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buckweet1980

join:2011-12-31
Allen, TX
reply to batsona

Re: FIOS internet - how much faster can FIOS get?

said by batsona:

Active Opto: I never thought of it that way. Given how different ethernet is, from Passive Optical on layer 1 & layer 2, there must be alot of CPU thats chewed up in aggregating 10's of thousands of layer-2 conversations on the OLT, into just a few layer-2 connections when everything is aggregated onto a core Internet router. Depending on what you're doing, it takes alot of CPU to fool around at layer2.

So, the over-subscription is not neccessarily related to bandwidth, but also the ability of the devices that take 10,000 conversations across multiple layer-1 cables, and put them onto 2-3 connections to an aggregation router.

You'd be surprised what a network device can do when it's tasks are implemented on ASICs, they allow for very little traditional CPU to be required. With network switches and high end routers all of the functions needed to service the network are handled via the line card ASICS and rarely ever punted to the device CPU. Typically the only time traffic is punted to the CPU is for control plane traffic.

In the FIOS use case the OLT devices are really nothing more than a bridge/transceiver to get the traffic off of the GPON medium and onto Ethernet at the CO. It doesn't really care about the layer-2 conversations, it just processes them transparently. The real work on FIOS is being done by the routers sitting behind the OLT boxes. FIOS for my node is serviced by a Juniper E series router, which I assume is common across most areas. The E series have been around for a long time and are specifically built for handling 10's of thousands of subscribers on a single box.

Traditional PC/Server computing rules don't apply to devices built specifically for these tasks in terms of traffic forwarding.

McBane

join:2008-08-22
Plano, TX

Yeah the connections per second are nothing for an OLT router or any time of backbone or provider router to handle. That is what network specific hardware is built for. The limiting factor is going to be all about the bandwidth available, on both sides of the OLT.

From my experience though Verizon has got the hang of managing and balancing the FiOS network pretty well. Originally back in '06 - '08 they absolutely sucked at managing it, though. Verizon also doesn't seem to have a problem at expanding capacity where needed as soon as possble compared to any other ISP I've ever had. Luckily their Network Engineers learn from their mistakes unlike some other providers, like most of the cable companies...

I just wish their customer service and billing departments were just as good.



Active Opto

@lstn.net
reply to buckweet1980

said by buckweet1980:

In the FIOS use case the OLT devices are really nothing more than a bridge/transceiver to get the traffic off of the GPON medium and onto Ethernet at the CO. It doesn't really care about the layer-2 conversations, it just processes them transparently. The real work on FIOS is being done by the routers sitting behind the OLT boxes. FIOS for my node is serviced by a Juniper E series router, which I assume is common across most areas. The E series have been around for a long time and are specifically built for handling 10's of thousands of subscribers on a single box.

Not as transparent as what GPON vendors want buyers to believe. The OLT still has to maintain a very long list of MAC addressing table and ONT IDs. It also have to continuously identify/monitor for ONTs for bandwidth mapping, time all the slots accordingly and GEM packaging for the 10s of thousands capacity which the vendors claim. I find them a little exaggerating. The OLT also has the ability to isolate VLANs with transmission containers(T-Conts)and places traffic prioritization on them. That's one way how they do garden walled IPTV services like FIOD TV.

No doubt many call the OLT a dumb Layer 1 switch that has most of the upper layers taken care of by the core routers such as IP routing, but there are some tasks which is unique to the OLT.

quote:
The real work on FIOS is being done by the routers sitting behind the OLT boxes.

This is the 2nd weakness of the GPON OLTs I pointed out earlier. The model itself is best suited to serve high density populated areas with many lines per port (>30 splits per port) to maintain its competitiveness against active switches. Now here's the catch: You buy a very expensive OLT set that claims to cater for 10s of thousands of ONTs after receiving all the demand from the locals. But your backplane of your OLT only takes in multiple 1GE, 10GE and 100GE at most.
How do you intend to keep up with the growing demand?

The key point is to learn from the cable industry where they too had faced this very same problem with the headends not keeping up with the rate cable modems installations. Many started complaining of slowdowns during peak hours and they are not getting close to their subscribed speeds.

Eventually they learn from their mistakes and solved the issue by creating more "mini nodes" to spread things out more evenly by means of effective rationalizing.

In the case of passive networks the same move can be done by increasing more OLT ports, buying more miniaturized OLTs and decreasing split ratios. But before you do that, don't you think the architecture of active switches were better suited for such situations? You are better organized and ready to serve with packages beyond 1gbps with dedicated active ports than you do with passive networks.Would you buy an expensive cabinet sized OLTs just to do few hundred lines? Better spend your extra on the core routing and transport.

I can count my dedicated active ports better with a 10GE than an expensive OLT with a single GPON line card with many logical connections over shared lines.

A monster still needs a matching digestive tract to suit its appetite.

We have to consider our options resonably that 1GE and 10GE are the only mainstream options for uplinks. 100GE is ready but equipments are still expensive. Why would you spent on a big box that claims a capacity which its backhaul can't keep up?

Fiber is not an issue with economics of scale. It's going to get cheaper since silica is plenty to be found in the ground. Manufacturing process improvements will only lower manufacturing cost over time till it becomes cheaper than copper one day. For new ISPs building new infrastructures, it's best they keep solely to Ethernet to simplify their setup. TDM and ATM should be phased out entirely for modern NGNs.With IPTV, very few service providers are using the RF overlay option for their cable tv services.

buckweet1980

join:2011-12-31
Allen, TX

1 edit

Yeah you said something I've been very shocked to find out when researching OLTs (for my education).. I work for a large networking manufacturer, mainly for the enterprise markets. One of the first thing's we always get asked about is over-subscription rates, so naturally that is the first thing I look for when looking at these boxes.

I see tons of ports out, but very few Gig/TenGig in. Some of these manufacturers have 4 ports or more per card. With that I'd expect a 10gig interface for the uplinks. Over-subscription must be very high when factoring in that we're being split 16/32/64 times in the field and then it's being subscribed even much higher at OLT level. My connection (150mb) doesn't ever to seem to have bandwidth issues currently, but I'm sure the day will come when it does..