Architecture and Protocol Layering

1. UNIT-1
ARCHITECTURE AND PROTOCOL LAYERING

2. Application level interconnection
Application gateways:
• Details of n/w connection
• Message protocol
• Advantage:
• No special hardware needed
• Original email system remains unchanged.
• Disadvantage:
• Only handle one specific application
• Differences in functionality
• Frequency of upgrades
• No reliable communication
• Impossible to maintain a set of appln gateway that interconnect all n/w’s.

3. Network level interconnection
• Switching packets-alternative to appln-level gateway.
• Advantage:
• Efficient
• Separates data communication activity from appln pgms
• Flexible
• Can add / change n/w technologies.
• Internetworking / internet
• To built a unified, cooperative interconnection of networks that supports a
universal communication service.
• focuses on encapsulation: we want to hide the underlying internet
architecture from users, and permit communication without requiring
knowledge of the internet’s structure.

4. Internet architecture
• how are networks interconnected to form an internetwork?
• two networks cannot be plugged together directly.
• hardware needed to connect to each network.
• Internet routers / IP routers – interconnect networks.
• Bridge - can only connect two networks that use the same
technology.

5. Interconnection of multiple networks with IP
router
• A realistic internet will include multiple networks and routers.
• Each router needs to know about networks beyond the networks to
which it connects directly.
• IP routers provide interconnections among physical networks.
• router must handle packets for networks to which the router does
not attach.
• Work: making decisions about where to send packets becomes more
complex.

6. User view
• Users view an internet as a single, virtual network will connect all
machines with physical connections.
• Advantage:
• only the internet software needs to react when new physical connections are
added or existing connections are removed.
• Subtle.

7. Protocol layering

8. Need for multiple protocols
• Hardware failure
• Network congestion
• Packet delay or packet loss
• Data corruption
• Data duplication or inverted arrivals

9. ISO-7 layer reference model

10. • Physical layer - physical interconnection between computers and
network packet switches.
• Data link layer –
• Format of frames, Frame boundaries
• Error detection
• Timeout mechanism
• Network layer – interaction b/w host and network. Destination
addressing and forwarding.
• Transport layer – end to end. Reliability check.
• Session layer - describe how protocol software can be organized to
handle all the functionality needed by application programs.
• Presentation layer - standardize the format of data that application
programs send over a network.
• Application layer - includes application programs that use the
network.

11. TCP/IP 5-layer reference model

12. • Application layer – chooses the style of transport needed (individual
message / continuous stream of bytes)
• Transport layer – provide communication from one appln pgm to
another. End to end. Flow control. Reliable transport.
• Internet layer – encapsulates the transport packet in an IP packet.
Forwarding.
• Network interface layer –
• MAC layer / data link layer
• Accepts IP packets and transmitting them over a specific network.
Protocol layering principles :
• Protocol design independence
• Definition of the end-to-end property

13. TCP/IP

14. Layering principle

15. Boundaries in TCP/IP model

16. • High level protocol address boundary
• Operating system boundary
• Multiplexing and demultiplexing