CCNA Notes: Cabling Types

Cabling Types

UTP (Unshielded Twisted pair)

Cat 1 - Telco, telephone line
Cat 2 - Token Ring, up to 4 MBPS speed
Cat 3 - 10BaseT Ethernet - 10 MBPS
Cat 4 - Token Ring, 16 MBPS
Cat 5 - Fast Ethernet, 100 MBPS
Cat5e- Fast Ethernet, 1000 MBPS (1 Gig)
Cat6 - Fast Ethernet, 1000 MBPS (1Gig), 24-gauge

UTP Ethernet cables typically use an RJ-45 adapter for connections.

Article explaining more about the UTP Ethernet cabling


Fiber Cabling

 Multi-mode Fiber - Used over shorter distances, uses LEDs to create light and bounces light signal on cladding. Cheaper than single-mode fiber. Greater speeds are attainable the shorter the distance traversed, from 100 MBPS at 2km to 10 GBPS at 550m.

Single-mode Fiber - Used over greater distances, uses laser to generate light, which is carried on a single line without bouncing. More expensive than multi-mode. Covers far greater distances based on speed and other factors, up to 60km in some cases

Fiber cables typically utilize an SFP/GBIC connector.

Comparison of Cabling Types

Cable Type             Maximum Length              Maximum Speed                 Notes

UTP                                  100m                        10 MBPS - 1 GBPS          Susceptible to interference

Coaxial                             500m                        10 - 100 MBPS                 Difficult to troubleshoot

Fiber                                 60+km                        10 MBPS - 10GBPS         Expensive


Speeds

Ethernet - 10 MBPS
Fast Ethernet - 100 MBPS
Gigabit Ethernet - 1000 MBPS

Article covering many different flavors of Gigabit Ethernet

WAN Cabling Types

 T-carrier

The following was taken from this Wikipedia article and covers a vanishing, but still present, WAN technology. Connections are typically made to routers by way of a serial cable or RJ-48 connector, and clocking for the line speed is set by the WAN provider. The standard naming convention is T-1 (or DS-1).

T-carrier and E-carrier systems	North American	Japanese	European (CEPT)
Level zero (channel data rate)	64 kbit/s (DS0)	64 kbit/s	64 kbit/s
First level	1.544 Mbit/s (DS1) (24 user channels) (T1)	1.544 Mbit/s (24 user channels)	2.048 Mbit/s (32 user channels) (E1)
(Intermediate level, T-carrier hierarchy only)	3.152 Mbit/s (DS1C) (48 Ch.)	–	–
Second level	6.312 Mbit/s (DS2) (96 Ch.) (T2)	6.312 Mbit/s (96 Ch.), or 7.786 Mbit/s (120 Ch.)	8.448 Mbit/s (128 Ch.) (E2)
Third level	44.736 Mbit/s (DS3) (672 Ch.) (T3)	32.064 Mbit/s (480 Ch.)	34.368 Mbit/s (512 Ch.) (E3)
Fourth level	274.176 Mbit/s (DS4) (4032 Ch.)	97.728 Mbit/s (1440 Ch.)	139.264 Mbit/s (2048 Ch.) (E4)
Fifth level	400.352 Mbit/s (DS5) (5760 Ch.)	565.148 Mbit/s (8192 Ch.)	565.148 Mbit/s (8192 Ch.) (E5)

Optical Carrier over SONET (Synchronous Optical Networking)

Don't be terrified by the intense wording - This is fiber. Fiber strands are bundled to reach different amounts of bandwidth, with each increment being multiplicative on the first, as follows:

OC-1 - 51.84 MBPS
OC-3 - 155.52 MBPS
OC-12 - 622.08 MPBS
OC-48 - 2488.32 MBPS
OC-192 - 9953.28 MBPS
OC-768 - 38,486.016 MBPS

Of course, multiple customers can reside on an OC, so it is common to have, for example, an OC-192 split among many different customer circuits as needed. Commonly, the largest fiber cables are bundled in the 'backbone' networks, and then multiplexers are used to divide the light signal off into smaller cables as they get nearer to customers, in some cases delivering it right to their door, where GBICS/SFPs are connected to the premise equipment. More commonly the WAN provider or local carrier will have a smartjack or some similar demarcation point, and then the customer equipment will connect to that.

Learn more about how optical carrier data is joined/split here.

CCNA Notes: The OSI Model

The OSI Model of Networking

There are easily hundreds of ways to try and explain the OSI Model of Networking to an audience. A quick Google search will net some of the best, but in general, what's important to understand about the Open Standard Interconnect model is that it breaks down host to host transmission into seven layers, listed above. The highest layer is the Application layer, where information is presented to the user. The lowest layer is the Physical layer, where the electrical/radio/light signals are transmitted along whatever medium exists between the hosts. The actual units of data are referred to by different terms beyond the Session layer, as you can see.


Note: The analogy presented below was not taken from a book, it is my own attempt to explain.

Application Layer

This layer deals with the protocols/services used by the actual applications used, which they will employ to transmit network information.

Pretend for a moment that we are in the Wild West. Sally Packett has just written a thrilling, loin-warming romance novel, and wants to send the manuscript to her publisher. At this layer of the OSI model, Sally Packett simply makes the decision to use Western Union Courier Services to get her important package to the publisher, who is anxiously awaiting the finished copy.

Presentation Layer

This layer defines how the information is to be presented to the user, file formats work at this layer, such as JPG, BMP, TXT, AVI, and so on.

Sally Packett needs to be sure that her manuscript will be readable, so she makes sure that she wrote the whole novel in English (she had a few glasses of wine for inspiration some nights). After that, she makes sure her grammar is correct and picks up her telephone.

Session Layer

This layer initiates the setup and teardown of connections, and differentiates between multiple network connections. This layer deals with hello packets, notifications, timeouts, the logistics of how data will be delivered.

Sally has a long talk with a very helpful gentleman from Western Union on the telephone, who assures her that they do deliver to the publisher's address. Sally schedules the pickup of her manuscript as soon as possible. The Western Union clerk has Sally verify how many pages there are in her book and other details about the package, as well as determining how soon it needs to get there and, depending on how much Sally wants to pay, may or may not offer a tracking number/receipt.

Transport Layer

This layer deals with the mechanics of setting up, maintaining, and tearing down connections. Transmission Control Protocol (TCP, of the famous TCP/IP suite) operates at this layer. User Datagram Protocol (UDP) also operates at this layer. The largest difference between TCP and UDP is that TCP is connection-oriented, meaning it keeps track of the data delivery attempt and will attempt to recover if it is having trouble (missed packets, corrupt data, packets arriving out of sequence). UDP is not connection-oriented. If TCP were a delivery driver, it would be the one that won't leave a package without a signature. If UDP were a delivery driver, the truck might slow down as the package was thrown at your house.

In our Wild West example, Sally Packett has elected to go with a more expensive option (after all, this romance novel will make her rich when it sells!). She receives a tracking receipt and soon afterward her manuscript is picked up by the Western Union courier. The courier goes back to the central office and informs the management that he's starting his trip to the publisher's address. The central office issues the courier the correct horse, a rifle and rations for the trip. The courier is ready to go, he has all the details of the delivery, except he doesn't know how to get there yet.

Network Layer

This layer provides the logical topology of the network, makes routing decisions to determine the best path to logical destinations, and allows logical addressing instead of otherwise obtuse physical addressing. IP addresses operate at the Network layer, saving us all from having to memorize hardware MAC addresses of source/destinations (At least for now - I'm looking at you, IPv6).

The Western Union courier (Let's call him Jim. It's easier that way) consults the map of the western territories to figure out his route. Unfortunately, the central office where he works only has a route to the next way station in line, not the entire map. He knows that the name of the way station is Tuscaloosa Valley Station, and how to get there. Jim knows what to expect, and he has all the proper tools for the journey. He leaves the office and takes the western road. Come hell or high latency, he's going to see that package delivered.

Data Link Layer

This layer uses physical hardware addressing, and defines how devices should communicate within a given physical media type. It also defines how a device accesses the network, the media's framing method and the transmission method on that media. This is the layer that uses MAC addressing to determine source/destination. This one is tough to understand, just remember that at this layer, there are no fancy IPs that are easy to read, just ugly MAC addresses.

Jim has just started his journey. Up ahead, he sees signs on the road, telling him that slower horses should stay to the right, and that stagecoaches have right of way. Jim isn't looking to run afoul of the Marshals, so he aims to pay attention to the rules of the road. He looks for a sign pointing him in the direction of the Tuscaloosa Valley Station, but he just sees signs for Alabama. Luckily, he knows from the office map that Tuscaloosa is in Alabama, and he is headed the right way.

Physical Layer

This layer deals with the physical properties of the network media. This includes connectors, multiplexers, adapters, lines, radio, light, and electrical signals. At this layer, it's raw signal, binary ones and zeroes moving across the medium. The Data link layer will determine who those signals are for and how they should be interpreted, the Physical layer's only concern is how to convey that signal.

It's been a long, hard road. Jim is parched, hungry, and has dodged his share of bullets from unfriendly natives and bandits alike. Only his wits and the speed of his horse saved him, as well as the fine condition of the road.

Now What?

Jim has arrived in Alabama alive and with Sally Packett's manuscript intact. Once in town, he gets directions from a friendly local to the Tuscaloosa Valley Station. At the station, two possibilities exist for Sally's package.

• If Tuscaloosa is indeed the final destination, Jim will turn over the package to the publisher, who will open it and verify everything arrived in order, then format it and prepare it for sale, moving up from the Network layer to the Application layer in sequence.
• If there are further legs of the journey, his trip will begin again, picking up from the Network layer back down to the Physical in a process called encapsulation/de-encapsulation until the final destination is reached.

 

CCNA Notes: Network Considerations and Topology/Media

Network Considerations

When designing a network, there are many factors at play. Some factors to consider:

1. Cost - What is an acceptable budget?
2. Speed - What is an acceptable speed?
3. Security - How much security is needed?
4. Topology - Where are the users? The services? What infrastructure separates them?
5. Scalability - Is this network capable of growing larger easily?
6. Reliability - Are the network solutions we are using reliable?
7. Availability - Do we have redundancy for connectivity/services?

There are different types of network locations that will help drive these questions/answers:

Small Office / Home Office (SOHO) - Small site that may or may not connect to a larger network

Central Office - Where most users/services are homed

Branch Office - An office which is geographically separated from central office but uses its services

Mobile Office - Users that connect via VPN or RAS to services, not physically connected to the network

When dealing with expectations of network speed/latency, determine whether you are talking about a LAN (Local Area Network) or WAN (Wide Area Network). LANs connect geographically close users together over high-speed links. WANs connect users over large geographical areas, as in the Central/Branch office setup, typically using much slower links.

LAN Topologies and Media

10Base5 and 10Base2 - Thicknet and thinnet coax.  This is obsolete technology and you are not likely to see it in use today. Connectivity was achieved via a vampire tap that literally tapped into the line to get signal, or the connection was terminated via BNC connector. This media was very prone to electrical interference as the cables had to have ground terminators, and was made largely obsolete by the advent of ethernet Cat5 cabling. Thicknet and thinnet were very prone to network collisions, which is what happens when two or more devices try to send signals across the wire at the same time, ruining the transmission. Later implementations of thinnet used a token ring to resolve this issue.  Token ring is a topology where collisions are avoided by having one networked device at a time utilize a logical 'token', and only the device with the token is allowed to transmit. This token was passed to other devices in turn, but this resulted in much slower speeds and ultimately token ring could not compete with ethernet collision detection/avoidance techniques.

More info on Thicknet (including pictures)
More info on Thinnet (including pictures)


10BaseT Ethernet - Category 5 (and later 6, 6e) cabling defines this standard. This is the most popular medium in use for LANs today. Most ethernet networks utilize a star, or hub and spoke topology where devices connect to network devices that aggregate connections. Network collisions are handled by CSMA/CD (carrier sense multiple access / collision detection), where when two devices detect a collision, both send a jam signal to the wire and then wait a random backoff interval before trying again.

More info on Cat5 Ethernet (including pictures)


Wireless (802.11a/b/g/n) - Radio waves comprise the physical 'media' in a wireless network. There are many different wireless standards, the differences mainly involving what channels on which the standards communicate and the speeds attainable. The topology in a wireless network is a star/hub and spoke with the wireless access point being the aggregating network device. Collision avoidance is accomplished by CSMA/CA (carrier sense multiple access / collision avoidance). Because users can communicate with the access point but not see each other's transmissions, the AP uses a system of RTS/CTS (Request to Send/Clear to Send) messages to grant exclusive transmitting capability to one device at a time, similar to a token ring.

More info on wireless standards


Fiber - Fiberoptic cables define this media type. There are enough types of fiber cabling to warrant its own entry, but in general, the signal is either carried in a single line, or there will be two lines, one dedicated to transmit signals and the other to receive them.



 FDDI - A dual fiber loop which utilized a proprietary token bus standard instead of the more prevalent token ring standard. The second fiber ring provided redundancy, but as faster ethernet standards were developed this technology was outclassed both in ease of use and price.


More info on FDDI

For the purposes of the CCNA, be aware of most different topologies and media, but focus on Ethernet and star/hub and spoke topologies.