Ethernet and Internet Protocol

Tokio Kikuchi

OSI Network Layers

7 Application layer
6 Presentation layer
5 Session layer
4 Transport layer
3 Network layer
2 Data Link layer
1 Physical layer

Internet Protocol Layers

Application layer (7+6+5) ... ftp/http/smtp/pop3
Transport layer (4) ... tcp/udp
Network layer (3) ... ip/routing
Data Link layer (2) ... ethernet

Ethernet

10Base-5

Vampire Tap
ALOHAnet
Metcalf diagram
terminator register (50 ohm) ... reflection
cable length (500m)

10Base-2

Thin ethernet
cable length (125m)

10Base-T

Twisted pair (cat 3)
RJ-45 (telephone ISDN)
repeater hub -> switching hub

100Base-TX

Twisted pair (cat 5)
switching hub

1000Base-T

Twisted pair (cat 5e)
Use all 8 lines (4 pairs)
switching hub

Other

1000Base-TX
10GBase

Ethernet (MAC) address

48 bit
24 bit ... Vendor code
24 bit ... Unique id

IP address

32 bit
network address / host address
variable boundary
from small to large, various size networks
special host addresses
- all 0 ... network itself
- all 1 ... broadcast

Class

nearly obsolete
class A
0nnnnnnn hhhhhhhh hhhhhhhh hhhhhhhh
class B
10nnnnnn nnnnnnnn hhhhhhhh hhhhhhhh
class C
110nnnnn nnnnnnnn nnnnnnnn hhhhhhhh
class D
1110xxxx xxxxxxxx xxxxxxxx xxxxxxxx
- multicast
class E
11110xxx xxxxxxxx xxxxxxxx xxxxxxxx
- reserved

CIDR

Classless Inter-Domain Routing
192.168.201.0/24
172.31.255.252/30
10101100 00001111 11111111 111111hh
Network (or host) address / netmask (bit)

Ethernet encapsulation

Ethernet

Destination Source Type Data CRC

Type
0800 IP datagram

Type
0806 ARP request / response PAD

Type
0835 RARP request / response PAD

IEEE 802.2

802.3 MAC 802.2 LLC 802.2 SNAP

Destination Source data length DSAP
AA SSAP
AA Control
03 Original Code
00 Type Data CRC

Type
0800 IP datagram

Type
0806 ARP request / response PAD

Type
0835 RARP request / response PAD
MAC ... Media Access Code
LLC ... Logical Link Control
SNAP ... Subnetwork Access Protocol

ARP/RARP/DHCP

ARP
- Address Resolution Protocol
- Ethernet Broadcast Address = All 1 (48bit)
- Broadcast Destination IP Address
- The node having the IP address returns its Ethernet Address
RARP
- Reverse Address Resolution Protocol
- A node broadcast its Ethernet Address
- RARP server replies with its IP address
- My Ethernet Address -> My IP Address
- Who am I?

ARP

RFC826 Ether Types

0										1										2										3
0	1	2	3	4	5	6	7	8	9	0	1	2	3	4	5	6	7	8	9	0	1	2	3	4	5	6	7	8	9	0	1
Hardware Type (=1)																Protocol Type (=0x0800)
Hardware Size (=6)								Protocol Size (=4)								Operation (req=1,res=2)
Sender Ethernet Address(1)
Sender Ethernet Address(2)																Sender IP Address (1)
Sender IP Address (2)																Target Ethernet Address(1)
Target Ethernet Address(2)
Target IP Address

RARP

0										1										2										3
0	1	2	3	4	5	6	7	8	9	0	1	2	3	4	5	6	7	8	9	0	1	2	3	4	5	6	7	8	9	0	1
Hardware Type (=1)																Protocol Type (=0x0800)
Hardware Size (=6)								Protocol Size (=4)								Operation (req=3,res=4)
Sender Ethernet Address(1)
Sender Ethernet Address(2)																Sender IP Address (1)
Sender IP Address (2)																Target Ethernet Address(1)
Target Ethernet Address(2)
Traget IP Address

DHCP

RARP can't set:
Netmask (Broadcast Address)
Default Gateway (Default Router)
DNS Server
RFC2131

IP Header

0										1										2										3
0	1	2	3	4	5	6	7	8	9	0	1	2	3	4	5	6	7	8	9	0	1	2	3	4	5	6	7	8	9	0	1
Version				IHL				Type of Service								Total Length
Identification																Flags			Fragment Offset
Time to Live								Protocol								Header Checksum
Source Address
Destination Address
Options																							Padding

IHL ... Internet Header Length (x32bit)

IP Protocols

1 ... ICMP (Internet Control Message Protocol)
17 .. UDP (User Datagram Protocol)
6 ... TCP (Transmission Control Protocol)
Others

ICMP

RFC 792
ping
- ICMP echo request
traceroute
- Send UDP diagram with small TTL
- Receive ICMP TTL exceeded

Quiz of the day

Divide following terms into groups.
IP address, 32 bit, Link layer, 48 bit, Network layer, Router, MAC address, Hub

Homework for master students

What is MAC address and IP address of your PC ?
Describe also how you find them.
Answer in email to tkikuchi@is.kochi-u.ac.jp

Answer for the quiz

IP address, 32 bit, Network layer, Router
MAC address, 48 bit, Link layer, Hub