5. User sends email
SMTP data
Source MAC address | Destination MAC address
23:34:aa:bb:cc:dd | 12:34:aa:bb:cc:dd
FCSPayload
PayloadSource Port | Destination Port
> 1024 | 25
Payload
PayloadSource IP | Destination IP
202.125.157.150 | 115.186.131.69
Payload
Application layer
Transport layer
Link layer
Internet layer
6. This is a mail client software
(e.g., Outlook Express (shown); Mozilla Thunderbird)
Compare with browser software:
(Internet explorer; Mozilla Firefox)
Webmail.niit.edu.pk
Webmail.niit.edu.pk
7. User receives email
POP request
Source MAC address | Destination MAC address
23:34:aa:bb:cc:dd | 12:34:aa:bb:cc:dd
FCSPayload
PayloadSource Port | Destination Port
> 1024 | 110 (POP)
Payload
PayloadSource IP | Destination IP
202.125.157.150 | 115.186.131.69
Payload
Application layer
Transport layer
Link layer
Internet layer
or IMAP requestor HTTP request
Source Port | Destination Port
> 1024 | 143 ( if IMAP)
Source Port | Destination Port
> 1024 | 80 ( if HTTP)
or IMAP requestor HTTP request
15. Multi-protocol label switching (MPLS)
• Packet based
• Unified data-carrying service for both
circuit-based and packet-based clients
Asynchronous Transfer Mode (ATM)
• Cell (small fixed sized packets) based
•Both ATM and MPLS allow traffic engineering
Core network technologies
16. • Uses analog telephone lines
• Utilizes a modulator/ demodulator
(Modem)
• Modems perform error correction/
compression
• V.34 (28.8, 33.6 kbps); V.90 and V.92 (56
kbps)
• Telephone networks limit a single
narrowband channel to 56 kbps
(Narrowband)Access technology
17. • Leased Circuits: E1 (2M), E2 (8M), E3
(34M)
• DSL: Utilizes telephone lines but
performs efficient digital coding
Types: ADSL, HDSL, SDSL, VDSL
• Cable: Utilizes co-axial cables and
provides similar access speeds to DSL
• WiMax: Wireless broadband
technology
(Broadband)Access technology
An intranet is a private computer network that uses Internet technologies to securely share any part of an organization's information or operational systems with its employees. Sometimes the term refers only to the organization's internal website, but often it is a more extensive part of the organization's computer infrastructure and private websites are an important component and focal point of internal communication and collaboration.
An intranet is built from the same concepts and technologies used for the Internet, such as client-server computing and the Internet Protocol Suite (TCP/IP). Any of the well known Internet protocols may be found in an intranet, such as HTTP (web services), SMTP (e-mail), and FTP (file transfer). Internet technologies are often deployed to provide modern interfaces to legacy information systems hosting corporate data.
An intranet can be understood as a private version of the Internet, or as a private extension of the Internet confined to an organization. The term first appeared in print on April 19, 1995, in Digital News & Review in an article authored by technical editor Stephen Lawton.[1]
Intranets differ from extranets in that the former are generally restricted to employees of the organization while extranets may also be accessed by customers, suppliers, or other approved parties.[2] Extranets extend a private network onto the Internet with special provisions for access, authorization and authentication (see also AAA protocol).
In computer networking and telecommunications, Multi Protocol Label Switching (MPLS) is a data-carrying mechanism that belongs to the family of packet-switched networks. MPLS operates at an OSI Model layer that is generally considered to lie between traditional definitions of Layer 2 (Data Link Layer) and Layer 3 (Network Layer), and thus is often referred to as a "Layer 2.5" protocol. It was designed to provide a unified data-carrying service for both circuit-based clients and packet-switching clients which provide a datagram service model. It can be used to carry many different kinds of traffic, including IP packets, as well as native ATM, SONET, and Ethernet frames.
A number of different technologies were previously deployed with essentially identical goals, such as frame relay and ATM. MPLS technologies have evolved with the strengths and weaknesses of ATM in mind. Many network engineers agree that ATM should be replaced with a protocol that requires less overhead, while providing connection-oriented services for variable-length frames. MPLS is currently replacing some of these technologies in the marketplace. It is highly possible that MPLS will completely replace these technologies in the future, thus aligning these technologies with current and future technology needs.[1]
DSL: DSL (VDSL) typically works by dividing the frequencies used in a single phone line into two primary "bands". The ISP data is carried over the high-frequency band (25 kHz and above) whereas the voice is carried over the lower-frequency band (4 kHz and below).
Digital subscriber line technology was originally implemented as part of the ISDN specification, which is later reused as IDSL. Higher speed DSL connections like HDSL and SDSL have been developed to extend the range of DS1 services on copper lines. Consumer oriented ADSL is designed to operate also on a BRI ISDN line, which itself is another (not IP) form of digital signal transmission, as well as on an analog phone line.
Using ADSL, up to 6.1 megabits per second of data can be sent downstream and up to 640 Kbps upstream.
G.Lite or DSL Lite
G.Lite (also known as DSL Lite, splitterless ADSL, and Universal ADSL) is essentially a slower ADSL that doesn't require splitting of the line at the user end but manages to split it for the user remotely at the telephone company. This saves the cost of what the phone companies call "the truck roll." G.Lite, officially ITU-T standard G-992.2, provides a data rate from 1.544 Mbps to 6 Mpbs downstream and from 128 Kbps to 384 Kbps upstream. G.Lite is expected to become the most widely installed form of DSL.
HDSL
HDSL (High bit-rate Digital Subscriber Line), one of the earliest forms of DSL, is used for wideband digital transmission within a corporate site and between the telephone company and a customer. The main characteristic of HDSL is that it is symmetrical: an equal amount of bandwidth is available in both directions. HDSL can carry as much on a single wire of twisted-pair cable as can be carried on a T1 line (up to 1.544 Mbps) in North America or an E1 line (up to 2.048 Mbps) in Europe over a somewhat longer range and is considered an alternative to a T1 or E1 connection.
SDSL
SDSL (Symmetric DSL) is similar to HDSL with a single twisted-pair line, carrying 1.544 Mbps (U.S. and Canada) or 2.048 Mbps (Europe) each direction on a duplex line. It's symmetric because the data rate is the same in both directions.
VDSL
VDSL supports upto 51 Mbps
