network design 8.pptx

NETWORK
DESIGN & ANALYSIS
Dr. Liyth Nissirat

Addressing and Routing Architecture
• Objectives
• Background
• Addressing Mechanisms
• Routing Mechanisms
• Addressing Strategies
• Routing Strategies
• Architectural Considerations

Addressing Mechanisms
• Classful Addressing
• Subnetting
• Variable-Length Subnetting
• Supernetting
• Private Addressing and NAT

Private Addressing and NAT
• Private IP addresses are those that cannot be advertised and forwarded by
network devices in the public domain.
• This was originally established to help with address space depletion in the
Internet, for if networks that would normally be allocated public address
space instead use private address space, those public addresses would remain
available.

Private Addressing and NAT
There is a side benefit of using private addresses.
 It turns out that because these addresses are not advertised and forwarded in the Internet, they have an
additional degree of security.
• NAT maps IP addresses between public and private spaces.
• In translating between public and private address spaces, NAT creates bindings between
addresses.
• These can be one-to-one address bindings (known as static NAT), one-to-many address bindings
(known as dynamic NAT), and address and port bindings (known as network address port
translation, or NAPT).
• Often combinations of static, dynamic, and NAPT bindings are used in a network. For example,
dynamic NAT is often used for user devices, and static NAT for servers.

Routing Mechanisms
• Establishing Routing Flows
• Identifying and Classifying Routing Boundaries
• Manipulating Routing Flows

Routing Mechanisms
Establishing Routing Flows
• In preparing to discuss boundaries and route manipulation, we want to understand
how flows will likely be routed through the network.
• Determining routing flows begins with the flow analysis process.
• Functional areas (FA) are groups within the system that share a similar function.
• Groups may be of users (workgroups), applications, devices, or combinations of
these, and they may share similar jobs/tasks, physical locations, or functions within
the network (e.g., backbone routing).
• Workgroups (WG) are groups of users that have common locations, applications, and
requirements, or that belong to the same organization.

Routing Mechanisms
• The purpose of functional areas is to simplify the routing architecture. They
can cross physical boundaries, such as rooms, floors, and buildings. A
workgroup is similar to a functional area, but one level lower in hierarchy.
• Consider Figure 6.12. In this figure there are multiple workgroups, in this
case based on organizations within a company. Functional areas are created:
the Scientists and Accounting groups in Building C, the two Management
workgroups in Building B, the Scientists groups across Buildings A and C,
and the backbone between the buildings. Notice that functional areas are
connected with routers.

Routing Mechanisms

Routing Mechanisms
Identifying and Classifying Routing Boundaries
• Routing boundaries are physical or logical separations of a network, based on
requirements for or administration of that network.
• Physical boundaries can be identified by isolation LANs or demilitarized
zones (DMZs); physical interfaces on network equipment; or physical
security.
• Logical boundaries can be identified by functional areas, workgroups,
administrative domains, such as autonomous systems (ASs), and routing
management domains.

Routing Mechanisms
Identifying and Classifying Routing Boundaries

Routing Mechanisms
Manipulating Routing Flows
• Manipulating (i.e., controlling) routing flows within the network is vital to the
proper operation and performance of the network.
• The right combination of addressing and routing is important in this
process, to localize routing flows whenever possible.
• There are several techniques for manipulating routing flows at hard and soft
boundaries.
• A default route is the route used when there is no other route for that
destination.

Routing Mechanisms
• Route filtering is the technique of applying route filters to hide networks from the rest
of an AS, or to add, delete, or modify routes in the routing table.
• A route filter is a statement, configured in one or more routers, that identifies one or
more IP parameters (e.g., an IP source or destination address) and an action (e.g.,
drop or forward) to be taken when traffic matches these parameters.
• Route aggregation is the technique exchanging of routing information between ASs,
usually between service providers with transit networks, and between large customer
networks.

Routing Mechanisms
• Policies are higher-level abstractions of the route filter technique described previously. Just as a route
filter takes an action (e.g., drop, accept, modify) on traffic that matches one or more parameters (e.g.,
IP addresses), a policy takes a similar action on traffic that matches one or more AS parameters (e.g.,
AS number or list of AS numbers and metrics, time of day, cost).

Routing Mechanisms

Addressing Strategies
• During the requirements analysis process, it is important to gather
information about device growth expectations, so that you can avoid having
to change addressing schemes and reconfigure device addresses during the
life cycle of the network.
• When applying subnetting, variable-length subnetting, classful addressing,
supernetting, private addressing and NAT, and dynamic addressing, we want
to make sure that our network addresses and masks will scale to the sizes of
the areas they will be assigned to. We also want to establish the degrees of
hierarchy in the network.

To scale the network addressing, we will use the numbers of
 Functional areas within the network
 Workgroups within each functional area
 Subnets within each workgroup
 Total numbers of subnets (current and future) in the organization
 Total numbers of devices (current and future) within each subnet

Routing Strategies
• Evaluating Routing Protocols
• Choosing and Applying Routing Protocols

Routing Strategies
Evaluating Routing Protocols
• Now we briefly examine and compare some popular IGPs and EGP:
 The routing information protocol (RIP and RIPv2)
 The open shortest-path first (OSPF) routing protocol
 The border gateway protocol version 4 (BGPv4)
• We also consider the limited use of static routes in the network.
 Static routes are routes that are configured manually, by network personnel or scripts, in
network devices, and that do not change until manually deleted or modified.

Routing Strategies
• A stub network is a network with only one path into or out of it, as in Figure 6.23.

Routing Strategies
• RIP and RIPv2 are IGPs that are based on a distance-vector routing
algorithm.
• This implies some characteristics of the dynamic behavior of RIP/RIPv2-
routed networks. RIP and, to a lesser degree, RIPv2 are relatively
straightforward to implement and maintain.
• RIP/RIPv2 should be considered when there is low to medium hierarchy
and diversity in the network. Degrees of hierarchy and diversity are shown in
Figure 6.24.

Routing Strategies

Routing Strategies
• OSPF is an IGP that is based on a link-state algorithm. Like RIP/RIPv2, the
choice of routing algorithm affects the characteristics of the protocol.
• In the case of OSPF, the use of a link-state algorithm results in a faster
convergence time when changes in the routing topology occur.
• OSPF also supports an area abstraction, which provides a hierarchy for
routing information.
• OSPF should be considered when there is high hierarchy and diversity in the
network, as shown in Figure 6.24.

Routing Strategies
• BGPv4 (or BGP) is a path-vector-based EGP. A path-vector algorithm is
similar to a distance-vector algorithm, such as that used in RIP; however, it
operates on ASs or lists of ASs (paths). In addition, BGP can use policies to
determine actions to be taken on paths.
• BGP exchanges routing information by establishing peering connections
using TCP with a user-defined list. BGP is used to enforce network transport
policies for an AS, such as allowing all routes from a certain AS to use this
AS as a transit route; rejecting all routes that have been learned from a
certain AS; and only announcing certain routes from this AS to other peers.

Routing Strategies
• BGP operates between ASs, yet there may be a number of routers (termed border
routers) that connect to external networks. As such, there needs to be a mechanism
for border routers from the same AS to communicate path information, so that it
can be passed to multiple ASs (see Figure 6.25).
• Therefore, there are two types of BGP:
 external BGP and internal BGP. External BGP (eBGP) is the “normal” operational mode
of BGP: passing path information between ASs.
 Internal BGP (iBGP) is used to form tunnels between border routers within an AS, in order
to pass path information across that AS.

Routing Strategies
Choosing and Applying Routing Protocols
Some recommendations for choosing and applying routing protocols for your
network.
1. Minimize the number of routing protocols used in the network. Two should be the
maximum number of protocols allowed, with only one IGP.
2. Start with the simplest routing strategy and routing mechanism/protocol.
3. As the complexity in routing and choices of routing protocols increase, reevaluate the
previous decisions.

Routing Strategies
• Starting with the simplest routing mechanism (static routes) and working our
way up to more complex mechanisms, we usually start with the outer edges
of the network, where hierarchy and diversity are lowest, and work our way
toward the center, or backbone, of the network, where hierarchy and
diversity are highest (Figure 6.26).

Routing Strategies

Routing Strategies
• In applying routing protocols we start by evaluating the degrees of hierarchy and
diversity of each functional area and considering any other factors for that
functional area or features of the routing protocols that may apply.
• When a change is made in the choice of routing protocol, such as from static routes
to RIP/RIPv2, from RIP/RIPv2 to OSPF, or from RIP/RIPv2/OSPF to BGP,
• We need to reevaluate functional areas where routing protocols or static routes have
already been chosen.
• In general, RIP/RIPv2 supersedes static routes, and OSPF supersedes RIP/RIPv2.
But remember that you can also consider combining the protocols within the
network. Figure 6.27 illustrates the process of applying routing protocols.

Architectural Considerations
• Internal Relationships
• External Relationships

Internal Relationships
• Depending on the type of network being developed, the set of candidate
addressing and forwarding mechanisms for a component architecture can be
quite different.
• Two types of interactions are predominant within this component
architecture:
 Trade-offs between addressing and forwarding mechanisms
 Trade-offs within addressing or within forwarding.

Internal Relationships

External Relationships
• External relationships are trade-offs, dependencies, and constraints between
the addressing/routing architecture and each of the other component
architectures (network management, performance, security, and any other
component architectures you may develop).
• There are common external relationships between addressing/ routing and
each of the other component architectures

External Relationships
Some of common external relationships between addressing/ routing and each
of the other component architectures
 Interactions between addressing/routing and network management.
 Interactions between addressing/routing and performance.
 Interactions between addressing/routing and security.

network design 8.pptx

Recommended

Recommended

More Related Content

Similar to network design 8.pptx

Similar to network design 8.pptx (20)

More from aida alsamawi

More from aida alsamawi (7)

Recently uploaded

Recently uploaded (20)

network design 8.pptx