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STUDYNOTES(ITEC 3210) > Chapter 6-7 > Flashcards

Chapter 6-7 Flashcards

1
Q

What are BBNs?

A

BBNs are high speed networks that:
Link an organizations Access Layers (LANs) and;
Provide connections to other BBNs, MANs, WANs and the internet

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2
Q

In the structured design approach, BBNs refer to the:

A
  • Distribution layer that connects access layers (or LANs) within a building (and the MAN/WAN/Internet if no core layer needed)
  • Core layer connects distribution layers different of different adjacent buildings
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3
Q

What are BBNs components?

A
  • Cables: Typically TP in distribution layer, Fiver in core layer
  • Intermediary devices: It depends but selection cannot be random, Layer-2 switch (same as device used for access layer or routers or VLAN switch ( aka Layer-3 switch o.e. a combination of switches and routers
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4
Q

Where are the physical locations of LAN and BBN devices?

A

Typically located centrally in main distribution facility
Longer cables needed but easier access when trouble shooting

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5
Q

Switched (or collapsed) BBNs

A

LANs are connected by a layer-2 switch:
- Most common type of distribution layer

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6
Q

What are the main advantages of Switched BBN?

A

Improved performance:
- Full duplex transmissions
- Faster processing
- Easier to manage

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7
Q

What are some minor disadvantages of switched BBN?

A
  • No protocol conversion
  • No segmentation into broadcast domain
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8
Q

Router (or hierarchical) BBNs

A

Layer 2 switches at distribution layer are connected by routers
- Within the LANs and distribution layers, traffic is based on data link address
- Between distribution layers, message are sent to core layer devices which forwards or routes message based on its network layer address

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9
Q

What are limitations of Router (or hierarchical) BBN?

A

Hardware cost + management cost + processing time

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10
Q

What are some benefits of Router (or hierarchical) BBN?

A
  • Segmentation into broadcast domain -security
  • routing if needed
  • some protocol conversions if needed
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11
Q

Virtual LANs (VLANs)

A

new flexible LAN(BBN architecture that assigns computers to LAN segments (or subnets) by software NOT by hardware

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12
Q

Switches that don’t use the VLAN functionality segment networks based on physical location

A
  • 80/20 rule is used as a basis for a network segmentation (see all previous figures)
  • Possible exception to the rule: Users in different physical locations need to access to the same LAN resources
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13
Q

VLAN switches

A

Special type of high speed layer-3 switches that enable VLANs which divide LANs in logical rather than physical segmants

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14
Q

Single-switch VLANs vs Multi-switch VLANs

A

Single-switch VLAN: One VLAN switch physically connects all computers and assigns
them to the different VLANs
Multi-switch VLAN use several VLAN switches:
- Each VLAN switch maintains a table that identifies membership with VLAN ID and IP
addresses (Fig. 8-7) and interconnected VLAN switches exchange copies of those tables;
- VLAN trunks are circuits that directly connect the different VLAN switches

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15
Q

Virtual LAN switches: Pros and cons

A

Pros:
- IF justified, they help better manage the flow of traffic the network than the traditional LAN/BBN architecture (which can lead to better performance)
- IF justified, because they create subnets, they filter broadcasts so only members of a VLAN receive broadcast messages (also more flexible subnetting)
- IF justified, VLAN switches are high-speed layer-3 switches with low latency
- IF justified, they support QoS protocols which allows to prioritize traffic
- IF justified, they support ACL

Cons:
- They are more expensive than Layer-2 switches
- They are more complex to manage

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16
Q

Best practice BBN design

A

Architecture:
- Default best practice: Layer-2 switches at the distribution layer and if a core layer is needed, routers or layer-3 switches (without using the VLAN functionality) at the core layer (see Fig. 8-4 and next slide)
- Otherwise, IF a flexible LAN/BBN architecture is required, VLAN(s) i.e., layer-3 switch(es) using the VLAN functionality is the best practice

17
Q

What does Access Control List (ACL) do?

A

Use devices and software that block unauthorized traffic

18
Q

How do you improve BBN performance?

A

Increase device performance
- Select faster routing protocols and devices that support them
- Select devices with lower latency i.e., devices with more RAM and/or faster CPU
- Use Layer-3 switches (due to their faster processing, see Slide 6) instead of routers at the core layer IF no routing or protocol conversion is needed (see product specs!)
Increase circuit capacity
- Increase nominal data rates from 100 Mbps to 1000Mbps for example
Reduce demand
- Have a policy on (or restrict) applications that use a lot of network capacity (relevant to
LANs NOT to BBNs)

19
Q

Increase BBN availability:

A

Redundant devices and cabling (aka fault-tolerance)

20
Q

Key features of leased circuits:

A
  • Create dedicated and permanent “point-to-point” circuits between LANs
  • Require a router and CSU-DSU but a multiplexer is optional (see next slide)
  • Billed at a flat fee per month
21
Q

T-Line Services

A
  • Most used dedicated circuits
  • Commercially available in combinations of nominal data rates varying from 64 Kbps (i.e., 1 channel or DS-0 of a fractional T-1 line) to about 1.5 Mbps (T-1 line equiv. to 24 simultaneous 64-Kbps channels) to about 45 Mbps (T-3 line equivalent to 28 T-1 lines)
  • Note: Fractional T-1 provides 64Kbps, 128Kbps, etc. depending on # of channels leased
22
Q

Synchronous Optical Network (SONET)

A
  • Commonly used for MAN with high security and high data rate requirements
  • Hierarchy in data rate defined as a multiple of Optical Carrier (OC)-1 and varies from about 50 mbps (OC-1) to about 10 Gbps (OC-192)
  • high-speed communication network technology that transmits data over fiber optic cables using a synchronous time-division multiplexing method. It is used for long-distance transmission of data, voice, and video signals in telecommunications networks.
23
Q

Dedicated-circuit networks

A

Are called point-to-point circuits and circuits is/are permanent and dedicated Devices: Router + CSU/DSU are required, Multiplexer (or MUX) is optional

24
Q

Router

A

Connects the organizations network to the outside networks

25
Q

CSU/DSU

A

CSU manages equipment connection, DSU translates between protocols

26
Q

MUX

A

Allows to carry multiple signals (voice, data and video) over a single circuit

27
Q

Dedicated-circuit topologies for WAN (types of design)

A
  • Ring-based design
  • Star-based design
  • Mesh-design
  • Simple point-to-point design
28
Q

Key advantages/disadvantages of Ring design

A

Advantages
- Robust to loss of any one circuit

Disadvantage
- Long routes can cause latency issues

29
Q

Key advantages/disadvantages of Star-based design

A

Advantages
- Simpler management
- Messages require 1 or 2 hops

Disadvantage
- Susceptible to traffic problems
- complete failure if central site fails

30
Q

Key advantages/disadvantages of Mesh design

A

Advantages
- Generally short routes
- Robust to circuit loss or overload

Disadvantage
- Expensive

31
Q

Key advantages/disadvantages of Mesh design

A

Advantages
- Generally short routes
- Robust to circuit loss or overload

Disadvantage
- Expensive

32
Q

Packet-switched network

A

Organizations connect to a common carrier’s network by leasing:
- Dedicated circuits from their offices to the packet switched network’s point-of- presence (aka POP, i.e., to the local
MAN/WAN service provider, see next slide)
- Shared virtual circuit(s) (VCs, switched or permanent) between POPs (see next slide)
- Device: Router required, packet assembly/ disassembly (PAD) depending on service
- Billed at a flat fee for a connection to the carrier plus a fee for the data transmitted

- Computer sends data, data broken down to packets and each sent separately

33
Q

Packet - swtiched networks

A

Are called multipoint circuits, include (1) dedicated circuits from LANs to the packet switched networks POP and (2) shared virtual circuits
Device: Router required, additional device depending on service

34
Q

Virtual Private Networks (or VPNs)

A
  • VPN device or software encrypts data and encapsulates them in IP packets before it is sent over a VPN
  • Typical data rates supported vary from 3Mbps to 300Mbps
  • Advantages: Low cost and service offered anywhere Internet is offered

Problems:
– Unpredictability of the Internet (response time and availability)
– Lack of standard: VPN devices or software from different vendors may not be compatible

35
Q

Software-defined Wide Area Network (SDWAN)

A

Benefits from SDWAN:
– Improved performance and availability: SDWAN provides centralized management (network status information + management of WAN circuits)
– Reduced costs by balancing traffic between circuits with different costs and capacity
– Improved security IF SDWAN router has built-in VPN capabilities
– Improved prediction of traffic future growth IF SDWAN router is a managed router

  • is a networking technology that simplifies the management of a Wide Area Network using software and cloud-based technologies. It improves network performance, security, and reduces costs by leveraging multiple WAN connections

** Application:** See Management Focus 9-3 in p. 260
– Organization signed up for more than 1 service, in this case MPLS and VPN
– Organization uses SDWAN to redirect traffic from a service that is close to saturation to the other to improve the performance of the MAN/WAN
– Additional benefits: Improved availability and cost management

36
Q

MAN/WAN Recommendations

A

** For networks with low to moderate data rate requirements (10 Mbps or less):**
– VPNs if cost is an issue and predictable availability and/or response time is less of an issue
– Ethernet of MPLS otherwise
* For networks with high data rate requirements (10 Mbps to 50Mbps):
– IF traffic is intermittent (burst), Ethernet or MPLS
– IF a steady stream of data is required (no burst), T-Carriers (T3)
* For networks with very high data rate requirements (50 Mbps to 100 Gbps):
– SONET if high level of security and a steady stream of data are required
– Otherwise Ethernet or MPLS

37
Q

Improve WAN Performance:

A

– Selecting high performance devices
– Improving/upgrading circuit capacity
– Reducing network demand:
* Use data compression hardware and software
* When possible, shift network usage from peak or high-cost time to lower- demand or lower-cost times
* Move data closer to users with shift from central to distributed systems and databases

STUDYNOTES(ITEC 3210) (5 decks)

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