1 fall 2005 internetworking: concepts, architecture and tcp/ip layering qutaibah malluhi cse...
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Fall 2005
Internetworking: Concepts, Architecture and TCP/IP
Layering
Qutaibah MalluhiCSE DepartmentQatar University
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Motivation
There are many different LAN and WAN technologies
LAN– Low cost
– Limited distance
WAN– High cost
– Unlimited distance
No single networking technology best for all needs
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Universal Service
Arbitrary pair of computers can communicate Fundamental concept in networking Desirable but difficult in a heterogeneous world
of incompatible networks– Electrical properties– Signaling and data encoding– Packet formats– Addresses– Link capacity mismatch– Different administrative authorities
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The Bottom Line
Although universal service is highly desirable, incompatibilities among network hardware
and physical addressing prevent an organization from building a bridged
network that includes arbitrary technologies
Although universal service is highly desirable, incompatibilities among network hardware
and physical addressing prevent an organization from building a bridged
network that includes arbitrary technologies
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Internetworking
Internetworking is a scheme for interconnecting multiple networks of dissimilar technologies
Uses both hardware and software – Extra hardware positioned between networks – Software on each attached computer
System called an internetwork or an internet
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Routers
A router is a hardware component used to interconnect networks
Can interconnect networks that use different technologies– different media and media access techniques, physical
addressing schemes, or frame formats. A router has multiple interfaces on multiple
networks Router forwards packets between networks
– Transforms packets as necessary to meet standards for each network
Some times called internet gatewayRouter
Two net. interfaces
Network 2Network 1
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Internet Architecture
Can have multiple networks with routers interconnecting them.
A host computer connects to a network A router may have multiple network interfaces
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Multiple Routers
Would be possible to interconnect all networks in an organization with a single router?
Most organizations use multiple routers – Router has finite capacity (CPU speed and memory) –
can not handle all traffic – Reliability -- ability to route around failures
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Create a Virtual Network
Internetworking software builds a single, seamless virtual network out of multiple physical networks – Universal addressing
scheme – Universal service
All details of physical networks hidden from users and applications
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Routing
Routers use routing tables Typically, routing tables specify the next hop for
each destination Network ID– Routing table may contain next hop for a destination
host (not a whole network)– Network routs simplify the routing table (dramatically
reduce the number of entries in the routing table Routing table typically have a default route
entry Route command in windows (netstat –r in
unix) to check the routing table
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Routing Table Example
R1
R2
R3
R4
N1
N2
N4
N3
R5
Internet
Destination Network Next Hop
N1 Local interface
N2 Local interface
N4 R4 (address of R4 on N1)
N3 R2 (address of R2 on N2)
Default R5 (address of R5 on N1
Routing table for R1
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TCP/IP Internet Protocols
Most widely used internetworking protocol suite Suite used in the public Internet First internetworking protocol suite
– Work began in 1970’s– Research originally funded by ARPA (currently DARPA)
and other government agencies followed Others internetworking protocol suites include
IPX, VINES, AppleTalk TCP/IP is vendor and platform independent
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TCP/IP Stack
Unlike ISO 7-layers model, TCP/IP has 5 conceptual layers
(Internet)
(Network Interface)
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Peer-to-Peer and Hop-to-Hop Processes
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Sending Data in the Internet model
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The physical layer is responsible for transmitting individual bits from one node to
the next.
The physical layer is responsible for transmitting individual bits from one node to
the next.
Physical Layer
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The data link layer is responsible for transmitting frames on the same network
from one node to the next.
The data link layer is responsible for transmitting frames on the same network
from one node to the next.
Data Link Layer
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Hop-to-Hop Delivery
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A node with physical address 10 sends a frame to a node with physical address 87. The two nodes are connected by one network. At the data link level this frame contains physical addresses in the header. These are the only addresses needed. The rest of the header contains other information needed at this level (e.g. frame type). The trailer contains error detection (CRC) bits.
Example 1
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Network Layer
The network layer is responsible for the delivery of packets from the original source
to the final destination.
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End-to-End Delivery
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Example 2 We want to send data from a
node with internetwork (IP) address A (e.g. and physical address 10, located on one LAN, to a node with a internetwork (IP) address P and physical address 95, located on another LAN. Because the two devices are located on different networks, we cannot use physical addresses only; the physical addresses only have local jurisdiction. What we need here are universal addresses that can pass through the LAN boundaries. The internetwork (logical) addresses have this characteristic.
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Transport Layer
The transport layer is responsible for delivery of a message from one process
to another.
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Reliable Process-to-Process Delivery
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Example 3
Data coming from the upper layers have port addresses j and k (j is the address of the sending process, and k is the address of the receiving process). Since the data size is larger than the network layer can handle, the data are split into two packets, each packet retaining the port addresses (j and k). Then in the network layer, internetwork addresses (A and P) are added to each packet.
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Application Layer
The application layer is responsible for providing services to the user.
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Summary of TCP/IP Layer’s Responsibilities
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TCP/IP Layers (1)
Layer 1: Physical Layer– Corresponds to layer 1 in the ISO model– Defines basic networking hardware
Layer 2: Network Interface (Data Link)– Corresponds to layer 2 in the ISO model– Hardware (MAC) frame format– MAC addressing– Interface between computer and network (NIC)
Layer 3: Internetwork (Network) – Defines uniform format of packets forwarded across
networks– Rules for forwarding packets in routers
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TCP/IP Layers
Layer 4: Transport – Corresponds to layers 4 and 5 in the ISO model– Provides reliable delivery of data
Layer 5: Application – Corresponds to ISO model layers 6 and 7– Used for communication among applications
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TCP/IP Vs. OSI
OSI Model TCP/IP
(Internet)
(Network Interface)
ApplicationApplication5
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Internet (Layer 3) Protocols
IP: combined with TCP they are known as the TCP/IP suite
ICMP (error-handling protocol) OSPF, RIP, BGP (routing protocols) IGMP (multicast protocol) MOSPF, DVMRP, PIM (multicast routing
protocols) ARP, RARP (addressing protocols)
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UDP
MIME
OSPFICMP
SNMPTELNETSMTPHTTPFTPBGP
TCP
IP
Some Protocols in the TCP/IP suite
Application Layer
Transport Layer
Internet Layer
SNMP
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Summary
An internet is a collection of possibly heterogeneous physical networks interconnected into a single virtual network
Routers provide the physical interconnection and forward packets between networks
TCP/IP is the most widely used internetworking protocol suite