tools
Here are a list of concepts and tools that you should research and understand.
ports ping, traceroute, nslookup and telnet
You will likely need to research TCP/IP, network addresses and subnetting
In addition you will need to learn how about network interfaces controllers, multi-homing IP addresses, public and private facing IP addresses.
I am working in a project to migrate a firewall application from IPv4 to IPv6. I have several questions:
What changes and modifications might be needed?
Will the popular protocols such as FTP, HTTP, POP3 also need to be adapted/modified?
Which IPv6 components should or must be implemented?
Which tunneling/transition mechanism to prefer?
As I am new to this network security field, I hope you guys could give me some valuable input. Thanks in advance.
There are a lot of things to consider. Off the top of my head:
Learn the difference between link-local (fe80::/10), global unicast, and multicast address ranges. Make sure you support interface scoping with link-local addresses (you will see addresses like fe80::1%eth1, which will indicate the link-local address on the eth1 interface).
ARP equivalent (IPv6 neighbor discovery) is now part of ICMP. This is important because if the user wants to block ICMP packets and isn't careful, they could lose all their connectivity!
Most (sane) protocols will not need major changes. FTP is one protocol that will potentially need changes, since it sometimes passes network addresses within the protocol itself (rather than letting the lower-level protocols take care of it)
The most basic tunneling/transition mechanism you will need is called 6in4; it simply encapsulates IPv6 packets within IPv4 packets and allows the user to manually configure the endpoints of the tunnel. Automatic tunneling mechanisms like 6to4 and Teredo can also be useful in some situations.
If you are selling a commercial product, I recommend you take a look at the USGv6 test selection tables. Also, read through the USGv6 profile which has pointers to many of the RFCs you will need to understand in order to develop an IPv6-compliant product. Not supporting the USGv6 profile for a network protection device (NPD) could severely limit your market. Finally, get some training! IPv6 is vastly different from IPv4 in many ways. If your employer wants this project to succeed, training will be critical given that it appears that many project members are new to both IPv6 and network security. (do you have a mentor on the team to ask questions?)
So I want to learn all about networks. Well below the socket, down to raw sockets and stuff. And I want to understand hubs, routers, access points, etc. For example, I'd like to be able to write my own software to do this kind of stuff.* Is there a great source for this kind of information?
I know that I'm asking a LOT here, and that to fully explain it all requires from high level down to low level. I guess I'm looking for a source similar in scope and depth to Applied Cryptography, but about networks.
Thanks to anyone who can help to point me (and others like me?) in the right direction.
* Yes, I realize using any of my hand-crafted network stack code would be a huge security issue, and am only looking to do it to learn :)
Similar Question: here. However I'm looking for more than just 'what's below TCP/UDP sockets?'.
Edited for Clarification: The depth I'm talking about is above the driver level. So assuming that the bits can make it to and from the other end of the wire, what next?
I learned IP networking from TCP/IP Illustrated. Highly recommended.
This may not help you learn it, but a packet sniffer like Wireshark will give you some insight into what the data looks like at a pretty low-level protocol (TCP/IP).
As you have obviously recognised, the universe does not start and end with the IP Protocol. Take a look at the OSI 7 Layer Model where IP is a Layer 3 (Network) protocol. Common IP Routers will operate at this level, but there is more complexity you probably should understand in the Data Link and Physical layers before you start coding your own network stacks.
Start with the fundamentals of data communications in all its myriad forms and work your way up the stack until you get to where you need to stop. Data Communications, Computer Networking and Open Systems is a good foundation text, and then look for more detail on each area you need to focus on. Previous answers include good links for IP and TCP/IP, and as mentioned Wireshark will let you look down through some of the layers
CISCO CCNA materials contain a great network fundamentals, but does not affect programming aspect. I'm not sure that there is an official free link, but you can try to find them.
You should equip yourself with a c compiler and the necessary libs and headers for your OS and play around. You may want to read for example:
http://snap.nlc.dcccd.edu/learn/fuller3/chap13/chap13.html
I had some more links in my delicious account, but they all went down the digital drain ;-)
Have you any embedded programming experience ? If so I recommend you buy one of these development boards. They are cheap and allow you work on every part of the networking stack plus all the software tools required are free.
Note that getting going on it isn't easy and I ended up reading the CS8900 IC datasheet to learn how to make it communicate with the ARM7 based processor. But if you enjoy that sort of thing (as I do) then they are great fun.
Hmmm ... have you looked into Computer Networks by Tanenbaum ?
The TCP/IP Guide
I have found the networking chapter in "understanding the linux kernel" and "understanding linux network internals" from oreilly to be very helpful.
The TCP/IP stack is a very good start but there is a lot more and a good understanding of how ethernet works and how ethernet != IP != the-interweb will go a long way.
books on network security often do a decent if not goos job explaining how networks work in a concise context.
what really did the trick for me was taking a job implementing NAT :)
This course worked for me: COS 461 at Princeton. Note that it assumes system-level programming experience with C.
Pretty much all the readings and lectures are available online under "Syllabus". And you can try the assignments too (unfortunately, you won't have access to the Virtual Network System).
Check this.. it is a good collection of information:
http://www.tcpipguide.com/free/t_toc.htm
I would like to do this because it would make peer location much more effective in my p2p network as I would know that all the addresses would be part of this network.
How could I do this while remaining compatible with current transport layer protocols such as SCTP, and the current hardware used on the big wide Internet?
Thanks,
Andreas
I suggest using IPv6.
There is enough address space that you can create up to 2^40 "unique unicast" ranges, each with 16 bits of subnet and 64 bits of host ID.
Protocols such as UDP, TCP, and SCTP already work on top of it
It already has major operating system support.
See http://www.rfc-editor.org/rfc/rfc4193.txt
Densely filling the 40-bit unique-id is discouraged. Use the random generation method mentioned in the RFC.
Put simply, you can't. IPv4 IPs are distributed by IANA to the five major IP registries: ARIN (North America), RIPE (Europe), APNIC (Asia/Pacific), LACNIC (Latin America/Carribean), and AfriNIC (Africa). These registries then distribute those out to ISPs.
There are blocks reserved for local networks, but those are not routable over the public Internet... they must be encapsulated; this is how VPNs work.
The best way to have this kind of functionality is probably to use a name lookup service, or even a peer discovery service in the protocol itself.
The fact is, no matter what you do, it is likely that you will have to get your application to perform extra work on top of the IP protocol anyway, because the IP protocol itself supports only 1 address space, you need to add another layer to add an independent address space.
It looks like you're trying to create a network inside of a P2P "world". So all the users using the P2P app would have a second IP address, say Alice has 10.0.2.40, that could be used by Bob, another user of the app, to get to Alice. Right?
With that regards, it looks like you'd want to set up a VPN on each client and use some sort of route table modifications so the VPN is only used for the address-space allocated by the the P2P program (say the 10.x.x.x network).
But there are problems with that.. for example you'll never find an address space that everyone has free to use. Home Routers use 192.168.x.x, corporate networks or enthusiasts (like myself) use 10.x.x.x, and the 172.something is used by other sysadmins for stuff I'm sure.
Disclaimer: Not a networking genius, I'm speculating here.
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Given two computers attached to the Internet that know nothing about each other before hand, is it possible for one computer to be able to broadcast a message so that the second computer could receive it and respond?
I know UDP broadcast exsits, but I believe that those are generally filtered by the ISP before it reaches the true Internet. Is this true?
The current best way to achieve a multinode network without centralized coordination is through the use of Distributed Hash Tables. That link explains a bit and links to various implementations you can leverage.
That said, you still need each machine to coordinate with at least some peers. It's just that you don't need it to coordinate with a central server. A solution using a central server that know both (all) participating machines will also work, but imposes further restrictions on anonymity and scalability, just remember what happened to Napster.
You need an intermediate third party that they both know, that could distribute messages directed towards it in a broadcast-like fashion.
A solution for this problem (where none of your peers know the final address of the other) could be relying on IM protocols.
In particular, the XMPP protocol is extensible, open and used by many providers such as Google Talk. Libraries exist for most languages and it has the plus of being able to work (slowly and going through a 3rd party server) even if both hosts are behind a NAT-box.
If communication must use another channel, you can use XMPP to exchange IP address and then proceed with the standard socket route (but if you encrypt your messages, there should be no problem even going through a 3rd party server - to be true all packets go through untrusted 3rd party routers so you should encrypt anyway if you have sensitive data..).
Hope this helps.
No, you can't broadcast like that over the internet. You need to know which address you want your packets to go to.
A possible solution for you is to use a dynamic DNS service.
Your application would need to know in advance which hostname the other host will be using, but this service would at least get around the fact that you don't know exactly which IP address the other computer is on.
Note that this won't solve the potential issue of firewalls between the two hosts blocking your packets. The only practical way around that is for both hosts to open an outbound connection to a central host which can then relay data between them.
Look at the chord or pastry algorithm. It is an overlay network (DHT based) which has a discovery mechanism involved. It's a P2P (Peer 2 Peer) routing algorithm.
UDP is a dead end - its just a protocol where the order the packets are received is less important and there are issues routing over WANS. You said that you want to connect two computer on the "internet" presumably with the end points moving around etc. The only way is to use a central server as a register/directory. If each end point allso a web service or something and registeres its current IP address and name periodically then the other end point can look up the IP address of the other using this service. (could host your own DNS server and code your end point to register on this DNS?)
One of the problems is that even if you have the IP address what is one or more nodes are behind a firewall or NAT router ? You will need to host a server to proxy traffic. The best example is SKYPE - look into how it works it is documented, very interesting.
The simplist answer might be to jump on the back on an existing service such as messanger, skype, bit torrent, etc.
Simon
If the computers are running Windows, I'd look at using PNRP.
Multicasting is also a possible solution. It's certainly feasible in a corporate network