isp services
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© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 1Version 4.1
ISP Services
Working at a Small-to-Medium Business or ISP – Chapter 7
2© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Objectives Describe the network services provided by an ISP.
Describe the protocols that support the network services provided by an ISP.
Describe the purpose, function, and hierarchical nature of the Domain Name System (DNS).
Describe and enable common services and their protocols.
3© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Introducing ISP ServicesCritical services for small-to-medium businesses:
Web hosting
Media streaming
IP telephony
File transfer
4© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Introducing ISP ServicesMeeting customer requirements:
Reliability
Availability
5© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Protocols That Support ISP Services The TCP/IP suite of protocols supports
reliability
6© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Protocols That Support ISP Services Transport needs determine the choice of
Transport Layer Protocol
7© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Protocols That Support ISP ServicesThe TCP three-way handshake:
Synchronization
Synchronization acknowledgement
Acknowledgement
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Protocols That Support ISP ServicesHow TCP supports reliability:
Acknowledgement
Retransmission
Sequencing
Flow control
9© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Protocols That Support ISP Services UDP: not connection-oriented, simple protocol
Used by online games, DHCP, DNS
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Protocols That Support ISP Services TCP and UDP use ports to support multiple
services
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Protocols That Support ISP Services Socket: combination of Transport Layer port
number and Network Layer IP address of host
Socket pair: source and destination IPs and port numbers identify each conversation
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Domain Name System (DNS) Networking naming systems translate human-
readable names into machine-readable addresses
srv2
13© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Domain Name System (DNS)Advantages of DNS:
Hierarchical structure
Small, manageable zones
Scalable
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Domain Name System (DNS)Components of DNS:
Resource records and domain namespace
Domain name system servers
Resolvers
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Domain Name System (DNS)DNS name resolution:
Dynamic updates
Forward lookup zones
Reverse lookup zones
Primary zones
Secondary zones
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Domain Name System (DNS)Implementing DNS solutions:
ISP DNS servers
Local DNS servers
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Services and Protocols ISPs provide many business-oriented services
Secure versions of Application Layer protocols support customer security requirements
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Services and Protocols HTTP is a request-response protocol
HTTPS adds authentication and encryption
19© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Services and Protocols FTP uses a protocol interpreter (PI) and data
transfer process (DTP)
Two connections: one to send commands, one for actual file data transfer
20© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Services and Protocols SMTP: specific message format and processes
running on both client and server
POP3: mail is downloaded from server to client and then deleted
IMAP4: keeps messages on server
21© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public
Summary TCP and UDP use port numbers to provide multiple
services to hosts.
DNS uses a hierarchical system of databases to resolve names and IP addresses of known hosts within networks and across the Internet.
The most common services used on the Internet include FTP, FTPS, HTTP, HTTPS and SMTP.
ISPs use high-performance servers to support these services.
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