ahhaha, I remember reading something about salmon spawning near MSFT in Redmond. I think it has something to do with that. ANTC is having trouble building Seattle for TCOMA, I think they are blaming it on salmon eggs jamming up the upstream paths.
ahhaha, they erase last weeks documents and put this weeks in,so I had to go through the archives. Here is the whole article,sorry.
In reality it is from the nodes to the headend,where all the major optoelectronics exist. HLIT and others use invisible hubs,passing the data along to the headend. The headend can have many types of error correction and checksums for the data.
New Snags Plague Upstream Path
By LESLIE ELLIS January 25, 1999
There's a new issue brewing in the upstream path, and it has nothing to do with signal ingress or impulse noise.
Instead, it's traffic management -- how to manage all of the services that are supposed to ride in the 5- to 40-megahertz upstream-signaling path.
The questions of how and when to become broadband-traffic specialists, MSO and vendor technologists said, must at least be posed this year.
That's because more and more advanced services are poised to crowd the already-slim upstream path. True, penetration rates for high-speed data and fledgling telephony services aren't large enough on an industrywide basis to command immediate attention. But they will be, if MSO intentions become reality.
"As you do high-speed data, and then stack on telephony -- whether switched or IP [Internet protocol] -- at that point, traffic patterns will have to be watched very closely," noted Paul Gemme, vice president of plant engineering for Time Warner Cable.
"This is the year to understand traffic modeling and engineering, as penetration rates increase for all of the advanced services," agreed Susan Marshall, senior vice president of advanced products for TCI.NET, the high-speed-data arm of Tele-Communications Inc.
Marshall said TCI is already working with @Home Network to tackle traffic issues, but the work is fairly preliminary.
Traditionally, cable-broadband operators haven't needed to be overly concerned about traffic patterns, because those issues were handled architecturally. Bandwidth upgrades handled downstream-channel expansions, and few services shared the 5- to 40-MHz upstream path.
That's in sharp contrast to the telephone industry, which has long used traffic engineering to establish how much switch capacity must be in place to adequately serve the communications needs in neighborhoods linked to central offices around the world.
"There will be another year or two of bandwidth abundance in the upstream, which pretty much makes 1999 the year that the industry should start asking, 'Then what?'" said Andy Paff, chief technology officer for WorldBridge Broadband Services Inc., a Lakewood, Colo.-based firm that specializes in upstream-path communications.
But fast-forward to a home of the not-too-distant future, and the resounding need for broadband-traffic management becomes more readily apparent.
Consider this scenario: Digital-video services, both broadcast and on-demand, are flowing over multiple digital set-tops to as many TVs. Four different family members use cable modems to access the Internet. The family has also subscribed to a primary and secondary telephony package from their cable operator, which gives them four lines of service. That's good for the two teen-agers in the house, who can chat with their friends for hours while they surf the Internet, without interrupting calls to their parents.
They've also subscribed to a video-telephony option for their telephony package, so that they can call and see geographically separated friends and relatives.
From a revenue perspective, it's a cable operator's dream. Using estimated prices, that home is easily forking over $150 per month to its cable-broadband provider.
But if that home falls into the "mainstream," and not the "early adopter" category -- meaning that 99 or so other homes served by the same 500-home node are taking identical services -- it quickly goes beyond a good problem to have, particularly without traffic-management techniques in place.
"You don't want to wake up one day and find out that, uh-oh, there's no bandwidth for those two customers that you're supposed to install," Gemme noted.
Even though nodes can be split in less than half a day to free up additional upstream spectrum, "it's still a situation that we'd obviously rather preplan, rather than having a panic point," Gemme added.
Identifying the bandwidth hogs is part science and part black art, engineers said. The easy-to-spot gobblers are video telephony and some work-at-home data applications. With video telephony -- which is not a broadband reality today -- a camera is attached to the set-top or personal computer and a bandwidth-chomping video session is established from the home.
Telecommuting users become problematic, from an available bandwidth perspective, when users send large files upstream to coworkers over the broadband plant, instead of sending small requests upstream and receiving the bulk of transmissions in the downstream direction.
What clouds matters is a complicated mix of prediction, network architecture, service-penetration rates, simultaneous usage and individual service characteristics.
What happens if upstream channels get clogged up with too much stuff? Phone calls could sound not unlike cellular phones in bad coverage areas, and high-speed-data transmissions could experience delay-related glitches.
There are currently two ways to deal with the need for additional bandwidth in the upstream path, Paff said: brute force and strategy.
"Brute force is shrinking the size of the node; strategy is routers and enhanced intelligence in the IP network," Paff said, adding that the latter "will take at least a year to develop."
Executives with TCI and Time Warner agreed that there is little on the drawing board these days to address the looming upstream-bandwidth crunch. But both MSOs said they could foresee solutions that tapped into cable-modem-headend systems, where most IP intelligence is currently anchored.
"At this point, it's on the radar screen" only, Gemme said.
Paff said the cable-broadband industry would soon be able to cash in on developments made by the alternative long-haul carrier segment.
"Companies like Level 3 [Communications Inc.] and Qwest [Communications International Inc.] have a more urgent need for packet management," Paff noted. "Finding a way to intelligently route packets to manage bandwidth is a core issue facing that industry, and a lot of usable technology will come out of their needs."
Hiram |
