Week 4 Flashcards
What are layers of a network?
Each layer implements a service, relying on services implemented by a layer below
Why is layering good?
- modularization
- ease of maintenance
What are the 5 Internet Layer Stacks
- App
- Transport
- Network
- Link
- Physical
What does the Application Layer do?
supporting network apps through HTTP, IMAP, SMTP, DNS
Info: MESSAGE
What does the Transport Layer do?
Process to process data transfer (TCP and UDP)
Info: SEGMENT
What does the Network Layer do?
moving packets known as DATAGRAMS.
What does the Link layer do?
Data transfer between neighboring elements (within the same network) called FRAMES
What does the Physical Layer do?
bits “on the wire”
Order of layering?
App > Transport > Network > Link > Physical
What are the 2 Main Network Architechtures?
- Client-Server Architecture
- P2P Architecture
Explain the Client-Server structure
Server:
- always on host, permanent IP address
- ideally data centers
Client:
- initiates contact with the server.
- Clients do not interact with other clients
example: HTTP, IMAP, FTP
Explain the P2P Architechture
- minimal or no reliance on dedicated servers
- direct communication between hosts.
How do Client-Servers processes interact with each other?
Through SOCKETS. send/receive through sockets, like a door.
What are sockets?
where a process sends messages into and receives messages from.
“door” of 2 houses, connecting the inside, outside, + road (link)
What info do we need to identify a process?
- Host’s address
- Port number
4 types/dimensions of transfer service an app needs?
- Reliable data transfer
- Throughput
- Timing / delay
- Security
What are the 2 Main Transport services provided by the internet?
TCP and UDP
For text-apps, what transfer servies would it need?
-No data loss
- Time sensitive (FOR TEXTS)
For images/video apps, what transfer services would it need?
- Throughput
- Timing / delay sensitive
Explain the TCP service.
- Connection oriented
- Has congestion control
Pros of TCP
- No loss (provides reliability)
- Congestion controlC
Cons of TCP
- does NOT provide:
- guaranteed timing, security, throughput
Explain the UDP service model
- lightweight transport protocol with minimal services
- no handshaking required
Pros of UDP
- UDP has no constraints unlike TCP, you can send as much as you wantC