Download Data Link Layer Switching

Connecting Networks by Relays
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Layer 1: Repeater / Hub
Layer 2: Bridge / Switch
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Spanning-tree algorithm
Source routing bridges
Remote bridges
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Application layer
4
Transport layer
3
Router
3
Network layer
2
Bridge
2
Data link layer
1
Repeater
1
Physical layer
Circuit switching
Message switching
Packet switching
Virtual circuit switching
Virtual circuit setup
Services
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Connection setup
QoS negotation
Flow control
A
H
IN0
H1
B0
H2
H3
H4
Connectionless
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Unreliable connections
No flow control
1
0
0
1
1
2
0
C
C
A
F
F
H
0
1
0
0
1
0
H
B
C
B
E
E
0
1
0
1
D
D
H
D
0
1
0
2
H
B
H
C
H
A
B
0
OUT
E 0
E 1
B1
E 2
E 3
C
D
C
F
F
C
A
E
A
A
A
Layer 4 - 5: Gateway / Protocol
Converter
18. May. 2006
A
B
H
H
A
H
F
Connection-oriented
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5
Types
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End system
Gateway
4
Layer 3: Router / Layer 3 Gateway /
Intermediate Systems
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Intermediate
system
5
Self-learning bridges
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End system
0
1
2
3
F
H
C
C
0
0
0
1
FE
B
B
D
0
0
1
0
D
D
H
B
0
1
0
1
2
H
H
H
H
F
0
1
2
3
0
Host
D
E
H
F
IMP
H
0
1
0
0
INF-3190: Overview
Internet

Address resolution
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Use broadcast to search
for an IP address
ARP and routing
Use broadcast to
acquire own IP address
18. May. 2006
H
H
@IP: 9.228.50.3
@HW: 0xa3e
H
H
@IP: unknown
@HW: 0xaa
DHCP
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H
ARP Response
source
@IP: 9.228.50.3
@HW: 0xa3e
target
@IP: 9.228.50.8
@HW: 0xaa
RARP
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ARP Request
source
@IP: 9.228.50.8
@HW: 0xaa
target
@IP: 9.228.50.3
@HW:
ARP
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H
H
RARP improvement
RARP Request
source
@IP:
@HW: 0xaa
target
@IP:
@HW: 0xaa
H
H
H
@IP: 9.228.50.3
@HW: 0xa3e
RARP Response
source
@IP: 9.228.50.3
@HW: 0xa3e
target
@IP: 9.228.50.8
@HW: 0xaa
2
INF-3190: Overview
Internet

Routing
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Routing tables
Direct routing / interior
protocols
Indirect routing / exterior
protocols
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Open Shortest Path First
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Spanning tree
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18. May. 2006
3
Distance path mechanism
Multicast routing
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AS boundary routers
Backbone routers
Area border routers
Internal routers
Link state routing
Border Gateway Protocol
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Autonomous systems
AS, AS backbone area,
area
Router classes
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EGP
Link state routing
Reverse path forwarding
with pruning
Core-based tree
Reverse path broadcast
Truncated reverse path
broadcast
INF-3190: Overview
Routing
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Routing
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define the route of packets
through the network
Routing algorithm
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Defines on which outgoing line an
incoming packet will be
transmitted
Desired properties
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Uses & Looks up
Data packets
Incoming
lines
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Forwarding
Process
Outgoing
lines
Routing table and
packet forwarding
Sink trees
Route determination

Routing
Process
Fills & Updates
Optimality principle
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
Correctness
Simplicity
Robustness
Stability
Fairness
Optimality
Router
Topology, link utilization, etc.
information
destilink
nation
A
0
Routing
B
3
table
C
1
D
4
Datagram
Virtual circuit
18. May. 2006
4
INF-3190: Overview
Routing
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Classes of routing algorithm
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Non-adaptive
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B (2,A)
2
Non-adaptive shortest path
routing
Flooding and selective
flooding
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1
3
D (●,-)
F (●,-)
2
2
4
H (●,-)
Dijkstra shortest path
A
B
Backward learning
D
C
G
E
H
F
I
Distributed routing
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2
G (6,A)
Centralized routing
Isolated routing
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3
E (●,-)
6
Adaptive
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2
A
C (●,-)
7
J
K
L
A
B
C
D
E
F
G
H
I
J
K
L
Distance Vector
Routing
delay
Distance vector routing

Count-to-infinity
problem
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Split-horizon
Link state routing
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Definitions of distance

Oscillations (route
flapping)
A
0
12
25
40
14
23
18
17
21
9
24
29
I
24
36
18
27
7
20
31
20
0
11
22
33
H
20
31
19
8
30
19
6
0
14
7
22
9
K
21
28
36
24
22
40
31
19
22
10
0
9
JA
8
JI
10
JH
12
JK
6
8
20
28
20
17
30
18
12
10
0
6
15
line
A
A
I
H
I
I
H
H
I
K
K
Link State Packets:
B
2
C
4
3
A
1
5
E
D
6
8
7
F
A
Seq.
Age
B 4
E 5
B
Seq.
Age
A 4
C 2
F 6
C
Seq.
Age
B 2
D 3
E 1
D
Seq.
Age
C 3
F 7
E
Seq.
Age
A 5
C 1
F 8
F
Seq.
Age
B 6
D 7
E 8
Link State Routing
18. May. 2006
5
INF-3190: Overview
Internet

Internet Protocol Stack
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IP
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TCP
Connectionless datagram
server
Segmentation /
reassembly
Route recording and
source routing
Transport
layer
UDP
IP
+ ICMP
+ ARP
Network
layer
Data link and
Physical layer
WANs LLC & MAC LANs
ATM
physical
MANs
Internet Protocols
IP networks
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IPv4 Addressing
Network classes
Subnetworks
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Netmasks to find
subnetworks
e.g. address
129.8.7.2:
Subnet mask:
Subnet address:
CIDR
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Application
layer
14
6
16 10
10
Network
Subnet Host Host
10000001000010000000011100000010
&
&
11111111111111111111110000000000
10000001000010000000010000000000
subnet address
with netmask use either
129.8.4.0/255.255.252.0
or
129.8.4.0/22
IPv4 address, netmask and
subnet address
Longest match prefix to
find subnetworks
IPv4 vs IPv6
18. May. 2006
6
INF-3190: Overview
Transport Protocols & Network Services
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Transport layer protocol
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ISO
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Transport layer protocol
depends on the quality of
the network layer service
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ISO Network types A, B,
C
Transport protocol
classes 0 – 4
TCP state machine
CLOSED
Internet protocols
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Timeout
LISTEN
User Datagram Protocol
Transmission Control
Protocol
SYN RCVD
Send FIN
FIN WAIT 1
Recv SYN Send SYN ACK
ESTABLISHED
Recv FIN Send ACK
SYN SENT
CLOSE WAIT
Recv FIN
Send ACK
LAST ACK
Send FIN
CLOSING
Recv ACK
Recv ACK
Timeout
FIN WAIT 2
18. May. 2006
7
Recv FIN Send ACK
TIME WAIT
INF-3190: Overview
TCP
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Features
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IP fragmentation vs TCP segmentation
RTT estimation for timer management
Initial sequence number allocation
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Reuse of session identifiers
High bandwidth or long-lived slow sessions
Limit transmission rate
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Both needed
Flow Control
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Congestion Control
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18. May. 2006
Receiver capacity
Network capacity
8
INF-3190: Overview
Flow Control
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Approaches
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Sliding window / static
buffer allocation
Sliding window / no buffer
allocation
Credit mechanism
TCP credit mechanism
Sender
Receiver
A wants 8 buffers
<req 8 buffers>
A has 3 buffers left

TCP’s flow control
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A has 2 buffers left

<seq=0, data=m0>
Message lost but A thinks it has 1 left
Sliding window and credit
mechanism
Nagle’s algorithm
Silly window problem
<seq=2, data=m2>
B acknowledges 0 and 1
permits 2-4
<ack=1, cred=3>
A has 1 buffer left
<seq=3, data=m3>
Everything acknowledged
but no free buffers
<seq=4, data=m4>
A has 0 buffer left, must stop
<seq=2, data=m2>
B found a new buffer
somewhere
<ack=4, cred=0>
<ack=4, cred=1>
A still blocked
<ack=4, cred=2>
A may now send next msg.
A has 1 buffer left
A still blocked
9
A has 1 buffer left
<seq=5, data=m5>
<seq=6, data=m6>
A is now blocked again
<ack=6, cred=0>
<ack=6, cred=4>
A is now blocked again
18. May. 2006
Message lost
<seq=1, data=m1>
A times out and retransmits

B grants messages 0-3 only
<cred=4>
time
time
INF-3190: Overview
Congestion Control
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Congestion control
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Can worsen without care
Approaches
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Repair
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Choke packets
B
C
A
D
E
F
Avoid
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18. May. 2006
Packet dropping
 Max buffer, min
buffer, content
related
Choke packets
 Threshold and
history, several
levels
Fair queueing
Traffic shaping
 Leaky bucket
 Token bucket
Reservation
Original packet arrival
Smoothed stream
Peak rate
time
Traffic shaping
10
INF-3190: Overview
Congestion Control and Avoidance
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Congestion control with TCP
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Additive increase, multiplicative
decrease
Congestion Window Development
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Slow start
Congestion window threshold
Congestion avoidance phase
Missing ACKs
Timeout
TCP congestion control
Congestion avoidance with RED
and ECN
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Random Early Detection
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receiver
80
75
70
65
60
55
50
45
40
35
30
25
20
15
10
5
Decrease


sender
time
Tail drop
Drop packets randomly when IS
queues fill up
RED
Early Congestion Notification

Mark packets instead of dropping
when IS queues fill up
ECN
Router queues with RED and ECN
18. May. 2006
11
INF-3190: Overview
Quality of Service

QoS: Characterizes the well defined, controllable behavior of a system
with regard to quantitatively measurable parameters

Techniques to Fulfill Requirements

Delay and jitter

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Continuity

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Reservation, Buffering, Scaling
Real-time packet re-ordering, Loss detection and compensation, Retransmission,
Forward error correction, Stream switching
Synchronity

Fate-sharing and route-sharing, Time-stamped packets, Multiplexing, Buffering,
Smoothing

QoS negotiation

Resource reservation

Styles
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18. May. 2006
Sender-oriented
Receiver-oriented
combined
12
INF-3190: Overview
Multimedia Protocols

Multimedia
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Application level framing

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Time-independent media  discrete media
Time-dependent media  continuous media
Interdependent media  multimedia
Applications know their needs, e.g. ordering and loss
Application defines data unit size
Try to avoid segmentation
Integrated layer processing

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Process several layers at once
Ordering constraints exist
18. May. 2006
13
INF-3190: Overview
Multimedia Protocols

RTP/RTCP

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Real-time Transport Protocol
ALF and ILP

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Application
Decoding
RTP Profiles
RTP
Sequencing, synchronization,
payload identification, quality
feedback
and session information
Multicast, mixers, translators
No reliability, no QoS support
Application
Encoding
RTCP
Encoding
RTCP
UDP/IP
Decoding
RTP
UDP/IP
RTP/RTCP interaction
Signaling protocols

RTSP
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
SIP

Useful for Video-on-Demand,
Near Video-on-Demand, live
broadcasts
RTSP signalling
Useful for internet
telephony and
conferencing
SIP signalling
18. May. 2006
14
INF-3190: Overview