Transcript TCP/IP Networking

TCP/IP Networking
Yue Cui
06/13/02
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Presentation Outline
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Introduction
Packets and Encapsulation
IP Addresses, Routing
ARP, DHCP and PPP
Security Issue
Addition of Machines
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Introduction
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TCP/IP and the Internet
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A brief history
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Internet Management
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ARPARNET(1969 by DARPA)
ICANN
IETF
ISOC
Standards and Documentation
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RFCs, FYIs, STDs and BCPs
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Introduction
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TCP/IP protocol suite
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IP – routes data packets from one machine to another
ICMP – provides lower-level support for IP, including
error messages, routing assistance and debugging help
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ARP
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UDP and TCP
– translates IP address to hardware address
(a.k.a. MAC address)
– deliver data to specific applications
on the destination machine
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Introduction
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TCP/IP family
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Presentation Outline
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Introduction
Packets and Encapsulation
IP Addresses, Routing
ARP, DHCP and PPP
Security Issue
Addition of Machines
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Packets and Encapsulation
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Packet
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Header—tells where the packet came from
and where it’s going
Payload—actual data to be transferred
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Encapsulation
Layer
M
5
M
4
H4
M
H4
M
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H3 H4
M
H3 H4
M
2
H2 H3 H4
M
H2 H3 H4
M
1
source
machine
destination
machine
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Presentation Outline



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Introduction
Packets and Encapsulation
IP Addresses, Routing
ARP, DHCP and PPP
Security Issue
Addition of Machines
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IP Addresses
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Historical Internet address classes
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Subnet masks
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IP addresses were grouped into “classes”
Class A,B and C denote regular IP addresses.
Class D and E are used for multicasting and
research purpose.
Part of the host portion of an address is
“borrowed” to extend the network portion.
Use ifconfig command to configure IP address
and subnet masks
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IP Addresses
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IP address crisis
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We were going to run out of class B
addresses by mid-1995
The routing tables of Internet backbone
sites were growing so large that they
would not fit in the memory of available
routers
IP addresses were being allocated with no
locality of reference
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IP Addresses
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Solution to the IP address crisis
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CIDR (Classless Inter-Domain Routing)
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A short-term solution
Manage the existing 4-byte address space that uses the
available addresses more efficiently and allows routing
tables to be simplified by taking numerical adjacencies
into account
IPv6
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A long-term solution
A revision of the IP protocol that expands the address
space to 16 bytes
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Routing
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Meaning
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Looking up a network address in the
routing table to forward a packet toward its
destination
Building the routing table in the first place
Configure
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netstat
route get (on BSD-based system)
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Presentation Outline
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Introduction
Packets and Encapsulation
IP Addresses, Routing
ARP, DHCP and PPP
Security Issue
Addition of Machines
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ARP, DHCP and PPP
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ARP: Address Resolution Protocol
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Discovers the hardware address(MAC address)
associated with a IP address
Usage:
Redhat% /sbin/arp –a
xor.com(192.108.21.1) at 08:00:20:77:5E:A0[ether] on eth0
earth.xor.com(192.108.21.180) at 00:50:DA:12:4E:E5[ether] on eth0
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ARP, DHCP and PPP
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DHCP: Dynamic Host Configuration Protocol
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Dynamically assigns network parameters to hosts
Leasable parameters include:
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IP addresses and netmasks
Gateways(default routes)
DNS name servers
Syslog hosts
WINS servers, proxy servers
TFTP servers(for loading a boot image)
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ARP, DHCP and PPP
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PPP: Point-to-Point Protocol
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Serial line encapsulation protocol that
specifies how IP packets must be encoded
for transmission on a slow serial line
Sometimes used with home
technologies such as Dial-up, DSL and
cable modem
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ARP, DHCP and PPP
System
Red Hat
Commands
/usr/sbin/pppd
/usr/sbin/chat
Free BSD /usr/sbin/pppd
/usr/sbin/chat
Config files
/etc/ppp/options
/etc/ppp/ppp.conf
/etc/ppp/allow
/etc/ppp/options
/etc/ppp/options.ttyserver
/etc/ppp/chat.ttyserver
PPP-related commands and configuration files example
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Presentation Outline


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


Introduction
Packets and Encapsulation
IP Addresses, Routing
ARP, DHCP and PPP
Security Issue
Addition of Machines
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Security Issues
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IP forwarding
ICMP redirects
Source routing
Broadcast pings and other forms of directed
broadcast
UNIX-based firewalls
Virtual private networks(VPN)
IPSEC: secure IP
(Refer to Chapter 21 for details)
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Presentation Outline






Introduction
Packets and Encapsulation
IP Addresses, Routing
ARP, DHCP and PPP
Security Issue
Addition of Machines
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Addition of machines
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Basic steps
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Assign an IP address and hostname
Set up the new host to configure its
network interfaces at boot time
Set up a default route
Point to a DNS name server, to allow
access to the rest of the Internet
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Assign an IP address and hostname
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/etc/hosts file
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Example from text book
127.0.0.1
localhost
192.108.21.48
lollipop.xor.com lollipop loghost
192.108.21.254
chimchim-gw.xor.com
chimchim-gw
192.168.21.1 ns.xor.com ns
192.225.33.5 licenses.xor.com license-server
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hostname command
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Assigns a hostname to a machine
Typically runs at boot time
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Configure network interface
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ifconfig command
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Common form:
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ifconfig interface address options… up/down
For example:
Ifconfig en0 128.138.240.1 netmask 255.255.255.0 up
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Options
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Netmask
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Sets the subnet mask for the interface
Broadcast
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Specifies the IP broadcast address for the interface
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Configure static routes
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route command
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Format:
route [-f] op [type] destination gateway [hop-count]
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Options
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Add, delete, (get, change, flush, monitor)
Default routes
route add default gateway-IP-address
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Configure DNS
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/etc/resolv.conf file
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All systems require to modify it
Sample:
Search cs.colorado.edu colorado.edu
Nameserver
128.138.242.1
Nameserver
128.138.243.151
Nameserver
192.108.21.1
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Configure DNS
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“service switch” file
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Some systems do not use DNS by default, these
systems use “service switch” file to resolve
hostname-to IP- address mapping
Service switch files by system
System
Switch files
Solaris
/etc/nsswitch.conf nis [NOTFOUND=return] files
HP-UX
/etc/nsswitch.conf dns [NOTFOUND=return] nis
[NOTFOUND=return] files
Red Hat
/etc/nsswitch.conf db files nisplus dns
/etc/host.conf
hosts, bind
FreeBSD /etc/host.conf
Default for hostname lookups
host,bind
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Thank you!
Questions?
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