Subject: RE: IP over Satellite Questions/References

From: "Samaraweera, Nihal" <[email-masked]>
Date: Tue, 6 Jun 2000 13:58:37 +0100

>- What about special satellite-specific link layers? Are MPEG frames 
>carried inside these L2 protocols?

No -  MPEG system layer for transport steam does this job for you.
(Reference - ISO/IEC 13818-1)

Regarding other Qs:

The DVB standard defines 5 different data broadcasting profiles (as listed
below) over DVB compliant broadcast networks.  Each profile is defined for a
different application area.
Data Piping (data is carried directly in the payloads of MPEG-2)
Data Streaming (data is carried in PES packets defend in MPEG-2)
Multiprotocol Encapsulation (data is encapsulated in DSM-CC sections, which
are compliant with the MPEG-2 private section format)
Data Carousels (data is transmitted in a DSM-CC data carousel as defend in
MPEG-2)
Object Carousels (data is transmitted according to the DSM-CC object and
data carousel specifications as defend in MPEG-2).

The data broadcast specification profile for multiprotocol encapsulation
(third in the list) supports data broadcast service that requires the
transmission of communication protocol datagrams over DVB networks. If the
LLC_SNAP_flag is set the payload carries LLC/SNAP encapsulated datagrams,
following the MAC_address_1 field.  When it carries an IP datagram directly,
the LLC_SNAP_flag is set zero.  The fragmentation and reassembling service
is provided using the section length, section number and last section
number.  For example, the section number indicates the fragment number, if
the datagram has been fragmented.  The Medium Access Control (MAC) address
(e.g., Ethernet address) of the destination device will be encapsulated
using the MAC address fields. 

The multi-protocol encapsulation profile is becoming an open standard within
industry, although other data broadcasting profiles have also implemented by
some manufactures 
In a simple configuration of a satellite-based DVB network, a low cost
receive only satellite terminal may be used to construct a cost-effective
high speed simplex distribution. The server transfers the data to the client
through the higher speed satellite link.  A client networking device (the
client computer itself or the router) has two network interfaces; one
connected to the receive DVB link and the other connected by an Internet
Service Provider to the terrestrial network. The hub router forwards data
through the satellite network while the return data may be sent through the
terrestrial - ISDN, ADSL, dialup links (or in future using a low power
satellite return link - see new Astra work).  

Reference:

'Digital Video Broadcasting (DVB) specification for data broadcasting',
ETSI, Draft EN 301 192 V1.1.1 (1997-08), 1997.

N. Samaraweera and G. Fairhurst, 'High Speed Internet Access Using
Satellite-Based DVB Networks', International Network Conference (INC'98),
IEE, Plymouth, UK, 23-28 (1998). 
http://www.erg.abdn.ac.uk/publications.html + more publications

A. N.K.G. Samaraweera, "Return Link Optimisation for Internet Service
Provision Using DVB-S Networks", in Computer Communication Review, a
publication of ACM SIGCOMM, volume 29, number 3, July 1999.
http://www.acm.org/sigcomm/ccr/archive/1999/jul99/ccr-9907-samaraweera4.html

-----Original Message-----
From: Chris Metz [mailto:[email-masked]]
Sent: 06 June 2000 3:27 AM
To: [email-masked]
Subject: IP over Satellite Questions/References

Hi-
Based on a reference to Dish Network and Gilat I heard the other day on 
CNBC I am suddenly very curious about the use of satellite for broadband 
access to the home or business and IP over Satellite in general. As a 
generalization of the TCP over satellite problems and solutions that have 
been well documented over the last few years I was wondering about the 
following:

- IP/MPEG/DVB? So are IP packets carried in the MPE capabilities of MPEG 
for transmission over DVB systems?

- What about special satellite-specific link layers? Are MPEG frames 
carried inside these L2 protocols?

- How is the satellite uplink for a bidirectional system done? I am 
familiar with the DirecPC approach of using a terrestrial (dial, ISDN) 
uplink from the home. Is the bandwidth symmetrical or asymmetrical?

- How much bandwidth is possible? I see that DirecPC advertises 400Kb. What 
are the issues that affect how much bandwidth one can use?

Any conferences/tutorials/whitepapers/books that people can recommend to 
learn about this stuff?

Thanks ...

Chris Metz
Lead IP Architect
Solutions Integration
Service Provider Line of Business
Cisco Systems
email: [email-masked]
offic phone: 408-525-3275
home office: 914-241-0423
pager: 800-365-4578
Internal URL: http://wwwin-people.cisco.com/chmetz/chmetz.htm

---

From: "Robert L. Dean" <[email-masked]>
Date: Tue, 6 Jun 2000 16:20:02 -0000

Chris,

I believe the University of Maryland event was held at U of M - College Park 
at the end of April and was our (ACT Conferences) 4th annual event.  If I'm 
wrong about the event Aaron was referencing, my apologies to all. I was told 
the event was incorrectly listed in an industry pub. as the University's 2nd 
annual event, so the confusion is understandable.  Actually, Aaron may be 
amazingly prescient -- the  director of the University's center for Satellite & 
Hybrid Networks has approached us about producing the event next year 
with the University.

Our main URL is www.actconferences.com which should have a link to past 
conferences-I'm on the road otherwise I'd get you the specific URL.  Also, 
look for a similar conf. in Nov. on the west coast.

Regards,

Robert Dean
VP, Program Development
ACT Conferences
417.865.7500

From:           	"Falk, Aaron" <[email-masked]>
To:             	"'Chris Metz'" <[email-masked]>
Copies to:      	[email-masked]
Subject:        	RE: IP over Satellite Questions/References
Date sent:      	Tue, 6 Jun 2000 09:05:31 -0400 

Chris-

> for transmission over DVB systems?

Yes.

> carried inside these L2 protocols?

The one I'm familliar with (HNS) is an alternative to MPEG/DVB rather than
just DVB. So, IP goes directly into their link layer. So, no MPEG. 

> 
> - How is the satellite uplink for a bidirectional system done? 

The primary difference is that the RF electronics has the capacity to
transmit rather than just receive. This increases the user equipment cost
significantly since the transmission tube is the most expensive part of a
VSAT terminal (and a receive-only terminal doesn't need one). In the
simplest form, you could do PPP over a fixed bandwidth RF link. Most
services do (& will) use something more sophisticated since (a) the duty
cycle for a single terminal is usually low and (b) satellite bandwidth is
expensive. The operators want to share the bandwidth across as many users
as possible (while still providing acceptable service). 

> I am 

Since most of these systems are designed for web access, the bandwidth
will almost always be asymmetrical. But in some designs, particularly the
Ka-band systems in development, that's a matter of provisioning rather
than the architecture. Meaning that if you had a user that needed
symmetric access (or, rather, was willing to pay for it), you could set up
channels with the same rates in both directions. Nevertheless, the
majority of these systems are designed expecting that most users will want
to consume more data than they generate.

> are the issues that affect how much bandwidth one can use?

Sharing satellite bandwidth is a zero-sum game. If your transponder can
handle 45Mbps (a typical value), you can share that across all the users
you want but it has to add up to 45Mbps. If you've ever studied
communications channels, you know you can trade channel utilization
(percentage of time that the channel is not idle) for data delay. In other
words, you make users wait in queues so they can transmit at the most
convenient time. However, if you make them wait too long, they get
annoyed. There can be significant overhead in these channel sharing (DAMA,
Bandwidth on Demand) schemes since you have to tell users when to
transmit.

> Any conferences/tutorials/whitepapers/books that people can 

Lots of conferences:
  -) University of Maryland has an annual Internet over satellite
  conference

     (I couldn't find a URL)
  -) The annual Ka-utilization conference talks about new Ka-band (duplex)
systems
  -) MOBICOM
  -) 'Internet Via Satellite,' marketing oriented but useful if you want
  to
find
     out what people are doing,
http://www.actconferences.com/Satv4/index.htm
  -) IEEE Communication Society usually has some sessions at ICC, 
     http://www.icc00.org/technic/pglance.htm

  ...Hopefully, folks on the mail list can contribute additional ones.

Hope this helps,

--aaron

---
Aaron Falk
NET/36 Network Architect
PanAmSat Corporation
Greenwich, Connecticut, USA
*	Phone: 	203.861.8326
*	Mobile: 	203.912.5689
*	Fax: 		203.861.8677
*	mailto:[email-masked] 
*	http://www.net-36.com