Fred Baker writes:
Hence, moving a file into a campus doesn't mean that the campus has the file and
will stop bothering you. I'm pushing an agenda in the open source world to add
some concept of locality, with the purpose of moving traffic off ISP
networks when I can. I think the user will be just as happy or
happier, and folks pushing large optics will certainly be.
As I mentioned to Fred in a bar once, there is at least one case where you have
to be a bit careful with how you push locality. In the wired campus case, he's certainly
right: if you have the file topologically close to other potentially interested users,
delivering it from that "nearer" source is a win for pretty much everyone.
This is partly the case because the local wired network is unlikely to be resource
constrained, especially in comparison to the upstream network links.
In some wireless cases, though, it can be a bad thing. Imagine for a moment that
Fred and I are using a p2p protocol while stuck in an airport. We're both looking
for the same file. The p2p network pushes it first to Fred and then directs me to get
it from him. If he and I are doing this while we're both connected to the same
resource-constrained base station, we may actually be worse off, as the
same base station has to allocate data channels for two high data traffic
flows while it passes from him to me. If I/the second user gets the file from
outside the pool of devices connected to that base station, in other words,
the base station , I, and its other users may well be better off.
To put this another way, the end user sees the campus case as a win primarily
because the campus is not resource constrained (at least as compared to its
upstream links). You can only really expect their cooperation when this is
true. In cases where their performance is degraded by this strategy, their
interests will run counter to the backbone's interest in removing congestive
flows. Accounting for that is a good thing.
regards,
Ted
Ted Hardie wrote:
Fred Baker writes:
Hence, moving a file into a campus doesn't mean that the campus has the file and will stop bothering you. I'm pushing an agenda in the open source world to add some concept of locality, with the purpose of moving traffic off ISP networks when I can. I think the user will be just as happy or happier, and folks pushing large optics will certainly be.
As I mentioned to Fred in a bar once, there is at least one case where you have
to be a bit careful with how you push locality. In the wired campus case, he's certainly
right: if you have the file topologically close to other potentially interested users,
delivering it from that "nearer" source is a win for pretty much everyone.
This is partly the case because the local wired network is unlikely to be resource
constrained, especially in comparison to the upstream network links.
In some wireless cases, though, it can be a bad thing. Imagine for a moment that
Fred and I are using a p2p protocol while stuck in an airport. We're both looking
for the same file. The p2p network pushes it first to Fred and then directs me to get
it from him. If he and I are doing this while we're both connected to the same resource-constrained base station, we may actually be worse off, as the
same base station has to allocate data channels for two high data traffic
flows while it passes from him to me. If I/the second user gets the file from outside the pool of devices connected to that base station, in other words, the base station , I, and its other users may well be better off.
A similar (and far more common) issue exists in the UK where ISPs are buying their DSL 'last mile' connectivity via a BT central pipe. Essentially in this setup BT owns all the exchange equipment and the connectivity back to a central hand-off location - implemented as a L2TP VPDN. When the DSL customers connects, their realm is used to route their connection over the VPDN to the ISP. The physical hand-off point between BT and the ISP is what BT term a BT Central Pipe, which is many orders of magnitude more expensive than IP transit.
In this scenario it's more expensive for the ISP to have a customer retrieve the file from another customer on their network, then it is to go off net for the file.
(LLU (where the ISP has installed their own equipment in the exchange) changes this dynamic obviously).
S
Sam Stickland wrote:
Ted Hardie wrote:
Fred Baker writes:
Hence, moving a file into a campus doesn't mean that the campus has
the file and will stop bothering you. I'm pushing an agenda in the
open source world to add some concept of locality, with the purpose
of moving traffic off ISP networks when I can. I think the user
will be just as happy or happier, and folks pushing large optics
will certainly be.
As I mentioned to Fred in a bar once, there is at least one case
where you have
to be a bit careful with how you push locality. In the wired campus
case, he's certainly
right: if you have the file topologically close to other potentially
interested users,
delivering it from that "nearer" source is a win for pretty much
everyone.
This is partly the case because the local wired network is unlikely
to be resource
constrained, especially in comparison to the upstream network links.
In some wireless cases, though, it can be a bad thing. Imagine for a
moment that
Fred and I are using a p2p protocol while stuck in an airport. We're
both looking
for the same file. The p2p network pushes it first to Fred and then
directs me to get
it from him. If he and I are doing this while we're both connected
to the same resource-constrained base station, we may actually be
worse off, as the
same base station has to allocate data channels for two high data
traffic
flows while it passes from him to me. If I/the second user gets the
file from outside the pool of devices connected to that base
station, in other words, the base station , I, and its other users
may well be better off.
A similar (and far more common) issue exists in the UK where ISPs are
buying their DSL 'last mile' connectivity via a BT central pipe.
Essentially in this setup BT owns all the exchange equipment and the
connectivity back to a central hand-off location - implemented as a
L2TP VPDN. When the DSL customers connects, their realm is used to
route their connection over the VPDN to the ISP. The physical hand-off
point between BT and the ISP is what BT term a BT Central Pipe, which
is many orders of magnitude more expensive than IP transit.
In this scenario it's more expensive for the ISP to have a customer
retrieve the file from another customer on their network, then it is
to go off net for the file.
(LLU (where the ISP has installed their own equipment in the exchange)
changes this dynamic obviously).
S
Also bear in mind that many wireless systems have constrained uplink
capacity and anything P2P can quite happily kill a wireless network by
using up too much uplink resource.
Hey Sam,
thats an excellent point made..
Altho I dont think its unique to UK/BT .. since last mile is recognised as most places as the big cost (in the UK its around 100x the cost of the backbone roughly) .. here anything traversing the last mile is not desirable, especially if it does it twice.
Steve