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Are You Smarter Than a CCENT? Transport Layer

Here is a query from a current project – enjoy!

  1. You are examining a packet capture from your local network. What two determinations can you make from this output? (Choose 2)

100-105a. This is a UDP packet
b. This is a TCP packet
c. The target destination is FTP
d. The target destination is HTTP

Correct Answer: b, d

Explanation: Due to its use of reliable transmissions, Transmission Control Protocol (TCP) uses many fields in its packet structure. These include:

  • source TCP port number
  • destination TCP port number
  • sequence number
  • acknowledgement number
  • TCP data offset
  • reserved data
  • control flags
  • window size
  • TCP checksum
  • urgent pointer
  • TCP optional data

In contrast, the unreliable User Datagram Protocol (UDP) packets feature these simple fields:

  • source port number
  • destination port number
  • length
  • checksum

From the destination TCP port number here of 80, you can determine the intended target service is the Hypertext Transfer Protocol (HTTP). Know the following common ports for this exam:

Port Number TCP or UDP Protocol
20 TCP FTP Data
21 TCP FTP Control
22 TCP SSH
23 TCP Telnet
25 TCP SMTP
53 UDP DNS
67, 68 UDP DHCP
69 UDP TFTP
80 TCP HTTP
110 TCP POP3
161 UDP SNMP
443 TCP SSL/TLS
514 UDP Syslog
520 UDP RIP

CCIE Evolving Technologies – Cloud Performance and Reliability

Evolving

Here is my latest installment in the complimentary CCIE Evolving Technologies training that all candidates must master for any CCIE written exam.

CCIE Evolving Technologies – Cloud Performance

Cloud technologies can cause great enhancements in the performance of your enterprise IT needs, or, they can cause nightmares. Understand that due to virtualization, contention for cloud resources, if not properly managed (especially in multitenant environments) can make performance unacceptable.

There are numerous public cloud providers who sell cloud server instances, typically by the hour and priced based on the memory (DRAM) size of the instance. In such an environment, an 8 Gbyte instance might cost roughly eight times as much as a 1 Gbyte instance. Other resources, such as CPUs, are scaled and priced according to the memory size.

The result can be a consistent price/performance ratio, with some discounts to encourage the use of larger systems. Some providers allow you to pay a premium for a larger allotment of CPU resources (a “high-CPU instance”). Other resource usage may also be monetized, such as network throughput and storage.

Cloud technologies provide the unique ability for dynamic capacity allocation. Companies can increase server instances as needed, in reaction to real load. This can also be done automatically via the cloud API, based on metrics from performance monitoring software. A small business or start-up can grow from a single small instance to thousands, without a detailed capacity planning study as would be expected in enterprise environments.

Storage in the cloud can be an area of concern since when compared to local disk, performance can vary considerably. As a result, some storage services allow an IOPS rate to be purchased when reliable performance is desired.

Fortunately, OS virtualization features great enhancements in performance. Have you ever virtualized Windows, providing the bare minimum of required RAM and witnessed it outperform tradition systems installs with dramatically more RAM. This is an excellent aspect of cloud computing.

CCIE Evolving Technologies – Cloud Reliability

While cloud performance is quite tricky and can be a risk or great reward, reliability thanks to the cloud, tends to be a much more reward based proposition.

Contingency planning efforts for continuity of operations and disaster recovery are concerned with designing and implementing cloud architectures that provide run-time reliability, operational resiliency, and automated recovery when interruptions are encountered, regardless of origin.

The technologies features in IT clouds today help ensure this and include:

  • Resource Pooling
  • Resource Reservation
  • Hypervisor Clustering
  • Redundant Storage

While these technologies address basic failover and availability demands, more specialized and complex approaches include:

  • Dynamic Failure Detection and Recovery
  • Zero Downtime

These help establish resilient cloud architectures that act as pillars for enterprise cloud solutions.

CCENT ICND1 100-105 Exam Cram Premium Edition and Practice Test