Internetworking Part 8

Ethernet cabling is a rather important topic, especially for those seeking certification.  However, on the same note, it is quite easy once you gain the hang of it.  There are three types of cabling:

  • Straight-through cable
  • Crossover cable
  • Rolled cable

Straight-Through Cable:

The straight-through cable is used to connect

  • Host to switch or hub
  • Router to switch or hub

Standard, Straight-Through Wiring Diagram(both ends are the same):

RJ45 Pin #

Wire Color

Wire Diagram

10Base-T Signal
100Base-TX Signal

1000Base-T Signal

1 White/Green   Transmit+ BI_DA+
2 Green   Transmit- BI_DA-
3 White/Orange   Receive+ BI_DB+
4 Blue   Unused BI_DC+
5 White/Blue   Unused BI_DC-
6 Orange   Receive- BI_DB-
7 White/Brown   Unused BI_DD+
8 Brown   Unused BI_DD-

Straight-Through Ethernet Cable Pin Out for T568A






RJ45 Pin #

Wire Color

Wire Diagram

10Base-T Signal
100Base-TX Signal

1000Base-T Signal

1 White/Orange   Transmit+ BI_DA+
2 Orange   Transmit- BI_DA-
3 White/Green   Receive+ BI_DB+
4 Blue   Unused BI_DC+
5 White/Blue   Unused BI_DC-
6 Green   Receive- BI_DB-
7 White/Brown   Unused BI_DD+
8 Brown   Unused BI_DD-

Straight-Through Ethernet Cable Pin Out for T568B

Crossover Cable:

The crossover cable is used to connect

  • Switch to switch
  • Hub to hub
  • Host to host
  • Hub to switch
  • Router direct to host

Essentially, this type of cable permits connecting like, or similar, equipment together.

Rolled Cable:

The rolled cable is used to connect a host to a router console serial communication (com) port.  The pinout of the cable itself is the direct opposite from each end (i.e., 1-8, 2-7, 3-6, 4-5, 5-4, 6-3, 7-2, 8-1).

See also: Part 1, Part 2, Part 3, Part 4, Part 5, Part 6, Part 7

Works Cited

Lammle, T. (2007). CCNA Cisco Certified Network Associate Study Guide. Indianapolis: Wiley Publishing, Inc.

Internetworking Part 7

Interconnection Part7

Connection-Oriented Communication (COC) was briefly discussed in Part 5, hopefully this will be a little more in-depth.  COC is a data communication mode, in which we must first establish a connection to either the remote host or server prior to any sending of data; otherwise, the possibility of data loss increases.  The process of establishing a connection-oriented session to a remote peer host is called a three-way handshake.

An end-to-end logical circuit is created for the sole purpose of transmitting the data, when transfer is finished the link/connection is terminated.

The establishment of the TCP connection can be summed up as follows:

  1. Host A needs to initialize a connection (or a “connection agreement) sends out a SYN (Synchronize) packet with proposed initial sequence number to the destination host B;
  2. When the host B receives SYN message, it returns a packet with both SYN and ACK packets set in the TCP header (SYN-ACK);
  3. When the host A receives the SYN-ACK, it sends back ACK (Acknowledgment) packet;
  4. Host B receives ACK and at this stage the connection is ESTABLISHED.

The connection-oriented protocol sends out acknowledgement (ACK) packets after a successful delivery.  After data packet is transmitted, the sending host waits for acknowledgement from receiver; if time expires, it is assumed that the data was not received and is then retransmitted.

When the data packet transmission is completed and the host wants to terminate the connection, a termination process is initiated.  The TCP connection termination is a four-step process:

  1. Host A, terminates the connection, sends a special message with the FIN (finish) flag, indicating that it has finished sending the data;
  2. Host B, receives the FIN segment, does not terminate the connection but enters into a “passive close” (CLOSE_WAIT) state and sends the ACK for the FIN back to the host A. Now the host B enters into LAST_ACK state. At this point host B will no longer accept data from host A, but can continue transmit data to host A. If host B does not have any data to transmit to the host A it will also terminate the connection by sending FIN segment;
  3. Host A receives the last ACK from the host B, it enters into a (TIME_WAIT) state, and sends an ACK back to the host B;
  4. Host B gets the ACK from the host A and closes the connection.

Transmission of segments needs flow control to ensure the efficient flow of data.  Due to the fact that there are differing types of flow control (buffering, windowing, and congestion avoidance), windowing will be used to aid in data transmission efficiency.  Windowing aids by controlling how many windows are opened at any given time.  If the data flows too quickly (i.e., there are too many windows open) then there will be data loss and datagrams dropped, which require retransmission of the data.  If there are too few windows open then the transmission would be slow, sluggish and inefficient.

Host A starts transmit with window size of 1000, one 1000byte frame is transmitted. Host B returns ACK with window size to increase to 2000. The host A receives ACK and transmits two frames (1000 bytes each). Then the receiver advertises an initial window size to 2500. Now sender transmits three frames (two containing 1,000 bytes and one containing 500 bytes) and waits for an acknowledgement. The first three segments fill the receiver’s buffer faster than the receiving application can process the data, so the advertised window size reaches zero indicating that it is necessary to wait before further transmission is possible.


The size of the window and how fast to increase or decrease the window size is available in various TCP congestion avoidance algorithms.

See also: Part 1, Part 2, Part 3, Part 4, Part 5, Part 6

REFERENCES images/ 0130424110/ samplechapter/ 0130424110_ch18.pdf

Lammle, T. (2007). CCNA Cisco Certified Network Associate Study Guide. Indianapolis: Wiley Publishing, Inc.


Internetworking Part 6

Flow Control ensures data integrity at the Transport Layer (Layer 4) by maintaining and allowing  users to request reliable data transport between systems.

Flow Control prevents the transmitting host from overflowing the buffers of the receiving host.  If the flow of data is not controlled it can result in lost data.  The ability to obtain reliable data transport uses a connection-oriented communications (briefly discussed in Part 5) session between the two, or more, systems and the protocols involved, which would permit the following:

  • All segments received are acknowledged to the sender upon their receipt;
  • Any segments lost or dropped, which are not acknowledged, will be retransmitted;
  • Segments are re-sequenced into their original order upon arrival at their destination;
  • Manageable data flow is maintained to avoid congestion, overloading and data loss.

The inherent purpose of flow control is to maintain a means for the receiving  host to govern the amount of data sent by the transmitting host.


Part 1, Part 2, Part 3, Part 4, Part 5

RFIDs Part 6

The Canadian’s seem to be doing the same thing that the US has attempted for years, that is getting rid of the Canadian Penny.  In the words of the Royal Canadian Mint “Today’s digital economy is changing faster than ever, and currency has to change too. It is, introducing MintChip, from the Royal Canadian Mint – the evolution of currency.”  Just as with the American Penny, the Canadian Penny’s days are numbered (and with all do respect – so is the American Penny, presently it costs 16.7 cents to mint a Penny.)  People, no matter which society it is, are partial to their currency and all of the variations of bills and coins.

The Evolution of Money – MintChip – is taking a drastic change, little by little.  The next generation of currency will be digital, which is something that has been in the works for years.  The ultimate goal is to go cashless; the first idea was to change everything to credit card, which was the next best thing to digital until credit cards went digital.  Now the next generation of digital is a chip, as well as, an application program (which I mentioned in a previous RFID blog, ISIS.)  ISIS is an application which is having its debut in Salt Lake City where your smartphone will possess your financial data so you can, for the sake of convenience, use your phone as a charge card.

MintChip uses a secure chip to hold monetary value and a secure protocol to transfer monetary value from one chip to another. MintChips can be stored in many ways: on MicroSD cards, on USB sticks, or remotely in the cloud, with no physical access.  But as we all know, those who deal with any aspect of Information Technology, nothing is truly secure…look at the news and all of the hackers that have bilked and stolen Billions in dollars.  So, what will be next?  The nickel?  The dime? Or, perhaps, everything will vanish from the face of the earth and just go digital.  You thought that inflation was bad with the dollar?  Just wait until everything goes digital, at that point inflation will cease and money will be siphoned out of your account.  Then what will be the next generation?  I personally believe it will be the introduction of the RFID chipping into the human body.

Not to change the subject, but who doesn’t love Disney?  I always have, but I am concerned now-a-days with the advent of their billion-dollar project dubbed “NextGen”.  Details of the plan emerged in February 2011 when Walt Disney Parks and Resorts Chairman Tom Staggs announced some major changes at an investors’ conference.  Which indicates, on a small scale, how cities, states, countries, and potentially the world will transact business in the not too distant future.  Many people seem to think this is great; however, if you have been following my posts you will note my disgust and disdain toward the abuse of privacy rights and the attack upon the individual’s desire to maintain some semblance of privacy.

One of the most obvious uses of the RFID system is ease of access to the parks. The system was tested at the fittingly future0themed Epcot in Walt Disney World, where guests willing to participate in the trial run were given a sticker embedded with the rice-sized transmitter to affix onto their regular souvenir ticket or annual pass. Many of the park ticket machines are being modified, or changed, over to a combination of RFID and fingerprint scanner.  Disney World and Disneyland are both small cities with an average daily occupation of about 41,000 people.  They are pretty efficiently run, which makes it quite appealing for the government to give it a try…but that is a little beyond the scope of this post.  However, the utilization of the RFID and fingerprint scanning technology is quite on target as it is used to access your money so that you do not have to carry around cash, your wallet, or credit card(s) because your data is stored in that little grain of rice called an RFID and the use of your fingerprint is to use that biometric that is all your own (as a dose of security).
Even though it is a theme park and Walt Disney always tried to capture his vision of the future, I am a little dismayed at the lack of privacy, security, and sovereignty of the people.  Unfortunately, each and every person just thinks it is the neatest thing since sliced bread and are just like sheep being lead to the slaughter.  My primary purpose for this post is to bring to light the death of the dollar and the future economics of the world via the technology we find so fascinating and secondarily the wave of the future both politically and economically.
I first heard of this through the Dr. Katherine Albrecht show (who is a big Privacy Advocate), more specifically the April 21st, 2012 show.  I hope there is a way to one day use the technology for what it was intended without the detrimental affects to people’s privacy.  We shall see!
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SEE ALSO:  RFID Part 1, RFID Part 2, RFID Part 3, RFID Part 4, RFID Part 5