Communication and network security Flashcards
The most important protocol at Layer 2 is
the Address Resolution Protocol (ARP)
The most important protocol at Layer 2 is the Address Resolution Protocol (ARP). This might be thought of as a technology-independent protocol, as
one side deals with Media Access Control (MAC) addresses and the other with IP addresses; but it has no need to be involved with or aware of the details of the other communications protocols used at Layer 2.
At layer 2 two other protocols (aside from ARP) provide the mechanisms for establishing a Layer 2 connection between two systems, such as an internet service provider (ISP) and a customer device
PPP and PPPoE
Layer 2: What are polling protocols
In the polling protocols model, each station is permitted a specific amount of time when it has exclusive access to the infrastructure. As the number of devices on the network increases, the bandwidth available to each device degrades in a more predictable manner. This approach is often characterized as a deterministic network.
Layer 2: Name the two main contention based protocols
CSMA/CD and CSMA/CA
Layer 2: What are bridges
Bridges are Layer 2 devices that filter traffic between segments based on MAC addresses In addition, they amplify signals to facilitate physically larger networks.
Network administrators can use —— —— to connect dissimilar Layer 2 architectures, such as Ethernet to Token Ring.
translator bridges
A common type of bridge for many organizations is a wireless bridge based upon …
one of the IEEE 802.11 standards
Layer 2 Since VLANs acts as discrete networks, communications between VLANs must be enabled through
services at higher layers of the protocol stack (i.e., Layer 3/routers, Layer 6/gateways and other devices).
Virtual local area networks (VLANs) allow network administrators to use switches to create
software-based LAN segments, which can segregate or consolidate traffic across multiple switch ports.
Layer 2: VLANs do not guarantee a network’s security. At first glance, it may seem that traffic cannot be intercepted because communication within a VLAN is restricted to member devices. However, there are attacks that allow a malicious user to see traffic from other VLANs. This is called
VLAN Hopping or 802.1Q attacks
Layer 3: Five different forms of transmission are defined at Layer 3
Unicast
Broadcast
Multicast
Anycast
Geocast
Layer 3: How is anycast different from unicast
Anycast provides a different approach to unicast, in that its intention is one-to-one transmission of data, but it uses the services of a group of devices to facilitate this. As a result, it’s often referred to as one-to-one-of-many. In effect, the “destination” address is a don’t care: the sending node wants somebody in its anycast group to receive the message and process it.
Layer 3: What is a common use of Anycast
Content distribution networks will use this to manage the push of continuous content to regional sub-distribution servers, for example.
Layer 3: IPv4 and IPv6 use a different packet header to provide addressing and other information, and thus
the same network cannot operate IPv4 and IPv6 simultaneously.
Layer 3: Why can the same network not operate IPv4 and IPv6
IPv4 and IPv6 use a different packet header to provide addressing and other information
Layer 3: How do we solve the problem of IPv4 not being on same network as IPv6
- Protocol and address translation is performed between network segments, which allows organizations a reasonably straightforward way to transition subnets or segments from IPv4 to IPv6.
- Dual stack: Uses specialized devices which can handle both protocols.
- Tunneling: Allows IPv6 to run in native mode on some segments of your network, while encapsulating those packets when they have to transit the IPv4 connections.
Layer 3: How many concurrently connected hosts can be inside a network with the subnet mask of 255.0.0.0
16,777,214
Layer 3: How many concurrently connected hosts can be inside a network with the subnet mask of 255.255.0.0
65,534
Layer 3: How many concurrently connected hosts can be inside a network with the subnet mask of 255.255.255.0
254
Layer 3: What is always in the form of 169.254.x.x where the values at x are automatically generated by using an offset algorithm and the real-time clock value
Automatic Private IP Addressing (APIPA)
Layer 3: How many addresses can ipv6 support
2 to the power of 128 (128 Bits)
Layer 3: Operating across both Layers 2 and 3 of the OSI model, this link-state routing protocol calculates the optimal path when communications between devices is initiated and informs its peers of the “label” for that route. Future communications use the label (without further lookups to determine the optimal path) to move the traffic.
Multiprotocol Label Switching (or MPLS)
Layer 3: The advantages of MPLS are significant. These include:
Traffic-engineering: The protocol provides much more control to network operators to determine where and how traffic is routed on their networks, improving capacity management, service prioritization and minimizing traffic congestion.
Multi-service networks: MPLS can support a variety of data transport services, as well as IP routing, across the same packet switched network infrastructure.
Network resiliency: Capabilities like MPLS Fast Reroute provides the ability to reroute traffic to meet QoS requirements for certain types of traffic. Despite these advantages, many organizations are choosing software-defined wide area networks (SD-WAN) as an alternative to MPLS because of the potential cost advantages. SD-WAN will be further developed in other chapters.