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Internship Time Table Nov 2017
DOMAIN ACTIVITY RESPONSIBLE DURATION IT Infrastructure 1. Data center layout and Physical equipment visit
- Switching and routing
- Security
- EUS/Help desk
Mark/ Denis 1 WEEK
IT Billing 1. Bill Generation & CDR check
- Inventory upload and Point of sale Management
- Dunning
- SIM order and bundling
- CSP and Back End Support
- Failed provisioning resolution
- SIM Activation
- HLR, Ability and IN Reconciliation
Joseph 1 WEEK
IT Charging 1. Voice , Data , SMS Charging system and application overview
- Voucher system and application overview
Abiy/ Amango 1 WEEK
IT BIB 1. Overview of BI and the part it plays in telecom
- CDR files checks and flow
- Introduction to SQL
- Reports creations
- Overview of Registration System
- Overview of backend and OS
Ibrahim 1 WEEK
IT VAS 1. SMSC
- USSD
- DMC & ADC
- other value added services
William 1 WEEK
Regards Joseph Ndemo
Basics components of networking
▲ Switch
▲ Router
▲ Access point
▲ Interfaces
▲ Hubs
▲ Cables
1-Router
A router [a]^ is a networking device that forwards data packets between computer networks. Routers perform the traffic directing functions on the Internet. A data packet is typically forwarded from one router to another router through the networks that constitute an internetwork until it reaches its destination node. [2]
A router is connected to two or more data lines from different networks. [b]^ When a data packet comes in on one of the lines, the router reads the network address information in the packet to determine the ultimate destination. Then, using information in its routing table or routing policy, it directs the packet to the next network on its journey.
Access [edit]
A screenshot of the LuCI web interface used by OpenWrt. This page configures Dynamic DNS.
Access routers, including 'small office/home office' (SOHO) models, are located at customer sites such as branch offices that do not need hierarchical routing of their own. Typically, they are optimized for low cost. Some SOHO routers are capable of running alternative free Linux-based firmware like Tomato, OpenWrt or DD-WRT. [8]
Distribution [edit]
Distribution routers aggregate traffic from multiple access routers, either at the same site, or to collect the data streams from multiple sites to a major enterprise location. Distribution routers are often responsible for enforcing quality of service across a wide area network (WAN), so they may have considerable memory installed, multiple WAN interface connections, and substantial onboard data processing routines. They may also provide connectivity to groups of file servers or other external networks.
Security [edit] See also: Universal Plug and Play § Problems with UPnP, and Wi-Fi Protected Setup § Vulnerabilities
External networks must be carefully considered as part of the overall security strategy of the local network. A router may include a firewall, VPN handling, and other security functions, or these may be handled by separate devices. Many companies produced security-oriented routers, including Cisco PIX series, Cisco Meraki MX series and Juniper NetScreen. Routers also commonly perform network address translation, (which allows multiple devices on a network to share a single public IP address[9][10][11]) and stateful packet inspection. Some experts argue that open source routers are more secure and reliable than closed source routers because open source routers allow mistakes to be quickly found and corrected. [12]
Core [edit]
In enterprises, a core router may provide a "collapsed backbone" interconnecting the distribution tier routers from multiple buildings of a campus, or large enterprise locations. They tend to be optimized for high bandwidth, but lack some of the features of edge routers. [13]
Internet connectivity and internal use [edit]
Routers intended for ISP and major enterprise connectivity usually exchange routing information using the Border Gateway Protocol (BGP). RFC 4098 standard defines the types of BGP routers according to their functions:[14]
- Edge router : Also called a provider edge router, is placed at the edge of an ISP network. The router uses External BGP to EBGP routers in other ISPs, or a large enterprise Autonomous System.
- Subscriber edge router : Also called a Customer Edge router, is located at the edge of the subscriber's network, it also uses EBGP to its provider's Autonomous System. It is typically used in an (enterprise) organization.
- Inter-provider border router : Interconnecting ISPs, is a BGP router that maintains BGP sessions with other BGP routers in ISP Autonomous Systems.
- (^) Core router: A core router resides within an Autonomous System as a back bone to carry traffic between edge routers. [15]
- Within an ISP: In the ISP's Autonomous System, a router uses internal BGP to communicate with other ISP edge routers, other intranet core routers, or the ISP's intranet provider border routers.
- "Internet backbone:" The Internet no longer has a clearly identifiable backbone, unlike its predecessor networks. See default-free zone (DFZ). The major ISPs' system routers make up what could be considered to be the current Internet backbone core.[16]^ ISPs operate all four types of the BGP routers described here. An ISP "core" router is used to interconnect its edge and border routers. Core routers may also have specialized functions in virtual private networks based on a combination of BGP and Multi-Protocol Label Switching protocols.[17]
- Port forwarding: Routers are also used for port forwarding between private Internet- connected servers.[6]
- Voice/Data/Fax/Video Processing Routers: Commonly referred to as access servers or gateways, these devices are used to route and process voice, data, video and fax traffic on the Internet. Since 2005, most long-distance phone calls have been processed as IP traffic ( VOIP) through a voice gateway. Use of access server type routers expanded with the advent of the Internet, first with dial-up access and another resurgence with voice phone service.
- Larger networks commonly use multilayer switches, with layer 3 devices being used to simply interconnect multiple subnets within the same security zone, and higher layer switches when filtering, translation, load balancing or other higher level functions are required, especially between zones.
Historical and technical information [edit]
From the mid-1970s and in the 1980s, general-purpose mini-computers served as routers. Modern high-speed routers are highly specialized computers with extra hardware added to speed both common routing functions, such as packet forwarding, and specialised functions such as IPsecencryption. There is substantial use of Linux and Unix software based machines, running open source routing code, for research and other applications. The Cisco IOS operating system was independently designed. Major router operating systems, such as Junos and NX-OS, are extensively modified versions of Unix software.
Forwarding[edit]
Further information: Routing and IP routing
The main purpose of a router is to connect multiple networks and forward packets destined either for its own networks or other networks. A router is considered a layer-3 device because its primary forwarding decision is based on the information in the layer-3 IP packet, specifically the destination IP address. When a router receives a packet, it searches its routing table to find the best match between the destination IP address of the packet and one of the addresses in the routing table. Once a match is found, the packet is encapsulated in the layer-2 data link frame for the outgoing interface indicated in the table entry. A router typically does not look into the packet payload,[ citation needed ] (^) but only at the layer-3 addresses to make a forwarding decision, plus optionally other
information in the header for hints on, for example, quality of service (QoS). For pure IP forwarding, a router is designed to minimize the state information associated with individual packets. [27]^ Once a packet is forwarded, the router does not retain any historical information about the packet.[d]
The routing table itself can contain information derived from a variety of sources, such as a default or static routes that are configured manually, or dynamic routing protocols where the router learns routes from other routers. A default route is one that is used to route all traffic whose destination does not otherwise appear in the routing table; this is common – even necessary – in small networks, such as a home or small business where the default route simply sends all non-local traffic to the Internet service provider. The default route can be manually configured (as a static route), or learned by dynamic routing protocols, or be obtained by DHCP. [e][28]
A router can run more than one routing protocol at a time, particularly if it serves as an autonomous system border router between parts of a network that run different routing protocols; if it does so, then redistribution may be used (usually selectively) to share information between the different protocols running on the same router. [29]
Besides making a decision as to which interface a packet is forwarded to, which is handled primarily via the routing table, a router also has to manage congestion when packets arrive at a rate higher than the router can process. Three policies commonly used in the Internet are tail drop, random early detection (RED), and weighted random early detection(WRED). Tail drop is the simplest and most easily implemented; the router simply drops new incoming packets once the length of the queue exceeds the size of the buffers in the router. RED probabilistically drops datagrams early when the queue exceeds a pre-configured portion of the buffer, until a pre-determined max, when it becomes tail drop. WRED requires a weight on the average queue size to act upon when the traffic is about to exceed the pre-configured size, so that short bursts will not trigger random drops.[ citation needed ]
Another function a router performs is to decide which packet should be processed first when multiple queues exist. This is managed through QoS, which is critical when Voice over IPis deployed, so as not to introduce excessive latency. [ citation needed ]
Yet another function a router performs is called policy-based routing where special rules are constructed to override the rules derived from the routing table when a packet forwarding decision is made.[30]
Router functions may be performed through the same internal paths that the packets travel inside the router. Some of the functions may be performed through an application-specific integrated circuit
(ASIC) to avoid overhead of scheduling CPU time to process the packets. Others may have to be performed through the CPU as these packets need special attention that cannot be handled by an ASIC.[ citation needed ]
2- Switches
A network switch (also called switching hub , bridging hub , officially MAC bridge [1]) is a computer networking device that connects devices together on a computer network by using packet switching to receive, process, and forward data to the destination device.
A network switch is a multiport network bridge that uses hardware addresses to process and forward data at the data link layer (layer 2) of the OSI model. Some switches can also process data at the network layer (layer 3) by additionally incorporating routing functionality. Such switches are commonly known as layer-3 switches or multilayer switches. [2]
Switches for Ethernet are the most common form of network switch. The first Ethernet switch was introduced by Kalpana in 1990. [3]^ Switches also exist for other types of networks including Fibre Channel, Asynchronous Transfer Mode, and InfiniBand.
Unlike less advanced repeater hubs, which broadcast the same data out of each of its ports and let the devices decide what data they need, a network switch forwards data only to the devices that need to receive it. [4]
Role of switches in a network[edit]
Switches may operate at one or more layers of the OSI model, including the data link and network layers. A device that operates simultaneously at more than one of these layers is known as a multilayer switch.
In switches intended for commercial use, built-in or modular interfaces make it possible to connect different types of networks, including Ethernet, Fibre Channel, RapidIO, ATM, ITU-T G.hn and 802.11. This connectivity can be at any of the layers mentioned. While the layer-2 functionality is adequate for bandwidth-shifting within one technology, interconnecting technologies such as Ethernet and token ring is performed easier at layer 3 or via routing.[6]^ Devices that interconnect at the layer 3 are traditionally called routers, so layer 3 switches can also be regarded as relatively primitive and specialized routers. [7]
Where there is a need for a great deal of analysis of network performance and security, switches may be connected between WAN routers as places for analytic modules. Some vendors provide firewall, [8][9]^ network intrusion detection, [10]^ and performance analysis modules that can plug into switch ports. Some of these functions may be on combined modules. [11]
In other cases, the switch is used to create a mirror image of data that can go to an external device. Since most switch port mirroring provides only one mirrored stream, network hubs can be useful for fanning out data to several read-only analyzers, such as intrusion detection systems and packet sniffers.
Chapter 4: Cabling
What is Network Cabling?
Cable is the medium through which information usually moves from one network
device to another. There are several types of cable which are commonly used with
5 100 Mbps (2 pair) 100BaseT Ethernet
1000 Mbps (4 pair) Gigabit Ethernet
5e 1,000 Mbps Gigabit Ethernet
6 10,000 Mbps Gigabit Ethernet
Unshielded Twisted Pair Connector
The standard connector for unshielded twisted pair cabling is an RJ-45 connector.
This is a plastic connector that looks like a large telephone-style connector (See fig.
2). A slot allows the RJ-45 to be inserted only one way. RJ stands for Registered Jack,
implying that the connector follows a standard borrowed from the telephone industry.
This standard designates which wire goes with each pin inside the connector.
Fig. 2. RJ-45 connector
Shielded Twisted Pair (STP) Cable
Although UTP cable is the least expensive cable, it may be susceptible to radio and
electrical frequency interference (it should not be too close to electric motors,
fluorescent lights, etc.). If you must place cable in environments with lots of potential
interference, or if you must place cable in extremely sensitive environments that may
be susceptible to the electrical current in the UTP, shielded twisted pair may be the
solution. Shielded cables can also help to extend the maximum distance of the cables.
Shielded twisted pair cable is available in three different configurations:
1. Each pair of wires is individually shielded with foil.
2. There is a foil or braid shield inside the jacket covering all wires (as a group).
3. There is a shield around each individual pair, as well as around the entire group
of wires (referred to as double shield twisted pair).
Coaxial Cable
Coaxial cabling has a single copper conductor at its center. A plastic layer provides
insulation between the center conductor and a braided metal shield (See fig. 3). The
metal shield helps to block any outside interference from fluorescent lights, motors,
and other computers.
Fig. 3. Coaxial cable
Although coaxial cabling is difficult to install, it is highly resistant to signal
interference. In addition, it can support greater cable lengths between network devices
than twisted pair cable. The two types of coaxial cabling are thick coaxial and thin
coaxial.
Thin coaxial cable is also referred to as thinnet. 10Base2 refers to the specifications
for thin coaxial cable carrying Ethernet signals. The 2 refers to the approximate
maximum segment length being 200 meters. In actual fact the maximum segment
length is 185 meters. Thin coaxial cable has been popular in school networks,
especially linear bus networks.
Thick coaxial cable is also referred to as thicknet. 10Base5 refers to the specifications
for thick coaxial cable carrying Ethernet signals. The 5 refers to the maximum
segment length being 500 meters. Thick coaxial cable has an extra protective plastic
cover that helps keep moisture away from the center conductor. This makes thick
coaxial a great choice when running longer lengths in a linear bus network. One
disadvantage of thick coaxial is that it does not bend easily and is difficult to install.
Coaxial Cable Connectors
The most common type of connector used with coaxial cables is the Bayone-Neill-
Concelman (BNC) connector (See fig. 4). Different types of adapters are available for
BNC connectors, including a T-connector, barrel connector, and terminator.
Connectors on the cable are the weakest points in any network. To help avoid
problems with your network, always use the BNC connectors that crimp, rather screw,
onto the cable.
Fig. 4. BNC connector
Fiber Optic Cable
Fiber optic cabling consists of a center glass core surrounded by several layers of
protective materials (See fig. 5). It transmits light rather than electronic signals
eliminating the problem of electrical interference. This makes it ideal for certain
environments that contain a large amount of electrical interference. It has also made it
the standard for connecting networks between buildings, due to its immunity to the
effects of moisture and lighting.
- Use cable ties (not tape) to keep cables in the same location together.
Wireless LANs
More and more networks are operating without cables, in the wireless mode. Wireless
LANs use high frequency radio signals, infrared light beams, or lasers to
communicate between the workstations, servers, or hubs. Each workstation and file
server on a wireless network has some sort of transceiver/antenna to send and receive
the data. Information is relayed between transceivers as if they were physically
connected. For longer distance, wireless communications can also take place through
cellular telephone technology, microwave transmission, or by satellite.
Wireless networks are great for allowing laptop computers, portable devices, or
remote computers to connect to the LAN. Wireless networks are also beneficial in
older buildings where it may be difficult or impossible to install cables.
The two most common types of infrared communications used in schools are line-of-
sight and scattered broadcast. Line-of-sight communication means that there must be
an unblocked direct line between the workstation and the transceiver. If a person
walks within the line-of-sight while there is a transmission, the information would
need to be sent again. This kind of obstruction can slow down the wireless network.
Scattered infrared communication is a broadcast of infrared transmissions sent out in
multiple directions that bounces off walls and ceilings until it eventually hits the
receiver. Networking communications with laser are virtually the same as line-of-sight
infrared networks.
Wireless standards and speeds
The Wi-Fi Alliance is a global, non-profit organization that helps to ensure standards
and interoperability for wireless networks, and wireless networks are often referred to
as WIFI (Wireless Fidelity). The original Wi-Fi standard (IEEE 802.11) was adopted
in 1997. Since then many variations have emerged (and will continue to emerge). Wi-
Fi networks use the Ethernet protocol.
Standard Max Speed Typical Range
802.11a 54 Mbps 150 feet
802.11b 11 Mbps 300 feet
802.11g 54 Mbps 300 feet
802.11n 100 Mbps 300+ feet
Wireless Security
Wireless networks are much more susceptible to unauthorized use than cabled
networks. Wireless network devices use radio waves to communicate with each other.
The greatest vulnerability to the network is that rogue machines can "eves-drop" on
the radio wave communications. Unencrypted information transmitted can be
monitored by a third-party, which, with the right tools (free to download), could
quickly gain access to your entire network, steal valuable passwords to local servers
and online services, alter or destroy data, and/or access personal and confidential
information stored in your network servers. To minimize the possibility of this, all
modern access points and devices have configuration options to encrypt
transmissions. These encryption methodologies are still evolving, as are the tools used
by malicious hackers, so always use the strongest encryption available in your access
point and connecting devices.
A NOTE ON ENCRYPTION: As of this writing WEP (Wired Equivalent Privacy)
encryption can be easily hacked with readily-available free tools which circulate the
internet. WPA and WPA2 (WIFI Protected Access versions 1 and 2) are much better at
protecting information, but using weak passwords or passphrases when enabling these
encryptions may allow them to be easily hacked. If your network is running WEP, you
must be very careful about your use of sensitive passwords or other data.
Three basic techniques are used to protect networks from unauthorized wireless use.
Use any and all of these techniques when setting up your wireless access points:
Encryption.
Enable the strongest encryption supported by the devices you will be
connecting to the network. Use strong passwords (strong passwords are
generally defined as passwords containing symbols, numbers, and mixed case
letters, at least 14 characters long).
Isolation.
Use a wireless router that places all wireless connections on a subnet
independent of the primary private network. This protects your private network
data from pass-through internet traffic.
Hidden SSID.
Every access point has a Service Set Identifier (SSID) that by default is
broadcast to client devices so that the access point can be found. By disabling
this feature, standard client connection software won't be able to "see" the
access point. However, the eves-dropping programs discussed previously can
easily find these access points, so this alone does little more than keep the
access point name out of sight for casual wireless users.
Advantages of wireless networks:
- Mobility - With a laptop computer or mobile device, access can be available
throughout a school, at the mall, on an airplane, etc. More and more businesses
are also offering free WIFI access ("Hot spots").
Networking cables are networking hardware used to connect one network device to other network devices or to connect two or more computers to share printers, scanners etc. Different types of network cables, such as coaxial cable, optical fiber cable, and twisted pair cables, are used depending on the network's physical layer, topology, and size. The devices can be separated by a few meters (e.g. via Ethernet) or nearly unlimited distances (e.g. via the interconnections of the Internet).
There are several technologies used for network connections. Patch cables are used for short distances in offices and wiring closets. Electrical connections using twisted pair or coaxial cable are used within a building. Optical fiber cable is used for long distances or for applications requiring high bandwidth or electrical isolation. Many installations use structured cabling practices to improve reliability and maintainability. In some home and industrial applications power lines are used as network cabling.
Contents [hide]
- 1Twisted pair
- 2Fiber optic
- 3Coaxial
- 4Patch
- 5Power lines
- 6References
- 7External links
Twisted pair [edit]
Twisted pair cabling is a form of wiring in which pairs of wires (the forward and return conductors of a single circuit) are twisted together for the purposes of canceling out electromagnetic interference (EMI) from other wire pairs and from external sources. This type of cable is used for home and corporate Ethernet networks. Twisted pair cabling is used in short patch cables and in the longer runs in structured cabling.
An Ethernet crossover cable is a type of twisted pair Ethernet cable used to connect computing devices together directly that would normally be connected via a network switch, Ethernet hub or router, such as directly connecting two personal computers via their network adapters. Most current Ethernet devices support Auto MDI-X, so it doesn't matter whether you use crossover or straight cables.[1]
Fiber optic [edit]
An optical fiber cable consists of a center glass core surrounded by several layers of protective material. The outer insulating jacket is made of Teflon or PVC to prevent interference. Optical fiber deployment is more expensive than copper but offers higher bandwidth and can cover longer distances.[2] There are two major types of optical fiber cables: short-range multi-mode fiber and long-range single-mode fiber.
Coaxial[edit]
Coaxial cables confine the electromagnetic wave inside the cable, between the center conductor and the shield. The transmission of energy in the line occurs totally through the dielectric inside the cable between the conductors. Coaxial lines can therefore be bent and twisted (subject to limits) without negative effects, and they can be strapped to conductive supports without inducing unwanted currents in them. The most common use for coaxial cables is for television and other signals with a bandwidth of several hundred megahertz to gigahertz. Although in most homes coaxial cables have been installed for transmission of TV signals, new technologies (such as the ITU-T G.hn standard) open the possibility of using home coaxial cable for high-speed home networkingapplications (Ethernet over coax).
In the 20th century they carried long distance telephone connections.
Patch[edit]
A patch cable is an electrical or optical cable used to connect one electronic or optical device to another or to building infrastructure for signal routing. Devices of different types (e.g. a switch connected to a computer, or a switch connected to a router) are connected with patch cords. Patch cords are usually produced in many different colors so as to be easily distinguishable, [1]^ and most are relatively short, no longer than a few meters. In contrast to on-premises wiring, patch cables are more flexible but may also be less durable.
Power lines[edit]
Although power wires are not designed for networking applications, new technologies like Power line communication allows these wires to also be used to interconnect home computers, peripherals or other networked consumer products. On December 2008, the ITU-T adopted Recommendation G.hn /G.9960 as the first worldwide standard for high-speed powerline communications. [3]^ G.hn also specifies communications over phonelines and coaxial wiring.
4- network hub
Networking hub
All devices connected to a network hub share all available bandwidth equally. This
differs from a switch environment, where each port is allotted a dedicated amount of
bandwidth.
Types of hubs
There are two types of network hubs: active and passive. A third designation,
intelligent hubs, is synonymous with a switch.
- Active hubs repeat and strengthen incoming transmissions. They are also
sometimes referred to as repeaters.
- Passive hubs simply serve as a point of connectivity, without any additional
capabilities.
An unrelated use of the word "hub" involves network topologies. In a star topology,
sometimes called hub and spoke, each host connects to a central hub; the hosts,
however, do not directly connect to each other. In this context, the "hub" is typically a
switch.
The OSI Model
OSI is a standard description or "reference model" for how messages should be transmitted
between any two points in a telecommunication network. Its purpose is to guide product
implementers so that their products will consistently work with other products.
The Model
The OSI model was created by the IEEE committee so different vendors products would work
with each other. You see the problem was that when HP decided to create a network product, it
would be incompatible with similar products of a different vendor e.g IBM.
So when purchasing 40 network cards for your company, you would need to make sure that the
rest of the equipment would be from the same vendor, to ensure compatibility. It is quite clear
that things were very restrictive, until the OSI model came into the picture.
As most are aware of, the OSI model consists of 7 layers.
Each layer has been designed to do a specific task. Starting from the top layer (7) we will see
how the data which you type gets converted into segments, the segments into datagrams and the
datagrams into packets, the packets into frames and then the frames are sent down the wire,
usually twisted pair, to the receiving computer.
Full in-depth analysis of each layer is available using the links to the articles at the bottom of this
page.
