Network Protocols

Dean (3rd), Chapter 4

Protocols

Rules that govern network communications

Voluntary Standards organizations:

• IETF: Internet Engineering Task Force

• ICANN: Internet Corporation For Assigned Names and Numbers

• ISO – Information Technology Committee

TCP/IP Provides suite of conventions and utilities used on

Internet Transmission Control Protocol (TCP) Internet Protocol (IP) Governed by voluntary compliance with Requests for

Comments (RFCs)• RFC 1 issued 7-Apr-1969 on Host Software by Steve Crocker

of UCLA• Latest RFC: 3994 Indication of Message Composition for

Instant Messaging. H. Schulzrinne. January 2005. (Format: TXT=27472 bytes) (Status: PROPOSED STANDARD).

• Not all RFCs are serious--include poetry (1121) and April fools jokes (1605, 2795)

TCP/IP and OSI

Applications

Presentation

Session

Transport

Network

Data Link

Physical

Transport—TCP, UDP

Internet—IP, ARP, ICMP

local network protocol

ApplicationsTelnet, FTP, TFTP, NTP, PING,

BOOTP, DHCP, HTTP

TCP/IP Model OSI Model

TCP/IP Data Encapsulation

TCP • Segments and sequences data

• Determines ports IP

• Packages segment in datagram

• Determines logical addresses Local network protocol

• Creates transmission frame

• Determines physical addresses

app

TCPsegment

IPdatagram

LANframe

. . bits . .

app

TCPsegment

IPdatagram

LANframe

TCP Segment Connection oriented: ports, handshaking Provides reliable delivery of data: sequence, checksum, ack

• Source port—port number at source node• Destination port—port number at

destination node• Sequence number—segment’s position in

stream of data• ACK number—used to acknowledge

receipt of segment• Header length—number of 32-bit words in

header• Reserved for later use—no used• Flags: Urgent, ACK, no buffering, reset,

synchronization, last segment• Window size—receivers buffer size• Checksum—used to determine corruption• Urgent pointer—DoD field pointer• Options and padding—complete header

Source Port Destination Port

Sequence Number

Acknowledgement

Window Size

Checksum Urgent pointer

PaddingOptions

Data

flagsLng Rsv

Establishing TCP Connection(Handshaking)

• Request for connection

• Acknowledge connection

• Response

• Connection established

SYN

SYN/ACK

ACK

UDP

User Datagram Protocol Transport level protocol

• Alternative to TCP Connectionless Does not assure delivery Used for steaming media and other

transfers where speed is more important than accuracy

IP Datagram

Connectionless Addressing and routing

• Version—IPv4 or IPv6• Header length• Services—priority info for router• Total length in bytes• Identification—message ID• Flags—is message fragment• Fragment offset• Time to live—number hops left• Protocol—TCP or UDP• Header checksum• Source IP address• Destination IP address• Options—routing/timing info• Padding—fill out multiple 32-bits• TCP (or UDP) segment

Identification

Total Length

Header Checksum

Source IP Address

Destination IP Address

Data – TCP or UDP Segment

Services

Padding

ProtocolTTL

Options

Flgs

Vers IHL

Frag. offset

ICMP

Internet Control Message Protocol Used to control message transfers

• Handshaking

• Report success or failure of packet transfers

• Announces TTL delivery errors

• Troubleshooting information

ARP

Address Resolution Protocol Internet (OSI Network) layer protocol Maintains table of IP (logical) addresses

and MAC (physical) addresses Looks up MAC address using IP address Reverse Address Resolution Protocol

(RARP) looks up IP using MAC

IP Addressing

Internet Protocol (IP) Internet (OSI Network) layer protocol Logical address used by routers Each node must have unique IP address Two versions

• 32-bit (IPv4)

• 128-bit (IPv6)

IPv4 Notation

IP addresses are bit patterns IPv4 uses hexadecimal or dot notation to

specify four bytes in address Dana’s IP address:

• 86 72 8A 02 – hexadecimal

• 134.114.138.2 – dot notation “nslookup” utility for looking up IPv4

address

Special IP Addresses Classes:

• A: 1-126--126 networks and 16,777,214 hosts• B: 128-191-- >16,000 networks and 65,534 hosts per network• C: 192-223-- >2,000,000 networks and 256 hosts per network

IP addresses for private networks:• 10.0.0.0 - 10.255.255.255• 172.16.0.0 - 172.31.255.255• 192.168.0.0 - 192.168.255.255

Reserved IP addresses• Loopback: 127.0.0.1• Broadcast: 255.255.255.255, x.255.255.255, x.x.255.255,

x.x.x.255• Network use only: 0.0.0.0 – usually DHCP failed to assign address• Network coordination: x.0.0.0, x.x.0.0, x.x.x.0

Subnet Mask

IP address has network part and host part Network part determined by subnet mask

• Class A: 255.0.0.0

• Class B: 255.255.0.0

• Class C: 255.255.255.0

ipconfig (WinNT) or ifconfig (Unix) display subnet mask information

Assigning IP Addresses

Each node must have unique IP address Static IP assigned manually or with script Dynamic IP assigned

• BOOTP—assigns based on MAC addresses

• Dynamic Host Control Protocol (DHCP)—assigns next available

Sockets and Ports

Transport layer function Port: number associated with process on

machine Socket: combination of IP address and

port• Dana telnet: 134.114.138.2:23

• CBA Web: 134.114.80.216:80

Commonly Known PortsPort Number Process

NameProtocol Used Description

7 ECHO TCP and UDP Echo

20 FTP-DATA TCP File transfer data

21 FTP TCP File transfer control

23 TELNET TCP Telnet

25 SMTP TCP Simple Mail Transfer Protocol

53 DNS TCP and UDP Domain Name System

67 BOOTPS UDP Bootstrap Protocol Server

68 BOOTPC UDP Bootstrap Protocol Client

69 TFTP UDP Trivial File Transfer Protocol

80 HTTP TCP and UDP World Wide Web HTTP

101 HOSTNAME TCP and UDP NIC Host Name Server

110 POP3 TCP Post Office Protocol 3

143 IMAP TCP Internet Message Access Protocol

161 SNMP UDP Simple Network Management Protocol

179 BGP TCP Border Gateway Protocol

444 HTTPS TCP Secure implementation of HTTP

IPv6

128-bit (8-bytes) addresses Increases number of IP addresses

available Uses colons (:) to separate bytes Bytes specified using hexadecimal “dig” utility for looking up addresses

under IPv6

DNS Domain Name System (DNS)—converts

between FQN and IP address Domain names—used instead of IP address Fully qualified host name

• Network name: ucc.nau.edu• Host name: dana• FQN: dana.ucc.nau.edu

Top-level domains• arpa, com, edu, gov, org, net, int, mil, biz, info, aero,

coop, museum, name, pro• ICANN country codes

Host Files vs DNS

Host files were used when all nodes on Internet were known to all users of internet

DNS has servers dedicated• Each top level domain

• Each layer below top level domain

• Layers know each other and immediate subordinates Example

• edu domain server knows nau

• nau knows cba and bus.cba

• cba knows all cba and bus.cba nodes

TCP/IP Applications

Telnet – remote terminal application FTP – file transfer TFTP – trivial file transfer NTP – network time protocol PING – Packet INternet Groper

Other Protocols

IPX/SPX – Novell NetBIOS and NetBEUI – Microsoft WINS – Windows Internet Naming

Service – handles NetBIOS name to IP address conversion

AppleTalk – Apple

Summary

Protocols are rules that govern connections TCP/IP suite of protocols used by Internet TCP – Transport layer protocol that segments,

sequences, and checks data and determines port to use

IP – Network layer protocol that does logical addressing and provides routing information

DNS – Domain name system that allows use of names rather than IP addresses

Questions?