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Closed 10 years ago.
So, I've been looking on different websites, and using different subnet calculators, where in some cases it's possible and others it isn't possible.
Are these IPs possible?
Class A: 11.66.12.49/6 (Less than 8 network bits)
Class B: 133.22.15.1/10 (Less than 16 net bits)
Class C: 201.2.115.25/18 (Less than 24 net bits)
Sources:
http://jodies.de/ipcalc?host=201.2.115.25&mask1=18&mask2=
http://www.subnet-calculator.com/subnet.php?net_class=C
So basically, can you have a class C IP address with 5 netbits? or a class B for that matter?
There haven't been classes A, B and C since CIDR was introduced in 1993.
So all of your given networks are possible.
Yes, it is possible.
Basically, the classes are the IP address ranges:
- Class A: 0.0.0.0 - 126.255.255.255
- Class B: 128.0.0.0 - 191.255.255.255
- Class C: 192.0.0.0 - 223.255.255.255
- Class E: ...
- Class F: ...
With that said, if your in a classful network, you have to use the default subnet masks: /8 - /16 - /24.
On the other hand, if your in a classless network, you may use any subnet mask, no matter the value of the first octet.
Hope this helps!
Sources:
[Classless Networks] http://en.wikipedia.org/wiki/Classless_Inter-Domain_Routing
[Classful Networks] http://en.wikipedia.org/wiki/Classful_network
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Is 255.0.255.0 a subnet mask?
If yes, then why?
The reason I thought is its a subnet mask of either class A(N.H.H.H) or class B (N.N.H.H). If there are 255 Network thrn there should be 255 hosts. Please correct me of I am wrong. I am learning the basics of computer networks
RFC 4631, ยง3.1 states that (emphasis mine)
a [subnet] prefix [...] describes the number of significant bits
So, subnet masks must be a contiguous sequence of ones, and 255.0.255.0 is not a valid subnet mask.
Note that this RFC introduced CIDR, which replaced the old style of Class A/B/C addressing.
This is a potential duplicate of https://superuser.com/questions/979915/are-subnets-always-contiguous-1s
i think it is not a subnet mask. because of my knowledge there are 255.0.0.0 for class A; 255.255.0.0 for class B; 255.255.255.0 for class C
theoretically it can be used as a subnet mask but in practical situation subnet mask have
all 1's continuously followed by all 0's. the reason why it can be theoretically be implemented because
no of 1's =NID +SID
no of 0's =HID
in practical situation it will make the computation much more complex
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Closed 10 years ago.
As written in the heading, my question is, why does TCP/IP use big endian encoding when transmitting data and not the alternative little-endian scheme?
RFC1700 stated it must be so. (and defined network byte order as big-endian).
The convention in the documentation of Internet Protocols is to
express numbers in decimal and to picture data in "big-endian" order
[COHEN]. That is, fields are described left to right, with the most
significant octet on the left and the least significant octet on the
right.
The reference they make is to
On Holy Wars and a Plea for Peace
Cohen, D.
Computer
The abstract can be found at IEN-137 or on this IEEE page.
Summary:
Which way is chosen does not make too much
difference. It is more important to agree upon an order than which
order is agreed upon.
It concludes that both big-endian and little-endian schemes could've been possible. There is no better/worse scheme, and either can be used in place of the other as long as it is consistent all across the system/protocol.
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Closed 10 years ago.
Does anybody know of an implementation of TCP on a FPGA WITHOUT using any sort of microblaze? Preferably open source, because it is for an university/research project.
Depending on what you want you maybe can get away with a relative small own implentation (e.g. for packet inspection). The statefulness of TCP makes an full hardware implementation vary big and cumbersome. If possible I would recommend to switch to UDP, that makes it much easier.
As project dealing with all the IP stuff I know NetFPGA, but I never checked their design, so it could be, that they utilize internal a microblaze for some stuff, but my guess would be not.
EDIT: I also remember, that I met one someone from the University of Copenhagen (not sure about this point) at a conference, who also implemented TCP stack on Xilinx FPGAs.
I know Easics has a TCP core. You can find a presentation on it here
As far as I know both Intelop and Velocytech have commercial TCP/IP cores available
A full and low latency TCP/IP Hardware Stack is also available at PLDA
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Closed 10 years ago.
My prof has told me that our final exam will contain a couple questions on IPTables. This is the first networking class offered at out university, but it is also a third year class.
I am wondering if people could help me think of some possible questions that he might ask.
We only have a half a page of notes on IPTables so the questions won't be very hard. He just showed us some simple syntax of adding rules to the tables, like:
%iptables -A FORWARD -i eth0 -p TCP -j ACCEPT
and so on, and ideas on what I should study?
Take a look at the iptables cheat sheet.
If you want more details, this might come in handy: Quick HOWTO: iptables.
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Closed 10 years ago.
Every day I write Web applications, and I have a good understanding of HTTP. However I want to close the gaps in my knowlege of network architecture. I'm not a sysadmin, so a hard-core sysadmin reference book would probably be a bit much for me, but I'm also not looking for a book on how to write code in any way -- I'm interested in the mechanisms underneath all that fun Web code I write.
Any recommendations?
TCP/IP Illustrated, Volume 1: The Protocols by W. Richard Stevens is the book you want to read.
http://www.amazon.com/TCP-Illustrated-Vol-Addison-Wesley-Professional/dp/0201633469
Also by the great W. Richard Stevens is Unix Network Programming (http://www.amazon.com/UNIX-Network-Programming-Networking-Sockets/dp/013490012X).