Networking Protocols

• Protocols are conventions and rules for communication, necessitating cooperative action in computer networking that goes beyond mere byte exchange. They ensure entities in different systems communicate effectively by "speaking the same language".

Protocol Architecture

• Data transfer tasks are divided into modules to manage complexity and facilitate interaction. File transfers uses three modules: file transfer application, communication service, and network access.

Real World Example

• Peer-to-peer protocols operate independently of each other. Secretaries exemplify this, changing the communication medium to email
• Translators might agree on using a common language. Each layer includes a header.

Simplified File Transfer Architecture

• Computer X links to Computer Y through a File Transfer Application Layer, Communication Service Module, and Network access module through communications.

General Protocol Architecture Principles

• It has a layered structure using a protocol stack. Each layer offers services to the layer above while expecting services from the layer below. Peer entities use their protocols for communication.

General Three Layer Model

• Includes network access, transport, and application layers, applicable across various applications like email and file transfer.

Network Access Layer

• Network access layers involve the exchange of data between the computer and the network and provides the destination addresses for routing, using techniques such as circuit switching, packet switching and LANS
• It may use specific drivers and interface equipment specific to the network types.
• Upper layers remain unaware of these specific details, maintaining independence.

Transport Layer

• Transport Layer enables reliable data exchange, ensuring packets arrive in the order sent and retransmitting any lost or erroneous packets; operating independently of both the network and the application.

Application Layer

• Supports various user applications, such as e-mail and file transfer.

Addressing Requirements

• Addressing necessitates two levels: unique network addresses for each computer and unique addresses (like ports) for each application on multitasking systems

Protocol Data Units (PDU)

• PDUs are formed as user data traverses through layers, with control information like headers and sometimes trailers being added or removed at each step; this combination, essentially a "packet", differs across layers.

Transport PDU

• Transport layers handles fragmentation of user data, adding a header with destination port, sequence number, and an error detection code, often found in the trailer. The transport layer may also split application data into smaller packets

Network PDU

• Network PDU's adds a network header with the destination computers address and optional network facilities like priority level.

Protocol Architecture Operation

• Consits of a source, destination, application, transport headers and a network access module that contains the network header.

Standard Protocol Architecture

• Standard Protocols uses a common set of conventions. Its standards can be designed only once. This allows products from different vendors to interoperate, whereas customers are not limited to one vendor.
• Failure to implement standard protocols on products will limit a products market; as these products are largely favorable.
• Two standard approaches includes the OSI reference model and the TCP/IP protocol suite.

OSI Reference Model

• OSI is a reference model framework for standardization, defining a set of layers and service that each layer provides. It allows for one or more protocols to become developed for a layer.
• It was developed by the International Organization for Standardization (ISO) and published by ITU-T (International Telecommunications Union)
• It is a layered model that compromised of 7 layers which has been presented as the optimal number of layers.
• It was delivered too late in 1984, where TCP/IP was becoming the de facto standard. However the model proves to still be valid within textbooks

OSI - Layer Model

• Each layer performs a subset of of the required communication functions
• Each layer relies on the the next lower layer to perform more primitive functions
• Each layer provides services to the next higher layer
• Changes in one layer should not require changes in other layers.

OSI as Framework for Standardization

• Layer functionalities are described by OSI. Different standards can be developed based on these functionalities.

Layer Specific Standards

• It has service definitions and addressing access points as well as a protocol specification for precise syntax and semantics for interoperability

Elements of Standardization

• Includes protocol specifications that operate between the same layer on two systems. These specifications have to be precise due to data units and all fields.
• Service definition for functional description of what is provided to the next upper layer. This also comes with Addressing via SAPs.

OSI Environment

• It comprises of the application layer, Transport, Network, session presentation, and data link layers.

OSI Layers (1)

• Consists of a Physical components that has an electrical and mechanical interface between devices
• The electrical level dictates voltage levels for transmission rates and coding
• The mechanical level dictates the interface specs
• Data Link deals with basic services of flow control, error detection and link level control. A sublayer is added, MAC, to deal with control access for broadcast networks.

OSI Layers (2)

• Network layer is responsible for the transfer of information through a communication network that also network related problems
• Network nodes must perform switching and routing functions.
• This layer also addresses: QoS and congestion control.
• It is also responsible for handling Internetworking issues, which includes differences in addressing and max data length requirements
• Upper layers do not need to know about the underlying networking technology
• Network layer is not needed on direct links

OSI Layers (3)

• Transport layers facilitates end to end exchange of data with no data loss or duplicates
• If needed, upper layer data can be split into smaller units.
• It is also responsible for sessions that has dialogues and whose turn to talk There is dialogue discipline of: full duplex and half duplex.
• There is also checkpointing and recovery capabilities.

OSI Layers (4)

• Presents data in various forms, allowing for compression and encryption
• Application layers support various applications and formats.

TCP/IP Protocol Suite.

• It is a widely interoperable network architecture specified and extensively used before OSI because OSI was slow to take place in the market
• TCP/IP Protocol Suite was funded by DARPA (US Defense Advanced Research Project Agency) for packet switching.
• Has made for enormous market for TCP/IP thanks to DoD. Used by the Internet and WWW

TCP/IP Protocol Suite

• it lacks an official layer structure, but some protocols do imply one
• Consists of application layers, host layers, internet layers, network access layers, and physical layers.
• It acts as a model built on it's own protocols for applications in TCP, IP and applications that are used on the protocol

OSI vs TCP/IP

• OSI consists of Application Layers which makes of Application.
• Presentation and Session whilst TCP/IP have HTTP and SMTP.
• Transport Layer uses TCP and UDP
• Network Layer uses IP
• Data Link uses Network Access
• Physical has a physical presence

Network Access and Physical Layers

• Focuses on connecting to a network efficiently for IP packet transmission, with protocols largely undefined by TCP/IP and predominantly implemented in hardware such as Ethernet

Internet Layer

• This layer manages routing across networks where each packet travels independently, may not arrive due to network issues, or may be received out of order. DoD established this process so the network remained flexible and response to the loss of some subnet devices
• It is implemented in end systems and routers and acts as the (IP) internet protocol

Transport Layer

• Enables end-to-end data transfer using two protocols
• Transmission Control Protocol (TCP): A connection-oriented, reliable and and ordered delivery of data as their main goals
• User Datagram Protocol (UDP): Connectionless services where delivery is not guaranteed.

Application Layer

• Provides support for user applications via separate modules such as HTTP, SMTP, and Telnet

IP (Internet Protocol)

• It is the core of the TCP/IP protocol suite. Two versions are co-existing: V4 and V6
• IPV4: Widely used IP Protocol
• IPV6: Standardized in 1996 but not highly deployed. This has a minimum header of 20 octets (160 bits)

IPv6

• IPv6 enhances modern high-speed networks over IPv4 and supports for multimedia data streams

• V6 increase in address space

• 128 bit vs the 32-bit of v4.

• This however is not backward compatible. Therefore all equipment and software must change.

TCP

• TCP (Transmission Control Protocol) involves end to end protocols that are built on reliable connections and have both error and flow control. Connections are in TCP terms for termporary association between entities in different systems.
• The PDU is called "TCP segment" and also includes destination and source ports

UDP

• UDP is an alternative to TCP that has end-to-end protocol. Has no guaranteed delivery, or preservation of sequence, no protection of duplication with the smallest amount of overhead

PDUs in TCP/IP

• Includes the network level header with the destination addresses, sequence numbers and checksums as well Destination ports and source addresses.

Operation of TCP and IP

• This makes for a logical connection across the Router subnet work in order to transport packets.

Protocols in TCP/IP Suite

• Includes telnet, FTP, SMTP, HTTP, DHCP,BGP, DNS, SNMP, TCP, TLS, RSVP, RTP,ICMP etc.

Internetworking

• Internetworking is the concept of interconnected networks that can be seen as a large network. Each constituent network can be seen as a subnetwork and considered an internet. Conceptually, this is the same idea as a specific network and the internet is the most important example for one.

Internetworking Devices

• Support communication among subnetwork devices called End systems (ESs)
• Subnetworks are connected by intermediate systems (ISSs), or "routers", that relay packets routed between subnetworks
• Routers must support multiple Network Access Protocols if subnetworks differ.
• In OSI, a router operates at layer 3 (Network Layer)

Routers

• Routers interconnect dissimilar subnetworks without modifying their architectures but must accommodate differences in addressing schemes and packet sizes and use the IP protocol.

Configuration for TCP/IP Example

• Routers handle dissimilar networks linked by protocols to workstations and routers.

Action of Sender

• The application protocol prepares a data block for transmission. The data are converted to a form the destination expects: different character code, encryption, or compression. TCP breaks the data block into a number of tracked segments,Each TCP segment includes a header for detection of errors. A copy is made of each TCP segment, retransmission is needed due to the loss/damage. IP breaks a TCP segment into a number of datagrams for various networks. Each datagram includes a header containing a destination address, a frame check etc. Finally an ATM header is added to each IP datagram to form/transmit an ATMS cell.

Action of Router

• the IP header is examined and outgoing links is determined and passed onto datagrams back to the link for transmission. Processing the cell, the ATM layer removes the header and processes it. This process interprets the signal as a call of bits and then process them. LLC is added to each IP datagram to to form an LLC DPU with sequence numbers and other address data. The media is then transmited over the communication channel

Action of Receiver

• The incoming information is interpreted as data to the MAC fram. The header is then processed in a LLC format for the layer to use for error correction etc.
• Processing the IP datagram means that the header is removed.
• TCP removes the header for the segment in question and checks for acknowledgement if there is an mismatch.
• The segments are reassembled if the segment has multiple parts.
• The necessary translations are preformed including transformations

Standards

• Required to allow for interoperability among equipment
• Ensures a large market for equipment and software as well as products to communicate
• Can freeze technology to improve products.

Standards Organizations in Networking

• The Internet Society
• ISO (International Organization of Standardization): more formalized NGO (but most members are from Governments)
• ITU-T (formerly CCITT): International Telecommunications Union

Internet Society (ISOC)

• Engages in Internet development and standardization with three subgroups:
• IAB (Internet Architecture Board)
• IETF (Internet Engineering Task Force)
• IESG (Internet Engineering Steering Group)

IETF Organization

• Grouped into applications, security and other domains
• Consists of area directories with groups contributing and standardizing protocols

Internet Drafts and RFCs

• Draft documents expires in 6 months (can be resubmitted, published online)
• RFC's can be used as comment (are final versions, obsolete and may have any types of standard.

Internet Standards Track

• Involve the steps of increasing amount of scrutiny and testing
• Steps 1-4: Internet draft, Proposed standard (needs at least six months to advance), Draft Standard for two independent implementation and internet Standard (consensus)
• Step 3 Key is the differences in ISOC.

Internet Assigned Numbers Authority (IANA)

• A ISOC organization responsible for numeric codes on the Internet. These protocols work with numeric parameters such as the meaning of all numeric codes are mostly specified in RFCs, including IP addresses, port numbers, error codes, status codes, message types, options, etc.