Become a fan of Slashdot on Facebook

 



Forgot your password?
typodupeerror
Slashdot Deals: Prep for the CompTIA A+ certification exam. Save 95% on the CompTIA IT Certification Bundle ×

Comment Re: wft ever dude! (Score 1) 215

Network, gateway and broadcast are still IP addresses so the company does indeed own 512 addresses.

Second, it is not true that you can not use 3 IP addresses. The most obvious is the gateway address - can the computer doing the routing not also run a web server? Does in fact not most home routers run various services, including a web server, dhcp client, NAT etc?

The subnet would be routed and usually the IP address used for routing would be provided by the IP transit company. As a routed subnet there is nothing that forces a particular subnetting scheme. They could deploy it as a big /23 subnet. Or as a bunch of /30 subnets, allowing only 128 "usable" IP addresses.. But they could equally also deploy /32 addresses and this technique would allow you to use all 512 IP addresses for hosts. Or it could be used as a NAT pool, again allowing you to use all addresses including the first and last address in the series.

As to how you deploy /32 addresses you can do that by DHCP or manually - on Linux eg:

# add the /32 address
ip addr add 123.1.2.0/32 dev eth0
# add a host route for the IP that will be used for gateway
ip route add 10.0.0.1/32 dev eth0
# add default gateway route
ip route add default via 10.0.0.1

Notice that you can use a completely different subnet for gateway, such as 10.0.0.1.

Comment Re:Noise also wasn't heard. Checksum still worked. (Score 1) 391

There is only a very small window where a bad cable gets you bit errors, but not so many that the networking becomes completely unusable. If just 1% of the packets are dropped, your effective TCP transmission rate will drop do 1 Mbit/s or lower.

If you are doing a file download from your NAS you will be doing a lot of 1,500 bytes ethernet frames. That is 15,000 bits per frame. If just one if those bits fail, the packet is dropped. Less than 1% of the packets can be dropped before you will notice that something is seriously wrong with your network, that means less than 1 error bit in 1,500,000 can be accepted. That is so close to zero, that in most cases you will go from perfect network directly to "this does not work" as soon as the signal degrades below the point where there are no bit errors.

Comment Re:Jitter (Score 1) 391

You can not have jitter at the bit level and still receive the signal error free. It is ethernet and you will get your jitter simply because there is other traffic on the cable, so there is no guarantee that the line is free for immediate transmission of your packet. Even with QoS you will have to wait until the current transmitting packet is done.

But jitter is a non issue because all applications that receive audio via ethernet will have buffers to deal with it.

And last, because ethernet is a packet network, you will need to buffer your audio so you can collect enough bytes to send a packet. If you had no buffer, you would be sending packets with 1 sample (4 bytes assuming 16 bit stereo). The overhead of that would be astronomical plus you would indeed die the jitter death.
 

Comment Re:Gigabit speeds, though? (Score 2) 120

Most speedtest servers are hosted on 1 gigabit/s which means you will probably never be able to get a clean 1 gigabit/s reading from those. That would require that you got the server all by yourself and that wont happen.

We are an ISP that sell gigabit. We host our own speedtest.net server on a 10 gigabit/s. It might be considered "cheating" as the user will only be measuring our internal network. But there is simply no other speedtest server nearby that is able to give consistent good readings. There are a couple that will give you ok readings ("almost 1 gig") but that depends on the time of the day and you might have to try several times.

And no, our transit connections are not congested. However ISPs that do not market themselves as selling 1 gig or more will have no reason to establish 10 gigabit/s at all interconnections. But that also means traffic to them will be limited by the interconnection.

Take a look at any IX member list and notice how many companies have only 1 gbps or slower ports. Our users will never get 1 gig to those guys if the traffic goes that route. Remember there will always be other traffic on the port as well.

However, if a user has traffic to multiple destinations he will usually be able to take full advantage. So it is good for families. You will never be slowed down by what others are doing in your household.

Comment Re: Wouldn't apply to Netflix (Score 3, Interesting) 85

I work for an ISP. The way it works is, the 2 isp's have a free peering agreement... Every month or 3 they compare traffic and true up. You ate up 100gig more than we did? You party us X. And vice versa.

I own an ISP. This is not the way it works at all.

Peering policy is actually a rather complex topic. How it works depends on what kind of ISP you are and your size. Small ISPs want to peer no matter what. Large ISPs typically do not want to peer at all. The balanced peering requirement is a poor excuse to say no to peering.

As a small ISP we want to peer with all and everything. This is because any byte transmitted over a free peering is a byte that did not have to go via our paid transit circuit. It does not really matter in what direction that byte is going.

As a residential ISP the majority of our traffic is download. The transit cost is determined by the larger of upload and download. If we can get rid of some download, we will save good money. Netflix is offering to bring some of that download to us for free.

It is very asymmetric and it is a very good deal for both companies. It is a win-win.

So why do large ISPs not want to do this? Because they can get away with forcing everyone to pay to deliver traffic to them. It is no longer a win for them if they think they can get Netflix to be a paying customer. Nor if they already have free peering with the big transit providers, because then they are already getting the stream for free.

Why do mid sized ISPs not want to peer with small ISPs? If the mid sized ISP has a peering agreement with the transit provider of the small ISP, they are already getting the traffic for free. So there is no gain for them. On the other hand, the mid sized ISP might believe the smaller ISP could become a transit customer and you never peer with your customers or potential customers.

But instead of coming clear and tell the real reason, you will typically get the balanced peering requirement quote instead.

In truth balanced peering is not really possible nor desirable for a residential ISP. Only other residential ISP would have balance with us but there will be very little traffic. Just a little bit of bittorrent etc. As a residential ISP we need to peer with content providers, hosting companies and the like.

Comment Re:it could... (Score 2) 148

You need torque to turn this thing. Due to the extreme reduction, the needed torque has little if any relation to what you put at the output. Instead it is just the internal friction of the plastic gears. Which means there is a point where further reduction does not make it any easier to turn.

You need strength in the part to use the output torque. Due to the extreme reduction, output torque is practically limited only to the point where the plastic gears break. There is a point where further reduction does not give you anything, because you are already past the point where the gears break.

Clearly this thing is way past both of those points.

You can not get infinite accuracy either. At some point the output shaft will stop moving smoothly compared to input, but instead move in a way determined by imperfections in the gears.

Comment Re:It's the end of the world as we know it! (Score 1) 307

That has already been invented. It is called address plus port (RFC 6346 or A+P): https://tools.ietf.org/html/rf...

But it will only be used for "compatibility" - to communicate with IPv4 hosts that have not yet been upgraded to IPv6. If you think about it, there are no reason to deploy devices that can understand "quints" as that is just as big an upgrade to the IP stack as switching to IPv6.

Your home router will run the A+P function. It will share an IP address with other customers at your ISP. You will be assigned a port range with that shared IP address. The router will simply do NAT, so your devices on the home network do not need to know anything about this.

At some point you will find that it sucks not to be able to run ssh on port 22 and http on port 80. Therefore your helpful ISP has also provided you with IPv6, where no such limitations apply.

Also the trick only works with UDP and TCP, as other IP protocols do not use ports.

Comment Re:No support for dynamic address assignment?!? (Score 1) 287

That is not what should happen if you have it configured proper.

Say your prefix is 2001:db8:1::/48

Your LAN is 2001:db8:1:1::/64
Your WIFI is 2001:db8:1:2::/64

Your laptop has 2001:db8:1:1::10 on the LAN and 2001:db8:1:2::20 on the WIFI.

Now if you type ping6 2001:db8:1:1::42 it will automatically prefer the LAN interface and use the 2001:db8:1:1::10 IP address. It will not use the WIFI address unless you force it.

On the other hand if you ping6 2001:db8:1:2::42 it will select the WIFI interface and use 2001:db8:1:2::20 as source address.

If you ping something on the internet or if you ping 2001:db8:1:3::99 (assuming the laptop is not connected directly to that), it will first select an outgoing interface (either LAN or WIFI) and then pick the source address from that interface. Again unless you force it to do something different. These are the default address selection rules.

Comment Re:No support for dynamic address assignment?!? (Score 1) 287

Typically your firewall is also the device that is handling the DHCP-PD with upstream and assigning /64s to your downstream routers or to different ports on the device. It will just work. It will not think that the traffic is spoofed. It will also do connection tracking and know exactly what is spoofed and what is not.

Devices will pick the correct IP from the outgoing interface. If your laptop has a Wifi connection, it will use the Wifi address when initiating connections that way. And the LAN address when sending out traffic on the wired network.

Applications can override that behavior but then you are dealing with misconfiguration or broken applications.

Trouble with devices connected to two subnets (links in IPv6 terms) at the same time are basically the same with IPv4 and IPv6.

Comment Re:No support for dynamic address assignment?!? (Score 1) 287

Android does not support DHCPv6 at all. Proposing that they should implement IA_PD but not IA_NA is silly. Doing that might very well break PD on networks where there is a requirement that the next hob for the PD is known and stable. Such as ours...

What you can't do? You can't do tethering except on 3G/4G networks. Why you would want to? Dunno, but I notice that not every Android device is a phone. There could be use cases for that.

Also there are universities and large companies that simply wont let you do SLAAC. I have no experience running such networks, so I can not tell if they are right in doing that. I imagine they could have some of the same issues that we have in our ISP network (ND cache exhaustion etc). A simple defense could be to use a /120 or /112 with DHCPv6.

Nothing succeeds like the appearance of success. -- Christopher Lascl

Working...