Assignment 3 1. One network manufacturer\'s VPN software uses UDP to communicati
ID: 673944 • Letter: A
Question
Assignment 3
1. One network manufacturer's VPN software uses UDP to communication between the PC running the software and the VPN concentrator. Why would they do that?
2. difference between between the physical topology and the logical topology of a network. Tell why this difference is important.
3. Explain why, putting more registers in the CPU will allow a processor to execute programs faster than a similar processor, running at the same speed, with fewer registers.
4. two machines, A and B, on the same area network. Machine A wants to send a message to B, and has B's IP address. However, to send a message on the local net, a MAC address is needed. Explain how A gets B's MAC address. (explain the process.)
Explanation / Answer
1) >>>>
1) L2TP encapsulates PPP frames to be sent over IP, X.25, frame relay, or ATM networks. When sent over an IP network, L2TP frames are encapsulated as User Datagram Protocol (UDP) messages. L2TP can be used as a tunneling protocol over the Internet or over private intranets.
2) Tunnel Maintenance with L2TP Control Messages
> In contrast to PPTP, L2TP tunnel maintenance is not performed over a separate TCP connection. L2TP call control and management traffic is sent as UDP messages between the L2TP client and the L2TP server. In Windows, the L2TP client and the L2TP server both use UDP port 1701.
> Note
The L2TP client and L2TP server in Windows always use UDP port 1701. The Windows Server 2003 L2TP server supports L2TP clients that use a UDP port other than 1701.
3) L2TP control messages over IP connections are sent as UDP datagrams. In the Windows Server 2003 implementation, L2TP control messages sent as UDP datagrams are sent as the encrypted payload of IPSec ESP transport mode
4) UDP encapsulation
The encapsulated L2TP packet is then encapsulated with a UDP header with the source and destination ports set to 1701.
IP encapsulation
The UDP message is encrypted and encapsulated with an IPSec ESP header and trailer and an ESP Authentication (Auth) trailer.
5) The L2TP protocol driver then submits the resulting packet to the TCP/IP protocol driver with information to send the L2TP packet as a UDP message from UDP port 1701 to UDP port 1701 with the IP addresses of the VPN client and the VPN server.
6) The TCP/IP protocol driver constructs an IP packet with the appropriate IP header and UDP header. IPSec then analyzes the IP packet and matches it with a current IPSec policy. Based on the settings in the policy, IPSec encapsulates and encrypts the UDP message portion of the IP packet using the appropriate ESP headers and trailers.
7) L2TP uses UDP messages over IP networks for both tunnel maintenance and tunneled data. The payloads of encapsulated PPP frames can be encrypted or compressed (or both); however, L2TP clients do not negotiate the use of MPPE for L2TP connections. Encryption for L2TP connections is provided by IPSec Encapsulating Security Payload (ESP) in transport mode.
User Datagram Protocol-Encapsulating Security Payload (UDP-ESP)
IPSec NAT-T provides UDP encapsulation of IPSec packets to enable IKE and ESP-protected traffic to pass through a NAT. IKE automatically detects that a NAT is present and uses UDP-ESP encapsulation to enable ESP-protected IPSec traffic to pass through the NAT.
>>> functions of UDP ports 625xx
The ports are used for the VPN Client communication between the actual shim / Deterministic NDIS Extender (DNE) and the TCP / IP stack of the PC, and are for internal developmental use only. For example, port 62515 is used by the VPN Client for sending information to the VPN Client log. Other port functions are shown here.
62514 - Cisco Systems, Inc. VPN Service to Cisco Systems IPsec Driver
62515 - Cisco Systems IPsec Driver to Cisco Systems, Inc. VPN Service
62516 - Cisco Systems, Inc. VPN Service to XAUTH
62517 - XAUTH to Cisco Systems, Inc. VPN Service
62518 - Cisco Systems, Inc. VPN Service to CLI
62519 - CLI to Cisco Systems, Inc VPN Service
62520 - Cisco Systems, Inc. VPN Service to UI
62521 - UI to Cisco Systems, Inc. VPN Service
62522 - Log Messages
62523 - Connection Manager to Cisco Systems, Inc. VPN Service
62524 - PPPTool to Cisco Systems, Inc. VPN Service
2) >>>
A logical topology is how devices appear connected to the user.
A physical topology is how they are actually interconnected with wires and cables.
For example, in a shared Ethernet network that uses hubs rather than switches, the logical topology appears as if every node is connected to a common bus that runs from node to node.
However, its physical topology is a star, in which every node on the network connects to a central hub.
Simple Description :
Network Topology refers to layout of a network and how different nodes in a network are connected to each other and how they communicate. Topologies are either physical (the physical layout of devices on a network) or logical (the way that the signals act on the network media, or the way that the data passes through the network from one device to the next)
Physical Topology :
The physical layout of devices on a network. Every LAN has a topology, or the way that the devices on a network are arranged and how they communicate with each other. The way that the workstations are connected to the network through the actual cables that transmit data -- the physical structure of the network -- is called the physical topology. The logical topology, in contrast, is the way that the signals act on the network media, or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices.
A network's logical topology is not necessarily the same as its physical topology. For example, twisted pair Ethernet is a logical bus topology in a physical star topology layout. While IBM's Token Ringis a logical ring topology, it is physically set up in a star topology.
Logical Topology :
Also called signal topology. Every LAN has a topology, or the way that the devices on a network are arranged and how they communicate with each other. The way that the workstations are connected to the network through the actual cables that transmit data -- the physical structure of the network -- is called the physical topology.
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The logical topology, in contrast, is the way that the signals act on the network media, or the way that the data passes through the network from one device to the next without regard to the physical interconnection of the devices.
Logical topologies are bound to the network protocols that direct how the data moves across a network. The Ethernet protocol is a common logical bus topology protocol.
A network's logical topology is not necessarily the same as its physical topology. For example, twisted pairEthernet is a logical bus topology in a physical star topology layout. While IBM's Token Ring is a logical ring topology, it is physically set up in a star topology.
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As we know the registers are temporary storage devices lies between CPU and Memory. It takes more time if we store the data passing between these two in maon memory. For this registers helps you in fasting the data transfer by holding it. So as many registers You have that much transfer speed you will be having.