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Network plus N10-007 ExamNotes sub-objective 1.3 routing and switching – Part 3 of 3 – Dumps4shared

Network+ N10-007 ExamNotes for sub-objective 1.3 Explain the concepts and characteristics of routing and switching – Part 3 of 3

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CompTIA Exam Sub-objective 1.3: “Explain the concepts and characteristics of routing and switching.”

For the previous two parts of these objectives go to Part 1 and/or Part 2.

Performance concepts
Traffic shaping: QoS – Diffserv – CoS
NAT/PAT
Port forwarding
Access control list
Distributed switching
Packet-switched vs. circuit-switched network
Software-defined networking

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Performance concepts

– Traffic shaping

Traffic shaping is a technique used on high volume networks to ensure the timely delivery of prioritized traffic and provide optimal performance to the users. The network is managed and optimized to control the type and amount of traffic by prioritizing important traffic. As an example, VoIP traffic will receive a higher priority than standard data.

– QoS

Quality of Service (QoS) is a group of techniques that ensure that voice and video communications are handled in a time-sensitive manner. This will avoid jittery VoIP or choppy video streams. Prioritized traffic is given all of the network bandwidth it needs. We’ll look at two of the standard techniques used for QoS next.

Diffserv

Differentiated Services (DiffServ) works at OSI Layer 3 to examine all traffic and prioritize time-sensitive packets like voice and video. DiffServ modifies the DiffServ field in an IPv4 packet or the Traffic Class field in an IPv6 packet. This information tells routers how to handle the packets.

CoS

Class of Service (CoS) is another QoS method that operates at OSI Layer 2. CoS improves the routing and switching of Ethernet frames between VLANs. Tagged frames are prioritized using eight priority levels (0 – 7). The level is assigned to the frame in a three-bit field in the header. The field is called the Priority Code Point (PCP).

NAT/PAT

Network Address Translation (NAT) was designed to reduce the need for public IP addresses required by a network. A gateway provides separation between a private network and the public network by assigning private IP addresses to its network. Only one Public IP address is used and the private network is invisible to outsiders. The private devices use the gateway to communicate with the Internet or other networks. The gateway translates the private address to the gateways public address. This is great for outbound sessions but presents a problem with inbound sessions since they are returned to the public address and do not contain the NAT information. This is where Port Address Translation (PAT) comes in. Each session between a local host and an Internet host is assigned to an individual TCP port. When the gateway receives traffic intended for the host it knows where to send it.

Port forwarding

Port Forwarding redirects traffic to a port other than its default. For example, FTP uses insecure port 21.  With port forwarding you can use a different, possibly secure, port to disguise the traffic. This is a feature of NAT and needs to be configured on the gateway. An external host must know the address and port number to communicate.

Access control list

ACLs (Access Control Lists) are used to permit or deny specific traffic on the network. Routers, firewalls, and Layer 3 switches can filter traffic based on their configuration. On a router, packets can be passed or dropped based on any or all of the following:

– Source IP address
– Destination IP address
– TCP/UDP port number
– Network layer protocol
– Transport layer protocol

Since a router examines all packets, it can drop any packets that are not permitted by the ACL. The ACL will compare the traffic to its ordered list of permit/deny rules. Each rule will either deny the packet or pass it to the next rule repeating the process. Only packets that are permitted by all rules will be allowed onto the network.

Distributed switching

In the virtual environment distributed switching provides a centralized control point for VMs and virtual server clusters across multiple points. This simplifies network management and reduces errors. On each physical host, an agent is installed.  A supervisor module on the distributed switch then controls the hosts.

Packet-switched vs. circuit switched network

Since switching determines how devices communicate on a network we will look at two major switching methods.

Circuit-switched networks are easy to relate to. Compare this type of switching to that of a telephone call. The first party attempts to connect, the second party accepts the connection establishing a circuit. All data on the circuit will use the same path. This circuit will be used only by the two parties and will remain connected until one of the parties disconnects. This is simple and direct.

Packet-switched networking is by far more efficient and adaptable to IP networks. IP protocols break the data into packets before transmission. Since each packet contains the necessary addressing information and sequencing, each packet is free to take the fastest route to its destination. The packets can arrive at the destination in any order. The destination node will use the control information in each packet to reconstruct the transmission. This method uses considerably fewer network resources than the circuit switched alternative.

Software-defined networking

With our networking environment consisting of both virtual and physical network management and even the creation of new networks represents quite a challenge. SDN (software-defined networking) centralizes the control of data flow by using software. In this process determinations that were traditionally handled by routers and switches, are now handled by the SDN controller.  The SDN controller integrates the functions of device configuration and device management into a single software interface. This simplifies device management as every physical or virtual device can be accessed, monitored and configured. The software interface or dashboard allows administrators to control devices simultaneously as a group, making it a clear alternative to individual device access. SDN will play a major role in Cloud technologies.

And this concludes our three-part post for CompTIA Network+ N10-007 Sub-objective 1.3.

Good luck on the test!

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For the previous two parts of these objectives click on Part 1 and/or Part 2.

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Network plus N10-007 ExamNotes sub-objective 1.3 routing and switching – Part 2 of 3 – Dumps4shared

Network+ N10-007 ExamNotes for sub-objective 1.3 Explain the concepts and characteristics of routing and switching – Part 2 of 3

CompTIA Exam Sub-objective 1.3: “Explain the concepts and characteristics of routing and switching.”

For the previous part of these objectives go to Part 1, for the remainder of the 1.3 objectives go to Part 3.

Routing

Routing protocols (IPv4 and IPv6) – Distance-vector routing protocols – RIP – EIGRP – Link-state routing protocols – OSPF – Hybrid – BGP – Routing types – Static – Dynamic – Default

IPv6 concepts

Addressing – Tunneling – Dual stack – Router advertisement – Neighbor discovery

For the rest of the 1.3 objectives go to Part 3.

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Routing

Distance-vector Routing protocols (IPv4 and IPv6)

Routers use routing protocols to determine the best path for communication. The protocols evaluate the reliability and the priority of data using three metrics.

  • Administrative distance (AD) assigns a numeric rating value to the protocol for prioritization. The lower the number the higher the priority. Administrators can modify this value to give one protocol precedence over another.
  • Convergence time. This measures the time it takes the protocol to determine the best path when there are changes or outages along the route.
  • Overhead measures the amount of resources needed to support the protocol.

Distance-vector routing protocols

Distance –vector routing protocols can use metrics as simple as the number of hops or they can calculate the latency and congestion. Neighboring routers can exchange this route information with each other. The protocols rely heavily on the routes they receive because they can’t measure network conditions more than two hops away. RIP (Routing Information Protocol), RIPv2 (Routing Information Protocol, version 2) and EIGRP (Enhanced Interior Gateway Routing Protocol) are distance-vector protocols. EIGRP is generally preferred over RIP.

RIP

See Distance-vector routing protocols.

EIGRP

See Distance-vector routing protocols.

Link-state routing protocols

OSPF

Link-state protocols allow routers to communicate with routers beyond the two hop limit of distance-vector protocols. OSPF (Open Shortest Path First) is a link-state routing protocol. The best path to a destination can be determined using a network map it creates from the other routers. Link-state protocols adapt quickly to network changes. OSPF was developed to improve RIP. OSPF is stable, converges quickly, and supports large networks.

Hybrid

BGP

The Border Gateway Protocol is considered a hybrid protocol in the CompTIA objectives as it employs elements of both Link-state and distance-vector protocols. Technically it is classified as an advanced protocol.

Routing types

Static

When using static routing a network administrator specifies the paths between networks in the routing table. This is efficient and has low overhead, but it cannot compensate for network failures without manual intervention.

Dynamic

Dynamic routing has the capability of determining the best path between networks. This method also allows the router to detect and compensate for network issues like congestion by rerouting the communication. When new routers are discovered or added their routing tables are updated.

Default

Default routing is a variant of static routing. A normal static route specifies communication between two known networks. A default route is configured to send packets destined to any unknown destination to the next hop address.

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IPv6 concepts

Addressing

IPv6 addresses consist of eight hexadecimal blocks separated by colons. Each block contains 16 bits making the IPv6 address 128 bits in length.

Here’s an example: 2001:0db8:85a3:0000:0000:8a2e:0370:7334

If an IPv6 address block contains all zeroes it can be truncated using double colons (::). The example address can be truncated to 2001:0db8:85a3::8a2e:0370:7334.

Tunneling

Tunneling aids the transition from IPv4 to IPv6 by allowing IPv6 routers and hosts to communicate with each other over the existing IPv4 infrastructure. To accomplish these IPv6 datagrams are encapsulated within IPv4 packets and travel on the IPv4 network.  The IPv6 datagram is extracted by the IPv6 destination device.

Dual stack

A network that uses both IPv4 and IPv6 is called dual stacked. Dual-stacked packets will not be handled by networks that do not support it. The solution is to tunnel these packets. The best example is the internet which is not completely dual stacked. All IPv6 internet traffic uses tunneling.

Router advertisement

Router advertisement is used as part of IPv6 autoconfiguration. An IPv6 host can auto-configure its own address. In this process, the host uses a standard prefix with its interface ID based on the host MAC address. The host requests configuration information from the router in a message called a router solicitation (RS). The router responds with a router advertisement (RA) containing the necessary configuration information.

Neighbor discovery

The Neighbor Discovery Protocol (NDP) is part of the IPv6 protocol suite. It serves as a replacement for IPv4 for ARP and ICMP and others. NDP uses five message types:

  • Router Solicitation-The Router Solicitation message is sent by IPv6 hosts to discover the presence of IPv6 routers on the link.
  • Router Advertisement – The Router Advertisement message contains the information required by hosts to determine whether or not to use address autoconfiguration, the link prefixes, MTU, specified routes.
  • Neighbor Solicitation – IPv6 nodes send the Neighbor Solicitation message to discover the link-layer address of an IPv6 node on-link.
  • Neighbor Advertisement – The Neighbor Advertisement contains the information required by nodes to determine the sender’s role on the network, and typically the link-layer address of the sender.
  • Redirect – An IPv6 router will send a Redirect message to inform a host of a better first hop address for a specific destination.

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For the previous part of these objectives go to Part 1, for the rest of the 1.3 objectives go to Part 3.

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Network plus N10-007 ExamNotes sub-objective 1.3 routing and switching – Part 1 of 3 – Dumps4shared

Network+ N10-007 ExamNotes for sub-objective 1.3 Explain the concepts and characteristics of routing and switching – Part 1 of 3

In order to understand routing and switching you should be comfortable with the logical and physical aspects of the networks, you will encounter along with the behavior of the devices that control their traffic.

CompTIA Exam Sub-objective 1.3: “Explain the concepts and characteristics of routing and switching.”

Properties of network traffic

Broadcast domains – CSMA/CD – CSMA/CA – Collision domains – Protocol data units – MTU – Broadcast – Multicast – Unicast.

Segmentation and interface properties

VLANs – Trunking (802.1q) – Tagging and untagging ports – Port mirroring – Switching loops/spanning tree – PoE and PoE+ (802.3af, 802.3at) – DMZ – MAC address table – ARP table.

For the rest of the 1.3 exam objectives go to Part 2 and/or Part 3.

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Properties of network traffic

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– Broadcast domains

A broadcast domain can be described as a LAN using switches as its boundaries. Switches can deliver port to port transmissions between nodes reducing overall network congestion. The switch will determine the destination of the traffic and whether or not it should be forwarded to a router.

A broadcast domain is connected to the router through switches. When nodes are connected to a hub a collision domain is created. Remember a hub delivers all traffic to all connected nodes creating the high probability of simultaneous transmissions. In a data collision, all packets are dropped and a resend is required.  The resend or retransmission has the same probability of success as the initial one. This calls for signal control over the media.

photo of a network hub
Hub

Media Access Control methods such as Carrier Sense Multiple Access (CSMA) were developed to alleviate the problem. Here the transmitting NIC senses or listens for traffic on the carrier media and waits for it to clear. Multiple access represents multiple nodes contending for time on the media. This approach is most applicable to 802.3 Ethernet with legacy hardware.

– CSMA/CD

Since all nodes in a collision domain are competing for access to the transmission media Carrier Sense Multiple Access (CSMA) methods are necessary. This is especially true on Ethernet connections. Carrier Sense refers to the transmitting NIC listening on the media for traffic before transmitting. Multiple Access refers to multiple nodes using the same media.

There are two methods of CSMA. First, we’ll look at CSMA with Collision Detection (CSMA/CD).  In this method, the NIC transmits when the media is clear and monitors the transmission. If a collision is detected it can send a jam signal to all nodes that the media is in use then continue the transmission.

– CSMA/CA

CSMA with Collision Avoidance (CSMA/CA) takes a different approach when dealing with collisions. Here once the media is clear, the transmitting node signals the whole collision domain that it will transmit and the other nodes back off their transmissions.

– Collision domains

See Broadcast domains.

– Protocol Data Units

A Protocol Data Unit (PDU) is a message or group of bits containing data and addressing information. As the PDU id is processed through the OSI model, each layer adds or removes formatting information to prepare the payload for the next Layer. As it moves through the layers it will be referred to by a different term. Here is how those terms break down by layer:

OSI Model
Term
Layer 1 Physical layer Transmission or bit
Layer 2 Data Link Layer Frame
Layer 3 Network Layer Packet
Layer 4 Transport layer TCP segment or UDP datagram
Layer 5

Layer 6

Layer 7

Session layer

Presentation layer

Application layer

Payload

– MTU

Essentially the MTU (Maximum Transmission Unit) represents the largest size supported by the Network layer (Layer 2) routers. The standard size is 1500 bytes. There are exceptions that would allow larger frames. For example, VLAN frames have an extra four bytes and a jumbo frame, used in special-purpose networks, which can be up to 9198 bytes.

– Unicast

Unicast transmission is a typical host to host transmission where the message is intended for a single destination.

– Broadcast

A Broadcast transmission will be sent to every node on the network or segment in a broadcast domain.  It is generally used for address resolution when the destination host is not known. Broadcast messages can be sent by a new connection to announce its presence. ARP requests are broadcasted. Router updates also rely on broadcasts.

– Multicast

Multicast refers to transmissions that are sent to multiple nodes simultaneously.  A good example of this is multimedia streaming. Here each intended recipient is configured to receive this traffic.

Segmentation and interface properties

Network segmentation improves performance and security within a broadcast domain. It breaks the domain into more efficient groupings. This can be done using subnets or using VLANs (virtual LANs). We’ll look at these methods next.

– VLANs

VLANS are created using the ports on a Layer 2 switch. The method allows traffic to be directed either to a router or to or a virtual broadcast domain. This allows larger broadcast domains and multiple virtual LANs to be created.

– Trunking (802.1q)

Trunking is the term used for using a switch to support multiple VLANs. On a switch, a trunk is a single connection that supports multiple virtual connections. An 802.1q VLAN tag is placed in an Ethernet frame following the addressing fields.

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– Tagging and untagging ports

Each port on a switch can be configured independently. This allows for ports to be grouped together and assigned to VLANs. When using a trunking protocol the 802.1q tag is read by routers or switches in the path to the destination. When the final switch is reached it removes the tag.

– Port mirroring

Port mirroring is also known as SPAN (Switch Port Analyzer). This technique sends a copy of all traffic on a port to a network security device such as a NIDS. The security device will monitor the traffic for anomalies and report them.

– Switching loops/spanning tree

In networks using multiple switches, it is possible for a failed broadcast transmission to be retransmitted by all the switches on the network (loop) until they eventually flood the network. This problem is addressed by the Spanning Tree Protocol (STP). STP identifies potential switching loops and blocks them. In Network+ N10-007 sub-objective 4.6 we’ll look at STP communication in greater detail. For now, we can say that STP uses Bridge Protocol Data Units (BPDU).

– PoE and PoE+ (802.3af, 802.3at)

IEEE standards 802.3af (PoE) and 802.3at (PoE+) define how electrical power can be transmitted over Ethernet cabling. (PoE) This is highly beneficial in networks that have devices that cannot be powered by the traditional electrical grid. Utilizing unused cable pairs in Cat5 or better cabling PoE delivers 15.4 watts of electricity to devices while PoE+ delivers 25.5 W. Two devices are specified by the PoE standard: The Power Supply Equipment (PSE) and the Powered Devices (PDs)

– DMZ

A Demilitarized Zone (DMZ) is a network space between your network’s internal and external firewalls. Let’s say that you have an external DNS server that you wish to be accessible to the internet. The firewall protecting your external DNS server will allow for a more relaxed configuration than the hardened firewall protecting your internal DNS server.

– MAC address table

The network switches we use maintain a list of MAC addresses. This list is comprised of Mac addresses it knows and those that are updated from other switches. A good example is where inbound communication is intended for a MAC address that is on your network and known to the switch. The source MAC address of this communication will be added to your switch’s MAC address table and the source would be known. The MAC address table is also used to drop incoming packets that are not intended for known internal devices.

– ARP table

The ARP (Address Resolution Protocol) is responsible for mapping IP addresses to MAC addresses in IPv4. ARP maintains a database of the MAC addresses on the local network and the corresponding IP address. This is known as the ARP table. This table is built by initially broadcasting requests to IP addresses in its range. The devices respond with their physical (MAC) address.

The ARP table contains two types of entries, static and dynamic. Static addresses are entered manually. Dynamic addresses are added when an internal host requests an address that is not in the ARP table. Once located that new IP to Mac address mapping will be added to the table. You can view the ARP table on a Windows machine by entering arp –a at the command prompt.

Screenshot of the arp –a command at the command prompt
arp –a at the command prompt

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Network plus N10-007 sub-objective 1.2 Explain devices, applications, protocols and services at their appropriate OSI layers – Dumps4shared

ExamNotes for Network+ N10-007 sub-objective 1.2 Explain devices, applications, protocols and services at their appropriate OSI layers

The OSI layers have been a recurring feature of the Network+ exams from one version to the next for over a decade now. CompTIA is so serious about it that it dedicates this entire sub-objective to this one item.

CompTIA Exam Sub-objective 1.1: “Explain devices, applications, protocols and services at their appropriate OSI layers.”

• Layer 1 – Physical • Layer 4 – Transport • Layer 7 – Application
• Layer 2 – Data link • Layer 5 – Session
• Layer 3 – Network • Layer 6 – Presentation

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OSI Layers & Function

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Mnemonic anyone?

One issue is, of course, to just remember all these layers in the right order on exam day. There are a few mnemonics out there listing the first letter of each layer from the bottom up i.e. from layer 7 to 1. Here are three examples of that:

– People Seem To Need Data Processing

– Please Do Not Throw Salami Pizza Away

– Please Do Not Tell Secret Passwords Anytime

Pick whichever one works best for you (or make up your own), and on exam date, jot it down immediately on the note pages made available to you at the testing center. That will be one less thing to remember (or mess up) as you go through the exam questions.

Layer 1 – Physical Layer

This is the Physical layer on the Network Interface Controller aka Network Interface Card or NIC. It receives the frame and places the actual transmission on the network.

Layer 2 – Data Link Layer

The packet is passed to the Link layer on the NIC, which encapsulates this data with its own header and trailer, creating what is referred to as a frame. The link layer’s frame includes the physical addresses used to find nodes on the local network.

Layer 3 – Network Layer

The Network layer adds a header to the segment. That header identifies the IP address of the destination host as well as the message aka a packet.

OSI Layer 4 – Transport Layer

The Transport layer protocol, typically TCP (for wide area networks or the internet) or UDP (mostly for local area networks) adds a header to the payload. The function of the header is to attach a port number that identifies the application on the destination host. From here on the message, depending on the protocol used, is either a segment or a datagram.

Layer 5 – Session Layer

The Session layer is responsible for establishing maintaining and terminating connections between computers. The connection is called a session. The session layer can also play a role in error handling and connection recovery.

Layer 6 – Presentation Layer

The Presentation layer handles the task of preparing the data and making it acceptable to the Application layer. This preparation includes encryption and decryption, compression and graphics handling.

Layer 7 – Application Layer

The Application layer is the only OSI layer that interacts with the user. As the user sends email or browses the internet the applications they use employ Application layer protocols such as SMTP or HTTP respectively to communicate with the lower OSI layers.

That’s all for objective 1.2! Good luck on the test!

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ExamNotes for Network plus N10-007 1.1 Explain the purposes and uses of ports and protocols – Part 2/2 – Dumps4shared

ExamNotes for Network+ N10-007 1.1 Explain the purposes and uses of ports and protocols – Part 2/2

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Welcome to ExamNotes for Network+ N10-007. This series of posts is one pear each CompTIA Network+ sub-objective. This one addresses sub-objective 1.1 “Explain the purposes and uses of ports and protocols”. Because this sub-objective covers so much ground we have split it up into two and this is Part 2 of 2. Click here for Part 1.

Please give us any feedback you deem appropriate. If you like it as is, we’d love to know. If you don’t like it, we’d love to know how to improve it. Best of luck in your quest for Network+ certification!

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– LDAP Port 389

Think of the Lightweight Directory Access Protocol (LDAP) as a phonebook for network services. The protocol serves to provide access to, and maintenance of, a distributed directory of the users, applications, available network services and systems throughout an IP network. Based on the x.500 standard’s directory services using the Directory Access Protocol (DAP) which relied on the 7 layer OSI model, LDAP uses only a portion of the x.500 standard set and uses the newer and more relevant four-layer Internet protocol suite on port TCP/UDP 389 at the application layer. By containing all the required network information including users and their credentials, LDAP servers can be used to quickly validate user access. LDAP can fulfill specific and detailed responses to queries about the network with precisely detailed information based on the parameters of the request. The more details specified in the request, the more concise the response. In addition to its own Distinguished Name (DN), object identification LDAP can ask DNS servers to locate other LDAP servers.

– LDAPS Port 636

The Lightweight Directory Access Protocol over TLS/SSL (LDAPS) is a secure implementation of LDAP. Since LDAP communication is transmitted in clear text they represent a vulnerability. Encryption is used to secure the LDAP transmissions. The encryption is provided by TLS or SSL and uses port 636.

– H.323 Port 1720

The H.323 standard is used to support point-to-point and multi-point VoIP and video conferencing. H.323 controls call signaling, bandwidth, and multimedia in VoIP calls and video conferences.

Protocol types

– ICMP

The Internet Control Message Protocol (ICMP) operates at the network layer of the OSI model. Considered a core protocol, it reports success or failure of packet transmissions. ICMP will not however correct a failure. Commands that utilize ICMP such as ping are used to diagnose network conditions when troubleshooting.

– UDP

UDP (User Datagram Protocol) is an unreliable connectionless delivery system for communication that also rides on top of IP. The difference here is that the packets are all individual and are all handled separately with no relationship to each other. This negates the flow control and other checks and balances offered by TCP. This means no solid connection, no inter-packet relationship like “I’m the 7th packet of 90”. Big things like error control, there’s no acknowledgment of packet receipt, dropped or lost packets. The sender has no information as to whether their communication was received or not. So why use UDP? It is fast due to this lack of ACK… UDP data streams continuously to the destination, ready or not. While TCP sends, waits for the ACK then sends more. This could add tangible time to large transmissions.

TCP 

TCP (Transmission Control Protocol) is a protocol that rides on top of the IP protocol (Internet Protocol) designed to address the reliability issues of IP. We’ll simply call IP unreliable for now. This is the main reason you see the TCP/IP protocol suite referenced as a single protocol in internet communication. TCP is responsible for the connection and the continuity necessary for reliable communication on any network, most notably the Internet. TCP opens a reliable “socket” on each end of the transmission throughout the entire communication. To effectively do this, TCP needs to know the IP addresses of the client and server plus the port each is using. This action is known as connection-oriented. Much like a traditional telephone call, pickup, dial, connect, chat and hang up. This is why Port/Protocol information that follows it truly significant. With the connection sockets established, TCP becomes responsible for breaking the data into packets of up to 64K but the lower level protocols that use it have much lower maximum sixes i.e. 1500K for Ethernet. TCP will break the data down to the necessary size and add its header. Now TCP is responsible for the delivery meaning that all failed packets are retransmitted (What? on the phone) and that they arrive intact in the correct sequence. Importantly each packet receipt is acknowledged (ACK). If it isn’t, it will be retransmitted. All data is delivered to the correct host in sequence and complete.

– IP

The Internet Protocol (IP) has two versions, IPv4 and IPv6. We will discuss each version later in this series. IP is a connectionless protocol. IP assigns source and destination information to packets. It does not specify a path or establish an end to end session. IP packets can take different routes to their destination and may arrive out of sequence.  For this reason IP is paired with the TCP protocol to create the familiar TCP/IP.

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Connection-oriented vs. connectionless

A connection-oriented protocol establishes a reliable end to end connection between devices. TCP, Frame Relay, and ATM are examples of some of the connection-oriented protocols. As mentioned earlier the reliable connection created is much like a standard phone call where the connection is established, the communication takes place and the connection is terminated. Much the same way a connection-oriented protocol will establish the connection, transmit the data and Connectionless protocols can be paired with connection-oriented protocols to provide reliability.

Connectionless protocols transmit data to the destination without first establishing a connection or guaranteeing delivery.  IP, UDP, HTTP, and ICMP are examples of connectionless protocols. So an HTTP transmission will use the TCP/IP for its session.

And that completes Network+ N10-007 Sub-objective 1.1!

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ExamNotes for Network plus N10-007 1.1 Explain the purposes and uses of ports and protocols – Part 1 of 2 – Dumps4shared

ExamNotes for Network+ N10-007 1.1 Explain the purposes and uses of ports and protocols – Part 1 of 2

Welcome to exam notes for Network+ N10-007!

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ExamNotes is one article for each and every one of the CompTIA Network+ sub-objectives. This one addresses sub-objective 1.1 “Explain the purposes and uses of ports and protocols”.

Because this sub-objective covers so much ground we have split it up into two parts and this is part 1 of 2. Click here for Part 2.

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Protocols and Ports

A protocol is basically the agreement between devices defining how these networked devices will exchange data. Protocols are often used together to take advantage of the particular protocols strengths as you will see below. TCP/IP is a prime example of this type of combination, where IP is responsible for transmitting data without establishing a session. This means the packets can take any possible route to the correct host, resulting in messages that arrive out of sequence. TCP then ensures the transmission is reliable. The Network+ exam objectives list the Protocol and the Port it uses together. The Port number is used to deliver the data of a specific process. For example, a transmission using HTTP protocol will be delivered to Port 80 by default.

– SSH 22

The Secure Shell (SSH) protocol opens a secure network channel that provides confidentiality and integrity for network services over an unsecured network using public key cryptography. This makes it a cryptographic network protocol. It is used to secure remote network logins and other confidential data. Passwords cannot be intercepted because the encryption is established before the login is required.

– DNS 53

The Domain Name System (DNS) is mostly known for its function of translating friendly domain name URLs like www.mysite.com into its actual IP address. These a human is less likely to remember (think IPv6!).

DNS uses two protocols: TCP and UDP on port 53. DNS servers update themselves using and maintaining a list of known host to address translations in a distributed database while obtaining unknown or moved domains. This supports the hierarchical nature of domain naming of domains and sub-domains. Each domain will have a designated authoritative name server to manage the domains and sub-domains and to communicate that information to the database.

– SMTP 25

The Simple Mail Transport Protocol (SMTP) uses TCP port 25 for internet mail transmission. It is an internet standard protocol. Due to the proliferation of SPAM and other email related vulnerabilities, other ports can be used, most notably port 587. A secure nonstandard implementation of this protocol is SMTPS which is not standard but quite effective because it is one of the protocols that can utilize SSL. SMTP is responsible for the transmission of email between servers and for sending email from a client. Other protocols are used for the reception of email on the client.

– SFTP 22

The Secure File Transfer Protocol (SFTP) is a secure and encrypted protocol that is based on the SSH protocol. It is the secure alternative to FTP.

– FTP 20, 21

The File Transfer Protocol is used in a client/server configuration to transfer files. It can operate in active or passive mode and uses TCP to control the connection. In active mode, the connection is initiated by the client. It informs the server about which port it intends to use to receive data. In active mode (although port 21 is used for command and control), the data will be sent out on port 20 which serves as the FTP servers data port. Passive mode is used in situations where inbound client TCP connections are not possible. Firewalls generally block inbound connections by default. Here the client sends a PASV command to the server and the server determines which client port can be used for the transfer.

– TFTP 69

The Trivial File Transfer Protocol (TFTP) is a simplified version of FTP. It does not offer features like authentication and remote directory viewing. It is light, fast but insecure.

– TELNET 23

Developed in the late 60’s, Telnet was designed to support remote logins and communication between computers in what was a “kinder and gentler” time for networks. It provides a functional command prompt on the remote host. These are plaintext and communication channels making them subject to interception. Today’s networks and the internet are not a place where this is acceptable and so Telnet is now considered obsolete. Telnet does not encrypt data, SSH has generally replaced Telnet for these connections.

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– DHCP 67, 68

The Dynamic Host Configuration Protocol (DHCP) has saved years of man hours and countless misconfigurations. As the most common IPv4 or IPv6 TCP/IP addressing method DHCP is responsible for the complete client configuration on a TCP/IP network. On a work network, there is usually an assigned DHCP server. Residential or SOHO implementations use the router provided by the ISP to perform this function. What DHCP does is assign or lease a unique IP address to each host. The duration of the lease is determined by the network administrator or weekly by default. It will define the internet gateway and Domain Name Server to be used. This means that your machine may not get the same IP address when rebooted or otherwise disconnected. The DNS and Gateway settings will remain. The DHCP server has an available pool of IP addresses available to assign to clients (hosts) that attempt to connect to the network. The client broadcasts a UDP discovery packet for an address to all connected networks. All DHCP servers will offer an address to the client then the client will accept the offer from the nearest server by requesting a lease and that server will lease that address to the client. The address assignment process is identical for both IPv4 and IPv6 addressing. In the interest of consistency, the ports used are UDP 67 for the server and UDP 68 for the client.

– HTTP 80

Web Browsers use the Hypertext Transfer Protocol (HTTP) for internet communications and can be considered the foundation of the World Wide Web. It uses the client/server method where a client uses a Uniform Resource Locator (URL) to locate and request information from the target server of the resource. The response is more often than not an HTML page. A typical URL begins with http:// (or increasingly https://) followed by the Fully Qualified Domain Name (FQDN) of the desired resource. URLs to websites can be distributed between parties in messages containing the address which can be converted into clickable links called hyperlinks in reference to the hypertext communication being used. HTTP uses TCP/UDP port 80 and sends unencrypted data by default. This is inherently un-secure.

– HTTPS 443

The HTTP Secure (HTTPS) uses encryption protocols to secure HTTP traffic. Most commonly Secure Sockets Layer (SSL) or Transport Layer Security (TLS).

– SNMP 161

As one of the more popular network management protocols Simple Network Management Protocol (SNMP) is used to monitor and configure network nodes such as Printers, hosts, routers, and servers to name a few using a network manager on TCP/UDP ports 161 and 162. SNMP agent software is used on the nodes to enable monitoring.

– RDP 3389

OK, so this is for the old timers that had their Telnet then Terminal Services. From Windows XP onward the Remote Desktop Connection (RDC) was available. Using the Remote Desktop Protocol (RDP) on TCP/UDP port 3389, RDC is able to bring the fully functional remote machine’s desktop and programs to your device. This requires that the client and server software be configured on Microsoft products but versions are available for most OS’s. You can bring your home PC up on your iPhone.

– NTP 123

One of the oldest protocols Network Time Protocol (NTP) is used to synchronize the time on packet switched networks. Time synchronization is crucial to systems and processes the update data. If a program considers your update older than its latest it may be dropped.

– SIP 5060, 5061

The Session Initiated Protocol (SIP) supports VoIP and multimedia. It works with the IP protocol to create or terminate a session while handling any necessary changes. SIP relies on other protocols such as H.323 to ensure real-time delivery. The SIP protocol can be used as a unicast or two-party session as well as multicast or multi-party sessions.

– SMB 445

Server Message Block (SMB) predates Active Directory and was the foundation of Microsoft’s Windows for Workgroups networking capability. Based on NetBIOS it can run on UDP ports 137, 138 and TCP ports 137, 139 as NetBIOS over TCP/IP. It can also run directly on TCP port 445. While being one of the oldest networking protocols it has been continuously improved and the 3.0 version implemented with Windows 8 (3.02 in 8.1) supports improved performance in virtualized data centers. It is pervasive in many network applications and embedded devices. With newer versions supporting end to end AES encryption. There have been further advances in Windows 10 however, those are outside the scope of these exam objectives. You may also see this service as Common Internet File System (CIFS) or Samba depending on the operating system.

– POP 110

Receiving email is done over several different protocols. There are two main protocols available depending on your service. The first is Post Office Protocol (POP) with the latest version being POP3. This protocol uses port 110 by default and is responsible for the management of messages on the server (saving them or deleting). Deleting the message after delivery is the default mode. Leaving messages on the server is useful if you use multiple devices for messaging.

– IMAP 143

Today’s email user is likely to be using it on a collection of devices as opposed to the traditional PC. They have any or all of the possible devices, Tablets, Smartphones, or Laptops. All are Internet-connected and waiting for email. Now if your smartphone downloads and deletes a work-related email (POP3 default) you have a problem when you check email on your PC or laptop because it’s gone. The Internet Message Access Protocol (IMAP) on TCP port 143 solves this problem by leaving the messages on the server regardless of the delivery status. Every device that checks will get the email. This is great unless you get spammed a lot. Consider that it’s possible that 18 out of 20 of your emails are junk. Your server space will fill up quite quickly. This calls for closer scrutiny of the undeleted messages on your server. You have to move them to the trash folder and purge it or configure the client to purge trash. In spite of this, IMAP is the preferred client messaging protocol.

This is it for Part 1! Click here to go to Part 2/2.

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Screenshot showing TCP & OSI Layers vs. Protocols for Network+ N10-007 Exam sub-objective 1.1 "Explain the purposes and uses of ports and protocols."
TCP & OSI Layers vs. Protocols

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