1. Working at a Small-to-Medium Business or ISP – Chapter 7
ISP Services
Working at a Small-to-Medium Business or ISP – Chapter 7

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.

3. Introducing ISP Services
Critical services for small-to-medium businesses:
Web hosting
Media streaming
IP telephony
File transfer

4. Introducing ISP Services
Meeting customer requirements:
Reliability
Availability

5. Protocols That Support ISP Services
The TCP/IP suite of protocols supports reliability

6. Protocols That Support ISP Services
Transport needs determine the choice of Transport Layer Protocol

7. Protocols That Support ISP Services
The TCP three-way handshake:
Synchronization
Synchronization acknowledgement
Acknowledgement

8. Protocols That Support ISP Services
How TCP supports reliability:
Acknowledgement
Retransmission
Sequencing
Flow control

9. Protocols That Support ISP Services
UDP: not connection-oriented, simple protocol
Used by online games, DHCP, DNS

10. Protocols That Support ISP Services
TCP and UDP use ports to support multiple services

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

12. Domain Name System (DNS)
Networking naming systems translate human-readable names into machine-readable addresses
srv2

13. Domain Name System (DNS)
Advantages of DNS:
Hierarchical structure
Small, manageable zones
Scalable

14. Domain Name System (DNS)
Components of DNS:
Resource records and domain namespace
Domain name system servers
Resolvers

15. Domain Name System (DNS)
DNS name resolution:
Dynamic updates
Forward lookup zones
Reverse lookup zones
Primary zones
Secondary zones

16. Domain Name System (DNS)
Implementing DNS solutions:
ISP DNS servers
Local DNS servers

17. Services and Protocols
ISPs provide many business-oriented services
Secure versions of Application Layer protocols support customer security requirements

18. Services and Protocols
HTTP is a request-response protocol
HTTPS adds authentication and encryption

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

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

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.