Garis Besar Wide Area Network (WAN)

Wide Area Network (WAN)  mempunyai konsep dasar yang sama dengan jaringan Local Area Network (LAN) dengan perbedaan pada:

1. WAN mencakup daerah yang lebih luas -> dibutuhkan perangkat (hardware) di layer 1 dengan kualitas dan perlakuan khusus.
2. Terdapat lebih banyak perangkat yang terhubung sehingga membutuhkan teknologi peroutingan yang lebih baik.
3. Karena WAN digunakan oleh orang banyak maka dibutuhkan service untuk mendukung hal tersebut sehingga antar user tidak saling merugikan dan dirugikan.

Konsep WAN secara garis besar dapat digambarkan sebagai berikut:

1. Pada OSI Layer 1

Terdapat beberapa teknologi jaringan yang dapat mendukung penyampaian data secara jarak jauh antara lain:

• Modem Analog
• DSL
• Internet Kabel
• Optic

2. Pada OSI Layer 2

Pada layer 2 terdapat sebuah protokol yang dapat memungkinkan data dikirimkan pada beberapa media yang berbeda. Protokol yang sering dipakai antara lain:

• PPP
• HDLC
• Frame Relay
• ATM

3. Pada OSI Layer 3

Layer 3 merupakan inti dari peroutingan, disini terdapat alamat IP yang menentukan alamat logic suatu host, alamat tersebutlah yang digunakan untuk peroutingan. Protokol peroutingan yang sering digunakan adalah:

• RIP
• OSPF
• IS-IS
• BGP

4. Potokol Pendukung

Selain protokol yang terdapat pada masing-masing layer, terdapat pula protokol yang terletak diantara beberapa layer atau protokol pendukung protokol utama, contoh:

• MPLS
• TLDP
• LDP
• RSVP-TE

5. Service Pendukung

Service digunakan untuk mengatur user sehingga tidak saling merugikan atau bisa juga digunakan untuk billing penggunaan bandwith oleh user.

• apipe
• cpipe
• VPRN
• VRRP
• IES
• SDP, dll

Service juga bisa digunakan untuk membangun jaringan secara logical antar router atau dalam satu router. Nama untuk service biasanya tergantung oleh vendor yang membuat router seperti Alcatel, Cisco, dan Juniper.

6. Hirarki Konfigurasi

Jaringan Wide Area Network merupakan suatu jaringan yang sangat besar, atau bisa dibilang jaringan internet (hubungan antar  jaringan). Namun jaringan tersebut bisa dipecah-pecah lagi kedalam jaringan yang lebih kecil yang mempunyai istilah tertentu yaitu:

Urut dari yang paling besar:

Internet -> Autonomous System (AS) -> IGP -> VLAN -> Host (user)

Uraian diatas merupakan suatu gambaran dari suatu jaringan WAN dengan berbagai unsur yang membangunnya. Memang uraian tersebut tidak membahas masing-masing unsur secara detail karena dimaksudkan untuk memberikan gambaran secara lebih luas tentang WAN dan unsur-unsur yang dibutuhkan. Uraian di atas hanya merupakan catatan saya pribadi biar lebih mudah memahami konsep WAN dan tidak lupa dikemudian hari. Apabila masih terdapat banyak kesalahan atau hal-hal yang terlewatkan silahkan untuk dikoreksi dan ditambahkan.

Source:

• ICND study guide
• JNCIA study guide
• www.wikipedia.org

Fundamentals of IP Addressing and Routing

OSI layer 3 : protocols define how packets can be delivered from the computer (source) to the computer that needs to receive the packet (destination), OSI defines following feature:

• Routing: the process of forwarding packets (Layer 3 PDUs)
• Logical addressing: address that can be used regardless of the type of physical network used (at least one address). Enable routing process to identify a packet’s source and destination
• Routing protocol: a protocol that aids routers by dynamically learning about the groups of addresses in the network, which in turn allows the routing (forwarding) process to work well
• Other utilities: For TCP/IP -> Domain Name System (DNS), Dynamic Host Configuration Protocol (DHCP), Address Resolution Protocol (ARP), and Ping

Routing (Forwarding)
Routing focuses on the end-to-end logic of forwarding data.
Routing has two main concepts:

• The process of routing forwards Layers 3 packets, also called Layer 3 protocol data units (L3 PDU), based on the destination Layer 3 address in the packet
• The routing process uses the data link layer to encapsulate the Layer 3 packets into Layer 2 frames for transmission across each successive data link.

IP Class :

• Class A networks have 1-byte-long network part. 3 bytes rest for host part
• Class B networks have 2-byte-long network part. 2 bytes rest for host part
• Class C networks have 3-byte-long network part. 1 bytes rest for host part

Number of Addresses per class with no subnetting:

Class	Number Network Bytes (Bits)	Number of Host Bytes (Bits)	Number of Addresses Per Network*
A	1 (8)	3 (24)	224 - 2
B	2 (16)	2 (16)	216 - 2
C	3 (24)	1 (8)	28 - 2

* There are two reserved addresses per network

Reserved address is an address that has been reserved for special purpose
- All host address has binary 0s example (with no subnetting) : 192.168.1.0 -> called network address
- All host address has binary 1s example (with no subnetting) : 192.168.1.255 -> called broadcast address
All Possible Valid Network Numbers

Class	First Octet Range	Valid Network Numbers	Total Number for This Class of Network	Number of Hosts Per Network
A	1 to 126	1.0.0.0 to 126.0.0.0	27 - 2 (126)	224 – 2 (16,777,214)
B	128 to 191	128.0.0.0 to 191.255.0.0	214 (16, 384)	216 - 2 (65,534)
C	192 to 223	192.0.0.0 to 223.255.255.0	221 (2,097,152)	28 - 2 (254)

127.0.0.0 reserved for loopback address
Host Routing
Host actually use some simple routing logic when choosing where to send a packet:

1. If destination IP address in the same subnet as I am, send the packet directly to that destination host
2. If the destination IP address is not in the same subnet as I am, send the packet to my default gateway.

Router forwarding Decisions and the IP Routing Table
A router uses the following logic when receiving a data-link frame – a frame that has an IP packet ecapsulated in it:

1. Use the data-link FCS field to ensure that the frame had no errors; if errors occurred, discard the frame
2. Assuming the frame was not discarded at step 1, discard the old data-link header and trailer, leaving the IP packet.
3. Compare the IP packet’s destination IP address to the routing table, and find the route that matches the destination address.
4. Ecaptsulate the IP packet inside a new data-link header and trailer, appropriate for the outgoing interface, and forward the frame.

Routing protocols use the basic logic:

1. Each router add a route to its routing table for each subnet directly connected to the router
2. Each router tells its neighbors about all the routers in its routing table, including the directly connected routes and routes learned from other routers
3. After learning a new route from neighbor, the router adds a route to its routing table

Network Layer Utilities

• Address Resolution Protocol (ARP)

ARP broadcast is sent to broadcast Ethernet Address, so everyone on the LAN receives it. Usually use to find address from neighbors.

• Domain Name System (DNS)

Resolve name server to IP address

• Dynamic Host Configuration Protocol (DHCP)

DHCP automatically supplies IP addresses to clients, also other information such as subnet mask and default gateway.

• Ping

To test basic IP connectivity without relying on any applications to be working. Uses the Internet Control Message Protocol (ICMP)

Taken from: CCNA-CCENT ICND1 Official Exam Certification Guide

Fundamental of WAN Summary

1. OSI layer 1 for point-to-point WANs

A point-to-point WAN link acts like an Ethernet trunk between two Ethernet switches in many ways. The big distinction between LANs and WANs relates to how far apart the devices can be still capable of sending and receiving data. Usually use telco company cable infrastructures.
Serial cabling option: EIA/TIA-232, EIA/TIA-449, V.35, X.21, EIA-530
WAN Speed Summary:

Name of Line	Bit Rate
DS0	64 kbps
DS1 (T1)	1.544 Mbps (24 DS0s, plus 8 kbps overhead)
DS3 (T3)	44.736 Mbps (28 DS1s, plus management overhead)
E1	2.048 Mbps (32 DS0s)
E3	34.064 Mbps (16 E1s, plus management overhead)
J1 (Y1)	2.048 (32 DS0s; Japanese standard)

2. OSI layer 2 for point-to-point WANs

Protocol used: High-Level Data Link Control (HDLC) and Point-to-Point Protocol (PPP)
HDLC needs to determine if the data passed the link without any errors; discards the frame if errors occurred. Additionally HDLC needs to identify the type of packet inset the HDLC frame
Point-to-Point Protocol -> ITU standards. Similar to HDLC, develops after HDLC, most popular and feature-rich of WAN data link layer protocols.
WAN Terminology -> synchronous, clock source, CSU/DSU, four-wire circuit, T1, E1, leased line, leased circuit, link, serial link, serial line, point-to-point link, circuit.

3. Frame Relay and Packet-Switching Services

Two types of packet-switching service are very popular today: Frame Relay and Asynchronous Transfer Mode (ATM)
The benefit of packet switching instead leased line: fewer interfaces needed, cheaper, fast as or probably faster than.

Fundamental of LAN Summary

1. An overview of modern Ethernet LANs
2. A brief history of Ethernet
3. Ethernet UTP cabling
4. Improving performance by using switches instead of hub
5. Ethernet data-link protocols

1. An overview of modern Ethernet LANs

Ethernet refers to a family of standards that together define physical and data link layers of the world’s most popular type of LAN.
IEEE Standards:

• 802.3 Media Access Control (MAC) sublayer
• 802.2 Logical Link Control (LLC) sublayer

Today’s Most Common Types of Ethernet

Common Name	Speed	Alternative Name	Name of IEEE Standard	Cable Type, Maximum Length
Ethernet	10 Mbps	10BASE-T	IEEE 802.3	Copper, 100 m
Fast Ethernet	100 Mbps	100BASE-TX	IEEE 802.3u	Copper, 100m
Gigabit Ethernet	1000 Mbps	1000BASE-LX 1000BASE-SX	IEEE 802.3z	Fiber, 550 m (SX) 5 Km (LX)
Gigabit Ethernet	1000 Mbps	1000BASE-T	IEEE 802.3ab	100 m

To build a modern LAN using UTP based you need this following components:

• Computer that have Ethernet network interface card (NIC) installed
• Either Ethernet hub or Ethernet switch
• UTP cables

Purpose build a modern LAN: file sharing, printer sharing, file transfer, gaming.

2. A brief history of Ethernet

Original Ethernet standard:

• 10BASE2 -> coaxial cable, 200m maximum length, 10 Mbps bandwidth
• 10BASE5 -> coaxial cable, 500m maximum length, 10 Mbps bandwidth

Using bus topology
Collision may occur, using carrier sense multiple access with collision detection (CSMA/CD) algorithm to avoid collision:

• A device that wants to send a frame wait until the LAN silent -no frames are currently being sent.
• If a collision still occurs, the devices that caused the collision wait a random amount of time and then try again.

Repeaters extended the length of LAN by cleaning up the electrical signal and repeating it (layer 1 function)
Hubs are essentially repeater with multiple physical ports. Collision still occur, layer 1 function, bandwidth sharing.

3. Ethernet UTP Cabling

UTP (Unshielded Twisted Pair) using RJ 45 connector, EIA/TIA standard Ethernet cabling pinouts: T568A: W/G, Green, W/O, Blue, W/Blue, Orange, W/Brown, Brown; T568B: W/O, Orange, W/G, Blue, W/Blue, Green, W/Brown, Brown -> W = White
Straight-through cable -> using same standard each end of cable: T568A or T568B
Crossover cable -> using different standard each end of cable: T568A and T568B

Devices that transmit on 1,2 and receive on 3,6	Devices that transmit on 3,6 and receive on 1,2
PC NIC, Routers, Wireless Access Point (Ethernet interface), network printers (printers that connect directly to the LAN)	Hub, Switches

Straight-trough : use when connecting device with different transmit and receive pin (PC NIC – Hub)
Crossover: use when connecting device with same transmit and receive pin (PC NIC – router)

4. Increasing performance using switches instead hub

What switches do:

• Interpret the bit in the received frame so that they can typically send the frame out the one required port rather than all other ports.
• If switch need to forward multiple frame out the same port, the switch buffer the frames in memory, sending one at a time, thereby avoiding collisions.

Full duplex, full bandwidth capacity

5. Ethernet Data-Link Protocols

Unicast Ethernet addresses identify a single LAN card.
Multicast Ethernet addresses allow a subset of devices on a LAN to communicate
Broadcast Ethernet addresses implies that all devices on the LAN should process the frame.
MAC (Media Access Control) sublayer of IEEE Ethernet
Burned-in address the 6-byte address assigned by the vendor making the card
Framing defines how a string of binary numbers is interpreted, in other words, defines the meaning behind the bits that are transmitted across a network.

Networking Basic: TCP/IP and OSI Layers Summaries

TCP/IP Architectural Layer and Protocol

Application	HTTP, POP3, SMTP
Transport	TCP, UDP
Internet	IP
Network	Ethernet, Frame Relay

1. Application Layer

provide services to the application software [defines services that application need : such as capability to ransfer a file in the case of HTTP].

provide interface between software and network.

same layer interaction using header (application layer header) as part of what is transmitted between the two computers.

2. Transport Layer

provide a service to the application layer

TCP provide an error-recovery feature to the application protocols using acknowledgments.

adjacent-layer interaction communication between 2 protocols in different layer on a single computer

3. Internet Layer

defines logical address, also defines routing, the process of how router should forward, or route, packets of data.

4. Network Access Layer

defines the protocols and hardware required to deliver data across some physical network

example; ethernet defines the required cabling, addresing, and protocols used to create an Ethernet LAN.

many people defind network access layer as two layers; data link and physical layer.

TCP/IP network access layer include: the protocols, cabling standards, header, and trailer that define how to end data accross a wide variety of types of physical networks.

Data Encapsulation

process of putting headers and trailers around some data

header term: segment, packet, frame

TCP/IP Architectural Layer

Example Protocols

• segment = transport layer
• packet  = internet layer
• frame   = network access layer

Five Steps Data Encapsulation — TCP/IP

				Data		Application
			TCP	Data		Transport
		IP	TCP	Data		Internet
	LH	IP	TCP	Data	LT	Network Access
Transmit Bit

OSI Reference Model (Open System Interconnection)

used as point reference for discussing other protocol spesification including  TCP/IP

Comparison of TCP/IP and OSI layer

OSI		TCP/IP
ApplicationPresentationSession		Application
Transport		Transport
Network		Internet
Data LinkPhysical		Physical

Layer 7,6,5 define functions focused on the application

Layer 4,3,2,1 define functions focused on end-to-end delivery of the data
OSI layer 2 : LAN switching based
OSI layer 3 : ROuting based

OSI Layers Definitions

7	provide an interface between communitaions software and applications that need communicate outside the computer including processes for user authentication
6	define and negotiate data format: ASCII text, JPEG, EBCDIC text, BCD (including encryption)
5	define how to start, control, and end conversations (include control and management of mutiple bidirectional messages
4	focuses on data delivery to another computer (error recovery and flow control)
3	defines three main feature: logical addressing, routing (forwarding) and path determination. Path determination: which route is the best
2	protocol that determine when a device can send data over particular medium also define the header and trailer format
1	deal with physical characteristic of transmission medium; connector use of pins, electrical currents, encoding, and so on.

OSI Layers Devices and Protocols

Layer	Protocol and Specification	Device
5-7	Telnet, HTTP, FTP, SMTP, POP3, VoIP, SNMP	Firewall, Intrusion detection system
4	TCP, UDP
3	IP	Router
2	Ethernet (IEEE 802.3), HDLC, Frame Relay, PPP	LAN Switch, Wireless Access Point, DSL modem
	RJ-45, EIA/TIA-232, V.35 Ethernet	LAN hub, repeater

OSI Layering Benefit

- Less Complex
- Standard Interface
- Easier to learn
- Easier to develop
- Multivendor interoperability
- Modular engineering

OSI Encapsulation Terminology

Protocol Data Unit (PDU) -> Layer X PDU => L7PDU, L6PDU, ..