Highest scored questions
16,963 questions
265
votes
6
answers
506k
views
188
votes
9
answers
119k
views
Why do we need a 3-way handshake? Why not just 2-way?
The TCP 3-way handshake works like this:
Client ------SYN-----> Server
Client <---ACK/SYN---- Server
Client ------ACK-----> Server
Why not just this?
Client ------SYN-----> Server
Client ...
- 1,993
137
votes
6
answers
882k
views
How do you calculate the prefix, network, subnet, and host numbers?
Example:
IP: 128.42.5.4
In binary: 10000000 00101010 00000101 00000100
Subnet: 255.255.248.0
How could you determine the prefix, network, subnet, and host numbers?
- 1,459
96
votes
12
answers
35k
views
IPv6 address space layout best practices
I'm comfortable with IPv4 address space allocations. By which I mean: Given services to plan for, or an organization to network, I have a good grasp of how to plan IP address space usage. (or at least,...
- 5,042
88
votes
4
answers
429k
views
Why and how are Ethernet Vlans tagged?
I hear about VLAN tagging, but I don’t quite understand the concept. I know a trunk cannot accept untagged packets without configuring a native VLAN, and that access ports only accept untagged ...
- 1,099
87
votes
21
answers
79k
views
When to choose fiber instead of twisted pair (copper)
These days both fibre and twisted pair are supporting 1000BASE-T and 10GBASE-T, but when do you choose one over the other? The obvious one is maximum cable length, but what are other factors which ...
- 4,231
81
votes
4
answers
88k
views
What's the difference between IKE and ISAKMP?
I've been building IPsec VPNs for years but to be honest I've never fully grasped the technical difference between IKE and ISAKMP. I often see the two terms used interchangeably (probably incorrectly)....
- 4,758
80
votes
5
answers
545k
views
Ping port number?
Yesterday an interviewer asked me what the port number for ping is and which protocol ping uses: TCP or UDP.
After the interview, I searched on the Internet and found different results: someone says ...
- 1,374
76
votes
5
answers
23k
views
Why are IPv4 addresses running out?
I understand that we are running out (or ran out already?) of IPv4 addresses, but I don't really understand why that is. Right now, every home has its own IPv4 address (dynamically assigned, but still,...
- 871
75
votes
5
answers
33k
views
Is "IPv10" a joke or a serious RFC draft?
Internet Protocol version 10 (IPv10) Specification
The name is funny (IPv4 + IPv6 == IPv10), but the actual proposal looks strange (one more packet format to battle incompatibility between packet ...
- 873
70
votes
6
answers
84k
views
What is the meaning / origin of the terms north-south and east-west traffic?
In context of networking I keep running into statements such as "east-west traffic is larger than north-south traffic". I have tried a bit of googling but have not been able to locate an authoritative ...
- 805
63
votes
10
answers
101k
views
Why only port 80 for web services?
Why isn't it sensible to dedicate more than one TCP/IP port to http? Although admittedly naive, isn't it intuitive to think that server performance could somehow be increased?
- 1,081
62
votes
9
answers
22k
views
Is 30 Mbit/s fibre for WAN faster than 30 Mbit/s copper? [duplicate]
A network engineer professional is overseeing our town's installation of fibre and was explaining how much faster it was.
I pointed out that it wasn't a silver bullet as you had to pay the provider ...
- 721
58
votes
14
answers
197k
views
Multi-Mode and Single-Mode Fiber Differences
When cabling a network using fibre, what is the difference between single-mode and multi-mode fibre? When should I be using one or the other? Are there compatibility and/or speed concerns with either?
- 945
57
votes
2
answers
390k
views
Why do I see a RST, ACK packet instead of a RST packet?
Looking in Wireshark, I often see TCP Streams end with a RST, ACK packet instead of a RST packet. Anyone know why this is?
An example of what I see:
SYN
SYN, ACK
...data...
RST, ACK
Wireshark is ...
- 651