Two quick observations of Facebook’s announcement of “6-pack” open hardware modular switch

Facebook announced an introduction to its "6-pack" open hardware module switch 20 hours ago. Here are my two quick observations of "6-pack".

Why should we turn off mobile phones when we travel in an airplane, Part 1

This video is funny. But some of the challenges from the passengers are quite true.

• "90-Million -dollar aircraft can't ignore the signals from my 40-dollar iPod Shuffle?"
• "Can I hold this plane hostage with my (Nintendo) 3DS?"
• "How come the plane is not interfering with my phone?"
• "Why don't other phones interfere my phone?"
• "I just always leave my phone on and nothing happened?"

I think all the fears of "interferences to navigation" was because of some sound like this one.

WDM, DWDM, and CWDM

Wavelength-division Multiplexing (WDM) is a technology we can put several laser light beams into the same optical fiber. The light beams are identified by their unique physical properties: wavelengths. Because of this, all such technologies are collectively called Wavelength-division Multiplexing.

By TotoBaggins on Wikipedia.

Three quick things I have learned from Facebook’s Next Generation Data Center Network

Facebook published this post about their next-generation Data Center Network. Here I am noting down three quick things I have learned from it.

A view to the Pacific Ocean inside Farglory Ocean Park, Hualian County, Taiwan

A simple example explaining why we need Prefix-List in addition to simple Access-List (ACL) on Cisco IOS

My example is: assume we want to filter out "all possible subnets/prefixes inside 192.168.1.0/24" from rushing into our router.

Red House Theater, at the West Gate of Taipei Wall (西門紅樓、紅樓劇場). 

We can first visualize what subnets are to be filtered in the following, but incomplete list:

192.168.1.0/24

192.168.1.0/25
192.168.1.128/25

192.168.1.0/26
192.168.1.64/26
192.168.1.128/26
192.168.1.192/26

(and even more ...)

RFC 3021: the "/31" subnets for IPv4 Point-to-point Links

(This RFC has been there for almost 14 years. Without writing a post down about it, it would never stay in my mind as if I have never known it. Too bad for me!)

Original location of West Gate of Taipei City Walls (西門、西門町).
The gate and the walls were removed long time ago.
The bottom right is one of the entrance of  MRT Ximen (e.g. West Gate) Station.

RFC 3021: Using 31-Bit Prefixes on IPv4 Point-to-Point Links

Since this RFC is quite old, almost all of today's routers already have this feature. It is very safe today to assign "/31" subnets to any point-to-point links. We can now save 50% of IPv4 addresses for point-to-point WAN links.

New product: Cisco UCS "Mini"

Cisco has a new update few days ago to her Unified Computing System (UCS): the UCS Mini. Here is what I have known of it from the public web sites.

Sun is rising at Hualian County of Taiwan on August 30, 2014.