Re: Help needed with intermittent internet

JM wrote:
- a "modem" is a device that converts/reconverts a particular type of
carrier signal to a signal that can be used by computers and
networking equipment
- a "router" is a device that specifies where network traffic goes

So, what is the Netgear doing? In my mind it's being a "modem," not a
"router."

A modem is a bridge. A bridge is normally used to connect two different
kinds of physical networks. In this case, it is a bridge between the HFC
network, and the Ethernet network. It operates at layer two of the OSI
network. It doesn't open the IP packets; it only changes the physical
medium over which they're carried.

A router can direct traffic to multiple devices, like the lay definition
would infer. But it doesn't have to. A router, in terms of completer
networking, is a device that works on layer three of the OSI model. It
opens the IP packets, and inspects them. Based on that inspection, it
can direct traffic to multiple devices, or it could do a number of other
things.

In it's application here, it is primarily used to segregate the
subscriber's network from the Comcast network. TCP/IP traffic using
private IP addresses cannot travel between networks. Neither can
transport or network protocols that aren't TCP/IP. The primary purpose
of using a router at this point is segregation of networks, not
direction of traffic. Forget the common dictionary definition of what a
route is, or that the device happens to be named a router. Just because
it's named a router doesn't mean it's directing traffic between multiple
devices, and just because it isn't directing traffic between multiple
devices doesn't mean it's not a router in networking terms.



However, in Comcast's world it's very much a router. Practically
speaking, Comcast doesn't route internet traffic "to" the subscriber
device (router, switch, NIC, etc) to which their equipment is
attached. They route internet traffic "to" their device, which then
"passes to" the subscriber device.

This is how I understand it. Of course, my understanding of all this
is changing almost by the hour, so don't hesitate to shoot that one
full of holes, too.

You're using a layman's concept of what a router is. Remember we're
talking networking here. When I say "router", I'm talking about a device
that works on level 3 of the OSI model, and therefore is partially
opening packets in order to decide what to do with them. I don't care if
there's only one path in and out on each side. That's not relevant in
networking terms.


>> Various computers on the LAN (I assume this includes the
server)

Yes.


GET THE NETGEAR REPLACED WITH A PLAIN OLD MODEM !!!!!

My thoughts and words precisely to at least 2-3 of the Comcast support
people. However, this view reflects a misunderstanding of how Comcast
(and perhaps cable providers in general??) do things. With a business
account using a *static* IP address, there is no such beast as a
"plain old modem." Plain Old Modems are for residential and business
accounts with a "dynamic" IP address.

In the Comcast system, there is no method of assigning a static IP
address to a plain old modem.

It's mostly a business decision to use a combo device. They *can* assign
a static IP address to a customer's equipment with just a modem. The
modem's IP address, a 10.x.x.x address, is only used to manage the
modem, and is not involved in how traffic gets to or through it. Before
DOCSIS, IP wasn't even used to manage the modem, so modems didn't even
have IP addresses. (The exception was the LanCity system, which could
really be thought of as an early version of DOCSIS.)

The apparent reason why they use a combo device for business customers
is that business customers often have more complex networks than home
users, and the router ensures that the two networks are segregated --
and are segregated by a device that the customer can't accidentally take
out of the picture. Essentially, they're afraid that the customer's
complex, mission critical network is going to be operated by someone who
doesn't understand the OSI model, and why it's essential to have a level
3 device segregating the networks.

And, what's even more frustrating, is that Comcast in my area offers
exactly ONE device for business/static provisioning: The Netgear unit
we have.

Then they need to get people who know how to manage it.

When you asked them about a "sleep mode", and they said that there was
no such thing, they were overlooking the ability of the router to block
IP services based on a schedule. Either they were having a cognitive
disconnect, and didn't realize you were talking about the whole device,
and not just the modem part of the combo, or they really don't know what
control they have over their router.

At this point, my confidence that it's the router, not the modem, is
high. You need to be talking to someone who not only knows the box is a
combo device, but understands the difference between the modem and the
router parts, and what they each do. And I'm starting to get the feeling
(based on what you said earlier) that you're not clear about what a
router is as well. Perhaps you don't normally need to know, but whoever
you talk to at Comcast better know, and in this case you need to know so
you can tell whether they know. In other words, someone needs to understand that a router really does.

(Hint: "A 'router' is a device that specifies where network traffic goes," as said earlier.)

--
Warren H.

==========
Disclaimer: My views reflect those of myself, and not my
employer, my friends, nor (as she often tells me) my wife.
Any resemblance to the views of anybody living or dead is
coincidental. No animals were hurt in the writing of this
response -- unless you count my dog who desperately wants
to go outside now.

Maintain your landscape with Black & Decker:
http://www.holzemville.com/mall/blackanddecker




.

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