Transcript Ch5c - Network/Transport (cont.) - UNCW/CSB Application Server

Chapter 5
Network and Transport Layers
Chapter 5 Outline
Transport & Network Layer Protocols
 TCP/IP
Transport Layer Functions
 Linking to the Application Layer
 Segmenting
 Session management
Addressing
 Assigning addresses and address resolution
Routing
 Types of routing, routing protocols, and multicasting
TCP/IP Examples
Copyright 2010
John Wiley & Sons, Inc
Network Layer
Computer 1
Computer 2
5.4 Routing
Process of identifying what path to have a packet take
through a network from sender to receiver
Routing Tables
 Used to make routing decisions
 Shows which path to send packets on
a given destination
 Kept by computers making routing decisions
Dest. Next
B
B
C
B
D
D
E
D
F
D
G
B
to reach
Routers
 Special purpose devices used to handle routing decisions on the
Internet
 Maintain their own routing tables
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5.4.1 Simple Routing Example
Possible paths from A to G:
• ABCG
• ABEFCG
• ADEFCG
• ADEBCG
A
Routing Table for A
Dest. Next
B
C
D
E
F
G
Each node
has its own
routing table
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5.4.1 Routing Example – LAN with Routers
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5.4 Routing
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5.5.1 TCP/IP Network Example
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5.4.1 Types of Routing
Centralized routing


Decentralized routing



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5.4.2 Routing Protocols – how tables are set up
Static routing:
 Uses fixed routing tables developed by network managers
• Each node has its own routing table
• Changes when computers added or removed
Dynamic routing or Adaptive routing:
 Uses routing tables at each node that are updated dynamically
 Based on routing condition information exchanged between
routing devices
 Types
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5.4.2 Dynamic Routing Algorithms
Distance Vector
 Uses the least number of hops to
decide how to route a packet
Link State
 Uses a variety of information types to decide how to route a
packet (more sophisticated)
• e.g., number of hops, congestion, speed of circuit
 Links state info exchanged periodically by each node to keep
every node in the network up to date
 Provides more reliable, up to date paths to destinations
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5.4.2.1 Routing Information Protocol (RIP)
A dynamic distance vector interior routing protocol
Operations:
 Manager builds a routing table by using RIP
 Routing tables broadcast periodically (every minute or so) by all
nodes
 When a new node added, RIP counts number of hops between
computers and updates routing tables
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5.4.2.1 Open Shortest Path First (OSPF)
A dynamic link state interior routing protocol
Became more popular on Internet
 More reliable paths
 Less burdensome to the network
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5.5.1 Sending Messages using TCP/IP
Required Network layer addressing information
1.
2.
3.
4.
Address information is obtained from a configuration file or
provided by a DHCP server
What additional information is needed for servers?
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5.5.1 TCP/IP Configuration Information
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5.5.1 Subnet Masks
Tells the computer what part of an Internet Protocol address
to be used to determine whether the destination is on the
same subnet or on a different subnet
Example
 Subnet: 149.61.10.x
 Subnet mask: 255.255.255.000
Example
 Subnets: 149.61.10.1-128,
 Subnet mask 255.255.255.128
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5.5.1 TCP/IP Network Example
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5.5.1 Moving Messages - TCP/IP and Layers
How layers are handled in a LAN:
• Host Computers
• Packets move through all layers
 Gateways, Routers
• Packet moves from Physical layer to Data Link Layer through
the network Layer
At each stop along the way (e.g. from router to router):
 Ethernet packets is removed and a new one is created for the next
node
 IP and above packets never change in transit (created by the
original sender and destroyed by the final receiver)
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5.5.1 Message Moving Through Layers
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5.5.2 Known IP Address
Transmit from A => E (A knows E’s IP Address)
How many Hops will it take?
PATH
IP
Source
IP
Destination
Ethernet
Source
Ethernet
Destination
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5.5.3 Unknown IP Address
Transmit from A => E (A doesn’t know E’s IP address)
How do we do this?
PATH
IP
Source
IP
Destination
Ethernet
Source
Ethernet
Destination
PATH
IP
Source
IP
Destination
Ethernet
Source
Ethernet
Destination
DNS
Request
DNS
Response
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5.5.4 Unknown Data Link Address
Transmit from A => E (doesn’t know E’s Ethernet address)
• An ARP request from D will occur once the message sent
by A is received by D.
PATH
IP
Source
IP
Destination
Ethernet
Source
Ethernet
Destination
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5.5.2 Known IP Address and Ethernet Address
Transmit from B => F (B knows F’s IP Address)
PATH
IP
Source
IP
Destination
Ethernet
Source
Ethernet
Destination
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5.5.3 Unknown IP Address
Transmit from B => F (B doesn’t know F’s IP address)
PATH
IP
Source
IP
Destination
Ethernet
Source
Ethernet
Destination
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5.5.4 Unknown Ethernet Address
Transmit from B => F (doesn’t know F’s Ethernet address)
PATH
IP
Source
IP
Destination
Ethernet
Source
Ethernet
Destination
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Implications for Management
Most organizations moving toward a single standard based
on TCP/IP
 Decreased cost of buying and maintaining network equipment
 Decreased cost of training networking staff
Telephone companies with non-TCP/IP networks are also
moving toward TCP/IP
 Significant financial implications for telcos
 Significant financial implications for networking equipment
manufacturers
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