ch 5 - Network and Transport Layers

IPv4 uses 4 byte addresses

1 billion possible addresses IP addresses often assigned in (large) groups

Packetization and Reassembly

1. Application layers sees message as a single black of data 2. TCP breaks a large message into smaller pieces (packetization) 3. Asks what size packet to use and is done though negotiations 4. TCP puts packets back together at the destination (reassembly) 5. Delivers incoming packets as they arrive (e.g. Web pages)or to wait until entire messages arrives (e.g. email)

Real-Time Transport Protocol (RTP)

1. used after a virtual connection setup by RSVP or RTSP 2. adds a sequence number and a timestamp for helming applications to synchronize delivery 3. uses UDP (because of its small header) as transport

IPv4

192 bits (24 bytes) header, uses 32 bit addresses (4 byte) dotted decimal notation (breaks the address into four bytes and writes the digital equivalent for each byte) ex. 128.192.56.1

TCP/IP was developed in

1974 by V. Cerf and B. Kahn as part of Arpanet (U.S. Department of Defense)

IPv6 uses 16 byte addresses

3.4 x 10^38 addresses

IPv6

320 bits (40 bytes) Mainly developed to increase IP address space due to the huge growth in Internet usage (128 bit addresses)

Routers ACL

Access Control List

Assignment of Addresses

Application Layer address (URL) Network Layer Address (IP address) Data Link Layer Address (MAC address) Servers have permanent addresses, clients usually do not

Protocols Supporting QoS

Asynchronous Transfer Mode (ATM) TCP/IP protocol suite

Programs for Dynamic Addressing

Bootstrap Protocol (bootp) Dynamic Host ControlProtocol (DHCP)

Routers contain

CPU, memory, ports/interfaces, OS

Example of IP variable length data field

Ethernet's man message size is 1492 bytes, so max size of TCP message field is: 1492 - 24- 24 = 1444 bytes 24 - TCP header 24 - IPv4 header

Subnets

Group of computers on the same LAN with IP numbers using the same prefix assigned addresses that are 8 bits in lengths assigned addresses could be more or less than 8 bits in length

Routing

How you decide where to get from one place to another. Only tells next step

Data Link Layer Address Resolution

Identifying the MAC address of the next node (that packet must be forwarded). Uses address resolution protocol (ARP)

Linking to application layer problem. Which application layer program to send a message to?

Port numbers located in TCP header fields; 2-byte each (source, destination)

Linking to Application layer. Nonstandard port numbers

Possible, but requires configuration of TCP and can be used for more security from commonly known ports

TCP/IP protocol suite

RSVP RTSP RTP

How DNS works

If desire URL is in clients address table - use the server address table If not: Use DNS to resolve the address that sends a DNS request packet to its local DNS server

Network Layer

Responsible for addressing and routing of messages

Internet Protocol

Responsible for addressing and routing of packets. Has packet formulations

Transport Layer

Responsible for end-to-end delivery of messages, segmentation and reassembly, interacts with Application Layer.

Transport and Network Layers

Responsible for moving messages from end-to-end in a network, and are tightly linked together

Types of Routing Protocols

Interior routing protocols (RIP, OSPF, EIGRP, ICMP) - operate within Exterior routing protocols (BGP) - operate between

TCP/IP's 5-Layer Network Model

Sender - ATNDP Receiver - PDNTA

Linking to Application Layer

TCP may serve several application layer protocols at the same time, standard port numbers, and nonstandard port numbers)

Most commonly used protocol

TCP/IP; compatible with a variety of application layer protocols and data link layer protocols.

Server Name Resolution

Translating destination host's domain name to its corresponding IP address uses one or more domain name service (DNS) servers to resolve the address

TCP/IP

Transmission Control Protocol/ Internet Protocol - most common, used by all internet equipment

Asynchronous Transfer Mode (ATM)

a high speed data link layer protocol

Autonomous System (AS)

a network operated by an organization protocols classified based on AS

Address Resolution

addresses must be translated from one type to another for a message to travel from sender to receiver

Network Layer Address (IP address)

assigned by network managers or by programs such as DHCP and placed in configuration files every network on the internet is assigned a rare of possible IP addresses for use on its network

If TCP is too large

breaks up a large message into smaller packets, numbers the packets and reassembles the packets at the destination end

UDP can also be used for applications where a packet

can be lost, such as information rich video (ex. when flooding ocean with all kinds of bottles)

Routers connecting to a router

console port, network interface (more common) port, auxiliary port

Decentralized routing

decisions made by each node independently of one another. information needs to be exchanged to prepare routing tables. used by the internet

Centralized routing

decisions made by one central computer. (small, mainframe-based networks)

QoS - Quality of Service

defines and assigns priorities to "classes of service"

QoS routing

defines classes of service, each with a different priority - real time apps, graphical file for a web page, email

Functions of Routers

determine path transmit packets support communication between variety of devices and protocols

Routers dont contain

disk drives, monitor, keyboard, mouse

Routing Information Protocol (RIP)

dynamic distance vector interior routing protocol (used on simple networks)

Most common programs for dynamic addressing

dynamic host control protocol

Open Shortest Path First (OSPF)

dynamic link state interior routing protocol incorporates traffic and error rate measures less burdensome to the network

Addressing

every device on our path has to have an address and have to be assigned and translated into the network dress worldwide

Application Layer address (URL)

for server only (clients don't need it) assigned by network mangers and placed in configuration files some servers may have several apps layer addresses

Dynamic Addressing

giving addresses to clients (automatically) only when they are logged in to a network uses a server to supply IP addresses to computers whenever the computers connect to network

IPv4 include

header length, another version of CRC

Both IPv4 and IPv6 have

hop limits (if a package jumps too many times, assumed the its lost and throw it out)

TCP/IP dominate because

reasonably efficient and error free transmission.

Transport Layer reconstructs the original message into a single whole at the

receiving end

Sending messages using TCP/IP

required network layer addressing information (IP, subnet mask, local DNS server IP, and IP address of the router) address information is obtained from a configuration file or provided by a DHCP server

Transport Layer breaks the message into several smaller pieces at the

sending end

Connectionless Routing

sending packets individually without a virtual circuit. Each packet is sent independently of one another and will be routed separately, following different routes and arriving at different times. ex. Small messages (independent order)

Real-Time Streaming Protocol (RTSP)

sets up virtual circuits for audio-video apps

Resource Reservation Protocol - RSVP

sets up virtual circuits for general apps

Connection Oriented

setting up a virtual circuit or a TCP connection. TCP asks IP to route all packets in a message by using the same path (from source to destination). Packet deliveries are acknowledged and is used by HTTP, SMTP, FTP ex. Large messages (consistent connection)

Routers

special purpose devices used to handle routing decisions on the internet maintain their own routing tables

QoS are timeliness

timely delivery of packets. Required by some applications, especially real time applications. ( ex. Voice over IP and video frames.) Emails doesn't requires this.

Data Link Layer Address *MAC address)

unique hardware addresses placed on network interfaced cards by their manufacturers (based on standardized scheme)

Domain Name Service

used to ermine IP address for a given URL provided through a group of name servers large organizations have their own name servers

Routing Protocols

used to exchange info among nodes for building and maintaining routing tables

Border Gateway Protocol (BGP)

used to exchange routing intro between AS based on a dynamic distance vector algorithm far more complex because has to deal with possible pathways only uses selective routes

Subnet Masks

used to make it easier to separate the subnet part of the address from the host part. you can make networks different sizes, most common is 8 bytes

Routing Tables

used to make routing decisions. kept by computers making routing decisions

Linking to Application layer. Standard port numbers (TCP)

useful practice numbers HTTP - 80 FTP - 21 SMTP - 25

Link State

uses a variety of information types to decide how to route a packet (more sophisticated) links state info exchanged periodically by each node to keep every node in the network up to date provides more reliable up to date paths to destinations used by open shortest path first (OSPF)

Static routing (decentralized)

uses fixed routing tables developed by network managers (used in simple networks)

Dynamic routing or Adaptive routing (decentralized) - costly but better

uses routing tables at each node that are updated dynamically, based on routing condition information exchanged between routing devices

Distance Vector

uses the least number of hops to decide how to route a packet used by routing information protocol (RIP)

MAC Address Resolution

when MAC address of the next node is unknown and the IP address is known use ARP *Broadcast to every device on network network makes connections between hardware and IP address IP addresses don't follow the hardware

How Classful addressing was used

you can assign number to different geographical regions and then eventually go into more into detail. We don't usually do this.

QoS (Quality of Service) Routing

A special kind connection oriented routing with priorities. ex. Video

Network Layer Functions

Addressing Routing

Transmission Control Protocol

Links the application layer to the network layer, performs packetization and reassembly, and ensures reliable delivery of packets

Session Management

Connection Oriented (TCP), Connectionless Routing (UDP), QoS Routing (RTP)

UDP commonly used for control message that are usually small, such as

DNS, DHCP, RIP and SNMP

UDP (User Datagram Protocol)

protocol used for connectionless routing in TCP/IP suite that uses no asks, no flow

Transport Layer Functions

linking to the application layer, segmenting, and session management

Internet Addresses

managed by ICANN (internet corporation for assigned names and numbers) manages the assignment of both IP and application layer are space (domain names)

Both IP versions have a variable length data field

max size depends on the data link layer protocol.

IPv6 is

much newer, some stuff is extraneous. Allows priority, tells total light and larger source and destination addresses. Overall size of header is longer

TAMU has

multiple B class addresses as an organization

Network Layer performs decapsulation

on receiving end, which removes the network layer header at receiving end and pass them up to the transport layer

Network Layer performs encapsulation

on sending end, which adds network layer header to message segments

UDP uses only a small packet header

only 8 bytes contains only 4 fields: Source port Destination port Message length Header checksum