GraphicsWindow.PenColor = "white"
GraphicsWindow.BrushColor = "black"
lingkaran1 = Shapes.AddEllipse(10,10)
GraphicsWindow.BrushColor = "red"
lingkaran2 = Shapes.AddEllipse(20,20)
Shapes.Move(lingkaran1, 5, 5)
Shapes.SetOpacity(lingkaran2, 50)

TextWindow.WriteLine(Program.Directory)

Firman Harian

03/11/12
Maz 90:12 :"Ajarlah kami menghitung hari-hari kami sedemikian, hingga kami beroleh hati yang bijaksana."

c:/windows/media

j = 50
'spasi antar bulatan
space = 20

For i = 0 To 20
  Shapes[i] = Shapes.AddEllipse(i, j)
  Shapes.Move(Shapes[i], i * (10 + space), 0)
EndFor

Contoh laporan hasil penghitungan suara pemilu 2014 di Indonesia

Belajar Memahami Antrian

Karakteristik Jaringan

Karakteristik suatu jaringan ditinjau dari, antara lain:
1. Konvergensi
2. Skalabilitas
3. Keamanan
4. Fault tolerance
5. Quality of Service (Menjamin layanan tetap baik disaat kondisi kritis)

Sekian, semoga bermanfaat, salam mandiri!

Network security

Contoh-contoh ancaman jaringan di dunia nyata bisa diklasifikasikan kedalam ancaman terhadap infrastruktur jaringan (ancaman terhadap perangkat jaringan) dan ancaman terhadap content/isi/data.

Berikut contoh ancaman terhadap keamanan infrastruktur jaringan:
1. Penjaga gedung mencabut perangkat jaringan yang penting.
Solusinya: kerangkeng perangkat jaringan, just kidding, beli rack perangkat jaringan yang berkunci dan bisa ditutup.

2. Kontraktor bangunan tidak sengaja memotong kabel jaringan saat menggali.
Solusinya: beritahu supaya berhati-hati.

3. Seorang hacker terhubung dengan sebuah perangkat dan mengutak-utik settingan perangkat lunak manajemen perangkat itu.
Solusinya: perangkat jaringan diberi username dan password, hindari penggunaan username dan password default (contoh: tp-link username admin password admin), nyalakan fitur-fitur jaringan lainnya milik cisco contoh: fitur untuk melawan brute-force)


Berikut contoh ancaman terhadap keamanan content:
1. Seorang karyawan kecewa terhadap perusahaan mengubah-ubah informasi pada database pelanggan.
Solusinya: beri username dan password untuk mengakses database itu.

2. Seorang kompetitor/pesaing bisa mengakses informasi yang peka/sensitif melalui jaringan wireless.
Solusinya: jangan biarkan user-user wireless bisa mengakses alamat-alamat IP intranet.

3. Seorang sekretaris membalas email yang keliru dengan informasi yang sensitif (dia kira dia mengirim email kepada bosnya, ternyata alamat emailnya milik orang lain, informasi bocor).
Solusinya: gw gak tau, masih belum tahu.

Sekian. Semoga bermanfaat, salam mandiri!

RIPv1

1. Administrative Distance
- Administrative Distance = ranking keterpercayaan protokol-protokol routing.
- Nilai default administrative distance dari RIPv1 = 120; RIPv1 paling terakhir dipercayai diantara protokol-protokol routing EIGRP, IGRP, OSPF, ISIS
- Cara cek administrative distance = show ip protocols atau show ip route

2. Konfigurasi dasar

Apa saja komponen dari protokol routing?

1. Data structure / tables / databases. Kept in RAM.
2. Algoritma: Best path determination.
3. Routing protocol messages
- Message to discover neighboring routers
- Exchange routing information
- Learn accurate information about the network
- Maintain accurate information about the network.

Network topology change

Network topology change may occur for several reasons, including:
1. Failure of a link
2. Introduction of a new link
3. Failure of a router
4. Change of link parameters

Kepada YTH router:
Setelah selesai cold start / power up:
1. Baca surat startup-config yang tersimpan di NVRAM
2. Temukan alamat IP dari kedua interface mu
3. And kan alamat IP interface mu dengan subnet masknya masing-masing untuk mendapatkan alamat network mu
4. Tulis alamat networkmu ke dalam routing tabel, cantumkan huruf C disampingnya.

Classless routing protocol dan classful routing protocol

Classless routing protocol
- Classless routing protocol mengirimkan/mencantumkan informasi subnet mask pada paket routing update.
- Classless mampu mendukung discontigous network
- Classless routing protocol contohnya: RIPv2, EIGRP dan OSPF

Clasful routing protocol
- Clasful routing protocol tidak mengirimkan/mencantumkan informasi subnetmask pada paket routing update.
- Clasful routing protocol contohnya: RIPv1 dan IGRP
-

Contohnya: RIPv1

Kunci karakteristik beberapa protokol distance vector routing

1. RIP
1. Hop count dipakai sebagai metrik dalam pemilihan jalur/path.
2. Jika jumlah hop count dari sebuah network > 15, RIP tidak dapat menyediakan sebuah route ke network itu.
3. Update-update routing adalah broadcast atau multicast setiap 30 detik secara default

2. IGRP
1. Bandwidth, delay, reliability digunakan sebagai composite metric
2. Routing update di broadcast setiap 90 detik secara default
3. IGRP adalah pendahulu dari EIGRP dan sekarang sudah tidak dipakai lagi.

3. EIGRP
1. EIGRP dapat melakukan load balancing unequal cost
2. EIGRP menggunakan DUAL untuk menghitung jalur terpendek.
3. Tidak menggunakan periodik updates seperti RIP dan IGRP. Routing updates hanya dikirimkan hanya ketika terjadi perubahan topologi.

RIP

Routing loop
convergence time makes routing loops possible

Split horizon
Routes learned through an interface are not advertised out that same interface

Route poisoining
Routes learned through an interface are advertised back out the same interface as unreachable.

Triggered updates
Topology change are immediately sent to adjacent routers

Hold down timers
allows time for topology change to travel through entire network

Count to infinity loop problems
Solution: hold down timers

Karakteristik dari paket update EIGRP
1. Hanya dipicu untuk perubahan topologi
2. bounded to affected next hop routers


Pada kondisi apa saja yang menyebabkan protokol routing distant vector untuk mengirimkan update routing tabel?
1. Ketika sebuah perubahan terjadi pada topologi jaringan
2. Ketika timer update timer habis
3. Ketika sebuah paket update triggered diterima dari router yang lain.

Summary

One way of classifying routing protocols is by the type of algorithm they use to determine the best path to a destination network. Routing protocols can be classified as distance vector, link state, or path vector. Distance vector means that routes are advertised as vectors of distance and direction. Distance is defined in terms of a metric such as hop count and direction is simply the next-hop router or exit interface.

Distance vector routing protocols include:
RIPv1
RIPv2
IGRP
EIGRP

Routers that use distance vector routing protocols determine best path to remote networks based on the information they learn from their neighbors. If Router X learns of two paths to the same network, one through Router Y at 7 hops, and another route through Router Z at 10 hops, the router will choose the shorter path using Router Y as the next-hop router. Router X has no knowledge of what the network looks like beyond Routers Y and Z, and can only make its best path decision based on the information sent to it by these two routers. Distance vector routing protocols do not have a map of the topology as do link state routing protocols.

Network discovery is an important process of any routing protocol. Some distance vector routing protocols such as RIP go through a step-by-step process of learning and sharing routing information with their neighbors. As routes are learned from one neighbor, that information is passed on to other neighbors with an increase in the routing metric.

Routing protocols also need to maintain their routing tables to keep them current and accurate. RIP exchanges routing table information with its neighbors every 30 seconds. EIGRP, another distance vector routing protocol, does not send these periodic updates and only sends a "bounded" update when there is a change in the topology and only to those routers that need that information. EIGRP is discussed in a later chapter.

RIP also uses timers to determine when a neighboring router is no longer available, or when some of the routers may not have current routing information. This is typically because the network has not yet converged due to a recent change in the topology. Distance vector routing protocols also use triggered updates to help speed up convergence time.

One disadvantage of distance vector routing protocols is the potential for routing loops. Routing loops can occur when the network is in an unconverged state. Distance vector routing protocols use holddown timers to prevent the router from using another route to a recently down network until all of the routers have had enough time to learn about this change in the topology.

Split horizon and split horizon with poison reverse are also used by routers to help prevent routing loops. The split horizon rule states that a router should never advertise a route through the interface from which it learned that route. Split horizon with poison reverse means that it is better to explicitly state that this router does not have a route to this network by poisoning the route with a metric stating that the route is unreachable.

Distance vector routing protocols are sometime referred to as "routing by rumor", although this can be somewhat of a misnomer. Distance vector routing protocols are very popular with many network administrators as they are typically easily understood and simple to implement. This does not necessarily mean link-state routing protocols are any more complicated or difficult to configure. Unfortunately, link-state routing protocols have received this somewhat unwarranted reputation. We will learn in later chapters that link-state routing protocols are as easy to understand and configure as distance vector routing protocols.