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Transcript of chap6 network layer protocol
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The Transport Layer
Chapter 6
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The Transport Service
Services Provided to the Upper Layers
Transport Service Primitives
Berkeley Sockets
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Services Provided to the Upper Layers
The network, transport, and application layers.
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Transport Service Primitives
The primitives for a simple transport service.
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Transport Service Primitives (2)
The nesting of TPDUs, packets, and frames.
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Transport Service Primitives (3)
A state diagram for a simple connection management scheme.
Transitions labeled in italics are caused by packet arrivals. The
solid lines show the client's state sequence. The dashed lines show
the server's state sequence.
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Berkeley Sockets
The socket primitives for TCP.
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Elements of Transport Protocols
Addressing
Connection Establishment
Connection Release Flow Control and Buffering
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Transport Protocol
(a) Environment of the data link layer.
(b) Environment of the transport layer.
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Connection Establishment
How a user process in host 1 establishes a connection
with a time-of-day server in host 2.
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Connection Establishment(1)
Packet lifetime can be restricted to a known maximum
using one of the following techniques
1. Restricted subnet design
2. Putting a hop counter in each packet
3. Time stamping each packet
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Connection Establishment (2)
Three protocol scenarios for establishing a connection using athree-way handshake. CR denotes CONNECTION REQUEST.
(a) Normal operation,
(b) Old CONNECTION REQUEST appearing out of nowhere.
(c) Duplicate CONNECTION REQUEST and duplicate ACK.
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Connection Release
Abrupt disconnection with loss of data.
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Connection Release (2)
The two-army problem.
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Connection Release (3)
Four protocol scenarios for releasing a connection. (a) Normal case of a
three-way handshake. (b) final ACK lost.
6-14, a, b
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Connection Release (4)
(c) Response lost. (d) Response lost and subsequent DRs lost.
6-14, c,d
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Flow Control and Buffering
(a) Chained fixed-size buffers. (b) Chained variable-sized buffers.
(c) One large circular buffer per connection.
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The Internet Transport Protocols: UDP
Introduction to UDP
Remote Procedure Call
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Introduction to UDP
The UDP header.
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Remote Procedure Call
Steps in making a remote procedure call. The stubs are shaded.
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TCP Protocol
- TCP has TCP entity- Break data into pieces not exceeding than 64KB & send as IP
datagram
- 16 bit port number
- Below 1024 are well known ports
- inetd (internet daemon)
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The TCP Service Model
Some assigned ports.
Port Protocol Use21 FTP File transfer23 Telnet Remote login
25 SMTP E-mail69 TFTP Trivial File Transfer Protocol
79 Finger Lookup info about a user80 HTTP World Wide Web
110 POP-3 Remote e-mail access
119 NNTP USENET news
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The TCP Segment Header
TCP Header.
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The TCP Segment Header (2)
The pseudoheader included in the TCP checksum.
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TCP Connection Establishment
(a) TCP connection establishment in the normal case.
(b) Call collision.
6-31
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TCP Connection Release
- Connections are full duplex
- Send FIN to release connection
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TCP Transmission Policy
Window management in TCP.
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TCP Transmission Policy
- Ex. Telnet connection to interactive editor that react on every key
stroke
- creates 21 byte TCP segment & 41 byte IP datagram
- Wastage of bandwidth
- delay Ack
- Nagle's Algorithm
Send first byte & buffer all until outstanding byte is
acknowledged
Send all buffered characterStart buffering again until they are all acknowledged
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TCP Transmission Policy (2)
Silly window syndrome.
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Clark solution
- Prevent the receiver from sending window update for 1 byte- forced to wait until it has decent amount of space available
- Receiver should not update window size until it can handle
maximum size
- Sender should not send tiny segments & wait till large data comes
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TCP Congestion Control
- Do not inject the packets until old one delivered
- Congestion can be prevented by
Specifying suitable window size
receiver can specify window based on it's buffer size
problem may occur due to internal congestion within network
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TCP Congestion Control
(a) A fast network feeding a low capacity receiver.
(b) A slow network feeding a high capacity receiver