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Ignition · 29-03-2006, 17:26

Development of access networks.

In 2004 Comcast, an MSO in the USA, began to construct the CRAN (Converged Regional Access Network). This essentially is a Metronet (Metropolitan Area Network). Rather than the traditional idea of taking signals from a node in the CATV network, backhauling it along with many other nodes to a central hubsite or headend then converting it to IP on a CMTS and transporting it to a core network the idea of the CRAN was to take the High Speed Internet traffic and convert it to IP at the earliest feasible opportunity, then rather than having inflexible fibre backhaul from hubsites to use 10gigabit Ethernet and a full layer 3 network.

The advantages of this are clear. Communications between subscribers in local areas no longer need to be backhauled to a central point on core network and instead can be contained on the CRAN in that region. Also this allows for more targeted IP services such as IP Telephony and indeed Video on Demand over IP.

Comcast aren’t alone in doing this, last year (2005) Telewest announced a project to install routers in all of their hubsites, and ntl have been building a Metronet in all of their on-net areas, with the plan to eventually backhaul everything across this network.

These metronets and the introduction of IP deeper in to the network allow cableco’s to save on bandwidth by keeping more traffic local and provide ‘IP everything’. As analogue switch off happens the spectrum freed up by removing these channels will be soaked up by DOCSIS 3 cable modem traffic, VoIP and IPTV. At present television channels are delivered to subscribers usually via an ATM network, then they are delivered as a stream of MPEG2 frames. There is no real targeting possible apart from the traditional VoD method of directing an STB to tune to a channel, and it relies on cable network segmentation at the RF level to be sufficient to allow for all streams required in a node to be deliverable. If too many people in a local area want VoD at the same time something has to give and they can’t all have it! VoD over IPTV would be no more difficult to direct to an individual subscriber than the current streaming video seen across the internet at this time.

There’s also bandwidth to be saved for broadcast television as well. If no-one in a local area is watching QVC ZOMFG BUY ME +1 then why waste the bandwidth multicasting it there?

Eventually the cable operator’s aim will be to deliver all services, broadcast TV, Video on Demand, Voice over IP via a single converged DOCSIS 3 fat pipe. As RF is seen less as an impediment to delivering targeted services and purely as a transport network for IP services so cable companies can also increase the bandwidth offered on their high speed internet services, and with all services using the same ultra fat pipes statistical contention will allow MSOs to push the bandwidth they have harder while still achieving levels of service that satisfy most subscribers.

In addition as the Metronets become more developed and the RF network more broken down with fibre deeper into the networks the case for FTTP (Fibre to the Premises) [img]Download Failed (1)[/img]
becomes a more viable one and pushing the fibre those last few hundred feet less of an obstacle (indeed already the main impidement in most cases is the costs of CPE (Consumer Premises Equipment rather than the actual fibre runs which tend to be quite short now).

Cablecos aren’t the only ones following this model. BT’s 21CN is based around the exact same model, and a ‘broadband dial tone’ to every customer on an exchange is their long term aim, with all customers rather than using the traditional switched telephone network being migrated to an IP Metronet. All lines connected to ADSL waiting to be switched on and all calls over IP after hitting exchange. Some telephone lines are already on an MSAN (Multi Service Access Node) – a device which can offer both broadband ADSL and transports telephone calls digitally. Just as Cable companies are converging their access networks onto an ‘IP everything’ model so are BT, with backhaul being provided by MPLS / IP enabled networks.

So what kind of bandwidths can we expect from these services? In a lot of ways it doesn’t actually matter that much as everything we do will be using the same pipe, everything delivered over a broadband network. Sky’s the limit.

29-03-2006, 17:26	#1
Ignition Permanently Banned Join Date: Jun 2003 Location: South-East London Age: 48 Services: Depends who's being serviced :p Posts: 2,588	Something for the geeks I found Development of access networks. In 2004 Comcast, an MSO in the USA, began to construct the CRAN (Converged Regional Access Network). This essentially is a Metronet (Metropolitan Area Network). Rather than the traditional idea of taking signals from a node in the CATV network, backhauling it along with many other nodes to a central hubsite or headend then converting it to IP on a CMTS and transporting it to a core network the idea of the CRAN was to take the High Speed Internet traffic and convert it to IP at the earliest feasible opportunity, then rather than having inflexible fibre backhaul from hubsites to use 10gigabit Ethernet and a full layer 3 network. The advantages of this are clear. Communications between subscribers in local areas no longer need to be backhauled to a central point on core network and instead can be contained on the CRAN in that region. Also this allows for more targeted IP services such as IP Telephony and indeed Video on Demand over IP. Comcast aren’t alone in doing this, last year (2005) Telewest announced a project to install routers in all of their hubsites, and ntl have been building a Metronet in all of their on-net areas, with the plan to eventually backhaul everything across this network. These metronets and the introduction of IP deeper in to the network allow cableco’s to save on bandwidth by keeping more traffic local and provide ‘IP everything’. As analogue switch off happens the spectrum freed up by removing these channels will be soaked up by DOCSIS 3 cable modem traffic, VoIP and IPTV. At present television channels are delivered to subscribers usually via an ATM network, then they are delivered as a stream of MPEG2 frames. There is no real targeting possible apart from the traditional VoD method of directing an STB to tune to a channel, and it relies on cable network segmentation at the RF level to be sufficient to allow for all streams required in a node to be deliverable. If too many people in a local area want VoD at the same time something has to give and they can’t all have it! VoD over IPTV would be no more difficult to direct to an individual subscriber than the current streaming video seen across the internet at this time. There’s also bandwidth to be saved for broadcast television as well. If no-one in a local area is watching QVC ZOMFG BUY ME +1 then why waste the bandwidth multicasting it there? Eventually the cable operator’s aim will be to deliver all services, broadcast TV, Video on Demand, Voice over IP via a single converged DOCSIS 3 fat pipe. As RF is seen less as an impediment to delivering targeted services and purely as a transport network for IP services so cable companies can also increase the bandwidth offered on their high speed internet services, and with all services using the same ultra fat pipes statistical contention will allow MSOs to push the bandwidth they have harder while still achieving levels of service that satisfy most subscribers. In addition as the Metronets become more developed and the RF network more broken down with fibre deeper into the networks the case for FTTP (Fibre to the Premises) [img]Download Failed (1)[/img] becomes a more viable one and pushing the fibre those last few hundred feet less of an obstacle (indeed already the main impidement in most cases is the costs of CPE (Consumer Premises Equipment rather than the actual fibre runs which tend to be quite short now). Cablecos aren’t the only ones following this model. BT’s 21CN is based around the exact same model, and a ‘broadband dial tone’ to every customer on an exchange is their long term aim, with all customers rather than using the traditional switched telephone network being migrated to an IP Metronet. All lines connected to ADSL waiting to be switched on and all calls over IP after hitting exchange. Some telephone lines are already on an MSAN (Multi Service Access Node) – a device which can offer both broadband ADSL and transports telephone calls digitally. Just as Cable companies are converging their access networks onto an ‘IP everything’ model so are BT, with backhaul being provided by MPLS / IP enabled networks. So what kind of bandwidths can we expect from these services? In a lot of ways it doesn’t actually matter that much as everything we do will be using the same pipe, everything delivered over a broadband network. Sky’s the limit.