TCP/IP networking1-1 TCP/IP networking TCP/IP m A networking protocol suite Use several protocols,...

TCP/IP networking 1-1

TCP/IP networking

TCP/IP A networking protocol suite

• Use several protocols, main ones are tcp and ip.• IP stands for Internet Protocol • TCP stands for Transmission Control Protocol.

The native language of the InternetSupported by most OSs (Unix, MacOS,

Windows, Netware, etc)Defines a uniform programming interface to

different types of network hardware


TCP/IP and Internet

1969 ARPAnet Experimental packet-switching network Study robust, reliable, vendor-independent data

communication Very successful

1975 ARPAnet became operation network Development continuing TCP/IP was developed

1983 TCP/IP protocols were adopted as Military Standards TCP/IP was implemented in Berkeley Unix. ARPAnet was divided into MILNET and ARPAnet


TCP/IP and Internet

1985 NSFNet Connected to the then existing Internet

( MILNET plus ARPAnet) Linked together the five NSF super

computer centers Wanted to extend the network to every

scientist 1987 new NSFNet backbone

Faster Three-tiered topology: backbone, regional

networks, and local networks.


TCP/IP and Internet

1990 ARPAnet passed out of existence 1995 NSFnet ceased its role as a primary

Internet backbone network Today Internet is build by commercial

providers. Infrastructure is being created by

• National network provider, caller tier-one providers• Regional network provider

Local access and user services is provided by Internet Service Providers (ISPs)

Network Access Points (NAPS): major interconnection points


TCP/IP and Internet How the internet is managed today

Commercial force Several organization

• Internet Corporation for Assigned Names and Numbers (ICANN)

– www.icann.org

• Internet Engineering Task Force (IETE) – www.ietf.org

• Internet Society (ISOC)– www.isoc.org


TCP/IP and Internet

Network standards and documentation Request for Comments (RFC)

• Over 4000 has been created• FY• STD• BCP

Dispatch central for RFC-related matters• www.rfc-editor.org


Networking Road Map

TCP/IP components IP, the Internet Protocol

• routes data packets from one machine to another ICMP, the Internet Control Message Protocol

• Provides several kinds of low-level support for IP– Error message

– Routing assistance

– Debugging help

ARP, the Address Resolution Protocol• Translates IP addresses to hardware addresses


Networking Road Map

UDP, the User Datagram Protocol • Delivers data to specific applications on the

destination machine• Provides “unverified”, “best effort” transport for

individual messages TCP, the Transmission Control Protocol

• Delivers data to specific applications on the destination machine

• Provides reliable, flow controlled, error corrected conversation between processes on two hosts.


TCP/IP network model

UTP copper, fiber, radia waves

ARP, Device Drivers

IP ICMP

TCP UDP

ARP SSH, FTP, WEB DNS, Quake Traeroute

Physical layer

Link Layer

Network Layer

Transport Layer

Application Layer


Packets and encapsulation

Data travels on a network in the form of packets

Each packet consists of A header – where it came from and where it’s going,

protocol info, checksum, etc. A payload - data

As a packet travels down the protocol stack encapsulation

• Each protocol adds its own header information• Each protocol’s finished packet becomes the payload

part of the packet generated by the next protocol.

On a receiving machine, the encapsulation is reversed as the packet travels back up the protocol stack.


Packets and Encapsulation

Example: A typical network packet

Ethernet header

IP header

UDP header

Application dataEthernet CRC

UDP packet(108 bytes)

IP packet(128bytes)

Ethernet frame(146 bytes)


Addressing

Packets addressing Packets must be properly addressed in order to

reach their destination Addressing schemes

• MAC (media access control) addresses for hardware• IP addresses for software• Hostnames for people

Ports 16 bit number Address particular processes or services Well-known ports are defined in /etc/services Unix systems restrict access port under 1024 to root.


Addressing

Address types Unicast – addresses that refer to a single host

(interface) Multicat – addresses that identify a group of hosts Broadcast – addresses that include all hosts on the

local network IP addresses

Four bytes long Network part and host part Written as decimal numbers, one for each byte

separated by periods When 127 is the first byte of an address, it denotes

the “loopback network”• Lookback address 127.0.0.1 - localhost


Addressing

IP address classes The traditional class determine which bytes

of the address were in the network portion and which were in the host portion

• A 1-126 N.H.H.H Very early network• B 128-191 N.N.H.H large sites (65536)• C 192-223 N.N.N.H (256)• D 224-239 Multiple addresses• E 240- 254 Experimental

addresses


Addressing

Subnetting and netmasks Host portion of an address is “borrowed” to

extend the network portion This reassignment is done by using ifconfig

command to associate an explicit “subnet mask” with a network interface.

Each bit of the netmask that corresponds to the network portion of an IP address is set to 1, host bits are set to 0

• The division of network part and host part need not fall on a byte boundary

• Network bits must be contiguous and must appear at the high order end of the addresses


Addressing

Notation• Ipaddress netmask• Ipaddress/length of the network part

– 128.138.243.0/26 Example

• 128.138.243.100/24– Netmask? – Network?– Broadcast?

• 128.138.243.100/26 100=01100100– Netmask?– Network?– Broadcast?

Use ipcalc to get the values.


Addressing

The IP address crisis Fundamental problems with the original

class allocating scheme• Run out of B classes• Routing table were growing so large• IP address were allocated on a first-com, first-

served basis with no locality of reference solutions

• Short term: Classless Inter-Domain Routing (CIDR)• IPV6: extend the address to 16 bytes

– 665,570,793,348,866,943,898,599 addresses


Addressing

Address allocation Regional IP address registries

• ARIN North and South America• APNIC Asia/Pacific region• RIPE Europe and surrounding

areas

Private addresses Packets bearing private addresses can not

get into internet IP address reserved for private use

• 10.0.0.0/8• 172.16.0.0/12• 192.168.0.0/16


Routing

Routing is the process of directing a packet through the maze of networks that stand between its source and its destination.

Routing info is stored in a table in the kernel. Examine it use “netstat –r” Configure dynamically Configure statically#route add –net 132.236.220.64 netmask 255.255.255.192

132.236.212.6#route add default 132.236.227.1


ARP

The address Resolution Protocol discovers the hardware address associated with a particular IP address.

APR uses broadcast packets, cannot cross networks “Does anyone know the hardware address for

128.138.116.4”? Check the arp cache table with arp command

#/usr/sbin/arp –a RARP

Reverse translation Query a central server to discover its own address Need configuration


Additions of machines to a network Basic steps are

Assign a IP address and hostname Set up the new host to configure its network

interfaces at boot time Set up a default route and perhaps fancier

routing Point to a DNS name server, to allow access

to the rest of the Internet. Debugging

• Always to reboot if changes affect booting


Assigning hostnames and IP addresses Mapping hostnames to IP

Hosts file NIS or NIS+ DNS Or Combination above

Hosts file /etc/hosts

• Each line start with IP, continues with various symbolic names by which that address is known.

• Entries– Localhost, gateway, special hosts, …

• Replicate same hosts file on machines

Configure hostname Command hostname run at the boot time Configuration file


Assigning hostnames and IP addresses Configure network interfaces: ifconfig

Enable or disable network interface Set IP address Set subnet mask Set other options Run at the boot time (use command with

the value from configure files ) Format

• $ifconfig interface address options … up|down• Ex:#ifconfig eth0 128.138.240.7 network 255.255.255.0 up


Assigning hostnames and IP addresses Interface name:

Identifies the hardware to which the command applies

Two or three character device name followed by a number.

The loopback interface is named lo0 The common interface names are

• Ie0, le0, ln0, we0, hme0, eri0, lan0, …

Display the interfaces $netstat –i

Display the setting of interfaces $ifconfig –a


Assigning hostnames and IP addresses Configure the network interface

The ifconfig commands support many options • Specify address • Specify netmask, otherwise it uses address class

(A,B,C)• Specify broadcast

– Default can be calculated from IP + netmask– Some sites set it to avoid certain types of denial of service

attacks. Not good. • Activate or deactivate the device driver

– Use keywork up, down. Ifconfig allows you to configure a interface card by

hand, but the value is only in kernel.• To make it survive the reboot, change the right

configuration file


Configure static routes

Command route defines static routes Static route will stay in the routing table in

most case configure the default routing when adding a

host to local network Routing is performed at what layer?

• The packets’ destination IP is compared with the route , if it matches, the packet is forwarded to the “next gateway” IP address associated with that route

• Routing added when configure the interface - Packets destined for host on a directory connected network

• Default route is invoked when there is no route that matches the destination address.



The format:• #route op [type] destination gateway [hop-count]• Where

– Op: add, delete, get, change, flush, monitor– Destination: host address, network address, or the

keyword “default” ( 0.0.0.0)– Gateway: a machine to which packets should be

forwarded» Must be on a directly connected network» Forwarding can only be performed one hop at a time

– Type: -net, -host Check the routing table:

• #netstat -nr



default route• #route add default gateway_ip_address• Change the configure file

– Solaris: /etc/defaultrouter

– Hp-UX: /net/rc.config.d/netconf

– Redhat: /etc/sysconfig/network


Configuring DNS

To configure a machine as a DNS client Configure /etc/resolv.conf

• List DBS domains that should be searched to resolve name that are incomplete

• Line the IP addresses of the name servers to contact for name lookups

• Example:[ruihong@dafinn ~]$ more /etc/resolv.conf

search cs.mtu.edu csl.mtu.edu mtu.edu

nameserver 141.219.152.253

nameserver 141.219.152.254


Configuring DNS

Configure the service switch file• Which one take effect? /etc/hosts, NIS, DNS?• Solaris, Hp-UX, Redhat: /etc/nsswitch.conf • Example:

hosts: files nis dns

• Clause: [NOTFOUND=return]


Network configuration files by system All

/etc/hosts /etc/recolv.conf

Solaris /etc/hostname.ifname /etc/nodename /etc/defaultrouter /etc/inet/netmasks /etc/inet/hosts

HP-UX /etc/rc.config.d/netconf

Red Hat /etc/sysconfig/network Network-scripts/ifcfg-ifname


Practice Check

IP address/netmask/broadcast route Arp table Hostname DNS

Modify Hostname Dns research list

• Ping wopr Dns servers Remote default route

• Ping wopr Add the default route back again

Reboot


DHCP

Dynamic Host Configuration Protocol Distribute network and administrative

parameters to DHCP client, include• IP address and netmasks• Gateways • DNS name servers• Syslog hosts• WINs Servers, X font servers, proxy servers, NTP

servers• TFTP servers ( for loading a boot image)• And more…


DHCP

How DHCP works Client sends “Who am I” DHCPDISCOVER

message • To broadcast 255.255.255.255• With 0.0.0.0 as its own address

Server responds with OFFER messages Client sends back a REQUEST messages Server responds with ACK or NAK

Client renew the lease by sending another REQUEST message

TCP/IP networking1-1 TCP/IP networking TCP/IP m A networking protocol suite Use several protocols,...

Documents

Transcript of TCP/IP networking1-1 TCP/IP networking TCP/IP m A networking protocol suite Use several protocols,...