[nsp] NM-DVB on Cisco Routers

Mark Tinka mtinka at africaonline.co.ug
Sun Aug 24 14:16:10 EDT 2003

Greenhalgh, John wrote:
> Hi Mark,
> Cisco bought a DVB IRD manufacture a few years back, but I don't
> think anything came of it and as far as I know there are no DVB
> interface cards. Usual practice is to use a third party DVB receiver.
> These are either Linux boxes with DVB cards, or dedicated hardware
> boxes (often themselves based on Linux). From the top of my head,
> brands include Broadlogic, Harmonic and Ipricot. The latter tend to
> be more popular these days because they support faster symbol rates.
> On our side (the operator teleport's side) we use third party DVB
> encapsulators connected to routers via Ethernet (and usually with a
> packet shaping device in between).         
> Regards,
> John
> New Skies Satellites

Hi John.

Correct, your description is the typical scenario. The reason I ask is
because certain satellite-hardware manufacturers have even gone further to
produce and sell Ethernet-based [de]modulators for the uplink portion of the
satellite carrier. It still runs SCPC, but also runs on Linux with
specialised modem cards.

The problem here is when you have two Ethernet-based connections to the
satellite hardware, and non of them offer direct connectivity to the
carrier's router [which means eBGP Multihop BGP sessions], issues such as
packet/traffic filtering come into play, because the router's Ethernet
interface is the network's default gateway interface, in and out,
Internet-based packets or not, unlike serial, ATM or POS interfaces in the
ordinary cases.

Firewalling on the Linux OS running on the DVB is possible, but certain
implementations don't do it well. A lot of the DVB boxes still run Linux 2.2
[because it's more stable and has been more rigidly tested for the DVB
cards], which means IPChains is your best bet, and a whole lot of other
issues involved with not having your router directly connected to the
provider's network. At best, you could be able to get away with it, after
breaking a few connections or having to recompile the kernel to support a
firewall feature, etcetera etcetera etcetera!

The assymetric nature of the Internet connection, especially where the
border router isn't directly connected to the satellite infrastructure, can
make for some interesting administration and egineering.

> -----Original Message-----
> From: Mark Tinka [mailto:mtinka at africaonline.co.ug]
> Sent: 22 August 2003 09:11
> To: cisco-nsp at puck.nether.net
> Subject: [nsp] NM-DVB on Cisco Routers
> Hello all.
> I was wondering whether Cisco support DVB network interfaces [coaxial
> 75-ohm terminators] on their routers, and if so, wich ones? 
> The reason I ask is because in Africa, DVB has become a very popular
> method to receive downlink services from US/European-based satellite
> teleports. The DVB stream, which basically carries video and audio
> services for several satellite TV service providers, also
> encapsulates IP packets along with the multicast.    
> ISPs with dedicated DVB receivers [usually running some flavor is
> Linux], tune into the downlink frequency, and use a pre-assigned PID
> to differentiate the several multicast streams on the downlink
> frequency, and use it to decapsulate the correct data streams. It has
> become very very popular because of the amount of bandwidth expansion
> it offers [up to 45Mbps on the DVB card], without the need to upgrade
> or purchase new hardware [such as satellite modems e.t.c].      
> Do Cisco support DVB services on satellite downlink carriers?
> Regards,
> Mark Tinka - CCNP
> Network Engineer, Africa Online Uganda
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Mark Tinka - CCNP
Network Engineer, Africa Online Uganda

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