Quality of Service
in IN-home digital networks
“An Architecture for QoS guarantees and Routing in
Wireless/Mobile Networks”
Indu Mahadevany and Krishna M. Sivalingamz
What is the paper about?
architecture that provides QoS support in mobile/wireless networks
along with support for fast routing during handoffs.
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use of “modified” RSVP protocol for QoS support in wireless/mobile
networks.
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routing architecture that includes features of Mobile IP.
Goals and contributions of the paper:
(a) a hierarchical scalable architecture is proposed for QoS guarantees
based on the concept of QoS-regions,
(b) a hierarchical architecture is proposed for fast routing based on routingregions which uses the advantages of Mobile IP and route table
changes,
(c) The implementation details of QoS guarantees and routing are
discussed
(d) Experimental testbed, some features of the architecture are supported
with results from experiments.
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Definition of Concepts
Mobile IP
Mobile IP uses the concept of a home agent (HA) for every mobile.
When a mobile is in a different subnet all data to the mobile are intercepted
by the HA. Packets are then encapsulated and sent to the foreign
agent (FA) residing in the subnet the mobile is currently located.
Advantage: all senders need to know only the address of the home
agent, HA keeps track of the current location of the mobile.
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Disadvantage of this method is that it is better suited for long term
mobility. If a mobile is moving frequently - hard to communicate fast
with the HA on another subnet.
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Solution: not contact the HA at every move, change the routing table
so that the location of the mobile is known.
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Current approach: use routing updates locally for faster handoffs and
Mobile IP for long range mobility and for a scalable solution.
Definition of Concepts
Routing domain
A Routing-domain can be any management-specified domain.
Ex: a subnet or a number of subnets can constitute a routing
domain.
Properties:
(a)
all route changes within the routing-domain is done with the
help of route table changes and
(b)
all routing for mobility between routing-domains is done
usingMobile IP.
Definition of Concepts
Routing domain
Fig aside: architecture with two
subnets A and B connected by
the router R.
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A router is the gateway up the
hierarchy.
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The router R can serve a dual purpose:
a) as the gateway between subnets A and B
b) as a base station.
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Definition of Concepts
QoS domain
A QoS-domain can be any management-specified domain.
Ex: a number of cells can constitute a QoS-domain.
A system that belongs to two QoS domains is called a router. (Not to
be mistaken with the traditional sense of the word)
Properties:
(a) all passive reservations for mobility within a QoS-domain is
done by extending the path of the original reservation
(b) all passive reservations for mobility between QoS-domains are
done by partial re-routing.
Definition of Concepts
Route table changes
Mechanism of changing routing tables in a routing-domain:
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All the base stations in a routing domain register with the routingdomain router.
The routing-domain router knows the current location
of the mobile.
When a mobile moves into another region, the base station in the
region informs the routing-domain router about the mobile.
The routing-domain router broadcasts this information to all systems in
the routing-domain.
All hosts in the routing-domain use this information when they want to
communicate with the mobile.
The Architecture
The Architecture
Routing issues - Scenario
Scenario context:
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Subnet A and B form one routing-domain, subnet C forms another
routing-domain.
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A mobile has a home agent (HA) in the same subnet as the sender.
Assumption: routers R1 and R2 can act as a FA.
Scenario:
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HA sends data to a designated host or a router which acts as a foreign
agent (FA). The FA is the gateway to a particular routing-domain.
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Fig. [a] : the mobile M is in the vicinity of subnet A: Routing from the HA
to the FA (R1) is done using Mobile IP (represented by (1) in fig.[a]).
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All mobility within subnets A and B (a routing-domain) is taken care of
by local route changes.
The Architecture
Routing issues - Scenario
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Routing from R1 to the mobile is done through the appropriate
base stations because the routing tables in the hosts in the
subnet A and B keep track of the mobile.
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When the mobile moves into the region of subnet C (fig. [b]), the
home agent will choose R2 as the foreign agent because it
belongs to another routing-domain.
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Any mobility within subnet C is taken care of by routing table
changes.
The Architecture
Routing issues - Scenario
The Architecture
QoS issues
Scenario
The Architecture
QoS issues - Scenario
Context scenario:
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mobile M initially in cell A.
Scenario:
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The sender makes an active reservation with the router R. The router
sends data to BSa ( the base station in this cell ) and resource
reservations must be made between BSa and M.
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When the mobile moves, it could move into any of the other six cells.
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At this point need to make two kinds of resource reservations
that are “passive”:
a) between the “current” base station Bsa and all other base stations
namely BSb, BSc, BSd, BSe, BSf and BSg,
b) base stations BSb, BSc etc. make a passive resource reservation
on their wireless interfaces to accommodate mobile M’s potential
requests.
The Architecture
QoS issues - Scenario
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BSa also informs router R about the addresses of all the neighboring base
stations.
The router examines these addresses to see if the addresses belong to the
same QoS-domain as the current base station or belong to another
domain.
In fig. (b) mobile M has moved into cell F.
The resources that were labeled passive in the wired environment between
BSa and BSf are made active and the resources on the wireless interface
of BSf is activated to be used for communication between BSf and M.
All other resources reserved passively can be deleted now.
BSf now sends to router R, the addresses of all the base stations in the
neighboring cells. The addresses include address of BSi, BSj and BSk.
R realizes that these base stations are in a different QoS domain and
hence, R makes passive reservations with BSi, BSj and BSk - fig. (c).
Fig.(d) – the mobile has moved into cell I.
At this point the reservation between router R and BSi are activated and all
other passive reservations are deleted.
The Architecture
Dataflow
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A sender in the Internet wants to send data to a mobile M which is currently
in the region of base station BSa (in subnet A).
The sender sends the request to the Home Agent (HA) which sends a
reservation request to the Foreign agent (FA) (which also happens to be
the routing-domain router).
The path from the sender to FA uses the mobile IP routing protocol while
the path from the FA to the mobile (through BSa) uses the routing table
entries on hosts in the same routing-domain which reflect the current
location on mobile M.
Currently the mobile is in the region of BSa.
At this point, passive reservations are to made locally for potential
movement of the mobile.
BSa informs the QoS domain router the addresses of all it’s neighboring
base stations.
The Architecture
Dataflow
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There are two possible ways of making passive reservations at this point:
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If all the neighboring base station are in the same QoS-domain, Bsa
makes passive reservation with all these neighbors.
If some of the neighbors are in a different QoS domain, BSa makes
passive reservation with the base stations in the same QoS -domain. The
QoS domain router makes passive reservation with the base stations in
the neighboring domain.
The mobile now moves into region of say BSf. Either:
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the reservations between BSa and BSf are activated or
the reservations between the QoS-domain router and BSf are activated
depending on which domain BSf resides.
According to the routing followed in the architecture:
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If the move is local, i.e. within the same routing-domain, the routing tables
in the hosts in this domain are changed to indicate that the mobile is now
in the location of BSf.
If the move is to another routing-domain, the current routing-domain
router/FA informs the HA about the move and the HA chooses another
QoS domain router the the other subnet as the FA.