Download - Chap 23 ip over atm
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TCP/IP Protocol Suite 1
Chapter 23Chapter 23
Upon completion you will be able to:
IP Over ATMIP Over ATM
• Review the features of an ATM WAN• Understand how an a datagram can pass through an ATM WAN• Understand how an IP packet is encapsulated in cells• Understand how cells are routed in an ATM network• Understand the function of ATMARP
Objectives
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TCP/IP Protocol Suite 2
23.1 ATM WANS
We review some features of the ATM WAN needed to understand IP We review some features of the ATM WAN needed to understand IP over ATM. The only AAL used by the Internet is AAL5, sometimes called over ATM. The only AAL used by the Internet is AAL5, sometimes called the simple and efficient adaptation layer (SEAL). the simple and efficient adaptation layer (SEAL).
The topics discussed in this section include:The topics discussed in this section include:
Layers Layers
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TCP/IP Protocol Suite 3
Figure 23.1 An ATM WAN in the Internet
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TCP/IP Protocol Suite 4
Figure 23.2 ATM layers in routers and switches
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TCP/IP Protocol Suite 5
End devices such as routers use all three layers, while switches use only
the bottom two layers.
Note:Note:
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TCP/IP Protocol Suite 6
Figure 23.3 AAL5
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TCP/IP Protocol Suite 7
The AAL layer used by the IP protocol is AAL5.
Note:Note:
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TCP/IP Protocol Suite 8
Figure 23.4 ATM layer
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TCP/IP Protocol Suite 9
Figure 23.5 ATM headers
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TCP/IP Protocol Suite 10
23.2 CARRYING A DATAGRAM IN CELLS
We show how an example of a datagram encapsulated in four cells and We show how an example of a datagram encapsulated in four cells and transmitted through an ATM network.transmitted through an ATM network.
The topics discussed in this section include:The topics discussed in this section include:
Why Use AAL5? Why Use AAL5?
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TCP/IP Protocol Suite 11
Figure 23.6 Fragmentation
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TCP/IP Protocol Suite 12
Only the last cell carries the 8-byte trailer added to the IP datagram.
Padding can be added only to the last cell or the last two cells.
Note:Note:
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TCP/IP Protocol Suite 13
The value of the PT field is 000 in all cells carrying an IP datagram
fragment except for the last cell; the value is 001 in the last cell.
Note:Note:
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TCP/IP Protocol Suite 14
Figure 23.7 ATM cells
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TCP/IP Protocol Suite 15
23.3 ROUTING THE CELLS
The ATM network creates a route between two routers. We call these The ATM network creates a route between two routers. We call these routers entering-point and exiting-point routers.routers entering-point and exiting-point routers.
The topics discussed in this section include:The topics discussed in this section include:
Addresses Addresses Address Binding Address Binding
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TCP/IP Protocol Suite 16
Figure 23.8 Entering-point and exiting-point routers
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TCP/IP Protocol Suite 17
23.4 ATMARP
ATMARP finds (maps) the physical address of the exiting-point router ATMARP finds (maps) the physical address of the exiting-point router given the IP address of the exiting-point router. No broadcasting is given the IP address of the exiting-point router. No broadcasting is involved.involved.
The topics discussed in this section include:The topics discussed in this section include:
Packet Format Packet Format ATMARP Operation ATMARP Operation
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TCP/IP Protocol Suite 18
Figure 23.9 ATMARP packet
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TCP/IP Protocol Suite 19
Table 23.1 Table 23.1 OPER fieldOPER field
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TCP/IP Protocol Suite 20
The inverse request and inverse reply messages can bind the physical
address to an IP address in a PVC situation.
Note:Note:
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TCP/IP Protocol Suite 21
Figure 23.10 Binding with PVC
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TCP/IP Protocol Suite 22
Figure 23.11 Binding with ATMARP
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TCP/IP Protocol Suite 23
The request and reply message can be used to bind a physical address to an
IP address in an SVC situation.
Note:Note:
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TCP/IP Protocol Suite 24
The inverse request and inverse reply can also be used to build the server’s
mapping table.
Note:Note:
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TCP/IP Protocol Suite 25
Figure 23.12 Building a table
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TCP/IP Protocol Suite 26
23.5 LOGICAL IP SUBNET (LIS)
An ATM network can be divided into logical (not physical) subnetworks. An ATM network can be divided into logical (not physical) subnetworks. This facilitates the operation of ATMARP and other protocols (such as This facilitates the operation of ATMARP and other protocols (such as IGMP) that need to simulate broadcasting on an ATM network.IGMP) that need to simulate broadcasting on an ATM network.
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TCP/IP Protocol Suite 27
Figure 23.13 LIS
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TCP/IP Protocol Suite 28
LIS allows an ATM network to be divided into several logical subnets. To
use ATMARP, we need a separate server for each subnet.
Note:Note: