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CCNA Discovery 2 - Chapter 7
- 1. ISP Services
Working at a Small-to-Medium Business or ISP –
Chapter 7
Version 4.1 © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 1
- 2. 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.
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 2
- 3. Introducing ISP Services
Critical services for small-to-medium businesses:
Email
Web hosting
Media streaming
IP telephony
File transfer
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 3
- 5. Protocols That Support ISP Services
The TCP/IP suite of protocols supports
reliability
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 5
- 6. Protocols That Support ISP Services
Transport needs determine the choice of
Transport Layer Protocol
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 6
- 7. Protocols That Support ISP Services
The TCP three-way handshake:
Synchronization
Synchronization acknowledgement
Acknowledgement
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 7
- 8. Protocols That Support ISP Services
How TCP supports reliability:
Acknowledgement
Retransmission
Sequencing
Flow control
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 8
- 9. Protocols That Support ISP Services
UDP: not connection-oriented, simple protocol
Used by online games, DHCP, DNS
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 9
- 10. Protocols That Support ISP Services
TCP and UDP use ports to support multiple
services
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 10
- 11. 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
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 11
- 12. Domain Name System (DNS)
Networking naming systems translate human-
readable names into machine-readable
addresses
srv2
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 12
- 13. Domain Name System (DNS)
Advantages of DNS:
Hierarchical structure
Small, manageable zones
Scalable
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- 14. Domain Name System (DNS)
Components of DNS:
Resource records and domain namespace
Domain name system servers
Resolvers
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 14
- 15. Domain Name System (DNS)
DNS name resolution:
Dynamic updates
Forward lookup zones
Reverse lookup zones
Primary zones
Secondary zones
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 15
- 16. Domain Name System (DNS)
Implementing DNS solutions:
ISP DNS servers
Local DNS servers
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 16
- 17. Services and Protocols
ISPs provide many business-oriented services
Secure versions of Application Layer protocols
support customer security requirements
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 17
- 18. Services and Protocols
HTTP is a request-response protocol
HTTPS adds authentication and encryption
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 18
- 19. 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
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 19
- 20. 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
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 20
- 21. 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.
© 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 21
- 22. © 2007 Cisco Systems, Inc. All rights reserved. Cisco Public 22