"no synchronization" in Cisco configurations

▼ This text used to be on the BGPexpert.com home page, but Cisco now includes "no syncronization" in the default configuration, so it's unlikely anyone is still going to run into trouble because of this, so I've moved this to a separate page out of the way.

When you run BGP on two or more routers, you need to configure internal BGP (iBGP) between all of them. If those routers are Cisco routers, they won't work very well unless you configure them with no synchronization.

The no synchronization configuration command tells the routers that you don't want them to "synchronize" iBGP and the internal routing protocol such as OSPF. The idea behind synchronizing is that when you have two iBGP speaking routers with another router in between that doesn't speak BGP, the non-BGP router in the middle needs to have the same routing information as the BGP routers, or there could be routing loops. The way to make sure that the non-BGP router is aware of the routing information in BGP, is to redistribute the BGP routing information into the internal routing protocol.

By default, Cisco routers expect you to do this, and wait for the BGP routing information to show up in an internal routing protocol before they'll use any routes learned through iBGP. However, these days redistributing full BGP routing into another protocol isn't really done any more, because it's easier to simply run BGP on any routers in the middle.

But if you don't redistribute BGP into internal routing, the router will still wait for the BGP routes to show up in an internal routing protocol, which will never happen, so the iBGP routes are never used.

The "no synchronization" configuration command tells the routers they shouldn't wait for this synchronization, but just go ahead and use the iBGP routes.

Permalink - posted 2015-02-04

Comparing depth of field: iPhone 6 vs camera

▼ In my post about the iPhone 6 as a camera, I talked about how phone cameras have extensive depth of field (objects near and far are both in focus) compared to regular cameras because their sensors are so small. This is even more pronounced in the iPhone 6 because it has a wide angle lens.

So I thought I'd do some comparisons. This is a photo taken with the iPhone 6. The camera is focussed at a distance of maybe 30 centimeters, so the parliament buildings in the distance are out of focus.

This is the same image taken with a Canon SX280 compact camera with a 20x zoom lens. At this wide angle, the minimum aperture of the zoom lens is f/3.5, which lets in only half of the light that the iPhone's f/2.2 lens lets in. The focal length of the lens is just under 6 mm, while that of the iPhone is just over 4 mm. So the sensor of the Canon camera is 1.4 times larger than that of the iPhone. The depth of field looks a bit larger than that of the iPhone.

Last but not least, the same image taken with a Nikon D7100 with an 18-55 mm lens at 18 mm, resulting in an image that's a bit wider than that of the iPhone and the SX280. The aperture is also f/3.5. The sensor of the Nikon is about 4.5 times larger than that of the iPhone, so even though the lens is a bit wider and the aperture a stop smaller, the depth of field is a lot smaller.

Here's two 100% zooms of the middle of the image. Click on the links to load the specified version of the image: iPhone 6, Canon SX280 or Nikon D7100. The ones with the ∞ symbol are focussed at infinity and should provide a sharp image, the others are focussed at 30 cm and should be more or less blurry. I've also included Nikon versions at f/8 and f/22, so you can see the effect of a smaller aperture on depth of field. Select two images of your choice to compare them.

If you compare the f/22 ∞ version to the f/3.5 ∞ or f/8 ∞ version, you'll see that the sharpness actually goes down at very small aperture sizes. Also, the f/8 ∞ is somewhat sharper than the f/3.5 ∞ version—f/8 is usually the sharpest aperture for most DSLR lenses. However, the SX280 already starts to suffer from the diffraction effect at f/8, so the f/8 ∞ version isn't quite as sharp as the f/3.5 ∞ version, and f/8 is the smallest aperture.

Permalink - posted 2015-01-10

2014 in IPv4 addresses: closing the books on IPv4

▼ Ten years ago, I published my first "IPv4 address use report" over 2005. After that, I did 2006, 2007, 2008, 2009, and 2010. Today, I'm going back to the well one last time and provide an overview of what happened with the IPv4 addresses the past decade, which will close the book on the IPv4 address space as far as I'm concerned.

At the end of 2005, 2056.30 million of the 3706.65 usable IPv4 addresses had been given out: 55%. Today, it's 3592.99 million, which is 97%. Can you imagine driving a car with a tank filled to 3%? Or work on a computer with a drive that's 97% full?

All the numbers I present here are based on those published on the FTP servers of the five Regional Internet Registries that give out IP addresses. So an address is "in use" if an RIR has given it to an ISP or directly to an end-user organization. Whether that ISP or that organization actually uses the address is something we can't tell from these numbers.

Let me first explain the 3706.65 million number. IP addresses are 32 bits long, which means there's 2³² = 4,294,967,296 of them: 0.0.0.0 to 255.255.255.255, or 256 blocks of 16,777,216 addresses that start with the same number. We call one of those a "/8" in the business. 0/8 (or 0.0.0.0/8, which is 0.0.0.0 - 0.255.255.255) and 127/8 can't be used because they each contain one special address. 224/4 (everything starting with 224 to 239) is used for multicast and 224/4 (240 - 255) is "reserved for future use". This prompted some programmers who are a bit too fond of input validation to reject those addresses. As a result, those addresses can't be used on many systems, some of which are no longer updated, but still used. So 268 million perfectly good IPv4 addresses will probably remain unused forever. Last but not least, there's the 17,891,328 addresses set aside for private use: 10/8,172.16/12 and 192.168/16. So the total usable IPv4 address space is 222 × 16,777,216 - 17,891,328 = 3,706,650,624.

By downloading the old address delegation records from the RIR FTP servers it's possible to see how many addresses were given out at the end of each year. (Looking at just the latest files gives different results because addresses that have been returned in the meantime aren't listed in those.) This is the number of IPv4 addresses given out as of the end of the last ten years:

This is the net difference between each year and the previous year:

In this graph, the year 2014 looks strange, as two old class A blocks (16.78 million addresses each) that are used in Europe now fall under the RIPE NCC, while they were previously listed in the ARIN statistics. If we exclude all the "legacy" /8 blocks, the trend makes more sense:

(However, now there's a spike in 2012 for ARIN as a few of these blocks changed their status.)

APNIC and the RIPE NCC have been running on fumes for the past several years: ISPs in their region can only get one last block of 1024 addresses after those two dipped below the 16.78 million address mark (a /8 block). This happened in 2011 for APNIC and in 2012 for the RIPE NCC. This year, ARIN and LACNIC also reached a similar status, although ARIN doesn't use the "one last block" policy.

As a result, organizations that need IPv4 addresses now have to buy them from others who can spare some. IPv4 address transfers were especially big in the RIPE region in 2014. In the ARIN region, the number of transfers was limited at 180 in five years, but the size of the blocks transferred tended to be large; apparently here transfers were mainly used to get larger amounts of address space than what could (then still) be obtained directly from ARIN. Inter-RIR transfers are now also possible, and happen exclusively from the ARIN region to the APNIC region. See the RIPE and ARIN transfer statistics on their websites and APNIC's on their FTP server.

This is how three kinds of numbers compare: the addresses given out with a datestamp of 2014, the net difference between the total number of IPv4 addresses given out, and the number of addresses transferred in 2014:

                   AfriNIC APNIC   ARIN    LACNIC  RIPE NCC
 
Given out 2014:    12.45    3.77   26.06   19.11    2.61
 
Intra-RIR
transfers 2014:             3.85    2.98            9.61
   
Inter-RIR
transfers 2014:             1.10   -1.10
 
Net difference
2014-01-01 -       12.72    4.62   18.82   18.74    0.27
2015-01-01:    
   

When I compiled my first statistics over 2005, this was the list of the 15 biggest IPv4 address users:

Country   Addresses
 
US      1324.93 M        United States
JP       143.00 M        Japan
EU       113.87 M        Multi-country in Europe
CN        74.39 M        China
CA        67.43 M        Canada
DE        51.13 M        Germany
FR        45.16 M        France
KR        41.91 M        Korea
UK        40.18 M        United Kingdom
GB        33.63 M        Great Britain
AU        26.87 M        Australia
IT        18.39 M        Italy
BR        17.17 M        Brazil
NL        16.40 M        Netherlands
ES        16.29 M        Spain

Nine years later, the list looks like this:

Country   Addresses
 
US       1596.02 M        United States
CN        331.99 M        China
JP        202.61 M        Japan
GB        123.75 M        United Kingdom
DE        118.91 M        Germany
KR        112.32 M        South Korea
FR         84.05 M        France
BR         81.02 M        Brazil
CA         80.41 M        Canada
IT         53.44 M        Italy
AU         48.48 M        Australia   
NL         45.94 M        Netherlands
RU         45.55 M        Russian Federation
IN         36.36 M        India
TW         35.47 M        Taiwan

Surprisingly little has changed, although the BRIC countries have claimed a bigger piece of the pie. I don't know why India has barely a tenth of the number of IPv4 addresses that China has.

So long IPv4, it's been good knowing you.

Permalink - posted 2015-01-08

Should Swiss watch makers attempt a smartwatch?

▼ Matt Richman thinks that TAG Heuer, maker of Swiss luxury watches, shouldn't waste time making a smartwatch:

TAG Heuer’s smartwatch won’t sell. There’s no market for it.

In order to have even a chance of being as feature-rich as Apple Watch, then, TAG’s smartwatch will have to pair with an Android phone. However, TAG wearers aren’t Android users. Rich people buy TAG watches, but rich people don’t buy Android phones.

I couldn't disagree more.

At this point, the Apple Watch is barely more than vaporware. The ascend of the smartwatch is in the very early stages. All kinds of things can happen.

Yes, Apple has three advantages: the most desirable potential smartwatch wearers tend to be iPhone users, and Apple can integrate the Apple Watch and the iPhone any way they see fit. They're also in the position to build custom chips.

So yes, Apple is going to be in the best position to do what Apple is doing: building a smartwatch that's barely more than a dumb terminal that uses the iPhone's computing power. However, that's more a limitation than a feature. Wouldn't a smartwatch with its own cellular connectivity be much better? It's probably too early for that right now, but that could change a few years down the road.

Also, how necessary is the deep integration between the phone and the watch? Most watch functions that need an assist from the phone could work just fine using a third-party app that runs in the background on the iPhone. The main issue would be the phone-related features, but apparently the Pebble can hook into those to a reasonable extent today.

Last but not least, Apple needs to sell tens of millions of watches to make for a viable new product category. This means the average price will have to be much lower than the price of a Swiss luxury watch. So Apple needs to depend on scale to provide value, while a company like TAG Hueur can use much more expensive materials and processes and still have good margins, although they'd have to depend more on off-the-shelf electronics.

Sure, it's entirely possible that the Swiss luxury watch makers are in trouble. But it's still way too early to write them off.

Permalink - posted 2015-01-07