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Allure of the Seas Cruise Review by shellys6: Spring Break week on Allure with 3 rambunctious boys!!

Allure of the Seas 4
Member Since 2012
127 Posts

Member Rating

Cabin 4.0
Dining 2.0
Embarkation 4.0
Enrichment Activities 3.0
Entertainment 2.0
Family & Children 4.7
Fitness & Recreation 5.0
Public Rooms 4.0
Rates 3.0
Service 3.0
Shore Excursions 4.0
Value for Money 4.0

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Spring Break week on Allure with 3 rambunctious boys!!

Sail Date: April 2012
Destination: Eastern Caribbean
Embarkation: Fort Lauderdale (Port Everglades)

So...this was our second cruise over Spring Break on Allure. I feel confident in writing a comprehensive review.

Embarkation: we arrived at the pier @ 10:30am. My husband dropped the kids & i off at the curb while he parked the car. The lot was seriously 100 feet away. Embarkation (even with 3 young sons) was expedious...10mins total. There were no lines and we processed efficiently. The downside...the ship was not ready for us so we had to wait in an upstairs lobby for 30-45mins, but it was air-conditioned, orderly and there was a small play area for kids.

Once onboard I proceeded immediately to the guest services area to retreive my iphones (that i had heard about on CC)...I was told to proceed to the card room. Once there, I was only the 3rd person in line but it was a long process and wait (the gentleman in front of me was renting 12 iphones!!). I was able to secure the phones ($30p/phone/week)...they allow you to gps track the other iphones on your acct More and text between eachother. This was great b/c i was able to track my 10yr old when i gave him sign-out priveledges in Adventure Ocean. I would highly recommend proceeding immediately to the location of the phones once onboard to acquire as there is no pre-reserving and the rent out almost immediately.

I met up with my family for a lovely, low-key lunch at the Central Park Cafe which serves make your own salads, paninis, light snacks, sandwiches and drinks for lunch. We ended up eating breakfast here every day.

Afterwards we proceeded to the pool. We had packed pool attire in a small bag for everyone but our room was ready by 1pm (better than the 4pm the year before). We had 2 connecting Central Park balconies for the 6 of us. A 2pp connected to a 4pp. I will say it was much quieter than the Boardwalk balconies we had the year before. Downside, the rooms are king beds and pull-out queen as opposed to bunks inside. This tends to be a pain and there is absolutely no walking room if the sofa is out. Made getting ready in the am difficult whereas with bunks u can just fold up for the space.

Pros: lots of activities (rock-climbing, surfing, multiple pools)
Cons: Bahamas not a good port (will discuss further), housekeeping could've been much better, Adventure Ocean was over-filled most evenings

Pools: Having just sailed on Liberty in Feb, I can now compare the 2 classes of ships. I prefer the larger pools in the Freedom and other classes to the many smaller pools on Allure. They were all very busy and cold, even though the weather was sunny and 80'sF everyday. Best day for the pool is port days when everyone is off the ship. You need to reserve a seat by 9-10am or you will not get one.

Ports: Bahamas was smelly, run-down and dirty. We had booked a tour to Blackbeard's Cay only to be emailed a few days before telling us that the tour was cancelled due to renovations on the island. My eldest and youngest sons opted to go to AO (Adventure Ocean) while the rest of us went ashore. That lasted 1 hour. It was not exciting. Only craftsmen selling there shells and such and a few stores that I would not classify as worth it!

St. Thomas: booked the Pirate Ship & Turtle Cove snorkel trip...WONDERFUL!!! Highlight of our cruise. Very well-organized. Jason & Rikki Dee do a wonderful job entertaining passengers with pirate antics on the 1 hour sail to the cove. While at the cove, they are very helpful with all persons regarding snorkeling, putting on gear and helping take pictures of the turtles. The turtles were everywhere and very easy to see. Highly recommend!!

St. Maarten: DH and eldest went on the Loterie Tree Farm Zip line and said it was wonderful. I took taxi (very easy, just walk out of terminal and get in appropriate cue) with sons to Orient Beach. Once there, easy to rent chairs/umbrella (2 loungers/1 umbrella/2 drink tokens for $15). We only occasionally viewed a topless person...nothing that my kids even noticed. Beach was exquisite, with only a few hagglers selling things.

DINING: this was our first time trying MY Time Dining. I was very impressed. I had tried to make nightly reservs for 6pm but did it too late and only could get 5:45pm. It worked out fine....if we were late (or early), it was no big deal. We were seated with a wonderful waitstaff the first night and requested his table every night. My sons did the FAmily Time dining each night and went off with the AO counselors at 6:45pm each night. This worked out well and the waitstaff was very accomodating. The food was ok...I've had better. I think with the larger ship and so many upcharge restaurants the MDR food has really gone down hill.

Specialty Restaurants:
Lunch @ Izumi: very disappointing this year. Very small menu--think 5 different rolls and a few types of sashimi.
Dinner @ Rita's Cantina Fiesta Party: average...the entertainment was great and the inclusion of guests and children was loved it. Set menu was average, at best. A lot of fried foods as appetizers and fajitas were just ok.
Chef's Table: ok, but not what I expected. The food was good, but not spectacular like i had been led to believe. For $95pp I thought it was going to be phenomenal. MY DH is a wine snob and very knowledgeable about wine and thought the pairings were good but the selections average. The food portions were large but it was a bit exotic for the average eater....I've been to much better restaurants in NYC and Vegas that were less expensive and better. There was little to no interaction from sommelier and chef with guests. Chef seemed impatient when guests were speaking and sommelier seemed bored and irritated with my DH's extensive wine knowledge.

Prohibition Party:
I had signed us up for this after many in our CC roll call were going. It was fun to get dressed up, but the drinks were average (albeit all you can drink) and the entertainment was just ok. I was under the impression it was going to be more like a murder mystery dinner which i quite enjoy.

Vintages Wine Bar:
My DH spent every evening here. The selections were top-notch as were the bartenders/sommeliers. Daniel was well-versed in all wines and remembered my DH from the year before...I think they are BFF's now!! Tapas was great there, too.

Adventure Ocean:
Wonderfully-run, organized and my children LOVED...except...overcrowded. There were several nights when there were 75 kids in the 9-11 yr old group after dinner. My son checked himself out because he felt clausterphobic with all those kids in one room! He was then going in during the day and just meeting up with friends later. My other 2 sons loved the 3-5yr and 6-8yr rooms.

I can't really comment on the nightlife as I was usually in bed by 9pm after a long day swimming!!!

Very disappointed in the Madagascar Aqua was just a meet and greet b/c the crew was changing and they didn't know the routine. I totally understand this.,.but seeing as this is SPRING BREAK and we paid basically rack rates (only Christmas/NY's is higher, I think)...RC would have picked a different time (like January??? or even a few weeks later in April or May??) to change performers!!

The regular Aqua Show was great as was the Fountain boys sat in front row center and loved getting sprayed!!

Overall it was a wonderful cruise, my boys had fun and we will sail RC fact we are sailing on Independence (yes, going down to the smaller ship!) Christmas Break!! Less

Published 04/17/12

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Cabin review: C110593

10593/10591 Connecting Central Park balconies...much quieter than Boardwalk balconies...seemed to be configured to allow more maneuverability in CP balcony rather than Boardwalk. Great views/low noise. Central location.

Port and Shore Excursions

Our shore excursion was cancelled only days before so we decided to just wing it! Was not very enchanted...Nassau was dirty and smelly. Shops were mediocre at best...nothing that was worth purchasing. We were back on the ship within an hour.
Read 3005 Nassau Reviews

Very clean and easy to get around island. Very safe. Easy island to tour on your own. Upon disembarking the ship, the taxi cue is very easy to maneuver and the rates are set. There are several different areas to venture to. We chose to go to Orient Beach. The beach was beautiful with many services. 2 loungers/1 umbrella/2 drink tokens was $15. Food and restrooms available if you rent loungers. There are taxis to take you back to the pier whenever you're ready. Minimal nudism. Clear, tranquil waters....motorized watersports for rent. My DH and son went on the Loterie Tree Farm zipline tour and said it was wonderful. Challenging and thoroughly enjoyed. Would consider returning to St. Maarten for an extended stay.

Schooner Tour

This was the HIGHLIGHT of our entire cruise!!! Amazing tour that i highly recommend. Well-run, very organized and highly entertaining. The pirate sailboat takes an hour sail to an uninhabited island where sea turtles swim freely. Jason & Rikki Dee do a fabulous job entertaining passengers with music and pirate antics. Included the children and allowed them to help with the moorings. Gave pirate eye masks and tatoos to passengers. Helped with snorkel gear and pictures underwater for anyone needing/wanting help. Fresh pina coladas and sodas for trip back. Awesome experience in a well-organized and safe environment!!! Will definitely do it again!!!

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Caribbean Princess Cruise Review by Judicruise: Canada and New England Yucky weather great cruise

Caribbean Princess 5
Member Since 2003
60 Posts

Member Rating

Cabin 5.0
Dining Not Rated
Embarkation 5.0
Enrichment Activities Not Rated
Entertainment 5.0
Family & Children Not Rated
Fitness & Recreation Not Rated
Public Rooms 5.0
Rates Not Rated
Service 5.0
Shore Excursions 5.0
Value for Money 5.0

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Canada and New England Yucky weather great cruise

Sail Date: June 2011
Destination: Canada & New England
Embarkation: New York (Manhattan)

We live in upstate NY so just an hour to travel to the Red Hook Pier. Embarkation was such an easy process. From the car to our cabin in under 15 minutes!

We had a mini suite mid ship. We liked the location and have absolutely no complaints about our stateroom. Wish we had better weather to enjoy our balcony but at least we had a couple of beautiful days.

We made the decision after always using traditional dining to go with eating in the Caribe Cafe each evening. It was so much easier for us and no time worries or dress ups. The food and variety were great.

We did 4 excursions through Princess and enjoyed them all. The whale watching in Bar Harbor was the highlight of our trip. To be so close to giant whales and watch them diving under the water was amazing. The other excursion we both liked was the Upper Deck Trolley in Boston. We had never been to Boston before and felt like we got a great overview of the city. We are not great walkers so this was super More for us.

The singers and dancers were the best we have seen on 6 Princess Cruises.

We found all staff to be polite and friendly. Cruise director was top notch. Less

Published 07/03/11

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Cabin review: AAD425

Great location Bathroom with tub and shower is a plus. Plenty of storage and lots of room.

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mislead dollyrox
We have traveled many time with Norwegian, but due to our most recent experience will think twice about cruising with ... Read more
My husband and I cruised the transatlantic inaugural cruise and felt the whole experience was average. The ship is ... Read more
The Sun was built in 2001 and dry-docked for remodel in 2011. The ship appears fresh and good looking. It is a smaller ... Read more
Never Again NDawn2012
Embarked in Quebec City for Canada and Colonial America cruise. Embark procedure unremarkable. Mini Suite Balcony ... Read more
We are a retired couple from Canada, and this is our 25th cruise, having cruised with NCL about 12 times. This was an ... Read more
It had been three years since we had cruised on a Norwegian ship, and we are so glad we returned to Norwegian! We ... Read more
Repositioning cruises offer great value for the money. People tend to not like flying one way and rarely does one live ... Read more
I had my first cruise with NCL. 2 days to nowhere was a great way to start. Check-in was over an hour but departure ... Read more
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Just came back from a 5 day repositioning cruise on the Norwegian Jewel, from Vancouver to Los Angeles. There were ... Read more
Not the greatest AWENINAZ
This was our 4th NCL cruise having previously sailed on Sky (AK), Pearl (AK), and Epic (Med). I was excited to be back ... Read more
This is our 18th cruise with NCL in 4 years and we are at the Platinum level. We recently moved to Florida, so Tampa ... Read more
This is my first review... so pardon me if I get too wordy. My wife & I flew from Portland into Vancouver ... Read more
After all the excitement of counting down to my first cruise, I was finally aboard for a fulfilled trip to LA. ... Read more
ABOUT US: I've been on three prior cruises, and my husband has been on two. All were NCL cruises, which we like because ... Read more
We live in Oregon and really need more cruises departing from the west coast. Flew to Vancouver BC via Horizon - ... Read more
I have cruised on Carnival, Dolphin (went out of business in early 1990s), Celebrity, Norwegian and Royal Caribbean ... ... Read more
POA - Hawaii nukester
We arrived at the port at 9 am and were gretted by NCL personnel who advised us where to go and drop off our luggage. ... Read more
Embarkation at Los Angeles was a nightmare. It took 2 hours to get through check in and on board. I understand the ... Read more
First time on NCL neolithik
We were a little cautious about NCL after reading some reviews. It turned out to be pretty much what we had read about. ... Read more
We have been on NCL 3 times previously so we knew exactly what to expect. This ship exceeded our expectations. The ... Read more
My husband and I cruised on the Star from October 2nd-October 8th; a repositioning cruise starting in Vancouver and ... Read more
Pre-cruise.. Flew to Seattle and spent 3 nights in Seattle. Great town great time, but this is a cruise review. Used ... Read more
28 Days At Sea - Part 1 - Vancouver to Los Angeles Sept 12 - Sep 24, 2010 We booked four back to back ... Read more
I love cruising, so writing this is not something I am enjoying. We arrived early to check in and soon realized that we ... Read more
Norwegian Star Sailing Date 2 October 2010 Itinerary: Pacific Coastal Number in party 6 (one from Seattle, and 5 from ... Read more

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Nymphea Review

Luxury Deals Luxury Ship Reviews Luxury Itineraries Luxury Features Luxury Cruise Forum
Nymphea - Cruising on the Upper Loire Nymphea - Twin cabin Nymphea - Sun Deck Nymphea - Cuisine
  • Just three cabins make for an intimate atmosphere
  • Each cabin has at least one small window that opens
  • There is a fully stocked bar and fridge in the saloon

Nymphea Overview

By Jana Jones, Cruise Critic contributor
Originally built in 1921 as a Dutch freight barge transporting beer, Nymphea was converted to a hotel barge in 1985. At 81 feet long and 14 feet wide, it's among the smallest of Go Barging's vessels, and is equipped to carry six passengers. Its shallow draft makes it ideal to cruise the sandy River Cher in France's Loire Valley.

The three cabins are cozy -- the largest is just under 130 sq. feet, and the smallest is 84 sq. feet. Extensive use of polished hardwoods anchors the decor, both in the cabins and in the dining saloon. Each cabin's en-suite bathroom contains a toilet, shower, sink, towels, hand soap and hairdryer. Each cabin also has at least one small window that opens, a reading lamp, small closet and individually controlled air-conditioning. In one of the cabins, the twin beds can convert to a double; the other rooms are twin only. All current is 220 volts (North American appliances need converters) with the exception of the bathrooms, which have a 110 outlet for shaving only.

The cabins are located on the same level as the dining saloon (although the bow cabin is three small steps up). The saloon has built-in sofas, a coffee table, dining table for seven, mahogany paneling, brass fixtures and stained-glass windows. Guests can also make use of the fully stocked bar and fridge 24 hours a day, as well as the stereo system and CDs. A small sitting area called the "upstairs saloon" is located a few steps up from the dining area.

The sundeck has seating for all guests, with reclining lounge chairs and an umbrella. Snacks and wine are often served on this deck. In the saloon, meals are served in a single seating, with breakfast and lunch offered buffet-style. Breakfast consists of a Continental repast with breads, croissants, yogurt, cereal, fruit, coffee and tea. Lunch is typically breads, cold-cuts, salads and cheeses, with the occasional hot entree or soup. The meal is served with wine, and finished with dessert and coffee. Dinner is an elegant candlelit affair, with regional cuisine paired with wine, desserts, cheeses, coffee and liqueurs. The dress code at all meals is resort casual, except for the Captain's dinner on the last evening, which requires cocktail attire.

As on all of the hotel barges in European Waterways' fleet, Nymphea is an all-inclusive product, with wines, soft drinks, bottled water, beer, liquor and liqueurs, as well as all onboard meals and snacks, included. (Certain vintages of wine and Champagne are not included, but can be provided for a fee.) Shore excursions, usually lasting from two to four hours, typically take place once a day; all entry fees are included with your cruise fare. Optional activities, such as golf or hot-air balloon rides, cost extra. An air-conditioned mini-bus follows the barge's route and is available at designated times for transport.

Nymphea sails through the central Loire Valley, primarily on the River Cher. Guests are met at the TGV station at St. Pierre des Corps and returned to the same location after the voyage. The itinerary is from Azay sur Cher to Nitray or vice versa, and includes excursions to Clos Luce (home of Leonardo da Vinci), several chateaux and their wineries, and a silkworm nursery.

The barge carries six mountain bikes for guest use, and the itinerary is so leisurely that guests often take the bikes and meet up with the barge at its mooring point. Some games and a small library are also provided. Nymphea offers theme cruise charters, which include wine, walking, cycling or family cruises.

Nymphea has three crew members: a skipper (captain), chef and a hostess/stewardess, all of whom speak English and French. Gratuities are discretionary and typically average between 4 and 7 percent of the fare paid, given to the Captain for distribution.

There is no smoking inside the boat; smoking is allowed outside on the deck only.

Nymphea Ratings

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Old 01-04-2007, 12:40 PM
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ChucksOK ChucksOK is offline
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Join Date: May 2006
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Couldn't agree with you more regarding Prinsendam - I'm looking at booking her on a North Cape cruise in 2008. I missed cruising on her during her days with Royal Viking but I have friends who did and loved her then.


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VIDEO: "Expelled from Paradise" Anime Movie Teaser and Life-Sized Heroine

Director Seiji Mizushima and writer Gen Urobuchi collaborate on anime movie

A new teaser offers a CG mech heavy advanced look at Expelled from ParadiseToei Animation's upcoming feature is set to be directed by Seiji Mizushima (Fullmetal AlchemistMobile Suit Gundam 00) with Gen Urobuchi (Puella Magi Madoka Magicawriting the script.

Meanwhile, a life-size reproduction of Rie Kugimiya voiced protagonist Angela Balzac is on the scene at AnimeJapan.

The display features special human-like skin and chest...

Saito Masatsugu provides character designs, with Junya Ishigaki on the mecha. Shinichiro Miki voices male lead Zarik "Dingo" Kajiwara. A November 15th release date has now been announced, along with Kamiya Hiroshi being added to the cast.

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Scott Green is editor and reporter for anime and manga at geek entertainment site Ain't It Cool News. Follow him on Twitter at @aicnanime.

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Focal Power Performance (FPP) amplifiers give your music the clean, powerful boost it needs to sound its best. Their ultra-high frequency response reproduces all the harmonics and overtones that make vocals and instruments sound natural.

4-channel versatility
You can use FPP 4100 4-channel amp to drive two sets of speakers with 75 watts RMS each, or you can bridge it to 2-channel mode to send up to 240 watts RMS each to a pair of subs for high-quality bass fill. In 3-channel mode, you can bridge the rear channels to power a sub with 240 watts, while still driving your front speakers with 75 watts each. Whatever role this amp plays, Focal power will give you superior performance for your system.

Superior design
The FPP 4100 sports a heavy aluminum chassis that disperses heat efficiently, so it runs cool even when you're pushing your system hard. This FPP amp also includes high-level inputs with signal-sensing, so you can hook one up to any receiver — even a factory stereo — without needing a separate turn-on lead. Focal includes a remote control that allows you to control your bass from the front seat.

Product Highlights:

  • 4-channel car amplifier
  • 75 watts RMS CEA-2006 x 4 at 4 ohms
  • 140 watts RMS x 4 at 2 ohms
  • 240 watts RMS x 2 bridged output at 4 ohms (4-ohm stable in bridged mode)
  • variable high- and low-pass filters (50-150 Hz, 12 dB/octave)
  • wired remote included
  • Class-AB amplifier design
  • differential-balanced inputs help eliminate noise from your vehicle's electrical system
  • frequency response: 10-60,000 Hz
  • speaker-level and preamp inputs
  • 4-gauge power and ground leads recommended — wiring and hardware not included with amplifier
  • fuse rating: 25A x 2
  • 14-15/16"W x 2-3/8"H x 7-7/8"D
  • warranty: 1 year
  • Our 60-day money-back guarantee

My system has plenty of power. Who needs an amp?

You might think you don't need an amp because you have a 400-watt system in your car, or because your new stereo puts out 50 watts a channel. But those are peak wattage ratings, which may boil down to 15 or 20 watts per channel, using the more realistic RMS rating. An amp sends your speakers the power they need to deliver your music with clarity and impact, whether you're using factory speakers or high-performance components. And low-frequency reproduction requires lots of power, so an amp is an absolute must if you're adding a sub to your system.

Focal FPP 4100 Reviews

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Focal FPP 4100

Written By Mark A., Deerfield Beach, FL on Monday, March 31, 2014

Crutchfield Customer Review (What's this?)

Excellent amplifier. I have been looking for a crisp, clean amplifier for my Z28 convertible and was recommended this unit by the Crutchfield advisor. Let me tell you.....This is awesome!!!!!! It makes my Focal speakers shine. The high are exceptional but not too bright, the mid-bass is fantastic. I am extremely impressed with this amp....You will be too.

Pros: Sound quality

Cons: None

High quality

Written By Matt, Milwaukee, WI on Saturday, January 11, 2014

Crutchfield Customer Review (What's this?)

I actually ended up returning the whole system as I was not satisfied by the sound quality and performance output. Because there are so many other components and factors, I am not sure of this amp was a contributing factor to the failure or not. So I am not sure what "star" rating to give it. It could have been many other things. I researched and tuned the system for a full week. Even though I spent a lot of money thinking I would get an extremely great sounding audio system, It did not sound all that much better than the factory bose system. At least not for what I paid.

Pros: seems very well built and high quality

focal fpp 4100

Written By john walder, lynchburg va on Sunday, November 10, 2013

Crutchfield Customer Review (What's this?)

Recently upgraded my car amp , 1. Clean & clear, without making the tweeters sounding too bright 2. Detailed mid bass. 3. Bass is now much more tight & punchy. Used to be kind of boomy earlier. 4. Supplied wired remote is quite responsive.

Focal FPP 4100

Written By AMP Boy, AZ on Saturday, May 04, 2013

Crutchfield Customer Review (What's this?)

Sound and works great so far.

Focal FPP 4100

Written By Dusty, CA on Monday, December 24, 2012

Crutchfield Customer Review (What's this?)

Great amp. Running w/ an Alpine (117) HU and imprint; sound is amazing. Music is crisp and well defined with power to spare.

SQ king, cannot beat it for the money!

Written By DerekF, Coeburn, VA on Wednesday, April 18, 2012

If you are reading this, you are on the right track. Crutchfield has this amp specified with 75x4 at 4 while the box and manual rate the minimum power at 90x4 at 4. This amp is aimed to please anyone with SQ in mind and at 240 x 2 at 2, you even have enough power to run two decent size woofers. The frequency response from 80 hz+ on my Focal's is INCREDIBLE. I have owned quite a few amps in my day and this is HANDS DOWN the best 4-channel amp I have ever heard. The crossover and filters are amazing to only have a 12db/octave. All my frequencies slowly roll off and sound much more like 24db/octave. Moreover, the HPF and LPF are fairly sensitive, but once you get it tuned correctly, WOW. The way this amp brings frequencies together makes you feel like you are in a recording studio. You won't beat this amp for the money, Guarnteed!!

Pros: Sound Quality is unbelievable, runs moderately cool compared to most AB class amps, great power.

Cons: None really, just wish it had 24db/oct to help out with the slopes.

Hands-on research

What's in the box?

Download owner's manual

  • Black four-channel amplifier
  • Four 25 amp ATO fuses (two installed)
  • Four 2-3/4" Allen-head self-tapping screws
  • Two 12" Speaker-level input harnesses (each with a 4-pin Molex plug on one end)
  • External remote control
  • 15' External remote control cable (RJ-14 plug on both ends)
  • 5mm Allen wrench
  • 3mm Allen wrench
  • 2.5m Allen wrench
  • 2mm Allen wrench
  • 4 Adhesive backed rubber washers
  • User Manual (English/ French)

Product Research

Overview: The Focal Power Performance series amplifiers feature a class-AB design for excellent sound quality. The aluminum chassis efficiently dissipates heat to protect the amp from thermal overload. The compact size makes the amp easier to install in tight places. The front-mounted connections and top-mounted controls are easily accessible for a clean installation.

CEA-2006 Compliant: CEA-2006 is a new system of testing and measurement methods for mobile audio amplifiers. This voluntary standard advocates a uniform method for determining an amplifier's RMS power output and signal-to-noise ratio. The criteria for measuring power uses a DC input voltage of 14.4 volts and the RMS power output is measured into a 4-ohm load, with 1% or less Total Harmonic Distortion (THD) plus noise, and at a frequency range of 20 Hz to 20,000 Hz (for full range amplifiers). Signal-to-Noise ratio is measured in weighted absolute decibels (dBA) at a reference of 1 watt into 4 ohms. CEA-2006 allows consumers to compare car amplifiers and receivers on an equal basis. Following the CEA-2006 criteria, the FPP 4100 is rated at 75 Watts RMS x 4 channels with an 80dBA signal to noise ratio.

2-Ohm Stable: When powering four speakers the amplifier is stable down to 2-ohms. The amplifier is rated at 140 Watts RMS x 4 channels in 2 ohms.

Bridgeable: Either half (channels 1-2 and/or channels 3-4) of the FPP 4100 can be bridged to one channel. If both sides are bridged, the power output is 240 Watts x 2-channels into 4 ohms.

Top-mounted Controls: The amplifier has controls conveniently mounted on the top panel under a removable cover. The controls include:

  • Gain Controls: independent rotary controls for channels 1-2 and channels 3-4; continuously variable from 0.2 volts to 5.0 volts for the line level inputs and 0.4 volts to 9.0 volts for the speaker level inputs
  • Crossover Switches: independent 3-way switches for channels 1-2 and channels 3-4; select the crossover operation as High-pass, Full-range, or Low-Pass
  • Frequency: independent rotary controls for channels 1-2 and channels 3-4; the crossover points are continuously variable from 50 Hz to 150 Hz; the slope is 12 dB/octave

Front-mounted Terminals: The FPP 4100 has all of its connections on the front of the amplifier for a clean installation. The terminals include:

  • Speaker Outputs: four pair of set-screw terminals for connecting speakers; they accept up to 10-gauge wire; tightened/loosened with the supplied 2mm Allen wrench
  • External Remote: RJ-14 jack for use with the included external remote control; the external remote controls the output level of channels 3 and 4
  • Line Inputs: Left and right channel 1-2 and left and right channel 3-4 RCA jacks for the input signal from the head unit
  • Hi Level Inputs: two 4-pin Molex jacks for use with the supplied speaker level input harnesses
  • Fader: when only one set of inputs is used (channels 1-2 and not channels 3-4), engaging the fader button sends those inputs to channels 3-4 in addition to channels 1-2
  • Fuses: the amp is protected by two 25-amp ATO-type fuses; spare fuses are included with the amplifier
  • Power: two set-screw terminals for connecting the power and ground cables; they can accept up to 3-gauge wire; a 4-gauge wiring kit is recommended for this amp; tightened/loosened with the supplied 3mm Allen wrench
  • Remote: set screw terminal for the remote turn-on lead; will accept up to 7-gauge wire; tightened/loosened with the supplied 3mm Allen wrench

External Remote Control: The amp has an RJ-14 jack for use with the included external wired remote control. The amplifier also includes a 15' cable to connect the remote to the amplifier. This remote allows you to adjust the output level of channels 3-4 from your listening position. The remote features a rotary knob and a power LED that illuminates when the amplifier is powered on. The remote has two screw holes and can be mounted under the dash (mounting screws not included). The wired remote dimensions are:

  • Width: 1-5/8"
  • Height: 1"
  • Depth: 1-3/4" (2-3/8" including knob and wiring)

Auto Power On: When using the speaker level inputs, the Auto Power On circuit senses an input signal and turns the amp on automatically. This feature makes it easier to add an amplifier to a factory radio or to a receiver with no preamp outputs.

Protection Circuitry: The FPP amplifiers employ four protection circuits: short circuit, thermal overload, over voltage, and polarity reversal.

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team. They verify what’s in the box, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.


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JL Audio C5-570

Evolution™ C5 Series 5"x7" component speaker system — also fits 6"x8" openings

Item #: 136C5570

In Stock

5 Reviews

Installation gear for most cars

Your price: $499.99 Earn up to 500 Rewards points

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JL Audio C5-570

Change how you listen in your car

JL Audio's Evolution™ C5 premium component speaker systems reproduce your music with impressive fidelity and power. Your music will sound smooth and balanced, from the splash of a cymbal to the thump of an electric bass, and everything in between.

The C5-570 5"x7" component system features a pair of silk dome tweeters that broadcast all the musical details without a hint of harshness. JL Audio built the 5"x7" woofers for extended cone travel so they'll move more air, putting more oomph in your music when the rhythm section kicks in. These woofers use the same patented cooling technology developed for the ZR Series speakers, allowing the C5 speakers to play with a wide dynamic range at all volumes.

The C5 crossovers feature 4-position tweeter and 3-position midrange levels that give you 12 possible adjustment combinations for exceptional control over the final sound.

Product Highlights:

  • component speaker system includes two 5"x7"" woofers, 2 tweeters, and two external crossovers
  • mineral-filled polypropylene woofer with butyl rubber surround
  • cast alloy frame with Elevated Frame Cooling
  • 3/4" silk dome tweeter
  • 2-way external crossover with 4-position tweeter level and 3-position midrange control
  • 4-ohm impedance
  • power range: 25-75 watts RMS (225 watts peak)
  • frequency response: 48-25,000 Hz
  • sensitivity: 90.5 dB
  • depth: 2-7/16"
  • warranty: 1 year
  • Our 60-day money-back guarantee

Why install component speakers?

A component speaker system gives you the best possible performance from your car audio system. A system consists of separate woofers, tweeters, and crossovers, each designed to cover one specific range of frequencies. As separate components, the woofer can move freely to deliver more powerful performance, while the tweeter can be custom-mounted in a better spot up closer to your ears, revealing a whole new world of detail. Separate crossovers are far superior to the simple filters wired into full-range speakers, so the components work together for smoother, more focused sound.

JL Audio C5-570 Reviews

Average Customer Review:

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c5 components

Written By Freddy, New Jersey on Tuesday, May 05, 2015

Crutchfield Customer Review (What's this?)

Very nice crossover network with lots of customization options. Nice, small tweeters which fit in my sail panels even though there is side view mirror wiring harnesses behind them. Pivoting tweeters is also a plus. The speaker itself is nice looking, but that matters little once it's installed. The basket eyelets where the screws go through are a little flimsy, I broke two eyelets while mounting the speakers. Don't tighten down too much and you'll be ok. Good sound, although for the price a little more midbass ability would be nice. All and all I would say if you're set on JL's, these are worth the sale price, but maybe not the full price of $500.

Pros: Pivoting tweeters, customizable crossover network, made in Germany.

Cons: Basket eyelets break and bend easily. More midbass ability would be nice for this price.

Totally Awesome

Written By bill4123, Centreville, VA on Wednesday, July 04, 2012

The speakers I had prior to these were the Polk Momo components. The numbers on the spec sheet say the Polks are way better. My ears tell me otherwise. The crossover for these JL speakers does not allow bi-amping but it is far more adjustable thus making bi-amping totally unnecessary (awesome). These things handle high volume levels so much better than the Polks would ever dream of handling. I seriously did not think it was possible for this one set of speakers to create such loud volume. Originally I wanted to have these in my front doors and some 6.75" subs in the rear doors but these things sound so good that I think I'll just do some fine tuning of the head unit and it will sound perfect.

Sure, you could spend $500 on the level of speaker cheaper than this to outfit your whole car, but these are so good you will only need to do the front set.

Pros: Nearly transparent sound. You definately hear more of the subtle instruments.

Cons: The connector on the tweeter if a female and a odd size at that. If they're going to force me to pay for a connector, it should be a size commonly used. Whatever, I got it to work and it sounds great.

Perfect Highs

Written By ZachW, Tomball, TX on Saturday, June 16, 2012

The tweeters are perfect on these speakers. I have the Slash 300v2 pushing them and they are incredible. They handle whatever I throw at them. From Country to Rock to Hip-Hop/Rap. The mid-bass could be better. It distorts at high volumes. But all in all these are great speakers. I would recommend them to anyone.

Pros: Great Highs

Cons: Price, Mid-Range could be better

great speakers and service

Written By One_Shot29, Denver, CO on Saturday, April 07, 2012

Crutchfield Customer Review (What's this?)

I have heard of crutchfield my whole life but this was my first purchase from them, Usually i would go to audio retailers in town to satisfy my habit of buying audio equipment but this time i decided to try something a little higher end. needless to say i was very impressed with my experience and the quality of the equipment. I purchased these speakers and the 2 way C5-570X speakers as open box items. upon arrival i found that the component C5-570's had extensive damage to the mounting holes and the baskets. I contacted crutchfield and found they no longer had any open box sets at the time but to get me on my way they sent me a brand new sealed set. I was very satisfied with the customer service they payed shipping for the new set and to send my old damaged set back. I had my new speakers within a week without any hassle. Now onto the speakers, I installed the crossovers in the doors right next to the speakers and the tweeters could not be flush mounted but i dont mind the way they look. At first the highs sounded a little harsh with real high notes but they wore in and sound great now. mids are very clear and the low notes these speakers can produce is very impressive. I replaced a set of infinity reference speakers with these and was very surprised with the difference. They blend much better with my subwoofer and the notes produced are alot cleaner at louder volumes. I am very satisfied with the speakers and crutcfield I will recommend them to anybody.

Nice "open box" set

Written By Paul, San Diego, CA on Tuesday, October 12, 2010

Crutchfield Customer Review (What's this?)

I bought this set as an "open box" item. The whole set looks like new. The product quality is definentely present. No cheap parts components. The sound is great, it has a natural presence, the high notes are clear and and not harsh, the mid bass sounds without distortion. I replaced an Infinity set with this JL audio and I did noticed that some door resonance sounds dissapeared with the new speakers. My amp is a 4 channel Sony (50 watts x ch). I m very happy with the purchase. Thanks Crutchfield.

Hands-on research

What's in the box?

Download owner's manual

  • 2 Woofers
  • 2 Tweeters (with attached 6" speaker wires)
  • 2 Tweeter flush-mount cups
  • 2 Crossovers
  • 2 Bottom mount adapter rings
  • 2 Self-adhesive JL Audio badges
  • 2 Tweeter mounting rings
  • Adhesive putty
  • 2 Metal spring clips for tweeter fixtures
  • Two 1-1/8" pan-head machine screws
  • 4 Crimp-on 2.8mm male quick slides
  • Twelve 1-1/4" self-tapping screws
  • 8 Speed clips
  • 12 Crimp-on spade connectors
  • 2 Crimp-on 6.4mm female quick slides
  • 2 Crimp-on 4.7mm female quick slides
  • Owner's Manual
  • Woofer cutout template

Product Research

Woofer Features
Tweeter Features
Crossover Features

Woofer Features

Cast Alloy Baskets: The Evolution C5 component speakers feature cast alloy woofer baskets, while incorporating JL Audio's patented "Elevated Frame" cooling system. This cooling technology, also found on the flagship ZR component systems and W7 and W6v2 subwoofers, allows air to flow directly across the top plate and onto the voice coil windings to greatly improve linearity at all listening levels.

Motor Structure: The DMA (Dynamic Motor Analysis)-optimized motor structure achieve outstanding linearity.

Woofer Cones: The cone and suspension elements were designed and manufactured by the world-famous Dr. Kurt Müller & Co of Germany. The speakers feature low-mass, mineral-filled polypropylene cones with butyl rubber surrounds. The cone and surround are inherently well damped to deliver neutral midrange without any coloration. The speakers are also equipped with symmetrical-roll, hybrid-weave spiders.

Mounting: The C5-570 can be top or bottom mounted. Bottom mounting requires using the included adapter ring. The adapter ring can be used (optionally) when top mounting, adding approximately 4/10" to the mounting height and subtracting approximately 4/10" from the mounting depth.

Tweeter Features

Silk Domes: The C5 component system's 3/4" silk dome tweeters is incredibly smooth on- and off-axis for accurate imaging and a big, stable soundstage.

Neodymium Magnets: The small neodymium magnets and small chassis give it excellent placement flexibility.

Performance: Each pair of C5 tweeters is tested and matched to within 1 dB of JL Audio's reference curve to ensure optimum system performance.

Mounting Options: The tweeters come mounted in JL Audio's RSR mounting system to permit precise angling of the tweeters after installation. There are five available positions for angling the tweeter inside the flush mount. The mounting dimensions are as follows:

  • Mounting Depth: 0.56" (1.67" screw depth)
  • Mounting Height: 0.36"
  • Frame Diameter: 1.758"
  • Cutout Diameter: 1.49"

Crossover Features

Two-way Crossover System: The C5 component system utilizes a true 2-way crossover system:

  • High Pass: On the tweeters is a second order high-pass filter utilizing premium Mylar capacitors combined with an air-core inductor. Four tweeter level settings are selectable via jumper pins: +2.0dB, Reference, -1.5dB, and -3.0dB.
  • Low Pass: The low-pass section features a first order filter with three levels of user-definable midrange presence: Low, Reference, and High.

Polyswitch: Polyswitch tweeter protection is incorporated into each C5 component system crossover system.

Barrier Strips: Connections to each crossover network are made via protected nickel-plated barrier strips.

Dimensions: The C5 crossover systems have the following dimensions: Width=3.367", Height=4.72", Depth=1.44"

Connection Note: The C5 component system comes with no speaker wire. Instead, a number of spade connectors and quick slides are included in the hardware pack to be crimped onto speaker wire you provide.

Our Product Research Team

At Crutchfield, you'll get detailed, accurate information that's hard to find elsewhere. That's because we have our own in-house Product Research team. They verify what’s in the box, check the owner's manual, and record dimensions, features and specs. We stay on top of new products and technologies to help people make informed choices.


text:
Wesley Tansey Selected as a 2014 KPCB Engineering Fellow

Wesley Tansey, a UTCS Graduate Student, was selected as a 2014 KPCB Engineering Fellow. This is the third year for the KPCB Engineering Fellows program with almost 2500 applicants from over 200 universities. Throught the KPCB Fellows Program, Wesley will have an opportunity to gain significant experience working on uniquely challenging technical, design and product problems while also developing new relationships that are meaningful to his career. He will also attend private events hosted by portfolio companies where he can meet talented engineering and design icons from across Silicon Valley. Wesley will be working with MyFitnessPal this summer.

When asked about his experience with the selection process, Wesley took us back to October 2013 when he had just met the MyFitnessPal team. Vijay, their VP of engineering, saw a post that Wesley made on Hacker News about his Ph.D. research, which looks at the effects of diet on chronic illness. Vijay thought there could be an opportunity there to collaborate. Since then, the MyFitnessPal team has grown at a rapid pace—from around 20 people in October to over 60 at the moment. Wesley spent this spring break in San Francisco working out of their offices to do some initial data preparation for the summer.

Specifically, Wesley will be working on modeling users and making recommendations. The goal is to understand which diets people are following, how those diets change over time, which diets work and which lead to people quitting, and how MyFitnessPal can make suggestions to people to help them reach their weight loss goals. These are challenging problems and will require a lot of cutting-edge machine learning techniques. With over 50 million users, the potential for impact is huge. MyFitnessPal could potentially help people to lose just 1 more pound on average.

It's also the first time the team will have a chance to really understand dieting with a large population of users. Most nutritional studies are either a small sample size (e.g. 10 people who each log their exact diets every day) or use simplified surveys (e.g. a questionnaire sent to 60,000 people will ask how much fish people eat on average every day). At MyFitnessPal, the team can actually look and see—at a fine grained level—what MILLIONS of people are eating every single day. It's an awesome opportunity to discover new scientific knowledge by leveraging this huge dataset that was only made feasible in the last couple of years.

About KPCB

Kleiner Perkins Caufield & Byers (KPCB) has backed entrepreneurs in more than 700 ventures leading to nearly 200 IPOs, over 375,000 jobs and a deep strategic network. The firm has partnered with pioneering companies like Align, Amazon, Electronic Arts, Genentech, Genomic Health, Google, Intuit, Juniper Networks, Netscape, Symantec, VeriSign and WebMD. KPCB partners serve on the boards of Amazon, Apple, Bloom Energy, Flipboard, Foundation Medicine, Google, Hewlett-Packard, Nest, Square, Tesaro, Twitter and Zynga, among others. KPCB accelerates the success of entrepreneurs with a team of partners delivering company-building services including strategy, operational scaling, recruiting, business development, product delivery and marketing communications. The firm invests in all stages from seed and incubation to growth companies. KPCB operates from offices in Menlo Park, San Francisco, Shanghai and Beijing. For more information, visit:http://www.kpcb.com.

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control printing from the garbage collector

General Form:
(gc-verbose arg)

Garbage collection (gc) is performed by every Lisp implementation; see gc$. However, different ACL2 builds might see more or fewer messages. This macro is intended to provide an interface for controlling the verbosity, which is off if the argument evaluates to nil and otherwise is on.

The above functionality is only supported for the following host Common Lisp implementations: CCL, CMUCL, and GCL. Otherwise, the only effect of this macro is to print a notice that it is not supported. You are welcome to contact the ACL2 developers if you would like to help in adding such support for another host Common Lisp.

Evaluation of a call of this macro always returns nil.


text:
Spatially realistic heart modeling

1. Introduction

reconstructed heart model from CT imagesheart5

Computer aided diagnosis and treatment of cardiovascular disease,
in particular atherosclerosis, left ventricular hypertrophy, valvular
dysfunction, increasingly rely on faithful patient specific mesh
models of heart that can be used in full-cycle simulation of pulsatile
blood flow through the heart.


text:
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text:
Consenting adults in a hot world | Centre for Science and Environment

Consenting adults in a hot world

November 17, 2000

Back to Basics by Anil Agarwal

Why is equity so important for mitigating climate change?

Very simple: because we are all human beings. Not Americans, Europeans, Japanese or Chinese. Or more intelligent or less intelligent. We are humans. Just humans. Full stop. Now we have to decide whether we want to be like a bunch of raucous kids or a group of consenting adults.

Mitigating climate change will be the biggest cooperative enterprise that humans have ever embarked upon. But cooperation, especially willing cooperation, only comes to humans when there is a sense of fairness. This is the only way humans have behaved since times immemorial. Coercion also works but rarely lasts. Long-term willing cooperation only comes when there is a fair deal. One alternative is to offer crumbs to get cooperation but we all know that countries which use this alternative soon run out of crumbs. The supply usually begets its own demand and for crumbs too big a one.

At Rio in 1992 and Berlin in 1995, industrialised countries agreed to take the lead to reduce their emissions. But sooner or later developing countries will have to engage as well. We all know that. The US and EU delegations do not have to keep reminding us of that. The material- and energy-intensive technological model of the 19th and 20th century West, which is slowly spreading is tentacles across the world thanks to the consistent efforts of Western governments, multinational corporations, international financial institutions and educational institutions like MIT and Oxford, will one day make developing countries as big polluters as Western countries today. Unfortunately, the Earth's atmosphere can only take that much abuse. Already, the emissions of just the industrialised countries have gone beyond 'that much'. The signs of trouble are already here. The decade of the 1990s was the hottest of the millennium.

In other words, all people have to work together in the 21st century to reinvent the world's energy system - the very system that drives all modern industry, agriculture, transport and lifestyles. Unless we all want to go back to pre-modern lifestyles or accept huge ecological and economic damages that will affect the poor the most, industrialised countries have to start reinventing their energy systems today and developing countries tomorrow. It will be the biggest hop, skip and jump we have ever seen and all partners will have to shuffle around in tandem. And they will do it only if there is 'equity'. Crumbs offered by the Clean Development Mechanism are neither enough nor will they last long.

What then is the equity issue in climate change? Firstly, the totality of greenhouse gases that we emit has to be limited and shared. But these emissions are closely linked to economic growth, and if we remain in a carbon-driven economy for long, then restricting carbon dioxide emissions in particular will also mean limiting economic growth. Who wants to accept a freeze in economic inequalities? Definitely not democratic and free people, especially given the fact that democracy and freedom was the biggest gain of the 20th century. Even within the EU, when emissions reductions targets were set, equal per capita emissions allowances were used to calculate commitments from the household sector. So equity is not just a Southern issue, it is a global issue.

So what is the answer? Simple: share the total greenhouse gas emissions on an equitable basis for as long as our economies remain carbon-driven, and move towards a zero-carbon economy as fast as possible so that there are no harmful emissions. All this can be done and it can even be done reasonably fast. But it needs co-habitating adults.

Lima, Peru
Doha, Qatar
Milan, Italy
Durban, South Africa
New Delhi, India
Cancun, Mexico
Marrakech, Morocco
Copenhagen, Denmark
The Hague, Netherlands
CoP5 Bonn, Germany
Bali, Indonesia
Buenos Aires, Argentina
Nairobi, Kenya
Kyoto, Japan
Montreal, Canada CMP 1
Geneva, Switzerland
Buenos Aires, Argentina
Berlin, Germany

Arjuna Srinidhi
Tel: +011 29955124, 29956394, 29956399
Extn. (307)


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Almost TCP over UDP (atou)

As part of our Net100 and Probe efforts in improving bulk transfers over high speed, high latency networks, we have developed an instrumented and tunable version of TCP that runs over UDP. The UDP TCP-like transport serves as a test-harness for experimenting with TCP-like controls at the application level similar to TReno. It is not a full transport protocol that one could use as the basis for a file transfer program (though we may consider that in the future). The implementation provides optional event logs and packet traces and can provide feedback to the application to tune the transport protocol, much in the spirit of Web100 but without the attendant kernel modifications. Part of the motivation for developing such a test harness arose from bugs in the AIX TCP stack.

The experimental UDP protocol includes segment numbers, time stamps, selective ACKs, optional delayed ACKs, sliding window, timeout-retransmissions with rate-based restart, bigger initial window, bigger MSS, burst avoidance, congestion avoidance (but more aggressive, experimenting with initial window size and AIMD parameters). The protocol continues to transmit on the first dup ACK's (limited transmit, RFC3042). The test harness consists of a configurable client (transmitter) and an ACK-server (receiver). The transmitter supports Reno, NewReno, and SACK/FACK and more recently HS TCP, scalable TCP, and TCP Vegas. (For a quick review of TCP, visit our bulk transfer page.

The protocol header includes timestamp and segment number. The receiver's header includes the transmitter's timestamp, the segment number of the last good contiguous segment and up to three optional two-word blocks of SACK info.

The cumulative ACK is just like TCP's, with optional delayed ACK support.

A simple configuration file controls the transmitter. The following aspects of the transmitter can be configured:

The receiver can be configured with a RCVBUF size, port number, SACK, delayed-ACK (amount of delay or none), and debug level. The receiver keeps track of missing and duplicate segments and supports a TCP-like cumulative acknowledgement scheme.

The transmitter behaves like TCP with Reno, Newreno, or SACK/FACK using slow-start and congestion avoidance. Upon termination a summary of the configuration and session statistics are printed as below.

config: portcli $Revision: 1.29 $ port 7890 debug 4 Tue May 22 05:18:54 2001 config: initsegs 2 mss 1460 tick 1.000000 timeout 0.500000 config: rcvrwin 300 increment 1 multiplier 0.500000 thresh_init 1.000000 config: newreno 1 sack 0 delack 0 maxpkts 12000 burst_limit 0 dup_thresh 3 config: sndbuf 32768 rcvbuf 32768 swift => 38.835049 Mbs win 300 rxmts 0 3.609111 secs 17520000 good bytes goodput 4854.381103 KBs 38.835049 Mbs pkts in 11542 out 11999 enobufs 0 total bytes out 17518540 loss 0.000 % 38.831813 Mbs rxmts 0 dup3s 0 packs 0 timeouts 0 dups 0 badacks 0 maxack 24 maxburst 300 minrtt 0.065249 maxrtt 0.098987 avrgrtt 0.077747 rto 0.067194 srtt 0.066705 rttvar 0.000122 win/rtt = 45.069119 Mbs bwdelay = 377 KB 258 segs snd_nxt 12000 snd_cwnd 300 snd_una 12000 ssthresh 300 snd_max 12000 The receiver also reports effective bandwidth, number of ACKs sent, and number of segments dropped (or arriving out of order) and the number of duplicated segments.

With a debug level of 4 or higher, a trace file is produced for each transmit and ack packet, data includes time stamp, segment number, round-trip time, congestion window, and threshold.

0.408133 258 xmt 0.408196 234 0.038062 26 26 ack 0.408259 259 xmt 0.408346 235 0.038069 26 26 ack From the trace file, one can plot tcptrace-like information (RTT over time, cwnd over time, average and instantaneous bandwidth, ack-sequence number, etc). Writing the trace file can slow performance for high speed interfaces. With the drop-list, one can induce loss for testing purposes.

Depending on the debug level, events (timeouts, retransmissions, etc.) are loggged on stderr.

3duprxmit pkt 416 nxt 616 max 616 cwnd 200 thresh 200 recover 0 timerxmit pkt 417 snd_nxt 616 snd_max 617 snd_cwnd 100 thresh 100 3duprxmit pkt 2744 nxt 2844 max 2844 cwnd 100 thresh 100 recover 0 packrxmit pkt 2747 nxt 2844 max 2845 cwnd 100 thresh 50 recover 2844 una 2744 packrxmit pkt 2750 nxt 2845 max 2845 cwnd 98 thresh 50 recover 2844 una 2747 badack 6636 snd_max 6808 snd_nxt 6808 snd_una 6661 badack 6892 snd_max 7048 snd_nxt 7048 snd_una 6899 The events above illustrate a retransmit resulting from a three duplicate ACKs, and a retransmit resulting from a timeout. The packrxmit are NewReno (or SACK) retransmits during "recovery". A badack is an out of order ACK or duplicated ACK. The event log and trace-file plots can indicate if the path is getting multiple losses in a window, or single losses, or packets out of order.

The following two excerpts contrast NewReno and SACK. The data sets for the plots are created from the trace file (debug 4). The example below shows a packet loss at time 2.22, and five other losses within the same RTT. NewReno sends a few new packets when after cwnd is halved, then gets a partial ack, and retransmits packet 2225 after one RTT (95 ms), and then retransmits packet 2227 after another RTT, and so on. So full recovery (2.83) takes over six RTT's.

3duprxmit 2.22 pkt 2210 nxt 2335 max 2335 cwnd 123 thresh 179 recover 1979 packrxmit pkt 2225 nxt 2345 max 2345 cwnd 135 thresh 73 recover 2335 una 2210 packrxmit pkt 2227 nxt 2351 max 2351 cwnd 126 thresh 73 recover 2335 una 2225 packrxmit pkt 2230 nxt 2355 max 2355 cwnd 128 thresh 73 recover 2335 una 2227 packrxmit pkt 2234 nxt 2358 max 2358 cwnd 128 thresh 73 recover 2335 una 2230 packrxmit pkt 2237 nxt 2361 max 2361 cwnd 127 thresh 73 recover 2335 una 2234
The next excerpt is from a flow with SACK enabled where there are a sequence of lost packets within a RTT. An initial packet (7149) is lost and retransmitted at 5.85 seconds. SACK provides information to the sender as to what other packets are missing, and so the sender almost immediately retransmits the missing segments as well as some new segments, all within one RTT (95 ms) when the retransmitted packets are finally acknowledged (5.95). Rampdown is also enabled in this example.

3duprxmit 5.85 pkt 7149 nxt 7324 max 7324 cwnd 103 thresh 103 recover 7323 packrxmit pkt 7152 nxt 7324 max 7325 cwnd 103 thresh 103 recover 7323 una 7149 packrxmit pkt 7153 nxt 7324 max 7325 cwnd 103 thresh 103 recover 7323 una 7149 packrxmit pkt 7155 nxt 7339 max 7340 cwnd 103 thresh 103 recover 7323 una 7149

By starting multiple clients and servers (using different port numbers for each pair). you can even do some parallel stream experiments. The TCP-like UDP transport also can make good round-trip estimates from the time stamps. Most TCP stacks use a coarse (0.5 second) resolution timer for estimating round-trip time, and TCP times only one packet per round-trip time. The TCP estimates are complicated by retransmissions and delayed/cumulative ACKs. Newer TCP implementations support a time-stamp option. From analysis of the time-stamp data for our UDP protocol over the ORNL-NERSC link, we chose to initially implement a simple one-second timeout. (Timeouts are rare, and packet loss is usually detected by multiple duplicate ACKs.)

In 2002, we (Tom Dunigan and student Ashraf Jahangeer) added TCP Vegas-like options to atou. Each RTT, Vegas calculates the difference (delta) of the expected throughput and actual throughput. Vegas compares this delta with preset thresholds (alpha, beta, gamma), and exits slow start if gamma is exceeded, and adjusts cwnd depending on delta's relation to alpha and beta during congestion avoidance Though Vegas with small values of alpha/beta/gamma doesn't compete well with standard congestion algorithms on the same link, we are interested in experimenting with larger parameter values for high delay/bandwidth paths. Most of the previous work with Vegas has been through simulation. Below is a plot from an ns simulation of TCP Reno continually experiencing losses (insufficient router buffer space) and exhibiting the classic sawtooth performance, yielding only 75% of the link's capacity. In contrast, TCP Vegas avoids losses in this case and throughput reaches the link capacity (The flows weren't competing, they each were simulated independently for 60 seconds, 1.6 Mbs link, 100 ms RTT, delayed ACKs.)

Our atou Vegas allows us to configure alpha, beta, and gamma, as well as select the type of RTT (minimum, last, maximum, or average) used in calculating the actual throughput. Also we have parameter for using Floyd's slow-start when gamma is exceeded. Other differences between our Vegas and the original Vegas paper and the ns implementation include:

As with the other Vegas implementations, no Vegas adjustments are done during loss recovery, so our Vegas will operate with our various AIMD tuning options.

We have experimented using the Vegas gamma threshold during slow-start to initiate Floyd's slow start (rather than max_ssthresh). The figure below shows two transfers using a Vegas implementation over our TCP-over-UDP from PSC to ORNL (OC12, 77ms RTT). The standard Vegas exits slow-start if the Vegas delta is larger than gamma and enters congestion avoidance phase. The standard Vegas (actually using the Floyd AIMD mods) slowly increases the window in congestion avoidance phase, further dampened by the Vegas alpha/beta (1/3 in this test) and only reaches 36 Mbs. The second transfer switches to Floyd's slow-start when gamma is exceeded. Both transfers exceed gamma at about the 0.5 seconds into the transfer. The Floyd version climbs quickly to the limiting window of 2000 segments and reaches an average throughput of 232 Mbs -- nearly a factor of 8 improvement. Interestingly, for these tests, the cwnd value when gamma (1) is exceeded is around 120 segments, close to Floyd's suggested max_ssthresh of 100.

The figure below illustrates three different TCP-over-UDP transfers from PSC to ORNL. The path was exhibiting packet drops during slow-start. The standard slow-start algorithm suffers a loss and recovers using Floyd's AIMD and reaches an average throughput of 198 Mbs after 10 seconds. By comparison, the Vegas-controlled transfers exit standard slow-start when gamma is exceeded and switch to Floyd's modified slow-start and have no packet losses. The Vegas flow with a gamma of 2 reaches 219 Mbs, the flow with a gamma of 60 reaches 229 Mbs.

The following plots show how standard Vegas (alpha=50,beta=80,gamma=400) is able to avoid queueing and reduce latency when the buffers are over provisioned at sender and receiver. The two atou runs were made from a 100 Mb Ethernet host at ORNL across OC12 to PSC (RTT 77 ms). The bandwidth delay product suggests a buffer size of 660 segments, but the transfers use buffers of 1500 segments. The following plot shows the congestion window for standard TCP versus standard Vegas (no Floyd slow-start exit), and the value of the Vegas delta variable during the transfer.

Both flows reach about 85 Mbs at the end of 10 seconds, even though the Vegas flow backs off in slow-start when delta exceeds gamma (400) and goes into linear congestion avoidance, slowly incrementing cwnd, metered by alpha (50) and beta (80). The standard TCP consumes more buffers and as a consequence the RTT is increased. The following plot illustrates how the overprovisioned buffers cause TCP to suffer increased RTT, while the Vegas RTT stays close to the minimum RTT for the path.

Here are links to more Vegas info.

Test Cases

We have used the TCP-like UDP client and server in network configrations other than the two AIX machinies at NERSC and ORNL. We conducted various experiments between swift and stingray, using different buffer sizes, different TCP options within AIX, and different interfaces. We evaluated both TCP and our TCP-like UDP transport. Figure 2 illustrates the throughput behavior of a TCP flow with no loss. (Actually, the data was collected from our TCP-like UDP transport.) TCP (and our TCP-like UDP protocol) starts with a small window and then exponentially increases it until loss occurs or the available bandwidth or receiver's window size is reached. As can be seen in the figure, in less than a second, available bandwidth is reached. The rate or time to reach peak can be calculated analytically as well, since one additional segment (MSS-sized) is transmitted for each ACK received, which takes one round-trip time. We can't do anything about the round-trip time, so if we wish to improve the startup performance we need to have a larger MSS or try a larger initial window size. (See the links page for papers on increasing the initial window size. Our UDP transport has options for an increasing the MSS and initial window size.) TCP reaches a steady-state, the transmitter is regulated by the ACK arrival rate. Note that it takes many seconds over our ORNL-NERSC path to reach capacity.

Figure 2. Average and instantaneous (0.1 sec samples) bandwidth for transfer from stingray to swift using our TCP-like UDP transport.

The startup rate can be slowed by a factor of two if the receiver utilizes delayed-ACKs (sending an ACK for every other segment received).

To improve this recovery rate, one either needs a bigger MSS or a larger additive increase in the recovery algorithm. (TCP adds one new segment per RTT.) Using our UDP transport or the simulator, we can experiment with altering this increment. (Increasing the increment turns out to be "fair", because as it is, if multiple TCP flows are sharing a link and there is congestion, they all halve their rates, but the nodes nearer (shorter RTT) will get more of the bandwidth than the distant node. As with startup, a delayed-ACK receiver also slows down the linear recovery. To futher speed recovery, one could reduce cwnd by less than half. We have done a few experiments adjusting these AIMD parameters with our tests harness. Figure 3a compares standard AIMD parameters (0.5,1) with setting cwnd to 0.9 of its value and adding 10 segments per RTT.

Figure 3a. Standard and agressive AIMD recovery from a single packet loss using our TCP-like UDP protocol between NERSC and ORNL.

See AIMD papers on links page.)

Most TCP-stacks utilize delayed ACKs, our UDP transport can disable delayed-ACKs and profit from a slightly faster startup rate. The effect of delayed-ACK's on throughput is evident in Figure 4. The figure shows average and instantaneous throughput of a TCP-like transfer with and without delayed ACK's. Using the droplist in our TCP-like UDP transport, we have dropped two packets in two transfers from ORNL to NERSC.

Figure 4. Average and instantaneous throughput with and without delayed-ACKs using our TCP-like UDP protocol between NERSC and ORNL.

Even though the transfers are competing with other Internet traffic, the non-delayed ACK transfer starts up faster and recovers from the loss faster.

Using this same simulation configuration, Figure 5 compares average and instantaneous throughput for an Ethernet-sized segment (1500B) versus a jumbo-frame segment (9000B). As noted earlier, both startup and recovery times are effected by the segment size. ATM supports a 9K segment size, and FDDI supports a 4K segment, so if both endpoints had different network interfaces and the intervening path supported the larger segment size, then throughput should be improved.

Figure 5. Average and instantaneous throughput for 1.5K mss versus 9K mss. (ns)

With our TCP-like UDP transport, we can experiment with larger MSS sizes. We used a larger MSS (2944 and 5888 bytes) with our UDP transport and got better throughput. For the same number of bytes transferred and the same effective window size we got 50 Mbs with 1472-byte datagram, 55 Mbs with 2944-byte datagram, and 58 Mbs with 5888-byte datagram. (Figure 6) The UDP datagrams greater than the 1500-byte Ethernet MTU are fragmented by IP. These larger datagrams have an effect similar to TCP's delayed-ACK, in that all fragments (MTU-sized) have to arrive before the receiver ACK's the datagram. Kent and Mogul, however, argue that IP fragmentation usually lowers network performance.

Figure 6. Average and instantaneous throughput for various datagram sizes.

The same effect can be gained by a "virtual MSS", that is choosing an initial startup of K segments (initsegs, and then adding K segments per RTT (increment) during recovery. The virtual MSS avoids the IP fragmentation. (Figure 6a) illustrates a transfer from NERSC to ORNL with two packets drops using the default MSS and then using a virtual MSS of 10 segments. The virtual MSS is also used for slow start, so there is improvement in starting the connection as well.

Figure 6a. Average and instantaneous throughput for virtual MSS of 10x.

We have recently ('03) added Kelly's scalable TCP modifications the additive increase. An early comparison of recovery from a single loss can be seen here. This is an atou transfer from ORNL to LBL (80 ms RTT) with window limit of 1500 segments and with no delayed ACKs.

Parallel TCP streams also has the effect of multiplying the MSS by the number of streams, but parallel streams also profits from TCP's fairness by letting the application acquire a greater proportion of the bandwidth from competing application flows. Parallel flows often sustain higher throughput in the presence of loss, because often only one stream is affected, and it can recover to its window-bandwidth faster than a single stream with a larger window.

The configuration values initsegs, ssincr, and thresh_init affect the rate and duration of slow start. As noted above, the initial window size (initsegs) can be used to create a virtual MSS, and there are several papers and RFC drafts on choosing the initial window size. Doubling the initial window size reduces the duration of slowstart by one RTT. By increasing ssincr from 1 to K, the duration of slowstart is reduced by factor of log(K)/log(2). In the figure below, standard slow-start (increment of 1) is compared to a 10s test using a slow-start increment of 100. The path is from ORNL to CERN (200 ms RTT) Though not illustrated below, a larger ssincr will also speed recovery in those cases where slow-start is used during the initial recovery phase (e.g., timeouts).

Slow start stops when ssthresh is reached. In most TCP implementations, the initial value of ssthresh is infinite, and is set to cwnd/2 when congestion occurs. If the transfer is not window-limited, our experience has been that packet loss often occurs during initial slow start, so one can set thesh_init to some fraction of rcvrwin to try to avoid this early loss. Setting thesh_init to zero makes the inital value of ssthresh infinite. Floyd's slow-start modifications (max_ssthresh) and Vegas (gamma) can also moderate slow-start.

An OC3 (150 Mbs) connects ORNL and UT. We tested throughput with between two 100 Mbs hosts and found that the ATM/OC3 has been provisioned as a VBR link. Using rate-based flooding of UDP packets, we can reach nearly 100Mbs for a short while, then the traffic policing cuts the sustained rate to about 50 Mbs. We saw similar behavior using AAL5. The VBR policy has an interesting affect on TCP, letting it ramp up during slow-start, then dropping segments to bring the sustained rate back down. Choosing a window of about 22KB avoids any packet loss and achieves a bandwidth of 41 Mbs. Larger window sizes induce loss and reduce bandwidth, smaller window sizes cause the transfer to be buffer-limited.

3. ORNL-cable

We tested throuhgput and loss characteristics from a home cable-modem system to ORNL. The route is asymmetric and tortuous, some 20+ hops all the way to the west coast and back. During one test period, the route into the home cable modem appeared to split the traffic across multiple routes. Rate-based UDP flooding could reach 6+ Mbs in to the home without loss, BUT our test software showed that the UDP packets were wildly out of order (60% of the packets). Packets could be displaced by as much as 30 positions. TCP inbound throughput over this path could only reach 700 Kbs, because TCP treats 3 out of order packets as a loss and does a retransmit. With our TCP-like UDP protocol, we increased the "dup threshold" to 9 to account for the massive re-ordering and improved the throughput to 1.7 Mbs.

A more dramatic illustration of the effect of re-ordering is illustrated in the following bandwidth plot of two flows from LBNL to ORNL (OC12, 80 ms RTT) with a window of 2000 segments, with delayed ACKs, and with SACK enabled. (The plot shows bandwidth measured every 0.1 second and the running average.) The path out of LBNL exhbits a lot of reordering. Using the standard threshold of 3, we can achieve only 18 Mbs after 10 seconds because of 9 congestion events resulting in 289 retransmits. However, the atou server reports 289 duplicate packets received and a max out-of-order of 7, so none of the packets were actually lost but were merely out of order. We ran another test with the client's dup_thresh set to 19. This flow experiences no losses and reaches 218 Mbs after 10 seconds. This particular period of heavy reordering lasted several hours and is probably the result of path through a particular router.

The following figures shows the re-ordering events (green columns) plotted with the instantaneous throughput. In each event, one packet was out of order by 8 slots. For the threshold 3 example, there were 47 reordering events (0.3% of packets were out of order). For the threshold 19 example, there were 309 reordering events (0.2% of packets were out of order). The reordering events seem to be related to congestion or data-rate. The time before the next in order packet arrived was less than a millisecond, suggesting a reordering anomaly in a particular router. See our references page for papers on adjusting TCP to packet reordering. Linux 2.4 TCP does a good job of adapating to reordering and "undoing" the associcated congestion avoidance (see our autotuning page).

4. ORNL-cable (ACK-limited)

The cable modem system we were testing limits data rates from the home to 128 Kbs. This limit in combination with the mutli-hop route actually limited our throughput into the home. Our TCP tests into the home cable modem were actually faster than what we could achieve with our TCP-over-UDP. Our TCP-over-UDP was not using delayed ACKs so there was twice as much bandwidth being consumed on the ACK path, and we were sending empty SACK blocks, further wasting ACK bandwidth. We trimmed off the empty SACK blocks in the ACK path and then enable delayed ACKs in our TCP-over-UDP software and that permitted us to meet or exceed the TCP bandwidth. So for this configuration, delayed ACK's provided a speedup. In some of our ns simulation work we noted that eliminating delayed ACK's also reduced the performance of TCP Vegas. We also have observed that no delayed ACK's during startup (observed with Linux 2.4) may cause packet burst from GigE interfaces that cause drops at some device in the path, so delayed ACKs may be desirable in this case.

We also tested the TCP-over-UDP protocol on slow dialup links, a dual ISDN link, wireless (802.11), Ethernet (10/100), FDDI, GigE, and HiPPI2/GSN links with 64K MTU (reached 1.3 Gbs). We have yet to do rigorous tests comparing the protocol's behavior to TCP, but throughput and loss rates for back-to-back tests are usually quite similar. (This presumes the network hasn't changed "much" ( :-) ) from one test to the next.)

How atou differs from TCP

Our TCP over UDP can do some things that most TCP implementations cannot do.

Our TCP over UDP also cannot do some things that TCP can do.

Work began on atou in the fall of 2000. We have tested our TCP-like protocol on a variety of networks, and on a number of operating systems, including Linux, Solaris, Sun OS, Irix, FreeBSD, Compaq's OSF, and AIX. We also did a port to Windows as well, though the source files do not contain those modifications. Where TCP could be tuned, we tried to get TCP to match or exceed the UDP client/server data rate. The TCP-like protocol has provided higher throughput in some cases than TCP.

The software provides both a time-stamped packet log and event-based information (entering/leaving recovery, timeouts, out-of-order ACKs, etc.) The debug modes give useful information on which packets were lost, window/threshold changes, bandwidth, round-trip times, and the classical sequence/ACK number graphs. The event and trace data have been very useful in understanding packet loss and throughput on various links.

The TCP-like UDP protocol is appealing because it does not require kernel mods to tweak TCP-like congestion/transport parameters. We have demonstrated striking changes in performance when modifing our transport's buffer size, MSS size, or the AIMD parameters. Disabling delayed ACKs and altering the dup threshold has also improved performance in some networks. For multiple losses within a window, the SACK/FACK options improved recovery as expected. We did not see much effect in altering the burst limit or the initial ssthresh value (limits initial slow start). Since we use slow-start after leaving a congestion event, bursts are reduced.

Future work

See our tech report A TCP-over-UDP Test Harness (June, '02), though the info on this web page is probably more current.

PSC's Treno uses UDP/ICMP packets and TCP-like slow-start and congestion control to estimate TCP capacity of a path. In November, 2001, Allman describes a UDP-based tool cap with TCP controls that can be used to measure the bulk transfer capacity of a path. Visit the network performance links page for related RFC's and papers.

Last Modified Monday, 12-Jan-2004 14:30:27 EST (touches: 467820 )
back to Tom Dunigan's page or the Net100 page or the ORNL home page