21-765 Slide 16

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Networking

Networks: Bus + Protocol(s)

The TCP/IP stack:

Network access (media, network interfaces, hardware address, frames)
Internet (structure, LAN, WAN, IP addresses, routing, packets/datagrams)
Transport (connections, TCP, UDP, ports, sockets, segments)
Application (client-server, session, encoding)

The network access layer

purpose: local delivery, hides media details
media: copper (twisted pairs, coax, phone lines), fiber optics (FIOS), radio (wireless, IR)
network interfaces: NIC, modem
communication: shared media (Ethernet, etc), peer-to-peer (PPP, SLIP, PPoE)
Ethernet:

hardware address: 01:03:00:cc:D2:EF
frames: header(source, destination, control), data
broadcast:FF:FF:FF:FF:FF:FF
bandwidth, latency
collision domain, broadcast domain

Switched LAN

Commands: ifconfig

ifconfig

The Internet layer

purpose: distance delivery, hides data travel details
structure: LAN, WAN, routing

Internet

packets/datagrams: header(source, destination, control), data
protocols: IP, Appletalk, IPX, NetBEUI
IP addresses: net+subnet+host = 128.2.24.153

Routed LAN

Networks:

network address (128.2.0.0, 128.2.24.0)
netmask (255.255.0.0, 255.255.252.0)
broadcast address (128.2.255.255, 128.2.27.255)
class A (first bit=0), B (start with 10), C (start with 110)
private (10.0.0.0, 172.16.0.0, 192.168.0.0)

net	128.2.0.0	128.2.24.0
net	10000000.00000010.00000000.00000000	10000000.00000010.00001100.00000000
mask	255.255.0.0	255.255.252.0
mask	11111111.11111111.00000000.00000000	11111111.11111111.11111100.00000000
broadcast	128.2.255.255	128.2.27.255
broadcast	10000000.00000010.11111111.11111111	10000000.00000010.00001111.11111111
host	128.2.25.9	128.2.25.9
host	10000000.00000010.00001101.00001001	10000000.00000010.00001101.00001001

Nameservices (/etc/resolv.conf):

domain (cmu.edu)
subdomain (math.cmu.edu)
host (osage)
full hostname (osage.math.cmu.edu)

Commands: ping, traceroute, ifconfig, route, host, arp

ping

route

The Transport layer

purpose: virtual circuit (data integrity, packet order)
protocols:

connection oriented (TCP) - reliable
connectionless (UDP) - fast

ports: label for service session
socket: data structure = source (IP,port) + destination (IP,port)
segments: header (socket, ordering info, control info), data
commands: netstat

Application

client-server: session, encoding
server:

runs in background or is started by xinetd
listens to a specific port (/etc/services)
uses wrappers (/etc/hosts.allow /etc/hosts.deny)
forks to handle connection via a socket

client:

is started and configured by the user
exits when the session ends

services: e-mail, http, https, telnet, ftp, ssh, nfs, cups, ntp

The electronic mail:
E-Mail System

E-Mail System

mail-v

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