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 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 ( ).(assigned).xxx.xxx –Class C ( ).(assigned).(assigned).xxx

Subnets Class A Class B –USU uses for subnetting buildings Class C

Internet Addressing Each address is 4, 8 bit, decimal numbers Like Area Code/Exchange/Subscriber 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

VersionLengType of SvcTotal Length IdentificationFlags Frag Offset Time to Live ProtocolHeader 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 PortDestination Port Sequence Number Acknowledgement Number Data Offset Reserved Flags Window 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 Flow Computer , Port info:1234, Returning Port Listens on port 23

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