IACC Professional Course Series

Network Certification Preparation

Module - 1Communication methods OSI reference model and layered communicationTCP/IP modelTCP and UDPIP addressing and subnettingMAC addressing

Todays’s networksService Provider

Job to connect all these different networks togetherDesign and other rules are different and more intenseMission critical more than any other networksMore complex and more issues

Enterprise There are hundreds and thousands of usersPolicies in placeSpeed and efficiency is importantNeed connectivity to remote sites or home users

ResidentialSmall Local area networksEvolving networks i.e. wireless, fiber, fax machines etc

OSI Model and Layered approachWhy we need layered approachOSI Model

Seven layers of OSI modelTCP/IP Model

Four layers in TCP/IP model

TCP/IP Model

TCP/IP Model - continued

TCP/IP Model - continued

OSI Model

OSI Model - Layered communication

OSI Model – layer communication

TCPTCP - Transmission Control Protocol Most commonly used protocol on the Internet. Reliable - It is connection oriented hence guaranteed deliveryTCP uses flow control which determines when data needs to be re-sent, and

stops the flow of data until previous packets are successfully transferred. This works because if a packet of data is sent, a collision may occur. When

this happens, the client re-requests the packet from the server until the whole packet is complete and is identical to its original, hence it is slow protocol.

Ordered DeliveryOffers error correctionExamples: World Wide Web (Apache TCP port 80), e-mail (SMTP TCP port

25), File Transfer Protocol (FTP port 21) and Secure Shell (OpenSSH port 22) etc.

TCP – 3 way handshakeHost A sends a TCP SYNchronize packet to Host BHost B receives A's SYNHost B sends a SYNchronize-ACKnowledgementHost A receives B's SYN-ACKHost A sends ACKnowledgeHost B receives ACK.

TCP socket connection is ESTABLISHED.

TCP Three Way Handshake(SYN,SYN-ACK,ACK) SYNchronize and ACKnowledge messages are indicated by a bit inside the header of the TCP segment.

TCP – 3 way handshake

UDPUDP - User Datagram Protocol – connectionless protocolUDP is never used to send important data such as webpages, database

information, etc; UDP is commonly used for streaming audio and video, because it offers

speed! The reason UDP is faster than TCP is because there is no form of flow control

or error correction. The data sent over the Internet is affected by collisions, and errors will be present. Remember that UDP is only concerned with speed. This is the main reason why streaming media is not high quality.

Not reliable Not ordered deliveryExample :Domain Name System (DNS UDP port 53), streaming media

applications such as IPTV or movies, Voice over IP (VoIP), Trivial File Transfer Protocol (TFTP) and online multiplayer games etc

TCP Frame

UDP Frame

MAC AddressA Media Access Control address (MAC address) is a unique

identifier assigned to network interfaces for communications on the physical network segment.

MAC addresses are used in the Media Access Control protocol sub-layer of the OSI reference model.

MAC addresses assigned by the manufacturer of a network interface card (NIC) and are stored in its hardware.

MAC address also referred to as the burned-in address, Ethernet hardware address (EHA), hardware address or physical address.

6 bytes of address. 3 bytes are for Manufacturer identifier and 3 bytes are NIC specific.

IP addressingIP address is a unique identifier which distinguishes

a node from other in a network.An IPv4 address is 4 bytes/32 bites longIP address has a format of a.b.c.d, where a,b,c,d are

octets in binary.Each ip address has two portions, network and hostDifferent classes of IP address schemes.Class A, Class B, Class C, Class D, and Class E

IP addressingClass ABinary address start with 0 i.e. most significant bit of first

byte is always 0.Hence the decimal number can be anywhere from 1 to

126. The first 8 bits (the first octet) identify the network and the

remaining 24 bits indicate the host within the network. An example of a Class A IP address is 102.168.212.226,

where "102" identifies the network and "168.212.226" identifies the host on that network.

IP addressingClass BBinary addresses start with 10 i.e. two most significant bits of

first bytes are always 10.Hence the decimal number can be anywhere from 128 to

191. (The number 127 is reserved for local machine and loopback interfaces).

The first 16 bits (the first two octets) identify the network and the remaining 16 bits indicate the host within the network.

An example of a Class B IP address is 168.212.226.204 where "168.212" identifies the network and "226.204" identifies the host on that network.

IP addressingClass CBinary addresses start with 110 i.e. three most significant

bits of first octet is always 110.Hence the decimal number can be anywhere from 192 to

223. The first 24 bits (the first three octets) identify the network

and the remaining 8 bits indicate the host within the network.

An example of a Class C IP address is 200.168.212.226 where "200.168.212" identifies the network and "226" identifies the host on that network.

IP addressingClass DBinary addresses start with 1110 i.e. four most significant bits are always

1110.Hence the decimal number can be anywhere from 224 to 239.Class D networks are used to support multicasting.

Local Subnet:Addresses in the range 224.0.0.0 to 224.0.0.255 are individually assigned

by IANA and designated for multicasting on the local subnetwork only. Routing Information Protocol (RIPv2) uses 224.0.0.9, Open Shortest Path

First (OSPF) uses 224.0.0.5 & 224.0.0.6, etc. Routers must not forward these messages outside the subnet in which

the originate.

IP addressingInternetwork control blockAddresses in the range 224.0.0.1 to 224.0.1.255 are individually

assigned by IANA and designated the Internetwork Control Block. It is used for traffic that must be routed through the public Internet,

such as for applications of the Network Time Protocol (224.0.1.1).

AD-HOC blockAddresses in the ranges 224.0.2.0 to 224.0.255.255, 224.3.0.0 to

224.4.255.255 and 233.252.0.0 to 233.255.255.255 are individually assigned by IANA and designated the AD-HOC block.

These addresses are globally routed and are used for applications that don't fit either of the previously described purposes.

BACKUP SLIDES

Access methodsAn access method is a set of rules on how the

network nodes share the transmission media.Rule could be Either first come first served or take

turnsContention methodsCSMA/CD (Carrier Sense Multiple Access with

Collision Detection)CSMA/CA (Carrier Sense Multiple Access with

Collision Avoidance)Token PassingDemand Priority

Access methodsContention Methods:

IEEE 802.3 Ethernet LAN use CSMA/CD method.WLAN uses CSMA/CA protocol and have mechanism of explicit packet acknowledgment.

Token Ring : Uses a token-passing method. Demand Priority : 100VG-AnyLAN uses this method.

Networks are connected to hubs and hubs are connected to other hubs. Contention occurs at hub level.

Demand Priority provides mechanism for prioritizing data types. If contention happens, data with highest priority takes precedence.