11

TRANSPORT LAYER PROTOCOLS

Chapter 6

TCP and UDPSPX and NCP

Chapter 6: TRANSPORT LAYER PROTOCOLS 2

TYPES OF TRANSPORT LAYER PROTOCOLS

There are two types of transport layer protocols: Connection-oriented

Transmission Control Protocol (TCP)

Sequenced Packet Exchange (SPX)

NetWare Core Protocol (NCP)

Connectionless User Datagram Protocol (UDP)

Chapter 6: TRANSPORT LAYER PROTOCOLS 3

TRANSPORT LAYER PROTOCOLS

There are two transport layer protocols in the Transmission Control Protocol/Internet Protocol (TCP/IP) suite: TCP

UDP

There are two transport layer protocols in the Novell Internetwork Packet Exchange (IPX)/SPX suite: SPX

NCP

Chapter 6: TRANSPORT LAYER PROTOCOLS 4

TRANSMISSION CONTROL PROTOCOL (TCP) The TCP protocol (described in Request for

Comments [RFC] 793) has the following characteristics: Uses Internet Protocol (IP) ID 06

Is a reliable, connection-oriented protocol

Provides guaranteed delivery of packets through sequencing and acknowledgments

Provides sliding-window flow control

Performs error detection and correction

Uses ports to identify the communicating process or application

Chapter 6: TRANSPORT LAYER PROTOCOLS 5

TCP HEADER AND FIELDS (PAGE 253)

Chapter 6: TRANSPORT LAYER PROTOCOLS 7

EXAMPLE OF A TCP HEADER

Chapter 6: TRANSPORT LAYER PROTOCOLS 8

ESTABLISHING A TCP CONNECTION THREE-WAY HANDSHAKE

Verify that both computers are operating and ready to receive data

Exchange initial sequence numbers (ISNs)

Exchange maximum segment sizes (MSSs)

Exchange port numbers

Chapter 6: TRANSPORT LAYER PROTOCOLS 9

ESTABLISHING A TCP CONNECTION THREE-WAY HANDSHAKE

TCP Connection

Chapter 6: TRANSPORT LAYER PROTOCOLS 11

TCP CONNECTION TERMINATION

Chapter 6: TRANSPORT LAYER PROTOCOLS 16

USER DATAGRAM PROTOCOL (UDP)

UDP (described in RFC 768) has the following characteristics: Uses IP ID 17

Provides fast, connectionless delivery of data

Has less overhead than connection-oriented protocols

Uses ports to identify the communicating process or application

Chapter 6: TRANSPORT LAYER PROTOCOLS 17

UDP HEADER AND FIELDS (PAGE 266)

Chapter 6: TRANSPORT LAYER PROTOCOLS 19

PORTS & SOCKETS

A port number refers to a specific application or process running on a computer.

A socket is a combination of a port number and an IP address. (ex: 192.168.2.10:21) this socket addresses port 21 on the system with address 192.168.2.10

The Internet Assigned Numbers Authority (IANA) assigns well-known port numbers to common Internet applications.

Chapter 6: TRANSPORT LAYER PROTOCOLS 20

CLIENT AND WELL-KNOWN PORTS

There are two types of TCP and UDP ports: Client ports

Variable ports with a value from 1024 through 65,534

Server (well-known) ports Commonly used by applications and services

Port values with a value from 1 through 1023

Chapter 6: TRANSPORT LAYER PROTOCOLS 21

EXAMPLES OF WELL-KNOWN PORTS (TABLE 6-2 Page 268) TCP ports

File Transfer Protocol (FTP) 20 and 21 Telnet 23 Simple Mail Transfer Protocol (SMTP) 25

UDP ports Trivial File Transfer Protocol (TFTP) 69 Domain Name System (DNS) 53 Bootstrap Protocol/Dynamic Host

Configuration Protocol (BOOTP/DHCP) 67

Chapter 6: TRANSPORT LAYER PROTOCOLS 22

SOCKETS

Chapter 6: TRANSPORT LAYER PROTOCOLS 23

NOVELL SPX AND NCP

Novell’s NetWare operating system has two connection-oriented protocols that function at the transport layer: SPX

NCP

Chapter 6: TRANSPORT LAYER PROTOCOLS 24

SPX Characteristics

SPX is the acronym for Sequenced Packet Exchange.

SPX is a connection-oriented protocol.

It provides packet acknowledgment and flow control.

It is used infrequently by NetWare.

Messages are carried in Internet Packet Exchange (IPX) datagrams.

Chapter 6: TRANSPORT LAYER PROTOCOLS 25

NCP Characteristics

NCP is the acronym for NetWare Core Protocol.

NCP is used for NetWare file sharing traffic.

It is much more frequently used than SPX.

Messages are carried in IPX datagrams.

NCP requires an acknowledgment for each transmitted message.

Chapter 6: TRANSPORT LAYER PROTOCOLS 29

SUMMARY

Connection-oriented transport layer protocols like TCP, SPX, and NCP provide guaranteed, reliable delivery of datagrams. They all exhibit the same characteristics:

sequencing, acknowledgments, flow control, error correction and detection, session establishment, and teardown.

Connectionless transport layer protocols like UDP provide fast but unreliable delivery of datagrams. They do not use sequencing, acknowledgments,

flow control, or error correction. There is no session establishment or teardown.