Ken Dick
Layered Protocols
In a perfect world bits would flow unhindered between
network devices. There would be no need for protocol layers as there would be no:
Bit errors Congestion Need for alternate routing Problems in determining destinations Security issues
Layered Protocols (1a)
Layers in the OSI model.
2-1
Layered Protocols (1b)
Who does what in the OSI model.
2-1
Applications (FTP, SMTP, etc) Not used Not used End to end connection (TCP & UDP) Addressing, accounting & routing
Framing, flow control & error handling
Moving bits
Layered Protocols (1c)
The PDUs & addresses in the OSI model.
2-1
Message Not used Not used Socket (IP+Port) - Port Packet - IP
Frame - MAC
Bits
Layered Protocols (2a)
A typical message as it appears on the network.
2-2
How IP Fits into TCP/IP
How IP Fits into TCP/IP
How IP Fits into TCP/IP
How IP Fits into TCP/IP
Layered Protocols (2b)
The overhead associated w/ the layers
2-1 data Not used Not used 20 Bytes 20 Bytes
72 Bytes (minimum frame size)
Bits
802.3 1-Persistent CSMA/CD LAN (Ethernet)
The IP Header
0 vers 4 8 16 32 hlen service type total length identification flags fragment offset time to live protocol header checksum source IP address destination IP address IP options (if any)
vers hlen service type total length identification flags fragment offset time to live protocol options
version of IP used to create datagram header length (in 32-bit words) hints quality of service desired length of datagram in octets if datagram fragmented, all fragments have same ID more fragments; don’t fragment where does this fragment fit into datagram? In practice, indicates number of hops before being killed which transport protocol should receive this packet routing, security info
The TCP Segment Header
TCP Header.
Dynamic Channel Allocation in LANs and MANs
Station Model. Single Channel Assumption. Collision Assumption. (a) Continuous Time.
(b) Slotted Time.
(a) Carrier Sense.
(b) No Carrier Sense.
Ethernet MAC Sublayer Protocol
Frame formats. (a) DIX Ethernet, (b) IEEE 802.3.
Ethernet MAC Sublayer Protocol (2)
Collision detection can take as long as 2 .
Ethernet Performance
Efficiency of Ethernet at 10 Mbps with 512-bit slot times.
IEEE 802.2: Logical Link Control
(a) Position of LLC. (b) Protocol formats.
The IP Protocol
The IPv4 (Internet Protocol) header.
The IP Protocol (2)
Some of the IP options.
5-54
The Main IPv6 Header
The IPv6 fixed header (required).
Extension Headers
IPv6 extension headers.
5-69
Extension Headers (2)
The hop-by-hop extension header for large datagrams (jumbograms).
Extension Headers (3)
The extension