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INTERNETWORKINGChapter 2
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TOPIC
Internetworking Basics Internetworking Model The OSI Reference Model Ethernet Networking Wireless Networking Data Encapsulation
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INTERNETWORK BASIC
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POSSIBLE CAUSES OF LAN TRAFFIC CONGESTION ARE
Too many hosts in a broadcast domain Broadcast storms Multicasting Low bandwidth Adding hubs for connectivity to the net
work A large amount of ARP or IPX traffic (IPX
is a Novell
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NETWORK SEGMENTATION
Collision domain Broadcast domain
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TWO ADVANTAGES OF USING R OUTERS IN YOUR NETWORK AR
E They don’t forward broadcasts by default. They can filter the network based on layer
3 (Network layer) information (i.e., IP address).
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FOUR ROUTER FUNCTIONS IN YOUR NETWORK CAN BE LISTED AS
Packet switching Packet filtering Internetwork communication Path selection
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INTERNETWORKING MODEL The Layered Approach Advantages of Reference Models
It divides the network communication process into s maller and simpler components, thus aiding compon
ent development, design, and troubleshooting. - It allows multiple vendor development through stan
dardization of network components. It encourages industry standardization by defining
what functions occur at each layer of the model. It allows various types of network hardware and soft
ware to communicate. It prevents changes in one layer from affecting othe
r layers, so it does not hamper development.
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THE OSI REFERENCE MODEL
The upper layers
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THE LOWER LAYERS
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LAYER FUNCTIONS
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INTERFACES: VERTICAL (ADJACENT LAYER) COMMUNICATION
Assist.Prof.
Itarun
Pitimon ([email protected])
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PROTOCOLS: HORIZONTAL (CORRESPONDING LAYER) COMMUNICATION
Assist.Prof.
Itarun
Pitimon ([email protected])
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PROTOCOL DATA UNITS (PDUS) AND SERVICE DATA UNITS (SDUS)
Assist.Prof.
Itarun
Pitimon ([email protected])
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APPLICATION LAYER
The Application layer of the OSI model marks t he spot where users actually communicate to the computer.
Sample -> World Wide Web (WWW) E-mail gateways Electronic data interchange (EDI) Special interest bulletin boards Internet navigation utilities Financial transaction services
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THE PRESENTATION LAYER It presents data to the Application layer and is
responsible for data translation and code formatting.
This layer is essentially a translator and provi des coding and conversion functions. A succe
- ssful data transfer technique is to adapt the d ata into a standard format before transmissio
n.
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THE SESSION LAYER
The Session layer is responsible for sett ing up, managing, and then tearing do wn sessions between Presentation laye
r entities. This layer also provides dialogue contro
l between devices, or nodes. It coordina tes communication between systems, a nd serves to organize their communicat ion by offering three different modes: si
mplex , half duplex , and full duplex.
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THE TRANSPORT LAYER The Transport layer segments and reas
sembles data into a data stream. Services located in the Transport layer
both segment and reassemble data fro - m upper layer applications and unite it
onto the same data stream. - - They provide end to end data transport
services and can establish a logical con nection between the sending host and
destination host on an internetwork.
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The Transport layer is responsible for providin - g mechanisms for multiplexing upper layer ap
plications, establishing sessions, and tearing down virtual circuits.
The Transport layer can be connectionless or c-onnection oriented.
Some of you are probably familiar with TCP an d UDP already.
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FLOW CONTROL Data integrity is ensured at the Transpo
rt layer by maintaining flow control and by allowing users to request reliable da ta transport between systems.
The segments delivered are acknowledged back to the sender upon their reception.
Any segments not acknowledged are retransmitted.
Segments are sequenced back into their pr oper order upon arrival at their destination.
A manageable data flow is maintained in or der to avoid congestion, overloading, and d ata loss.
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- CONNECTION ORIENTED COMMUNICATION
a call setup , or a three way handshake
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TRANSMITTING SEGMENTS WIT H FLOW CONTROL
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ACKNOWLEDGMENTS
It guarantees that the data won’t be du plicated or lost.
This is achieved through something call ed positive acknowledgment with retra
nsmission a technique that requires a r eceiving machine to communicate with
the transmitting source by sending an a cknowledgment message back to the s
ender when it receives data.
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WINDOWING
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THE NETWORK LAYER The Network layer (also called layer 3)
manages device addressing, tracks the location of devices on the network, and
determines the best way to move data, which means that the Network layer m
ust transport traffic between devices th at aren’t locally attached.
Two types of packets are used at the Ne twork layer:
Data packets : routed protocolrouted protocol Route update packets : routing routing
protocolprotocol 31
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ROUTING TABLE USED IN A ROUTER
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HERE ARE SOME POINTS ABOUT ROUTERS THAT YOU SHOULD REALLY COMMIT TO MEMORY:
Routers, by default, will not forward any broadcast or m ulticast packets.
Routers use the logical address in a Network layer head er to determine the next hop router to forward the pack et to.
Routers can use access lists, created by an administrat or, to control security on the types of packets that are a
llowed to enter or exit an interface. Routers can provide layer2 bridging functions if nee
ded and can simultaneously route through the same interface.
Layer 3 devices (routers in this case) provide connecti ons between virtual LANs (VLANs).
Routers can provide quality of service (QoS) for specific types of network traffic.
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THE DATA LINK LAYER The Data Link layer provides the physical tran
smission of the data and handles error notifica tion, network topology, and flow control.
The Data Link layer formats the message into pieces, each called a data frame , and adds a c
ustomized header containing the hardware de stination and source address.
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DATA LINK LAYER WITH THE ETHER NET AND IEEE SPECIFICATIONS.
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THE IEEE ETHERNET DATA LINK LAY ER HAS TWO SUBLAYERS:
Media Access Control (MAC)8023. Defines how packets are placed
on the media. Contention media access is “first come/first served” access wher e everyone shares the same bandwidth
—hence the name. Physical addressing is defined here,
Logical Link Control (LLC)802.2 Responsible for identifying Network
layer protocols and then encapsulatingthem.
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SWITCHES AND BRIDGES AT THE DAT A LINK LAYER
Layer2 switching is considered hard- ware based bridging because it uses sp
ecialized hardware called an applicatio- n specific integrated circuit (ASIC).
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THE PHYSICAL LAYER we find that the Physical layer does two things
: It sends bits and receives bits. Bits come onl y in values of 1 or 0 —a Morse code with nu
mericalval ues. The Physical layer specifies the electrical, me
chanical, procedural, and functional requirem ents for activating, maintaining, and deactivat
ing a physical link between end systems. This layer is also where you identify the interf
ace bet ween t he data terminal equipment (DTE) and t he data communication equipment (DCE).
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HUBS AT THE PHYSICAL LAYER
A hub - is really a multiple port repeater. A re peater receives a digital signal and reamplifi
es or regenerates that signal, and then forw ards the digital signal out all active ports wit hout looking at any data.
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ETHERNET NETWORKINGLecture 2-2
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THE SUCCESS OF ETHERNET IS DUE TO THE FOLLOWING FACTORS: Simplicity and ease of maintenance Ability to incorporate new technologies Reliability Low cost of installation and upgrade
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802.3 ETHERNET IN RELATION TO THE OSI MODEL
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IEEE 802.X STANDARDS
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ETHERNET TECHNOLOGIES MAPPED TO THE OSI MODEL
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ETHERNET ADDRESSING
W e get into how Ethernet addressing w orks. It uses the Media Access Control ( MAC) address burned into each and eve
ry Ethernet Network Interface Card (NIC).
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MAC ADDRESS FORMAT
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GENERIC FRAME FORMAT
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IEEE 802.3
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ETHERNET II FRAME FORMAT
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ETHERNET II AND IEEE 802.3 FRAME FORMAT
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MEDIA ACCESS CONTROL (MAC)
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MAC RULES AND COLLISION DETECTION/BACKOFF
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MAC RULES AND COLLISION DETECTION/BACKOFF
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ETHERNET TIMING
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INTERFRAME SPACING
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BACKOFF
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ERROR HANDLING
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TYPES OF COLLISIONS
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THE EFFECTS OF HAVING A CSMA/CD NETWORK SUSTAINING HEAVY COLLISIONS INCLUDE
Delay Lowt hr oughput Congestion
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ETHERNET ERRORS
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ETHERNET ERRORS
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FCS ERRORS
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PARAMETERS FOR 10 MBPS ETHERNET OPERATION
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MANCHESTER ENCODING EXAMPLES
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PARAMETERS FOR 100-MBPS ETHERNET OPERATION
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MLT-3 ENCODING EXAMPLE (100BASE-TX)
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NRZI ENCODING EXAMPLES (100BASE-FX)
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PARAMETERS FOR GIGABIT ETHERNET OPERATION
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ACTUAL 1000BASE-T SIGNAL TRANSMISSION
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GIGABIT ETHERNET LAYERS
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GIGABIT ETHERNET MEDIA COMPARISON
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PARAMETERS FOR 10-GBPS ETHERNET OPERATION
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10GBASE LX-4 SIGNAL MULTIPLEXING
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WIRELESS NETWORKING
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BENEFITS OF WLANS
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EVOLUTION OF WIRELESS LANS
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UNLICENSED FREQUENCY BANDS
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WIRELESS TECHNOLOGIES
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DISTANCE VERSUS SPEED
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WIRELESS TECHNOLOGIES
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IN-BUILDING WLANS
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THE IEEE 802 STANDARDS
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IEEE 802.11 PROTOCOLS
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IEEE 802.11 STANDARDS
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DATA ENCAPSULATION
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DATA ENCAPSULATION
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SUMMARY - OSI model—the seven layer model used to help applica
tion developers design applications that can run on any type of system or network. Each layer has its special jo
bs and select responsibilities within the model to ensur e that solid, effective communications do, in fact, occur
. Remember that hubs are Physical layer devices and rep
eat the digital signal to all segments except the one it was received from.
Switches segment the network using hardware address es and break up collision domains.
Routers break up broadcast domains (and collision dom ains) and use logical addressing to send packets throug
h an internetwork.
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![arXiv:1210.1947v1 [physics.plasm-ph] 6 Oct 20123 Lramp = 10c=! p.It is constant and equal to Bext y = 0:6 for L at = 40 c=! p and then drops back to zero with Bext y = 0:6sin 2[ˇz=(2Lramp)](https://img.pdfslide.net/doc/110x75/607342e2c9af9b397e1c0302/arxiv12101947v1-6-oct-2012-3-lramp-10c-pit-is-constant-and-equal-to-bext.jpg)
