Network Layer

NETWORK LAYER
move data between cable segments
ADDRESSING
the Layer
ELEMENTS
IPv4
Local Network Address
702 Nguyen Van Linh Boulevard
category
publicly concerned (TCP/IP)
private
IPX/SPX, SNA…
unconnected TCP/IP networks
Service Address
Medical office: 1.10
inside Local Network Address
identify numbers of
targeted machines
socket
port numbers
many purposes
http: 80
https: 8080
ftp: 21
sftp: 22
private printing: 35
telnet: 23
smtp: 25
DNS: 53
...
Network address + Service Address ==> uniquely identify the connection
SWITCHING
def
the way packets are routed
within connected network
type
CIRCUIT switching
telephone conversation
maintain connection during the session
MESSAGE switching
eg: emailSMS
one hop at a time
PACKET switching
data packets sent thru multiple routes
at destination
assembled
checked
collected
read
ROUTERS
purpose
the mechanism used to determine THE PATH
connect 2 networks
via a series of intermediate networks
maintain connectivity among adjacent networks
ROUTE TABLE
def
determine the path, used to connect 2 networks
store
in
router
networked computer
what?
the topology of the network
the routes to particular network destinations
MAINTAIN "table" identifies networks it attaches to availability at an interface
router share with others abt networks it knows
they build up a 'route' to connect to a certain networks
HOPS
distances to connect routers
ROUTE
DISCOVERY
Number of hops = distance vector
discover networks by exchanging router tables
ROUTE
SELECTION
dynamic
when a decision about the route is made at each connection
static
the preferred route for all communications between 2 networks
If one router goes down then all interconnected networks become unavailable
GATEWAY SERVICES
Network Layer translation
relay packets thru different networks
CONNECTION
SERVICE
Network-Layer flow control
Error control
Packet sequence control
31