TCPIP Notes

1
TCP/IP Notes

• Seree Chinodom

2
TCP/IP Architecture Layers
Applications (mail, news, ftp, web)
Transport (TCP or UDP)
Network (IP)
Data link (Ethernet)
Physical (computers, wires)
3
IPv4 Addresses

• 32-bit numbers usually written out as four
  8-bit numbers
• Examples 128.10.8.49, 255.255.255.255,
  128.10.8.0
• Hierarchy of addresses - classes
• A 0..
• B10..
• C 110..

4
IP Addresses and Routing

• Multicast addresses
• Broadcast addresses
• Routing a packet
• gateways and routers
• hierarchy of routers
• An IP address is static (phone jack), identifies
  an outlet in a LAN
• Allocated to users by NIC

5
Domain Names

• Aliases of IP addresses an IP address may have
  multiple aliases
• Structured hierarchically
• top-level domainscom,edu,mil,gov,org,net or
  countries ca, jp, de, uk, au, us
• organizations purdue, sun, acm
• departments cs, eng, corp
• hosts (nodes) ector, lore, www, pc15

6
Domain Name Servers

• Translate names into IP addresses
• Hierarchy roughly corresponding to domain
  hierarchy
• Caching names and addresses
• They are not routers
• An application must use the IP address to
  communicate

7
TCP End-point Identifiers

• Ports mailboxes for communication, muliplexing
  and demultiplexing data
• Privileged ports 1-1024 well-known ports 80,
  21, 25, 79
• TCP connections (host1port1,host2port2)
• For the system a combination (hostport)
  identifies application an application may use
  many ports for multiple connections

8
Client/Server Model

• One program (server) starts and waits for
  requests another program (client) initiates
  communication
• Servers listen for incomming packets and
  connections clients connect to the servers
• Servers can service multiple requests clients
  may connect to many servers

9
Servers and Daemons

• Servers start first - ideally they are always
  running (in background)
• Daemons - stand-alone or running under inetd
• inetd starts a server based on a port in a
  configuration file
• Web server are usually stand-alone

10
Things To Configure

• Host - IP address(es), gateway(s) - I.e., routes,
  name(s), domain name server(s)
• Application
• Server - port(s) to listen to, inetd entry(ies),
  handling multiple requests
• Clients - servers (hosts and/or ports) to connect
  to