Transcript Defining Network Protocols

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
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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
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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 Packet
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
IP header, TCP header, then your data
Ethernet Checksum
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
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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
IP Header
Version
Leng Type of Svc
Total Length
Identification
Flags
Frag Offset
Time to Live Protocol Header Checksum
Source Address
Destination Address
TCP Header then your data...
TCP fields
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Ports (service identifiers)
Sequence numbers
Acknowledgement numbers
Windowing
– More retries (less acks) smaller packets
– Less retries (more good data) larger packets
TCP Header
Source Port
Destination Port
Sequence Number
Acknowledgement Number
Data
Offset
Reserved
Window
Flags
Checksum
Urgent Pointer
Your Data… next 500 octets
ARP
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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)
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Datagrams
Connection Oriented
End to End error checking
Source Port, Destination Port
• Sockets, Well Known Ports
Data Flow
Listens on port
23
129.123.7.33, 129.123.1.86
Computer
1234
Returning Port
129.123.1.86
Port info:1234, 23
Services
• /etc/services or multinet:services.master_server
• lists service name and port number
• Common (well known) ports:
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FTP 21
TELNET 23
SMTP 25
HTTP 80
SSH 22
Finger 79
UDP (user datagram protocol)
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Connectionless
One Way
Fast, Simple
No guarantee of delivery
NFS, DNS, DHCP, NTP, TALK
ICMP (Internet control message
protocol)
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Error Messages
Intended for the TCP/IP software itself
PING (host unreachable messages)
Simple Headers
IPX/SPX
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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