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IEEE Tunes Ethernet for Telcos

Light Reading
News Analysis
Light Reading
1/19/2001

This was a big week for the emerging resilient packet ring (RPR) technology, a new protocol that will allow metropolitan area service providers to create high-speed, survivable ring networks designed for Internet protocol (IP) and other packet data.

Why should you care? It means the equipment vendors are getting serious about providing standards for packet-based data services that also deliver the fault tolerance of older ring technologies such as Sonet.

The Institute of Electrical and Electronics Engineers Inc. (IEEE) Resilient Packet Ring (RPR) working group 802.17 hosted its first official meeting on Tuesday and Wednesday in California. And a group of vendors -- including Cisco Systems Inc. (Nasdaq: CSCO), Dynarc, Lantern Communications, Luminous Networks Inc., and Nortel Networks Corp. (NYSE/Toronto: NT) -- announced on Monday the formation of the Resilient Packet Ring Alliance to support the standardization and market adoption of RPR (see Resilient Packet Ring Alliance Formed).

In a nutshell, resilient packet ring technology provides Ethernet and other packetized transport the same kind of protection and resiliency found in Sonet rings. Ethernet is a point-to-point technology. This means that when the network is set up in a ring, as nearly 80 percent of metro networks are, traffic moves in only one direction. When an Ethernet connection is interrupted, packets must time out before they are retransmitted -- a process that can take seconds.

But Sonet is different. Traffic can move around the ring in both directions, which means connections can be restored much faster if there is an interruption. Why not stick with Sonet? Because it’s not optimized for data and is more expensive than Ethernet.

This is where RPR comes in. Layered on top of Ethernet, it provides the best of both worlds: Sonet-like protection at Ethernet prices.

The standard is still in its earliest days, but at least four vendors, including Dynarc, Cisco, Luminous and Nortel, claim they are shipping products with RPR-like features. And another routing company, Riverstone Networks, announced this week that it will support the feature on its latest metro router, the RS 38000 (see Riverstone Scores a Coup).

So far, discussion within the working group and the RPR Alliance has been amicable, according to those who were at the meetings. But as the standards process plods on, controversy is liable to surface.

“From what I have seen, people are pretty much resigned to the fact that there will be trade-offs in various proposals,” says Patrick Conlon, VP of business development for Dynarc. “But I’m sure as we get further along, there will be some debate, even though the current commercial products are already implementing most or all of these features.”

The next IEEE working group meeting will be held in March in North Carolina. A full standard isn’t expected to be adopted for at least nine months.

-- Marguerite Reardon, senior editor, Light Reading, http://www.lightreading.com

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Marguerite Reardon
Marguerite Reardon
12/4/2012 | 9:00:19 PM
re: IEEE Tunes Ethernet for Telcos
Do you think RPR will actually be able to fulfill all of its promises? It seems like ATM made a lot of the same claims.
Marguerite Reardon
Marguerite Reardon
12/4/2012 | 9:00:19 PM
re: IEEE Tunes Ethernet for Telcos
You're absolutely right. Sonet does provide quality of service and QOS provisions will be part of the RPR standard when it's completed.

MR
Jey
Jey
12/4/2012 | 9:00:19 PM
re: IEEE Tunes Ethernet for Telcos
Good news. But how about another issue of quality of service which sonet provides?
Jey
Jey
12/4/2012 | 9:00:18 PM
re: IEEE Tunes Ethernet for Telcos
How does the ethernet cost differ from Sonet? How much percentage?
cubsko
cubsko
12/4/2012 | 9:00:18 PM
re: IEEE Tunes Ethernet for Telcos
and security?
anonymous
anonymous
12/4/2012 | 9:00:18 PM
re: IEEE Tunes Ethernet for Telcos
If I have an RPR interface on my router and I want a circuit to somewhere else in the metro, I still plug it into a transport of some type -- either a SONET ADM or DWDM node, both of which offer protection of their own.

So what is compelling about RPR that would make it better than, say, GigE directly over DWDM? My guess is that two vanilla GigE cards and a single optically protected metro DWDM channel would cost less than or about the same as the RPR alternative. This, with greater simplicity, engineering, and without dropping packets when protection events occur...

The place where RPR is attractive is actually within a location. Lots of ports are wasted for router interconnects, and RPR allows one to interconnect several routers using a single port on each router. (I'm basing this upon what I understand about DPT.)
wdog
wdog
12/4/2012 | 9:00:17 PM
re: IEEE Tunes Ethernet for Telcos
The myth that GigE is going to be lower cost than Sonet is based on either intentional bending of the truth, or a lack of understanding. Sonet like ethernet is evolving. What is happening is a comparison of what GigE promises to be compared to old Sonet Add Drop Muxes. Hardly a apples to apples comparison. If you take a look most of the next generation Sonet equipment coming on the market, you would see that the much of the components used for these new Sonet products are the same or very similar to those used in GigE. The equipment costs won't be very different if at all. The real difference between Sonet and GigE is the frame format and sync. versus async. protocols. Both have strong advantages and both will exist for many years.
Steve Saunders
Steve Saunders
12/4/2012 | 9:00:17 PM
re: IEEE Tunes Ethernet for Telcos
wdog makes a really good point.

People associate Ethernet with being cheap.

But that association comes from the price points that it has delivered in the LAN.

And that's also Ethernet now, today (Ethernet hasn't *always* been cheap -- remember when Cisco charged $20K for a 10 meg Ethernet router port?))

There's absolutely no reason why Ethernet in the WAN is going to be dirt cheap. And with the new, small, cheap, ADMs coming in from, er, just about everyone, the price comparison is going to be a lot harder than people think.

I'd like to see some tough questioning of the vendors supporting this standard to find out what they're REALLY planning to charge.

Steve
Steve Saunders
Steve Saunders
12/4/2012 | 9:00:16 PM
re: IEEE Tunes Ethernet for Telcos

Brief history of ATM VP ring technology.

It came. It saw. It got laughed at and fell flat on its face (remmeber Atmosphere?)

What is the difference between RPR and ATM VP ring technology?

Why isn't history about to repeat itself?

Steve
shawn
shawn
12/4/2012 | 9:00:16 PM
re: IEEE Tunes Ethernet for Telcos
my own two cents about ethernet over fiber advantages
1: Sonet's TDM based while metro-ethernet is packet based. The statistical gain in efficiency will be more than 4 times.
2: Sonets QOS is dumb (use your time slot or loose it). RPR will use the newer diffServ or other QOS models.
3:have to statically configure most of the stuff in SONET while metro-ethernet will have all the advantages of packet based technologies (routing etc.,).
4: IP over fiber means less overhead than ip over ATM over SONET etc.,
5: ethernet over fiber also achieves sub 50 millisec failover times like sonet.(bell core standard for transmission of voice).
SONET is on the way out..

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