Ethernet and Internet Protocol

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

• OSI 1 + 2
• Physical layer
• ethernet frame
• CSMA/CD

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 [email protected]

Answer for the quiz

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