4. Proprietary and Confidential
Network Devices
4
The various devices used to build a data communication network can be classified into type of
equipment depending on how Ethernet packets are forwarded.
HUB
BRIDGE / SWITCH
ROUTER
5. Proprietary and Confidential
Functions of OSI layers
5
Physical
Data Link
Network
Transport
Session
Presentation
Application
OSI model layers
Type of communication: e-mail, file transfer, web browsing
Encryption, data conversion: ASCII to EBCDIC, BCD to binary et.
Starts, stops sessions. Maintains order
Routes data to different LANs and WANs based on network addresses
Transmits packets from node to node based on station address
Electrical signals and cabling (physical medium)
Ensure delivery of entire file or message
6. Proprietary and Confidential
Protocols in OSI layers
6
Physical
Data Link
Network
Transport
Session
Presentation
Application
OSI model layers
HTTP, FTP, IRC, SSH, DNS, SNMP
SSL, SFTP, IMAP, SSH, Jpeg, GIF, TIFF, MPEG, MIDI, mp3
VARIOUS API’S, SOCKETS
IP, IP Sec, ICMP, IGMP
Ethernet, Token Ring, SLIP, PPP, FDDI
Coax, Fiber, Wireless
TCP, UDP, ECN, SCTP, DCCP
8. Proprietary and Confidential
OSI and TCP/IP model
8
Physical
Data Link
Layer 2,5
Network
Transport
Session
Presentation
Application
Physical
Data Link
Layer 2,5
Network
Transport
Session
Presentation
Application
Network
Interface
Layer 2,5
Internet
Application
Session Protocol
Presentation Protocol
Application Protocol
P SFD MAC MPLS IPv4/6 TCP/UDP DATA FCS
S-VLAN
DATA
MAC MPLS IPv4/6 TCP/UDP DATA FCS
S-VLAN C-VLAN
MPLS IPv4/6 TCP/UDP DATA
IPv4/6 TCP/UDP DATA
TCP/UDP DATA
TCP/IP model
OSI model
layers
OSI model
layers
E
L
E
L
7 1 12 4 4 4 2 20/40 20/8 4
46-1500
P Preamble TCP Transmission control protocol
SFD Start frame Delimiter UDP User datagram protocol
MAC = Destination + Source MAC Address FCS Frame check sequence
EL Ether Length/Type
VLAN Virtual local area network
MPLS Multiprotocol Label Switching
IP Internet protocol
C-VLAN
Size in bytes:
Transport
14. Proprietary and Confidential
Virtual Local Area Network (VLAN) concept
14
• Imagine that you have a network and three different customer
• Customer 1
• Customer 2
• Customer 3
NETWORK
15. Proprietary and Confidential
Virtual Local Area Network (VLAN) concept
15
The most common protocol used today in configuring virtual LANs is IEEE 802.1Q
VLANs are created to provide the segmentation services traditionally provided by routers
in LAN configurations
16. Proprietary and Confidential
OSI and TCP/IP model
16
Physical
Data Link
Layer 2,5
Network
Transport
Session
Presentation
Application
Physical
Data Link
Layer 2,5
Network
Transport
Session
Presentation
Application
Network
Interface
Layer 2,5
Internet
Application
Session Protocol
Presentation Protocol
Application Protocol
P SFD MAC MPLS IPv4/6 TCP/UDP DATA FCS
S-VLAN
DATA
MAC MPLS IPv4/6 TCP/UDP DATA FCS
S-VLAN C-VLAN
MPLS IPv4/6 TCP/UDP DATA
IPv4/6 TCP/UDP DATA
TCP/UDP DATA
TCP/IP model
OSI model
layers
OSI model
layers
E
L
E
L
7 1 12 4 4 4 2 20/40 20/8 4
46-1500
P Preamble TCP Transmission control protocol
SFD Start frame Delimiter UDP User datagram protocol
MAC = Destination + Source MAC Address FCS Frame check sequence
EL Ether Length/Type
VLAN Virtual local area network
MPLS Multiprotocol Label Switching
IP Internet protocol
C-VLAN
Size in bytes:
Transport
18. Proprietary and Confidential
Length / Type < 1500 - Parameter indicates number of Data Bytes
Length / Type > 1536 - Parameter indicates Protocol Type (PPPoE, PPPoA, ARP etc.)
Preamble + SFD DA SA Length / Type DATA + PAD FCS
6 Bytes 6 Bytes
8 Bytes 2 Bytes 46 - 1500 Bytes
4 Bytes
(32-bit
CRC)
FCS is created by the sender and recalculated by the receiver
Minimum 64 Bytes < FRAME SIZE < Maximum 1518 Bytes
Untagged Ethernet Frame
18
19. Proprietary and Confidential
• Additional information is inserted
• Frame size increases to 1522 Bytes
4 Bytes
TPID = Tag protocol ID
TCI = Tag Control Information
CFI = 1 bit canonical Format Indicator
Preamble + SFD DA SA Length / Type DATA + PAD FCS
3 Bit 1 Bit 12 Bit
TCI
CFI
VLAN TAG
P-TAG VLAN ID
TPID = 0x8100
Tagged Ethernet Frame
19
20. Proprietary and Confidential
VLAN ID uses 12 bits, therefore the number of maximum VLANs is 4096:
• 212 = 4096
• VID 0 = reserved
• VID 4090-4096 = reserved (dedicated for IP-10’s internal purposes such as MNG etc.)
• VID 1 = default
• After tagging a frame, FCS is recalculated
• CFI is set to 0 for ETH frames, 1 for Token Ring to allow TR frames over
ETH backbones (some vendors may use CFI for internal purposes)
Tagging a Frame
20
21. Proprietary and Confidential
TPID / ETHER-Type / Protocol Type…
21
TPID in tagged frames in always set to
0x8100
It is important that you understand the
meaning and usage of this parameter
Protocol type Value
Tagged Frame 0x8100
ARP 0x0806
Q-in-Q (CISCO) 0x8100
Q-in-Q (other vendors) 0x88A8
Q-in-Q (other vendors) 0x9100
Q-in-Q (other vendors) 0x9200
RARP 0x8035
IP 0x0800
IPv6 0x86DD
PPPoE 0x8863/0x8864
MPLS 0x8847/0x8848
IS-IS 0x8000
LACP 0x8809
802.1x 0x888E
22. Proprietary and Confidential
• Additional VLAN (S-VLAN) is inserted
• Frame size increases to 1526 Bytes
Q-in-Q
4 Bytes
Preamble + SFD DA SA Length / Type DATA + PAD FCS
3 Bit 1 Bit 12 Bit
CFI
S - VLAN
TPID = 0x88A8
P-TAG VLAN ID
TCI
CFI P-TAG
VLAN ID
TCI
TPID = 0x8100
C - VLAN
4 Bytes
3 Bit 1 Bit 12 Bit
22
