Cisco ICND1 Flashcard: WAN Hardware and Encapsulation

ICND1: PPP
ICND2: Frame Relay

Wide Area Networks

A LAN will cover an area in the same building or vicinity; a WAN spans a much larger geographically connected sites. Setting up and maintain a WAN is very expensive, most private companies would rather purchase a WAN connection from the ISP, who will manage the WAN infrastructure and back-end network backbone.  Services include T1, T3, E1 and E3, DSL, cable, frame-relay and ATM.

WAN operations cover the Layer 2 Data Link Layer (Metro Ethernet, MPLS, frame-relay, ATM, HDLC)and Layer 1 Physical Layer components (electrical, mechanical, operational connections).


WAN Devices
Equipment required includes a modem CSU/DSU to connect to the service provider, and edge devices modify the Ethernet encapsulation to the serial WAN

Wan Ecapsulation Answer Hack. Is this legal?

Modem - modulates an analog carrier signal to encode the digital signal, and modulates the carrier signal to decode the transmitted information.

CSU/ DSU - Channel Service Unit/ Data Service Unit. CSU is termination for the digital signal ensures integrity, error correction, and line monitoring. DSU converts T Carrier line frames into LAN frames. Provides a clocking signal to the customer equipment interface from the DSU, terminate the channelized transport media of the carrier on the CSU. CSU also provides a loopback test diagnostic.

Demarcation Point, the point where a service provider considers the services delivered, such as the CSU/DSU on customer's premises to the provider's Central Office.
Access Server - I'll check my notes what that is for.

WAN Switch - used in carrier networks to carry Frame Relay, ATM, X.25 and PSTN in the cloud

Router - The router can be a WAN connection device, with serial interface ports to connect to the  service provider and the internetwork for the LAN. Basically a router will connect to the POP router of the ISP

Core Router -  needs explaining

CPE - Customer Premise Equipment that includes a DCE/ DTE.
DCE - Data Circuit-terminating Equipment or Data Communications Equipment, the device that ports data on the local loop.Configure the clock rate for the DCE interface.
DTE - Data Terminal Equipment, customer equipment that passes data to the DCE such as the routers. Synchronizes to the clock rate.

There is a lengthy description of EIA/ TIA connectors, but the most important part is the router end of the shielded serial transition cable which has a DB-60 connector. The DB-60 port on a serial WAN interface car is a 5 in 1 port. There is a new type of cable called a Smart Serial Cable.

Summary of WAN Links Hierarchy
Three main WAN types: Dedicated, Circuit Switched and Packet Switched.

DEDICATED
Leased Lines: T1/ E1
For companies who constantly send traffic, expensive.
SWITCHED
Circuit Switched: PSTN, ISDN, analog modem
For companies who send occassional traffic, least expensive.

Packet Switched: Frame Relay, x.25
Ideal for companies requiring a minimum constant service without the cost of dedicated lines.

Cell Switched: ATM
INTERNET
Broadband:VPN
Other: DSL Cable, Broadband, Wireless

The Last Mile
This refers to the local loop, the last mile connection that defines how the local user gets to the ISP perhaps? One example is for example, installing a new fiber optic cable from the exchange outside the building into the networking lab perhaps. Another example could be a satellite hop.

Long Range Connectivity
The protocols SONET and Synchronous Digital Hierarchy (SDH) have been around for ages. These are used to move large amounts of data over great distances through fiber optic cables, mostly refering to voice and data.  A newer optical technology, Dense Wavelength Division Multiplex (DWDM) provides extremely long range communications by assigning a specific frequency (or wavelength) of light to incoming signals.  Equipment can amplify  the wavelength to boost  signal strength. A single DWDM fiber can have more than 80 different wavelengths or channels multiplexed, each channel carrying up to 10 Gb/s.  The other important feature is that DWDM can carry IP, SONET, ATM at the same time on the same optical fiber.

At the receiving end, the router needs the right optical SFP.

Related Topics: PPP Encapsulation, ISDN
Next Topic: DSL two types-ADSL and SDSL
Followed by: Cisco IPSec VPN

Really not Born This Way Makeup Tutorials

My sister sent me some links for makeup techniques, that are not necessarily ulzzang but I'd say the first one is an asian person who converts herself quite well into Lady Gaga.

Lady Gaga Bad Romance Look
A makeup tutorial featuring extreme eye makeup with the fake lashes and white underliner. Then she takes it up notch with some CGI techniques to track her face, and make the eyes even bigger.
http://www.youtube.com/watch?v=bHVOxhEpjp0&feature=related

Me as Angelina Jolie !!!A Make-up Transformation !!!!!
Really amazing makeup tutorial posted by a talented makeup specialist.
http://www.youtube.com/watch?v=gsqahGYl21w

RAID Configurations: Standards and Usage

Everytime I have to rebuild a Dell Server, it's already been decided which RAID configuration to use. Well I just want to know why they chose that RAID configuration and what is it for?

RAID is Redundant Array of Independent Disks and the main purpose for any chosen configuration is to 1) increase data reliability and 2) increase input/output performance. I'll put in a third reason 3) to make a hot swappable drive in case one of them fails.

Here is an example of an old beat up Dell 2850 with six perfectly salvagable drives I had to swap out and rebuild on another unit. Counting from the left, the first two drives are 73GB top and bottom. The remainder 300GB drives are in the in remainder four slots. Order matters. Considering labeling them in a numbered sequence. The first two drives are mirrored logical drives in a RAID 1 configuration; the last four drives are the physical drives in a RAID 5 configuration.

At the BIOS setup, you just choose the RAID for each drive in the bay array, but what does it all mean?

Settings available:
RAID level: 0, 1, 5, 10, or 50
RAID status of the virtual disk: failed, degraded, or optimal
Size of the virtual disk
Stripe element size
Operation currently in progress

RAID 0
* Striped copy
* data split evenly across disks
* no data redundancy
* makes a large logical disk out of a few smaller physical disks, say two 100GB striped together to make one 200GB
* it's bad when drives fail, file system cannot recover because data is split across the disks
* useful for large read-only NFS server where mounting many disks is clunky and redundancy is irrelevant.

RAID 1
* exact copy (or mirror) of data across two or more disks.
* read performance more important than data storage capacity
* the is array only as big as the smallest member disk.
* It's possible to "split the mirror," declare one disk as inactive, do a backup of that disk, then "rebuild" the mirror.

RAID 2
* obsolete
* stripes data at the bit (rather than block) level by Hamming code for error correction.

RAID 3
* less useful, now obsolete
* uses byte-level striping with a dedicated parity disk.
* cannot process multiple requests simultaneously
* requires synchronized spinning spindles in lockstep

RAID 4
* uses block-level striping with a dedicated parity (copy) disk, possible bottleneck.
* allows each member of the set to act independently when only a single block is requested.
* run by a disk controller
* can service multiple read requests simultaneously.
* does not need synchronized spinning spindles
* well implemented at the enterprise level by one company, NetApp using a Write Anywhere File Layout (WAFL) which stores system metadata (like inodes, block maps, and inode maps) in the same way application data is stored
* allows write to file system metadata blocks anywhere on the disk

RAID 5
* replaces RAID 3 and 4
* block-level striping with parity data distributed across all member disks

Example:
* four 1 TB drives can be made into two separate 1 TB redundant arrays under RAID 1
* or 2 TB under RAID 1+0
* the same four drives can be used to build a 3 TB array under RAID 5.
parity, an error checking bit

RAID 6
* extends RAID 5 by adding an additional parity block
* uses block-level striping with two parity blocks distributed across all member disks
* fast
* uses firmware and specialized ASICs for intensive parity calculations
* provides fault tolerance of two drive failures; the array continues to operate with up to two failed drives

Hot sparing
Hardware and software RAIDs with redundancy may support a hot spare drive; when a physical drive in the array is inactive until an active drive fails, then the system automatically replaces the failed drive with the spare, rebuilding the array with the spare drive.

Not Hot swappable
On another unit, I was trying to figure out why the drives from different manufacturers were not swappable. Turns out hardware RAID controllers use their own data layout formats, so it is not possible to span controllers from different manufacturers.

References: http://support.dell.com/support/edocs/storage/RAID/PERC5/en/UG/HTML/chapterh.htm

Wikipedia RAID

The Number One Ulzzang

Not so Ulzzang Image Source

Ulzzang is best defined as a Korean word meaning "best face" or "good-looking", and refers to a style of makeup and self portrait photography that accentuates the eyes and slims the face.  Many images and videos posted online demonstrate the transformation from an ordinary asian girl with ordinary facial features into an anime character-like Internet celebrity with fair skin, a small nose and thin small lips.

Ulzzang Slim Face Big Eyes Image Source

Note: These are not photos of me, nor any of my friends or anyone I have ever seen in real life. I grabbed them from the Internet! Just google Ulzzang images and you will find these, before and after poses as well. I would never be caught dead in a photo without makeup on.

Ulzzang Before and After Image Source

Ulzzang has developed into a subculture and style popular among Korean girls, as well as Japanese and Chinese girls overseas and in North America. I've seen this as another trend in glamour wedding photography where the bride and groom both look like super models, and you end up with a bound hardcopy portfolio album..  There are even TV game shows featuring a competition between several rather "geeky-looking" asian girls wearing very thick glasses and they demonstrate the makeup application techniques to transform into someone very amazing, such as Goo hye sun, Nam Sang-mi, Park Han-byul, Kang Eun-bi and Kim Hye Sung.

My favorite definition I pulled from Urban Dictionary is quoted:
"Superficial, terrifying Asians who go through mountains of eyelid glue, circle lenses, makeup, trick camera angles, and photoshop to look like blank-faced aliens."

Before Ulzzang

The little miss who wrote "Attempt to be Ulzzang... FAIL" has the best description and nerdy transformation hands down, especialy with the description of the camera angles and photoshop.

After Ulzzang, same chic!

She calls herself ordinary and average. To describe average, I'd say a typical asian girl (wears glasses) probably plays piano and violin, excels in math and chess, has a tyrant Tiger Mom, and if she's not destined for Medicine, she'll end up in Electrical Engineering among other geeky asian girls. Now do all asian girls in Engineering look like this? At UBC maybe. On the Facebook profile, yes.  Amazing what the web cam or cell phone camera can do.

The first Ulzzang I would have to list is not from Korea, but from the USA and that would be Wonder Woman. They already figured this out half a century ago before netizens knew about it, to lose the glasses and glam it up with loads of eyeliner and waterproof eyeliner. Lynda Carter as Leading Seaman Diana Prince in super geek mode, holding a top secret file with nuclear launch codes for missiles from attack subs...

Lynda Carter aka Diana Price Image Source

And thirty seconds later after an elaborate change scene, she is Wonder Woman with bullet proof bracelets and light body armour.

Wonder Woman Image Source