Defining Network Protocols

• Application Protocols– Application Layer– Presentation Layer– Session Layer

• Transport Protocols– Transport Layer

• Network Protocols– Network Layer – Data-Link Layer– Physical Layer

Application Protocols

• SMTP: Simple Mail Transport Protocol• X.400: International Email • HTTP: Hyper Text Transport Protocol• SNMP: Simple Network Management Protocol• FTP: File Transfer Protocol• Telnet: Interactive login• SSH: Secure Shell telnet• Appletalk: Apple’s networking protocol suite• NCP: Novell Netware applications• DNS: Domain Name Service

Transport Protocols

• TCP: Transmission Control Protocol

• SPX: Sequenced Packet Exchange

• Nwlink: Microsoft’s IPX/SPX

• Netbeui: Netbios Extended User Interface

• ATP: Appletalk Transaction Protocol

Network Protocols

• IP: Internet Protocol

• IPX: Internet Packet Exchange

• NWlink: Microsoft’s implementation of IPX

• NetBEUI: similar to Transport

• DDP: Apple’s Datagram Delivery Protocol

Ethernet destination Address (first 32 bits)

Ethernet Dest (last 16) Ethernet Src (16 bits )

Ethernet source Address (last 32 bits)

Type Code or Length of packet

Ethernet Checksum

IP header, TCP header, then your data

Ethernet Packet

TCP/IP Network Communication

• Network Layer (IP, Layer 3) (TCP, Layer 4)• Protocols are described in RFCs (Request for

Comments)• Available from nis.nsf.net/internet/documents/rfc• TCP/IP Addressing

– Class A (1-126).xxx.xxx.xxx

– Class B (128-191).(assigned).xxx.xxx

– Class C (192-223).(assigned).(assigned).xxx

Subnets

• Class A 255.0.0.0

• Class B 255.255.0.0– USU uses 255.255.255.0 for subnetting

buildings

• Class C 255.255.255.0

Internet Addressing

• Each address is 4, 8 bit, decimal numbers• Like Area Code/Exchange/Subscriber• 129.123.7.170• 129.123 is assigned to USU (domain)• 7 is assigned to Computer Science• 170 is assigned to PC named java4• Every Internet device must have a number• Number to name conversion is done by DNS

IP header

• Source and Destination IP addresses

• Type of Service – Selects delivery speeds vs. accuracy

• Protocol (TCP,ICMP, UDP)

• Time to Live (Router hops)

• Identification and Fragment offset– Reassembly of a fragmented datagram

Version Leng Type of Svc Total Length

Identification Flags Frag OffsetTime to Live Protocol Header Checksum

IP Header

Source Address

Destination Address

TCP Header then your data...

TCP fields

• Ports (service identifiers)

• Sequence numbers

• Acknowledgement numbers

• Windowing– More retries (less acks) smaller packets– Less retries (more good data) larger packets

Source Port Destination Port

Sequence Number

Acknowledgement Number

DataOffset

Reserved

FlagsWindow

Checksum Urgent Pointer

Your Data… next 500 octets

TCP Header

ARP

• Address Resolution Protocol• Associates an ethernet address to an IP address• arp -a or multi show/arp• only local (router port) addresses shown• ARP entries have a finite (timed) lifetime• ARP entries are created by routers for non ethernet protocols

(token ring, PPP)• tracing an ethernet address

– Host system– Router– Switch

DHCP

• Dynamic Host Configuration Protocol• Assigns IP address, gateway (router) address,

name server, netmask, time server, and other configuration information based on a NIC’s MAC address

• IP addresses may be fixed or taken from a pool of available addresses

• Allows assigning temporary addresses for transient computers.

TCP, UDP, ICMP

• TCP (Transmission Control Protocol)– Datagrams– Connection Oriented– End to End error checking– Source Port, Destination Port

• Sockets, Well Known Ports

Data FlowC

omputer

129.123.7.33, 129.123.1.86

Port info:1234, 23 129.123.1.861234Returning Port

Listens on port23

Services

• /etc/services or multinet:services.master_server• lists service name and port number• Common (well known) ports:

– FTP 21– TELNET 23– SMTP 25– HTTP 80– SSH 22– Finger 79

UDP (user datagram protocol)

• Connectionless

• One Way

• Fast, Simple

• No guarantee of delivery

• NFS, DNS, DHCP, NTP, TALK

ICMP (Internet control message protocol)

• Error Messages

• Intended for the TCP/IP software itself

• PING (host unreachable messages)

• Simple Headers

IPX/SPX

• Internet Packet Exchange• Sequenced Packet Exchange• Novell Servers• Routes on a WAN but not the Internet• Generates Service Advertisements (SAP)• Address based on a number assigned to the

network segment (wire) plus the MAC address.

IPX continued

• RIP: Routing Information Protocol– Find fastest route to network number

• SAP: Service Advertising Protocol– Server name, type, address, node, socket

Netbeui

• Simple Non routable• NetBIOS name resolution

– based on tables in each system

• NetBIOS Datagram service– Message sending, no guarantee of arrival

• NETBios Session Service– Peer to Peer connection system

• For small Microsoft networks• Sends a lot of data on the network wire

X.25

• Packet Switching Protocol– Small (128 byte) packets– Uses the PDN (Public Data Network)– Uses store and forward method which requires

a lot of buffering– Node to node error checking