details of one router connection to another

[xyyz]

first of all... not knowing this is sad 'cause i work for a telco...

but, since i've really only done LAN stuff, I don't know how one router is connected to another router through ALL the physical componets.

say you have two offices.

how are they connected from one office to the other, right down to the detail...

i'm talking about the router going to the DSU going to the telephone cable then how it's terninated at the CO, how that thin cable is connected to the cross connect, how that is connected to another cross connect and how that is connected to a MUX... once it gets there, how exactly is it routed? cause you have one MUX connected to another MUX using fiber, but then how does it route to it's final destination, doe that MUX break down to another series of routers which points the traffic to other routers connected to other MUX's?

what's the deal?

 

[spidey07]

router---v.35 serial cable---csu---T1 interface--(whole slew of differerent things)--T1 interface---csu---v.35 serial cable---router

The whole slew of things could be anything. T1 and T3 connections are called Time Division Multiplexing (TDM), because you're getting timeslices of a circuit...clocked just to you. In the background its probably ATM, which is kinda like a virtual mux but instead of muxing time slices it muxes them into 53 byte cells. The circuit endpoints are defined by the ATM network.

Do a search on things like TDM and T1 and you'll get more than I could explain in a post.

oh, T3s work teh same way...exactly. But normally a T3 has a fiber mux at the site running. On a thing called SONET with an optical carrier (OC).

SONET uses things similar to T1 channels called STS which are (basically) a T3. So an OC-3 has three STSs or 3 T3.

blah, blah, blah. And you say you work in telco? C'mon man! This is the basics.
😉

last thing, most of this stuff is ATM. You asked how does it get where? ATM has addresses, just like any other network technology. You gotta know where you came from and where your goind to. SONET has addresses as well.

 

[xyyz]

i know... it's pretty pathetic aint it... but to my defense, i've only been here a few months... i didn't do any WAN elements other than worry about what happens from the CO to the CPE. so beyond the CPE it's all a cloud... no pun intented. i've pulled as much internal documentation i have, but so far i haven't seen an overview, only specifics about one part.

here's the thing though. if you have only one connection, either an ATM or OC between CO's, how is traffic routed? can't exactly route when you only have a point to point connection between CO's.

how does layer-3 routing interface with ATM and SONET? i really wish in what i read Cisco did a bit more about what happens once traffic enters the telco network... not just on the router level, but covering how routers engage with these layer 2 devices to shape traffic.

if i had an overview, then i could go into the components and figure out how they work... so what i'm saying is that i need to know about all those "slew of things" 🙂

BTW, you know anything about SS7?

 

[spidey07]

of course you can route when there's only one path (and there is almost always more than one). That's all a network is, a collection of paths.

SONET has addresses which all the sonet muxes use to "route" the frame to the correct destination. This is layer2 stuff (kinda, sonet is a mix of layer1 and 2)

All the router sees (as a DTE) is a clock, clear to send, data set ready. so the router just spits bits onto the wire. And depending on the technology, possibly some kind of layer2 address (X.25 and frame-relay). Otherwise it is point to point and there is no layer2 addressing, just transmit and receive with some framing around it.

Its hard to explain without a whiteboard. Search on sonet and ATM.

One more thing, the telco doesn't necessarily do anything with your traffic other than attempt to deliver it. Sure we could go into other technologies like Frame-Relay and ATM and MPLS that DO do some traffic management. But its friday night and I'm gonna grab a beer.