overview of tcp/ip1-1 overview of tcp/ip system administrators and network administrators why...

Overview of TCP/IP 1-1

Overview of TCP/IP

System Administrators and network administrators

Why networking - communication Why TCP/IP

Provides interoperable communications between all types of hardware and all kinds of operating systems.

What is TCP/IP An entire suite of data communication protocols, Transmission Control Protocol (TCP) and the Internet

Protocol (IP) are two of those protocols in the suite


TCP/IP and Internet

1969 ARPAnet Experimental packet-switching network Study robust, reliable, vendor-independent data

communication Very successful

1975 ARPAnet became operation network Development continuing TCP/IP was developed

1983 TCP/IP protocols were adopted as Military Standards TCP/IP was implemented in Berkeley Unix. ARPAnet was divided into MILNET and ARPAnet


TCP/IP and Internet

1985 NSFNet Connected to the then existing Internet

( MILNET plus ARPAnet) Linked together the five NSF super

computer centers Wanted to extend the network to every

scientist 1987 new NSFNet backbone

Faster Three-tiered topology: backbone, regional

networks, and local networks.


TCP/IP and Internet

1990 ARPAnet passed out of existence 1995 NSFnet ceased its role as a primary

Internet backbone network Today Internet is build by commercial

providers. Infrastructure is being created by

• National network provider, caller tier-one providers

• Regional network provider Local access and user services is provided by

Internet Service Providers (ISPs) Network Access Points (NAPS): major

interconnection points


Internet structure: network of networks

roughly hierarchical at center: “tier-1” ISPs (e.g., UUNet, BBN/Genuity,

Sprint, AT&T), national/international coverage treat each other as equals

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

Tier-1 providers interconnect (peer) privately

NAP

Tier-1 providers also interconnect at public network access points (NAPs)


Tier-1 ISP: e.g., SprintSprint US backbone network


Tier-1 ISP: e.g., UUNETUUNET Backbone Connectivity



“Tier-2” ISPs: smaller (often regional) ISPs Connect to one or more tier-1 ISPs, possibly other tier-2

ISPs

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP

Tier-2 ISPTier-2 ISP

Tier-2 ISP Tier-2 ISP

Tier-2 ISP

Tier-2 ISP pays tier-1 ISP for connectivity to rest of Internet tier-2 ISP is customer oftier-1 provider

Tier-2 ISPs also peer privately with each other, interconnect at NAP


Tier-2 ISP: e.g., Abilene (Internet2)

http://loadrunner.uits.iu.edu/weathermaps/abilene/abilene.html



“Tier-3” ISPs and local ISPs last hop (“access”) network (closest to end systems)

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP



Tier-2 ISP

localISPlocal

ISPlocalISP

localISP

localISP Tier 3

ISP

localISP

localISP

localISP

Local and tier- 3 ISPs are customers ofhigher tier ISPsconnecting them to rest of Internet



a packet passes through many networks!

Tier 1 ISP

Tier 1 ISP

Tier 1 ISP

NAP



Tier-2 ISP

localISPlocal

ISPlocalISP

localISP

localISP Tier 3

ISP

localISP

localISP

localISP


TCP/IP and the Internet

Internet has evolved From a simple backbone network Through a three-tiered hierarchical structure To a huge network of interconnected, distributed

network hubs. Doubling in size every year since 1983 est. 50 million host, 100 million+ users One thing remained constant:

Internet is build on the TCP/IP protocol. The growth of the Internet spurred interest in

TCP/IP – it is popular. Other network applications, email, html, http,

Mosaic,instant messaging, games Local area networking even not connected to Internet. Enterprise networks intranets.


TCP/IP Features

TCP/IP met the need at the right time. Open protocol standards

Free Developed independently from any specific

computer hardware or operating system Independence from specific physical

network hardware. Ethernet DSL connection Dial-up line Optical networkVirtually any other kind of transmission

medium.


TCP/IP Features

Common addressing scheme – allow uniquely address any device in the entire network.

Standardized high-level protocols for consistent, widely available user services.


Protocol Standards What is protocol?

Formal rules of behavior. Internet Standards are developed by Internet

Engineering Task Force (IETE) in open, public meetings.

Requests for Comments (RFCs) Standards (STD) Best current practices (BCP) Informational (FYI)

Official Internet standard is rigorous Proposed Standard Draft Standard

• At least two interoperable implementations Internet Standard

• Extensive testing • Significant benefit to the internet community.


Protocol Standards

Two categoriesTechnical Specification – defines a

protocolApplicability Statement – defines

when the protocol is to be used.• Required• Recommended• Elective

More than 3000 RFCs.


Internet protocol stack application: supporting network

applications FTP, SMTP, HTTP

transport: host-host data transfer TCP, UDP

Internet: defines the datagram and handles the routing of data. IP, routing protocols

Network Access Layer: Consist of routines for accessing physical network. PPP, Ethernet

Application

Transport

Internet

Network Access


Internet protocol stackApplication Layer : Data

Transport Layer Header : Header DataHeader Data

Internet Layer : Header Header Data

Network Access Layer: Header Header Header Data


Network Access Layer

provide the means to deliver data to other device

Encompass functions of Network, Datalink and Physical in OSI Reference Model

Many access protocol – one for each physical network. New hardware needs new protocol. Typically show as device drivers and related programs.

Functions: Encapsulation of IP datagrams to frames Mapping IP addresses to physical addresses.


Internet Layer

Internet Protocol (IP) is the most important in this layer IPv4 and IPv6 Internet Protocol Functions

Defining the datagram Defining the Internet addressing scheme Moving data between Network Access Layer and the

Transport Layer Routing datagrams to remote hosts Performing fragmentation and re-assembly of datagrams.

IP is connectionless protocol IP depends on other layers to do error

detection and error recovery – some time called unreliable protocol


The Datagram

Version IHL Type of Service

Total Length

Identification flags Fragmentation offset

Time to Live

Protocol Herder Checksum

Source Address

Destination Address

Options Padding

Data begins here

IP datagram format

1

2

3

4

5

6


Datagrams IP delivers by checking destination address

Host on same network, diver directly Otherwise, routing via gateway

Routing datagrams Host -> gateway -> gateway … -> host

Fragmenting datagrams Maxium transmission unit (MTU) for each type of

network If the datagram received from one network is longer

than the other network’s MTU, it must be divided into smaller fragments.

Header word 2 contains info that identifies which datagram and info how to re-assemble them

• Identification – what datagram the fragment belongs to• Offset – what piece of the datagram • Flag – more fragments bit


Passing datagrams to the transport layer

Done by using protocol number from word3

Internet Control Message Protocol (ICMP) Part of internet layer Uses the IP datagram delivery facility to

send message Functions

• Flow control – ICMP Source Quench Message, ask source to stop sending temporarily

• Detecting unreachable destinations – Destination Unreachable Message for host and port

• Redirecting routes – ICMP Redirect Message• Checking remote hosts – ICMP Echo Message

– Ping


Transport Layer Two most important protocal

Transition Control Protocol (TCP)• Reliable data delivery

User Datagram Protocol (UDP)• Low-overhead, connectionless datagram delivery

UDP No techniques in the protocol to verify data

reached the other end 16-bit sort port and destination port Why use UDP?

• Small data• Query-response model application• Application provide their own techniques for

reliable data delivery


Transport Layer UDP Message format

Source Port Destination Port

Length Checksum

Data begins here

0 16 31


Transport Layer TCP

Reliable• Positive Acknowledgment with Retransmission

(PAR) connection-oriented

• Establish a logical end-to-end connection• Three-way Handshake before data is transmitted

Host A Host BSYN SYN,ACK

ACK,data


Transport Layer TCP

Byte-stream data• TCP views data as continuous stream of bytes• Sequence Number and Acknowledgement

Number keep track of the bytes• Exchanging initial sequence number (ISN) –

random number• First byte of data has Sequence number ISN+1• Sequence number identifies the sequential

position in the data stream of the first data byte in the segment.

Acknowledgment Segment (ACK)• Positive acknowledgement• Flow control - window


Transport Layer TCP segment format

Source Port Destination port

Sequence Number

Acknowledgement number

Offset Reserved

Flags Window

Checksum Urgent Pointer

Options Padding

Data begins here

0 16 31


Application Layer Included all processes that use the Transport

Layer protocols to deliver data telnet

• Remote login over network ftp

• File transfer protocol for transferring files between hosts

SMTP• Simple Mail Transfer protocol, which delivers electronic

mail HTTP

• Hypertext transfer protocol, delivers web pages over the network.

Domain Name System (DNS)• Map IP addresses to the names assigned to network

devices.


Application Layer Network File System (NFS)

• Allows files to be shared by various hosts. Programming network application: socket

API


Summary

We’ve talked about TCP/IP and Internet TCP/IP four layers: applications,

transport, Internet and Network Access.

Next, we will look how IP datagram moves through a network when data is delivered between hosts.

overview of tcp/ip1-1 overview of tcp/ip system administrators and network administrators why...

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