RPR: Deadlock Ahead?

LONDON -- Lightspeed Europe 2001 -- Lantern Communications Inc. and Luminous Networks Inc. today briefed attendees at the Lightspeed Europe conference on progress in the Institute of Electrical and Electronics Engineers Inc. (IEEE) 802.17 Resilient Packet Ring working group.

Companies made significant progress at the last working group meeting in November, they say. But a battle seems to be heating up as the two main camps -- "Gandalf," led by Cisco Systems Inc. (Nasdaq: CSCO) and its supporters; and "Alladin," including Alcatel SA (NYSE: ALA; Paris: CGEP:PA), Nortel Networks Corp. (NYSE/Toronto: NT), Luminous, Lantern, and other vendors -- haggle over traffic management and a packet format definition.

And it appears the two groups still have a long way to go before January, when they plan to release a single draft proposal (see Cisco Clarifies Ring Strategy ). Indeed, the two camps seem to be on the verge of a deadlock.

In a previous article, Light Reading reported that Cisco had made significant concessions in the final proposal it helped to draft for the technical paper in November (see Cisco in U-Turn on RPR). The company compromised on some key issues, which will ultimately result in it redeveloping its ASICs and software to handle the new standard.

But opponents to the Cisco-backed Gandalf proposal say that the networking giant is dragging its feet on the final two points. Cisco flatly denies these assertions, implying that it is the Alladin side that's unwilling to compromise.

Issue 1: Traffic management

The most hotly contested issue is traffic management, for which each side has a pet solution. The Alladin proposal calls for virtual output queuing, in which packets entering a device are buffered until a message from the output port or queue allows them to enter. This is analogous to cars trying to get onto the highway at rush hour; packets must wait at a “stoplight” until there is enough room on the ring to allow them access.

Alladin supporters say that Gandalf doesn’t provide traffic management. Steve Wood, manager of hardware engineering at Cisco, disagrees. He says Gandalf uses a simple fairness scheme to divide the ring bandwidth among stations. And he claims this is a simpler approach than implementing virtual output queuing, which uses a more complex MAC (media access control) scheme without providing significant performance improvement.

“Gandalf puts the power in the hands of the implementer to do whatever they want to do in terms of traffic management,” says Wood. “Let people make their engineering decisions and see what the market selects."

Some argue that Gandalf’s proposal is technically not the best way to handle congestion on a ring.

“I’ve been studying this for ten years,” says Charles F. Barry, co-founder and CTO of Luminous and co-presenter at the Lightspeed session today. “This is what I did my thesis on for my PhD. I know that technologically this way works better.”

Barry says that mathematical and statistical evidence proves that handling congestion at the input device on the ring is faster and more efficient than waiting for Layer 3 mechanisms to detect congestion and then handle it.

Others in the Alladin camp argue it is not just a technical issue, but an expense issue. Leaving virtual output queuing out of the standard would essentially force vendors using the RPR standard to implement MPLS or some other Layer 3 technology to handle traffic management.

This would be expensive, especially for companies like Alcatel, which are building RPR-enabled Sonet add/drop multiplexers (ADMs) to deliver Ethernet services over rings. It might also hurt DWDM vendors that want to use RPR to deliver Ethernet services over lambdas. These devices do not require routing or MPLS functions, and adding them could be costly.

“If traffic management isn’t included in the standard, it could limit the use of RPR to those wishing to connect devices to routers,” says Frederic Thepot, vice chairman of international affairs for the Resilient Packet Ring Alliance and an independent contractor. “But the standard needs to be as open to DWDM or Sonet ADM vendors as it is for the routing vendors.”

But Cisco disagrees. Wood says that Gandalf fits nicely into ADM or DWDM systems. He also points out that Gandalf opponents also tend to criticize Cisco's use of SRP -- spacial reuse protocol, Cisco's proprietary and controversial implementation of RPR (see Cisco Clarifies Ring Strategy ).

”Opponents of SRP and Gandalf continue to propagate the falsehood that only IP can be transported,” he says. “This is a convenient falsehood with the obvious political benefits.”

Issue 2: Packet format

The working group's other main issue in contention is packet format. Alladin supporters are proposing that the standard use the same packet format as Ethernet with an RPR-specific shim or tag added to it. This is similar to MPLS. Using the Ethernet packet format allows vendors to use cheap, off-the-shelf Ethernet parts to build their systems, says Barry of Luminous. It also means they can use currently available Ethernet testing equipment, he adds.

Conversely, Gandalf’s packet format doesn’t use Ethernet framing. Instead it uses a completely new format, which Barry concedes optimizes IP efficiency. In this format, fewer bytes are used, which means there is less overhead in the network, making the network run more efficiently. But Barry argues that because the format is not based on Ethernet, it cannot take advantage of the inexpensive Ethernet components already available, and it requires new testing gear.

Cisco disagrees entirely with these assertions. Wood says that neither Alladin nor Gandalf can be used with unmodified test equipment. But he has every confidence that the test-set vendors can modify their existing equipment for 802.17, just as they did for SRP when it was originally developed.

As for the ability to use standard Ethernet parts in equipment, Wood concedes that it is handy for first prototypes and easier for startups. But he says it is not the right long-term answer.

“The two leading pre-standard RPR implementations both took the approach of a new frame format that was not compatible with Ethernet,” Wood says. “802.17 is defining a new MAC, and that means that a new MAC silicon will be created. Small parts of an 802.3 MAC will be borrowed for the PHY reconciliation layer, but not the whole design.”

Currently, the RPR work is on schedule, according to Mannix O’Connor, executive secretary for the RPR Alliance and marketing executive at Lantern. The timeline calls for the group to have a single first draft completed by January with the ultimate standard being ratified by the spring of 2003.

But if these issues are not worked out in the January meeting, the standard itself could be in jeopardy.

“These two issues will be the focus of the next meeting,” says Thepot. “We will really be in trouble if we cannot come to some agreement there. The industry may lose faith in RPR altogether, if that happens.”

— Marguerite Reardon, Senior Editor, Light Reading
Fiberfreak 12/4/2012 | 7:29:29 PM
re: RPR: Deadlock Ahead? Hmm...let me see. Leave traffic management in the hands of Routers. Now which company was going for that one.....Cisco??!!! Naaww! They wouldn't try and corrupt a design spec process just to get some more market share now would they? Huh?!

Talk about blatent.
fabless 12/4/2012 | 7:29:28 PM
re: RPR: Deadlock Ahead? Last time I checked, both of SRP (and by extension Gandalf) and Alladin provide bandwidth management mechanisms. I am at a loss to understand how people can claim (let alone believe) that SRP/Gandalf forces people to do traffic management at layer 3. Furthermore, as Mr. Wood suggests Gandalf allows people to decide to implement VOQ or a simple client.

I am even more confused by something else. Dr Barry states that the Alladin proposal is the
best technological proposal. But I checked the original Luminous proposals from the July 2000 meeting. The Luminous scheme relies on RED (which most people would think of as a TCP congestion management scheme). So who is actually pushing a layer 3 scheme? Luminous does not use a fairness scheme that even vaguely resembles Alladin or SRP.
The frame format that Luminous presented at that meeting did not look like the Ethernet Frame format either.

So was Luminous completely wrong about their scheme and did Dr. Barry waste 9.5 years of his life only to see the light a few months ago?

I do agree however that the January meeting will be most interesting.

techmedia 12/4/2012 | 7:29:21 PM
re: RPR: Deadlock Ahead? Funny, at the presentation I saw both Charles F. Barry and Manix O'Connor claimed to be very happy indeed with the progress of 802.17
fundamental_guy 12/4/2012 | 7:28:55 PM
re: RPR: Deadlock Ahead? One of the biggest hurdles for RPR is wrangling
with QoS (call it fairness or traffic management).

9.5 years or even 19.5 years of analysis will
still lead people confounded in this area.
Somtimes, it even becomes a dogma or a religion
because you start inhaling the smoke coming
out of your brains as the wheels move to produce
a finite number for this irrational fraction
during these years.

One could argue that QoS shoud be left in the
dark alleys where people pay their dues for
9.5 or 19.5 years and have RPR just provide
basic hooks like messaging schemes and let each
vendor choose their poison. However, the
interoperability bigots wont leave RPRians scott
free. They want to know how each of these schemes
will work when boxes from different vendors are
put together.

The issue with interoperability on a ring is that
it must makes sense from an external network-to-
network point of view. None of these vendors offer
today interfaces on the customer side with the
same function behind it - so, how is
interoperability going to rationalised to the
user? Leave fairness alone for the moment, whatabout interoperability in terms of
provisioning services? will the Interoperability
bigots take care of that.

BTW, buffering at the edge of the network always
makes sense. However, like any VOQ based swicth
fabric the back pressure/grant mechanisms can get

As Yoda would say - visualize with your mind and
not your eyes (especially after 9.5 years they
tend to glaze over)

HarveyMudd 12/4/2012 | 7:28:52 PM
re: RPR: Deadlock Ahead? Lantern Communications Start up with RPR products only), Luminious Networks ( Start-up with Prestandard RPR products, Cisco ( with some product and boght a RPR chip Company). Both Lantern and Luminous have collected over $80 million and Lminous has collected even more. This should make the polics and positioning statements very clear. Often times there is no technical merit in what many companies say. The companies want to have their position accepted ( many times without merit) based on the products they have developed.

Cisco's strategy may be tied up with the upgrdae of its existing products or it may be a marketing gimmic.

Cisco or any company has to cast its statements in terms of concessions. The product has to have certain requirements that the carriers impose on the vendors. Vendors should make products as per carriers requirement. Of course, if Cisxco or any other company wishes to market to Enterprises they are not bound by anthing except the requirements imposed the Enterprise.

Any network management should mimic the performance and reliability of SONET/SDH rings. This concept is well known and the carriers have very good experience with this technology.

Cisco, Lantern and Luminous have gained a lot of notrity althogh none of these vendors have any significant number of customers. About a year ago, Luminous had one very small trial customer outside of USA.

I think that some of the following points should be taken into account for a robust network management system. These points are just a sketch and not the complete story.

-- manager should be able to manaage multiple RPR rings including SONET/SDH rings.
-- Manager must satify all interoperability requirement besides the one mentioned above.
-- Manager must pass the OSMINE requirements
-- Manager must provide surveillance and provisioning requirements.
-- Interface with DWDMs
-- Manager must provide managability at the transport level
-- Manager must have all operations, administration and management requirements ( alarms, etc)
-- Manger should be able to manage multiple configurations
-- Manager should provide effective management of ( Switched Services, IP services, Preivate Lines, STS-n, and Lambdaervices.

PS: Recent book by Mr. Jack Welch, Former President & CEO of GE ( General Electric) should serve as a guide to any company desirous of acquring California Companies)
rjmcmahon 12/4/2012 | 7:28:41 PM
re: RPR: Deadlock Ahead? PS: Recent book by Mr. Jack Welch, Former President & CEO of GE ( General Electric) should serve as a guide to any company desirous of acquring California Companies)

I haven't read the book (yet) though I have read some excerpts pertaining to CA culture. My opinion is that loyalty comes from great leadership - leadership which is able to identify and reward those that create long term value - leadership that isn't afraid of competition.

The book I'd recommend is written by Peter Drucker titled Innovations and Entrepreneurship.

PS. 20 years from now the carriers may look like the railroads because those that inherited the companies (including the the companies' cash reserves and their revenue generating assets) don't seem motivated by value creation but rather seem motivated by protectionism.

In my experiences, very few that inherit seem to be able overcome entitlement and fulfill their potential. This seems true on both the micro and the macro levels.
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