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On Fri, 14 May 2010 13:53:14 -0700, Patrick Elliott wrote:
> On 5/14/2010 1:12 AM, Invisible wrote:
>>> Yes. Who served the IP address to your machine? Time Warner San Diego?
>>> I doubt it.
>>
>> AFAIK, IP addresses are assigned by a central allocation agency.
>>
>> Sure, you don't usually talk to them directly; usually you use one of
>> the IP addresses from the block assigned to your ISP. But my point is,
>> you can't just pick a random number out of the air and try to use that
>> as your IP address. It won't work.
> Mind, in principle, IPV6 could have each "device" us its own IP, kind of
> like routing to you via MAC address. But.. In a practical sense, its
> still the same DNS system being used for it.
That's one of the nice features of IPv6 (taken from IPX, actually, from
what I've read, that essentially did the same thing).
Jim
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Jim Henderson wrote:
> Depends on how the router implements forwarding for multicast - ISTR that
> some routers can be configured to forward multicast traffic up to a
> specified TTL, but what's forwarded is still multicast traffic.
Yes. And if you have a router with three ethernet connections plugged into
it, it's going to duplicate each multicast packet onto each ethernet
connection. Otherwise it isn't multicast.
The whole multicast protocol is nothing more than telling each router on the
path which outputs it needs to duplicate packets on to, so you *don't* get
multicast going onto network segments where nobody is listening for them.
Of course when it's duplicated it's still a multicast packet. That's defined
by the source address, and on any given segment that supports broadcast it
is treated as a broadcast packet. It's still point-to-point between routers.
I.e., it's still point to point if you treat "all the people listening to
the same broadcast address on the same network segment" as one point of the
multicast transmission.
--
Darren New, San Diego CA, USA (PST)
Ada - the programming language trying to avoid
you literally shooting yourself in the foot.
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Jim Henderson wrote:
> Depends on how the router implements forwarding for multicast
Or, to phrase it differently, multicast is somewhat more point-to-point than
a telephone party line is.
--
Darren New, San Diego CA, USA (PST)
Ada - the programming language trying to avoid
you literally shooting yourself in the foot.
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On Fri, 14 May 2010 15:36:09 -0700, Darren New wrote:
> Jim Henderson wrote:
>> Depends on how the router implements forwarding for multicast
>
> Or, to phrase it differently, multicast is somewhat more point-to-point
> than a telephone party line is.
Not really, a party line is many-to-many, but multicast is one-to-many.
The routers act as repeaters, but still operate a multicast "domain" (if
you will) within their local network, as long as there's a client that
has registered with the router to listen in on the multicast.
Jim
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On Fri, 14 May 2010 15:30:22 -0700, Darren New wrote:
> Jim Henderson wrote:
>> Depends on how the router implements forwarding for multicast - ISTR
>> that some routers can be configured to forward multicast traffic up to
>> a specified TTL, but what's forwarded is still multicast traffic.
>
> Yes. And if you have a router with three ethernet connections plugged
> into it, it's going to duplicate each multicast packet onto each
> ethernet connection. Otherwise it isn't multicast.
Assuming the switch isn't multicast aware. I wouldn't be surprised if
some were these days (but I haven't looked at it recently).
> The whole multicast protocol is nothing more than telling each router on
> the path which outputs it needs to duplicate packets on to, so you
> *don't* get multicast going onto network segments where nobody is
> listening for them.
Right.
> Of course when it's duplicated it's still a multicast packet. That's
> defined by the source address, and on any given segment that supports
> broadcast it is treated as a broadcast packet. It's still point-to-point
> between routers. I.e., it's still point to point if you treat "all the
> people listening to the same broadcast address on the same network
> segment" as one point of the multicast transmission.
It's more like multiple people listening to a radio station - the data is
only transmitted once per subnet. The difference between, for example,
using unicast to push an image down to 15 workstations on a subnet and
using multicast to push an image down to 15 workstations on a subnet is a
significant reduction in overall network traffic.
Jim
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On 05/12/10 23:50, Stephen wrote:
> On 13/05/2010 7:34 AM, Neeum Zawan wrote:
>> On 05/11/10 05:45, Mike Raiford wrote:
>>>>> Or Carl Sagan, for that matter.
>>>>
>>>> Who?
>>>>
>>>
>>> Inventor of the communications satellite, physicist, cosmologist ... and
>>> sci-fi writer....
>>
>> Communications Satellite?
>>
>> Methinks you have two writers mixed up.
>>
>> And he sucked as a sci-fi writer.
>>
> Sir Arthur would agree. ;-)
I'm sure he'd be a bit more elegant in the phrasing.
--
All hope abandon, ye who enter messages here.
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Jim Henderson wrote:
> Assuming the switch isn't multicast aware. I wouldn't be surprised if
> some were these days (but I haven't looked at it recently).
Um, no. Even so.
If you have one cable coming into the university campus, and a network for
each building, the router is going to have to send the packets to each
building, duplicating the packets, regardless of how "aware" anyone is.
> It's more like multiple people listening to a radio station - the data is
> only transmitted once per subnet.
Right. But you have to duplicate it for each subnet, which is the "party
line" equivalent.
> The difference between, for example,
> using unicast to push an image down to 15 workstations on a subnet and
> using multicast to push an image down to 15 workstations on a subnet is a
> significant reduction in overall network traffic.
Only for that one subnet.
It's better than a unicast stream to each destination, yes. That doesn't
mean IP isn't point-to-point, if you factor in the broadcast address as
meaning "one subnet is the point."
--
Darren New, San Diego CA, USA (PST)
Ada - the programming language trying to avoid
you literally shooting yourself in the foot.
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Jim Henderson wrote:
> Not really, a party line is many-to-many,
Er, not really, no. A party line is one switch to many phones.
> The routers act as repeaters, but still operate a multicast "domain" (if
> you will) within their local network, as long as there's a client that
> has registered with the router to listen in on the multicast.
Yes, I know how it works. Now we're just arguing over analogies.
My point is that it's *not* like a radio broadcast. It's point-to-point
between routers. The only place you're saving bandwidth is on subnets.
--
Darren New, San Diego CA, USA (PST)
Ada - the programming language trying to avoid
you literally shooting yourself in the foot.
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Le_Forgeron wrote:
> Rejoice, the end of IPv4 addresses is coming... less than 1 year of
> available blocs for some continents... 2 years for the lucky ones!
>
> Get your visa & mastercard ready to pay for a routable ipv4 if ipv6 does
> not happens transparently for joe-user and you want a public server!
That's why I spent the last few days adding IPv6 support to some C++ code
that uses BSD sockets directly :/
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Nicolas Alvarez wrote:
> That's why I spent the last few days adding IPv6 support to some C++ code
> that uses BSD sockets directly :/
Oh, I have joy at work. The resolver on the work box I'm supposed to be
programming is happy to return IPv6 addresses for names in /etc/hosts, even
tho there's no IPv6 in the network stack. It's really quite the PITA.
--
Darren New, San Diego CA, USA (PST)
Ada - the programming language trying to avoid
you literally shooting yourself in the foot.
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