internet: network nodes

Faruk Hadziomerovic: Internet notes

Internet: network nodes

Host: any computer executing protocol

Hub: repeats signal heard one each port to all ports.

Bridge: understands physical layer addresses, MAC addresses, and learns where each device is located. It listens to all traffic on LAN. If it finds that packet should go to another segment it forwards the frame to it. It is store-and-forward device.

Switch: same as bridge however much faster. It redirects a frame only after readingdestination address on a ongoing basis.

Router: Internetwork layer device. It reads entire packet, based on destination address finds the best route for the packet and sends it.


Internet: network of networks

star star

Ethernet Ethernet

token ring

hub

hub

bridge

bridge

bridge

switch

router


Internet protocol stack vs. OSI model (Fig. 1.2)

Physical Layer

Presentation Layer

Session Layer

Transport Layer

Network Layer

Data Link Layer

Application Layer

Manchester

Ethernet, Token ring (ATM, Frame Relay**)

IP, ARP

TCP, UDP

E-mail, FTP, HTTP

Physical Layer

Host-to-host Layer

Internet Layer

MAC* Layer

Process Layer

* Medium Access Control. MAC and Physical layers are called Network Interface Layer.** not exactly MAC, however, layer above physical


Two networks connected with a router (Fig. 1.3)

FTPclient

TCP

IP

Ethernet driver

Ethernet driver

Token ring driver

Token ring driver

FTPserver

TCP

IP IP

FTP protocol

TCP protocol

Ethernet

router

Ethernet protocol

IP protocolIP protocol

Ethernet protocol

Token ring

Ethernet host Token ring host


Internet protocol suite

Telnet

FTP

HTTP

DNS

BOOTP

DHCP

SNMP

TFTP

RIP

23 20/21 80 53 67/68 69 151/162 520

TCP UDP

6 17

IP

IGRP

88

ICMP

01OSPF

89

ARP RARP

Process Layer

Host to Host Layer

Internet Layer

Network InterfaceLayer

08000806 0806

Port Numbers

Protocol Codes

Ethernet, Token Ring, FDDI, SLIP, PPP, etc.


Internet protocols

TELNET - remote terminal connection service. Allows user terminal to mimic the terminal at the remote side.FTP - File Transfer Protocol (put/get file to/from remote machine).HTTP - Hypertext Transport Protocol.DNS - Domain Name Server On-line distributed database for translating IP machine names into IP addresses.BOOTP - Bootstrap Protocol defines each device autoconfiguration on the server (improvement to the RARP).DHCP - Dynamic Host Configuration Protocol (improvement to BOOTP) allows network administrator to configure workstation by providing dynamic address assignment.TFTP - Trivial File Transfer Protocol (same as FTP with minimal capability).SNMP - Simple Network Monitoring Protocol used to monitor IP gateways and networks they are attached to.RIP - Routing Information Protocol used to exchange the routing information among small set of computers (every 30 sec hosts exchange information).TCP - reliable Transmission Control Protocol (connection oriented).UDP - unreliable Universal Transport Protocol (connectionless).IGRP - Interior Gateway Routing Protocol (proprietary routing protocol developed by Cisco). ICMP - Internet Control Message Protocol part of IP that handles error and control messages.OSPF - Open Shortest Path First routing protocol.ARP - Address Resolution Protocol used to dynamically bind IP addresses to physical addresses.RARP - Reverse ARP used by newly installed machine to find its IP address.IP - Internet Protocol.


Encapsulation (Fig. 1.7)

Ethernet

14 bytes 20 to 60 bytes

IP header

UDP

8 bytes variable

Application

TCP

20 or 24 variable

Application

ICMP

6 + bytes

CRC

4 bytes


Demultiplexing (Fig. 1.8)

application

TCP

IP

Ethernet driver

UDP

ICMP

incoming frame

application application application

IGMP

RARPARP


Sample (book) network

aix

.1.92

gateway

.1.4

bsdi

.13.35

solaris

.1.32

gemini

.1.11

Solaris 2.2 SunOS 4.1.1

Ciscorouter

netb

.1.183

TelebitNetBlazer

modem

sun

.1.29SunOS 4.1.3modem

.13.33

SLIP (dialup)

svr4

.13.34

SVR4BSD/386 1.0

.13.66slip

.13.65

BSD/386 1.0

Ethernet

Ethernet

All IP addresses belong to class B network ID 140.252.xxx.xxx


Link Layer (Fig. 2.1)

SLIP (Serial Line IP)

c0 db dc db dd c0

c0 db

ESC

Point-to-point (PPP) protocol

IP datagram

Flag 7E

Contr 03

protocol

0021

1 1 1 2 up to 1500 2 1

CRCdataaddr FF

Flag 7E

Link control dataC021

network control data8021


Ethernet Header

Destin. Addr. Source Addr. Type

Vendor addr component

Broadcast

ff ff ff ff ff ff 00 00 c0 a0 51 24 08 06

Unicast ARP

Multicast

01 00 5e 00 00 00 00 00 c0 a0 51 24 08 00

Unicast IP

Unicast

01 00 c0 a0 51 24 00 c0 93 21 88 a7 81 4c

Unicast SNMP

Vendor ser. number


IP addressing convention4 bytes (dec): 140.252.1.13 = 01100000.10101010.00000001.00001011

Class A: Large networks (GM, Ford, etc)

0NNNNNNN LLLLLLLL LLLLLLLL LLLLLLLL

N-Network bitsL-Locally administered126 Class A networks16,777,214 hosts/network

0 - unused, 1 .. 126 ; 127 - loop back

10NNNNNN NNNNNNNN LLLLLLLL LLLLLLLL 16,384 Class B networks65,534 hosts/network(0 not used, all 1’s broadcast) 128 .. 191 0 .. 255

Class B: medium size (universities, medium business)

110NNNNN NNNNNNNN NNNNNNNN LLLLLLLL 2,097,152 Class C networks254 hosts/network

192 .. 223 0 .. 255 0 .. 255

Class C: small networks (small business)

1110MMMM MMMMMMMM MMMMMMMM MMMMMMMM 2,097,152 Class C networks254 hosts/network

224 .. 239 0 .. 255 0 .. 255 0 .. 255

Class D: broadcasting


IP subnetting with subnet masks

IP address: 191 255 193 44

Subnet mask: 255 255 252 000

Binary addr: 10111111 11111111 11000001 00101100

Binary Mask: 11111111 11111111 11111100 00000000

Address bits: NNNNNNNN NNNNNNNN SSSSSSI I I I I I I I I I

N - network bitsS - subnet bitsI - Interface bits.

Natural masks:

Class A : 255.0.0.0 B : 255.255.0.0 C : 255.255.255.0


Subnetting example

source: 161.55.121.33target: 161.55.131.49

mask: 255.255.248.0

248 = 11111000 mask121 = 01111001 source

subn= 01111 source subnet

248 = 11111000 mask248 = 10000011 target

subn= 10000 target subnet

Are this two hosts in the same subnet?

internet: network nodes

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