[PPT] - Networking Network layer Three concepts Naming A way to identify PowerPoint Presentation

SLIDE 1

Networking — Network layer

Three concepts

Naming
A way to identify the source/destination
E.g., house address
Routing
Finding “how to” move towards the destination
E.g., which airplane should the stuff go on
Forwarding
Actually “moving” towards the destination
E.g., Using airplane/truck/rail

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Network layer — Forwarding

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Network layer — Forwarding

Lets come up with an approach? Generalize Ethernet ideas?

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Network layer — Forwarding

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Attempt 1: Broadcast

Network layer — Forwarding

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Attempt 1: Broadcast

Send to everybody

Network layer — Forwarding

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Attempt 1: Broadcast

Send to everybody
Goods

Network layer — Forwarding

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Attempt 1: Broadcast

Send to everybody
Goods
Oh, well, simplicity

Network layer — Forwarding

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Attempt 1: Broadcast

Send to everybody
Goods
Oh, well, simplicity
Not-so-goods

Network layer — Forwarding

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Attempt 1: Broadcast

Send to everybody
Goods
Oh, well, simplicity
Not-so-goods
Oh, well, everything else

Network layer — Forwarding

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Attempt 1: Broadcast

Send to everybody
Goods
Oh, well, simplicity
Not-so-goods
Oh, well, everything else
Bandwidth overheads

Network layer — Forwarding

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Network layer — Forwarding

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Attempt 2: Time division Multiplexing

Network layer — Forwarding

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Attempt 2: Time division Multiplexing

Each source-destination pair assigned a time slot

Network layer — Forwarding

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Attempt 2: Time division Multiplexing

Each source-destination pair assigned a time slot
Can send data only during that slot

Network layer — Forwarding

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Attempt 2: Time division Multiplexing

Each source-destination pair assigned a time slot
Can send data only during that slot
Goods

Network layer — Forwarding

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Attempt 2: Time division Multiplexing

Each source-destination pair assigned a time slot
Can send data only during that slot
Goods
No collisions

Network layer — Forwarding

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Attempt 2: Time division Multiplexing

Each source-destination pair assigned a time slot
Can send data only during that slot
Goods
No collisions
Not-so-goods

Network layer — Forwarding

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Attempt 2: Time division Multiplexing

Each source-destination pair assigned a time slot
Can send data only during that slot
Goods
No collisions
Not-so-goods
Underutilization of resources

Network layer — Forwarding

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Network layer — Forwarding

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Attempt 3: Frequency division Multiplexing

Network layer — Forwarding

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Attempt 3: Frequency division Multiplexing

Each source-destination pair assigned a subset of resources

Network layer — Forwarding

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Attempt 3: Frequency division Multiplexing

Each source-destination pair assigned a subset of resources
Can use only “assigned” resources (e.g., bandwidth)

Network layer — Forwarding

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Attempt 3: Frequency division Multiplexing

Each source-destination pair assigned a subset of resources
Can use only “assigned” resources (e.g., bandwidth)
Goods

Network layer — Forwarding

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Attempt 3: Frequency division Multiplexing

Each source-destination pair assigned a subset of resources
Can use only “assigned” resources (e.g., bandwidth)
Goods
Predictable performance

Network layer — Forwarding

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Attempt 3: Frequency division Multiplexing

Each source-destination pair assigned a subset of resources
Can use only “assigned” resources (e.g., bandwidth)
Goods
Predictable performance
Not-so-goods

Network layer — Forwarding

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Attempt 3: Frequency division Multiplexing

Each source-destination pair assigned a subset of resources
Can use only “assigned” resources (e.g., bandwidth)
Goods
Predictable performance
Not-so-goods
Underutilization of resources

Network layer — Forwarding

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Network layer — Forwarding

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Attempt 2 and 3: Circuit Switching

Network layer — Forwarding

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Attempt 2 and 3: Circuit Switching

Source establishes connection

Network layer — Forwarding

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Attempt 2 and 3: Circuit Switching

Source establishes connection
Resources along the path are reserved

Network layer — Forwarding

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Attempt 2 and 3: Circuit Switching

Source establishes connection
Resources along the path are reserved
Source sends data

Network layer — Forwarding

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Attempt 2 and 3: Circuit Switching

Source establishes connection
Resources along the path are reserved
Source sends data
Transmit data using the reserved resources

Network layer — Forwarding

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Attempt 2 and 3: Circuit Switching

Source establishes connection
Resources along the path are reserved
Source sends data
Transmit data using the reserved resources
Source tears down connection

Network layer — Forwarding

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Attempt 2 and 3: Circuit Switching

Source establishes connection
Resources along the path are reserved
Source sends data
Transmit data using the reserved resources
Source tears down connection
Free resources for others to use

Network layer — Forwarding

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Network layer — Forwarding

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Circuit Switching

Network layer — Forwarding

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Circuit Switching

Goods:

Network layer — Forwarding

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Circuit Switching

Goods:
Predictable performance

Network layer — Forwarding

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Circuit Switching

Goods:
Predictable performance
Reliable delivery

Network layer — Forwarding

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Circuit Switching

Goods:
Predictable performance
Reliable delivery
Simple forwarding mechanism

Network layer — Forwarding

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Circuit Switching

Goods:
Predictable performance
Reliable delivery
Simple forwarding mechanism
Not-so-goods

Network layer — Forwarding

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Circuit Switching

Goods:
Predictable performance
Reliable delivery
Simple forwarding mechanism
Not-so-goods
Resource underutilization

Network layer — Forwarding

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Circuit Switching

Goods:
Predictable performance
Reliable delivery
Simple forwarding mechanism
Not-so-goods
Resource underutilization
Blocked connections

Network layer — Forwarding

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Circuit Switching

Goods:
Predictable performance
Reliable delivery
Simple forwarding mechanism
Not-so-goods
Resource underutilization
Blocked connections
Connection set up overheads

Network layer — Forwarding

SLIDE 46

Circuit Switching

Goods:
Predictable performance
Reliable delivery
Simple forwarding mechanism
Not-so-goods
Resource underutilization
Blocked connections
Connection set up overheads
Per-connection state in switches (scalability problem)

Network layer — Forwarding

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Network layer — Forwarding

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Attempt 4: Packet Switching

Network layer — Forwarding

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Attempt 4: Packet Switching

Divide the message into packets

Network layer — Forwarding

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Attempt 4: Packet Switching

Divide the message into packets
Put destination address in the header of each packet

Network layer — Forwarding

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Attempt 4: Packet Switching

Divide the message into packets
Put destination address in the header of each packet
Just like shipping stuff

Network layer — Forwarding

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Attempt 4: Packet Switching

Divide the message into packets
Put destination address in the header of each packet
Just like shipping stuff
Each device stores a “look-up table”

Network layer — Forwarding

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Attempt 4: Packet Switching

Divide the message into packets
Put destination address in the header of each packet
Just like shipping stuff
Each device stores a “look-up table”
Whats the next hop towards the destination?

Network layer — Forwarding

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Attempt 4: Packet Switching

Divide the message into packets
Put destination address in the header of each packet
Just like shipping stuff
Each device stores a “look-up table”
Whats the next hop towards the destination?
Destination receives the packet(s)

Network layer — Forwarding

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Attempt 4: Packet Switching

Divide the message into packets
Put destination address in the header of each packet
Just like shipping stuff
Each device stores a “look-up table”
Whats the next hop towards the destination?
Destination receives the packet(s)
And reconstructs the message

Network layer — Forwarding

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Network layer — Forwarding

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Packet Switched forwarding

Network layer — Forwarding

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Packet Switched forwarding

Hop-by-hop forwarding

Network layer — Forwarding

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Packet Switched forwarding

Hop-by-hop forwarding
Each router has a “look-up table” (forwarding information base)

Network layer — Forwarding

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Packet Switched forwarding

Hop-by-hop forwarding
Each router has a “look-up table” (forwarding information base)
What should be stored in this table?

Network layer — Forwarding

SLIDE 61

Packet Switched forwarding

Hop-by-hop forwarding
Each router has a “look-up table” (forwarding information base)
What should be stored in this table?

Network layer — Forwarding

SLIDE 62

Packet Switched forwarding

Hop-by-hop forwarding
Each router has a “look-up table” (forwarding information base)
What should be stored in this table?
Prefix-based forwarding (longest-prefix matching)

Network layer — Forwarding

SLIDE 63

Packet Switched forwarding

Hop-by-hop forwarding
Each router has a “look-up table” (forwarding information base)
What should be stored in this table?
Prefix-based forwarding (longest-prefix matching)
Maps prefixes to the next-hop

Network layer — Forwarding

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Network layer — Forwarding

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Packet Switching

Network layer — Forwarding

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Packet Switching

Goods:

Network layer — Forwarding

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Packet Switching

Goods:
No resource underutilization

Network layer — Forwarding

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Packet Switching

Goods:
No resource underutilization
A source can send more if others don’t use resources

Network layer — Forwarding

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Packet Switching

Goods:
No resource underutilization
A source can send more if others don’t use resources
No blocked connection problem

Network layer — Forwarding

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Packet Switching

Goods:
No resource underutilization
A source can send more if others don’t use resources
No blocked connection problem
No per-connection state

Network layer — Forwarding

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Packet Switching

Goods:
No resource underutilization
A source can send more if others don’t use resources
No blocked connection problem
No per-connection state
No set-up cost

Network layer — Forwarding

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Packet Switching

Goods:
No resource underutilization
A source can send more if others don’t use resources
No blocked connection problem
No per-connection state
No set-up cost
Not-so-goods:

Network layer — Forwarding

SLIDE 73

Packet Switching

Goods:
No resource underutilization
A source can send more if others don’t use resources
No blocked connection problem
No per-connection state
No set-up cost
Not-so-goods:
Packet header overhead

Network layer — Forwarding

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Packet Switching

Goods:
No resource underutilization
A source can send more if others don’t use resources
No blocked connection problem
No per-connection state
No set-up cost
Not-so-goods:
Packet header overhead
Network failures become a problem

Network layer — Forwarding

SLIDE 75

Networking — Network layer

Three concepts

Naming
A way to identify the source/destination
E.g., house address
Routing
Finding “how to” move towards the destination
E.g., which airplane should the stuff go on
Forwarding
Actually “moving” towards the destination
E.g., Using airplane/truck/rail

SLIDE 76

Network layer — Example

C

1 2 3 1 7

B A Dest.

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Network layer — Routing

SLIDE 78

Lets come up with a routing scheme

Network layer — Routing

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Network layer — Routing

C

1 2 3 1 7

B A Dest.

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Network layer — Routing

C

1 2 3 1 7

B A Dest.

A wants to find a path to Dest. {(A, 0)}

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Network layer — Routing

C

1 2 3 1 7

B A Dest.

A wants to find a path to Dest. {(A, 0)} A wants to find a path to Dest. {(A, 0), (B, 2)}

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Network layer — Routing

C

1 2 3 1 7

B A Dest.

A wants to find a path to Dest. {(A, 0)} A wants to find a path to Dest. {(A, 0), (B, 2)} A wants to find a path to Dest. {(A, 0), (C, 7)}

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Network layer — Routing

C

1 2 3 1 7

B A Dest.

A wants to find a path to Dest. {(A, 0)} A wants to find a path to Dest. {(A, 0), (B, 2)} A wants to find a path to Dest. {(A, 0), (C, 7)} Path to Dest. {(A, 0), (B, 2), (D, 3)}

SLIDE 84

Network layer — Routing

C

1 2 3 1 7

B A Dest.

A wants to find a path to Dest. {(A, 0)} A wants to find a path to Dest. {(A, 0), (B, 2)} A wants to find a path to Dest. {(A, 0), (C, 7)} Path to Dest. {(A, 0), (B, 2), (D, 3)} Path to Dest. {(A, 0), (C, 7), (D, 1)}

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Network layer — Routing

C

1 2 3 1 7

B A Dest.

A wants to find a path to Dest. {(A, 0)} A wants to find a path to Dest. {(A, 0), (B, 2)} A wants to find a path to Dest. {(A, 0), (C, 7)} Path to Dest. {(A, 0), (B, 2), (D, 3)} A wants to find a path to Dest. {(A, 0), (B, 2), (C, 1)} Path to Dest. {(A, 0), (C, 7), (D, 1)}

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Network layer — Routing

C

1 2 3 1 7

B A Dest.

A wants to find a path to Dest. {(A, 0)} A wants to find a path to Dest. {(A, 0), (B, 2)} A wants to find a path to Dest. {(A, 0), (C, 7)} Path to Dest. {(A, 0), (B, 2), (D, 3)} A wants to find a path to Dest. {(A, 0), (B, 2), (C, 1)} Path to Dest. {(A, 0), (C, 7), (D, 1)} Path to Dest. {(A, 0), (B, 2), (C, 1), (D, 1)}

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Network layer — Routing

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Attempt 1: Dynamic Source Routing

Network layer — Routing

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Attempt 1: Dynamic Source Routing

Broadcast a Route Request Packet for destination d

Network layer — Routing

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Attempt 1: Dynamic Source Routing

Broadcast a Route Request Packet for destination d
Put source ID in the packet header

Network layer — Routing

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Attempt 1: Dynamic Source Routing

Broadcast a Route Request Packet for destination d
Put source ID in the packet header
At each router

Network layer — Routing

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Attempt 1: Dynamic Source Routing

Broadcast a Route Request Packet for destination d
Put source ID in the packet header
At each router
If a path not known to the destination

Network layer — Routing

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Attempt 1: Dynamic Source Routing

Broadcast a Route Request Packet for destination d
Put source ID in the packet header
At each router
If a path not known to the destination
Put its {ID, cost} in the packet header

Network layer — Routing

SLIDE 94

Attempt 1: Dynamic Source Routing

Broadcast a Route Request Packet for destination d
Put source ID in the packet header
At each router
If a path not known to the destination
Put its {ID, cost} in the packet header
Broadcast the Route Request Packet

Network layer — Routing

SLIDE 95

Attempt 1: Dynamic Source Routing

Broadcast a Route Request Packet for destination d
Put source ID in the packet header
At each router
If a path not known to the destination
Put its {ID, cost} in the packet header
Broadcast the Route Request Packet
Else

Network layer — Routing

SLIDE 96

Attempt 1: Dynamic Source Routing

Broadcast a Route Request Packet for destination d
Put source ID in the packet header
At each router
If a path not known to the destination
Put its {ID, cost} in the packet header
Broadcast the Route Request Packet
Else
Respond with a Route Reply packet

Network layer — Routing

SLIDE 97

Attempt 1: Dynamic Source Routing

Broadcast a Route Request Packet for destination d
Put source ID in the packet header
At each router
If a path not known to the destination
Put its {ID, cost} in the packet header
Broadcast the Route Request Packet
Else
Respond with a Route Reply packet
Put known path in the packet header

Network layer — Routing

SLIDE 98

Attempt 1: Dynamic Source Routing

Broadcast a Route Request Packet for destination d
Put source ID in the packet header
At each router
If a path not known to the destination
Put its {ID, cost} in the packet header
Broadcast the Route Request Packet
Else
Respond with a Route Reply packet
Put known path in the packet header
Challenge?

Network layer — Routing

SLIDE 99

Network layer — Routing

C

1 2 3 1 7

B A Dest.

SLIDE 100

Network layer — Routing

C

1 2 3 1 7

B A Dest.

{(A-B, 0), (A-C, 7)}

SLIDE 101

Network layer — Routing

C

1 2 3 1 7

B A Dest.

{(A-B, 0), (A-C, 7)} {(A-B, 2), (B-C, 1), (B-D, 3)}

SLIDE 102

Network layer — Routing

C

1 2 3 1 7

B A Dest.

{(A-B, 0), (A-C, 7)} {(A-B, 2), (B-C, 1), (B-D, 3)} {(A-C, 7), (B-C, 1)}

SLIDE 103

Network layer — Routing

C

1 2 3 1 7

B A Dest.

{(A-B, 0), (A-C, 7)} {(A-B, 2), (B-C, 1), (B-D, 3)} {(A-C, 7), (B-C, 1)} {(B-D, 3), (C-D, 1)}

SLIDE 104

Network layer — Routing

C

1 2 3 1 7

B A Dest.

{(A-B, 0), (A-C, 7)} {(A-B, 2), (B-C, 1), (B-D, 3)} {(A-C, 7), (B-C, 1)} {(B-D, 3), (C-D, 1)} {(A-B, 0), (A-C, 7)}

SLIDE 105

Network layer — Routing

C

1 2 3 1 7

B A Dest.

{(A-B, 0), (A-C, 7)} {(A-B, 2), (B-C, 1), (B-D, 3)} {(A-C, 7), (B-C, 1)} {(B-D, 3), (C-D, 1)} {(A-B, 0), (A-C, 7)} {(B-D, 3), (C-D, 1)}

SLIDE 106

Network layer — Routing

C

1 2 3 1 7

B A Dest.

{(A-B, 0), (A-C, 7)} {(A-B, 2), (B-C, 1), (B-D, 3)} {(A-C, 7), (B-C, 1)} {(B-D, 3), (C-D, 1)} {(A-B, 0), (A-C, 7)} {(B-D, 3), (C-D, 1)} {(A-C, 7), (B-C, 1)}

SLIDE 107

Network layer — Routing

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Attempt 2: Link State Routing

Network layer — Routing

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Attempt 2: Link State Routing

Each router maintains its local “link state” (LS)

Network layer — Routing

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Attempt 2: Link State Routing

Each router maintains its local “link state” (LS)
Each router periodically “floods” its LS

Network layer — Routing

SLIDE 111

Attempt 2: Link State Routing

Each router maintains its local “link state” (LS)
Each router periodically “floods” its LS
And forwards all the LS received from other routers

Network layer — Routing

SLIDE 112

Attempt 2: Link State Routing

Each router maintains its local “link state” (LS)
Each router periodically “floods” its LS
And forwards all the LS received from other routers
At one point

Network layer — Routing

SLIDE 113

Attempt 2: Link State Routing

Each router maintains its local “link state” (LS)
Each router periodically “floods” its LS
And forwards all the LS received from other routers
At one point
Every router knows the entire topology

Network layer — Routing

SLIDE 114

Attempt 2: Link State Routing

Each router maintains its local “link state” (LS)
Each router periodically “floods” its LS
And forwards all the LS received from other routers
At one point
Every router knows the entire topology
Run a shortest path algorithm (e.g., Dijkstra) locally

Network layer — Routing

SLIDE 115

Attempt 2: Link State Routing

Each router maintains its local “link state” (LS)
Each router periodically “floods” its LS
And forwards all the LS received from other routers
At one point
Every router knows the entire topology
Run a shortest path algorithm (e.g., Dijkstra) locally
Find path to the destination

Network layer — Routing

SLIDE 116

Network layer — Routing

SLIDE 117

Network layer — Routing

SLIDE 118

Network layer — Routing

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Attempt 3: Distance Vector Routing

Network layer — Routing

SLIDE 120

Attempt 3: Distance Vector Routing

Each router

Network layer — Routing

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Attempt 3: Distance Vector Routing

Each router
maintains its “current distance to destination”

Network layer — Routing

SLIDE 122

Attempt 3: Distance Vector Routing

Each router
maintains its “current distance to destination”
Periodically announces it to all its neighbors

Network layer — Routing

SLIDE 123

Attempt 3: Distance Vector Routing

Each router
maintains its “current distance to destination”
Periodically announces it to all its neighbors
Update its local table

Network layer — Routing

SLIDE 124

Attempt 3: Distance Vector Routing

Each router
maintains its “current distance to destination”
Periodically announces it to all its neighbors
Update its local table
d(A, dest) = min{d(A, neighbor) + d(neighbor, dest)}

Network layer — Routing

SLIDE 125

Attempt 3: Distance Vector Routing

Each router
maintains its “current distance to destination”
Periodically announces it to all its neighbors
Update its local table
d(A, dest) = min{d(A, neighbor) + d(neighbor, dest)}
{dest — distance, neighbor-that-minimizes-distance}

Network layer — Routing

SLIDE 126

Attempt 3: Distance Vector Routing

Each router
maintains its “current distance to destination”
Periodically announces it to all its neighbors
Update its local table
d(A, dest) = min{d(A, neighbor) + d(neighbor, dest)}
{dest — distance, neighbor-that-minimizes-distance}
Broadcast to all its neighbors

Network layer — Routing

SLIDE 127