final presentation on the network layer

Topic

Network Layer Introduction

AndIts procols:

Presentation by:

Zulfqar Ali Chishti(Bssit.11.14)

Authors of

Presentation:

INTRODUCTION:

Network Layer Introduction:

Layer-3 in the OSI model is called Network layer. Network layer manages options pertaining to host and network addressing, managing sub-networks and internetworking.Network layer takes the responsibility for routing packets from source to destination within or outside a subnet. Two different subnet may have different addressing schemes or non-compatible addressing types. Same with protocols, two different subnet may be operating on different protocols which are not compatible with each other. Network layer has the responsibility to how to route packets from source to destination, mapping different addressing schemes and protocols.

Network Layer functionalities:

Devices which works on Network Layer mainly focus on routing. Routing may include variety of tasks aimed to achieve a single goal. These can be:• Addressing Devices and Networks.• Populating Routing tables (or static routes).• Queuing incoming and outgoing data and then

forwarding them according to Quality of Service constraints set for those packets.

• Internetworking between two different subnets.• Delivering packets to destination with best efforts.• Provides connection oriented and connection less

mechanism.

Network Layer features:

With its standard functionalities, Layer 3 can provide various features:• QoS management.• Load balancing and link management.• Provides Security.• Interrelates different protocols and subnets with

different schema.• L3 can produce different logical network design

over the physical network design.• L3 VPN and tunnels can be used to provided end to

end dedicated connectivity.

Network Layer Protocols (cont):

• CLNP Connectionless Networking Protocol• EGP Exterior Gateway Protocol• EIGRP Enhanced Interior Gateway Routing

Protocol• ICMP Internet Control Message Protocol• IGMP Internet Group Management

Protocol• IGRP Interior Gateway Routing Protocol• IPv4 Internet Protocol version 4• IPv6 Internet Protocol version 6• IPsec Internet Protocol Security• IPX Internetwork Packet Exchange

Network Layer Protocols :

• MPLS Multiprotocol Label Switching• SCCP Signaling Connection Control Part• BGP Border Gateway Protocol• RIP Routing Information Protocol• Fiber Channel network protocols• SMTP Simple Mail Transfer Protocol• SFTP Secure File Transfer Protocol• POP post office protocol• PPP Point to Point Protocol• NNTP Network News Transfer Protocol

1) CLNP:

CLNP :

• Def:

1) EGP:

EGP :

• Def:

1) IGRP:

IGRP:

• Def:

1) EIGRP:

EIGRP :

• “Enhanced” Interior Gateway Routing Protocol• Based on IGRP and developed to allow easy transition

from IGRP to EIGRP. (“Like IGRP+”)• Cisco proprietary, released in 1994• EIGRP is an advanced distance-vector routing protocol

that relies on features commonly associated with link-state protocols. (sometimes called a hybrid routing protocol).

EIGRP :

Note: The Hybrid term sometimes misleads people into thinking EIGRP has the topology benefits of a link state routing protocol. It does not. EIGRP is a distance vector routing protocol and suffers from all of the same disadvantages of any other distance vector routing protocol, i.e. routing loops.

Note: “Often described as a hybrid routing protocol offering the best of distance-vector and link-state algorithms.” - I would say “features of distance-vector and link-state” not necessarily “the best.”

IGRP and EIGRP: A migration path

IGRP EIGRP

Classful Routing Protocol Classless Routing Protocol• VLSM, CIDR

bandwidth = (10,000,000/bandwidth kbps)delay = delay/1024 bit metric for bandwidth and delay

bandwidth = (10,000,000/bandwidth kbps) * 256delay = (delay/10) * 256 32 bit metric for bandwidth and delay

Maximum Hop Count = 255 Maximum Hop Count = 224

No differentiation between internal and external routes.

Outside routes (redistributed) are tagged as external routes.

Automatic redistribution between IGRP and EIGRP as long as “AS” numbers are the same.

Four key technologies set EIGRP apart from IGRP

EIGRP Technologies

Features of EIGRP• Classless Routing Protocol (VLSM, CIDR)• Faster convergence times and improved scalability• Multiprotocol support: TCP/IP, IPX/SPX, Appletalk

– There is no IPX/SPX or Appletalk in CCNA or CCNP• Rapid Convergence and Better handling of routing loops – (DUAL) (coming)• Efficient Use of Bandwidth

– Partial, bounded updates: Incremental updates only to the routers that need them. – Minimal bandwidth consumption: Uses Hello packets and EIGRP packets by default use no more that 50% of link’s bandwidth EIGRP packets.

• PDM (Protocol Dependent Module)– Keeps EIGRP is modular– Different PDMs can be added to EIGRP as new routed protocols are enhanced or developed: IPv4, IPv6, IPX, and AppleTalk

• Unequal-cost load balancing same as IGRP (unlike OSPF)

EIGRP Terminology • Neighbor table – Each EIGRP router maintains a neighbor table that lists adjacent

routers. This table is comparable to the adjacency database used by OSPF. There is a neighbor table for each protocol that EIGRP supports.

• Topology table – Every EIGRP router maintains a topology table for each configured network protocol. This table includes route entries for all destinations that the router has learned. All learned routes to a destination are maintained in the topology table.

• Routing table – EIGRP chooses the best routes to a destination from the topology table and places these routes in the routing table. Each EIGRP router maintains a routing table for each network protocol.

• Successor – A successor is a route selected as the primary route to use to reach a destination. Successors are the entries kept in the routing table. Multiple successors for a destination can be retained in the routing table.

• Feasible successor – A feasible successor is a backup route. These routes are selected at the same time the successors are identified, but are kept in the topology table. Multiple feasible successors for a destination can be retained in the topology table.

EIGRP

• Enhanced Interior Gateway Routing Protocol (EIGRP) is an advanced distance-vector routing protocol that is used on a computer network to help automate routing decisions and configuration. The protocol was designed by Cisco Systems as a proprietary protocol, available only on Cisco routers, but Cisco converted it to an open standard in 2013.

EIGRP• EIGRP allows a router to share information it

knows about the network with neighboring routers within the same logical area known as an autonomous system. Contrary to other well known routing protocols, such as routing information protocol, EIGRP only shares information that a neighboring router would not have, rather than sending all of its information. EIGRP is optimized to help reduce the workload of the router and the amount of data that needs to be transmitted between routers.

1) ICMP:

Position of ICMP in the network layer :

MESSAGES

ICMP messages are divided into two broad categories: error-reporting messages and query messages. The error-reporting messages report problems that a router or a host (destination) may encounter when it processes an IP packet. The query messages, which occur in pairs, help a host or a network manager get specific information from a router or another host. Also, hosts can discover and learn about routers on their network and routers can help a node redirect its messages.

MESSAGES

General format of ICMP messages :

ICMP always reports error messages to the original source.

Note

ICMP always reports error messages to the original source.

Note

Error reporting messages:

Contents of data field for the error message:

1) IGMP:

IGMP (cont):

• IGMP is used by IP hosts to register their dynamic multicast group membership. It is also used by connected routers to discover these group members.

Multicast streams• Bandwidth reduction• Only UDP• Multicast ‘always-on’

IGMP:

IGMP (internet group management protocol)

• Protocol for multicast stream in order to reach their destination

• Class D address: 224.0.0.0-239.255.255.255 (1110)

IGMP Message Types:

IGMP Message Format:

IGMP Operation:

IGMP basics Step 1

IGMP basics Step 2

IGMP basics Step 3

IGMP versions:

IGMP v1• Membership query• Membership report

IGMP v2• Membership query• V2 Membership report (Fast Leave)• Leave group• V1 Membership report

IGMP v3• Membership query• V3 Membership report (Explicit Host

Tracking)• V2 Leave group• V2 Membership report• V2 Leave group• V1 Membership report

1) IPV4:

IPv4 :

• An IPv4 address is a 32-bit address that uniquely and universally defines the connection of a device (for example, a computer or a router) to the Internet.

• The address space of IPv4 is 232 or 4,294,967,296.

IPv4 :

• 192.168.1.1In Above IP Address:192 is168 is1 is1 is• IPv4 is Easy to remember by

using DNS. i.elocalhost 127.0.0.1

IIT Kanpur 45Apr 2005

Internet Protocol

Transports a datagram from source host to destination, possibly via several intermediate nodes (“routers”)

Service is:• Unreliable: Losses, duplicates, out-of-order delivery• Best effort: Packets not discarded capriciously,

delivery failure not necessarily reported• Connectionless: Each packet is treated independently


IP Datagram Header

VERS HLEN TOS TOTAL LENGTH

IDENTIFICATION FLAG FRAGMENT OFFSET

TTL PROTOCOL CHECKSUM

SOURCE ADDRESS

DESTINATION ADDRESS

OPTIONS (if any) + PADDING

0 4 8 16 19 31


Problems with IPv4: Limited Address Space

• IPv4 has 32 bit addresses.• Flat addressing (only netid + hostid with

“fixed” boundaries)• Results in inefficient use of address space.• Class B addresses are almost over.• Addresses will exhaust in the next 5 years.• IPv4 is victim of its own success.


Problems with IPv4: Routing Table Explosion

• IP does not permit route aggregation(limited supernetting possible with new routers)

• Mostly only class C addresses remain• Number of networks is increasing very fast

(number of routes to be advertised goes up)• Very high routing overhead

– lot more memory needed for routing table– lot more bandwidth to pass routing information– lot more processing needed to compute routes


Problems with IPv4: Header Limitations

• Maximum header length is 60 octets.(Restricts options)

• Maximum packet length is 64K octets.(Do we need more than that ?)

• ID for fragments is 16 bits. Repeats every 65537th packet. (Will two packets in the network have same ID?)

• Variable size header.(Slower processing at routers.)

• No ordering of options.(All routers need to look at all options.)


Problems with IPv4: Other Limitations

• Lack of quality-of-service support.– Only an 8-bit ToS field, which is hardly used.– Problem for multimedia services.

• No support for security at IP layer.• Mobility support is limited.


IP Address Extension• Strict monitoring of IP address assignment• Private IP addresses for intranets

– Only class C or a part of class C to an organization– Encourage use of proxy services

• Application level proxies• Network Address Translation (NAT)

• Remaining class A addresses may use CIDR• Reserved addresses may be assigned

But these will only postpone address exhaustion.They do not address problems like QoS, mobility, security.


IPng Criteria

• At least 109 networks, 1012 end-systems• Datagram service (best effort delivery)• Independent of physical layer technologies• Robust (routing) in presence of failures• Flexible topology (e.g., dual-homed nets)• Better routing structures (e.g., aggregation)• High performance (fast switching)• Support for multicasting


IPng Criteria

• Support for mobile nodes• Support for quality-of-service• Provide security at IP layer• Extensible• Auto-configuration (plug-and--play)• Straight-forward transition plan from IPv4• Minimal changes to upper layer protocols


IPv6: Distinctive Features

• Header format simplification• Expanded routing and addressing capabilities• Improved support for extensions and options• Flow labeling (for QoS) capability• Auto-configuration and Neighbour discovery• Authentication and privacy capabilities• Simple transition from IPv4


IPv6 Header Format

Traffic Class Flow LabelVers

Payload Length Next Header Hop Limit

Source Address

Destination Address

0 4 12 16 24 31


IPv6 Header Fields• Version number (4-bit field)

The value is always 6.

• Flow label (20-bit field)Used to label packets requesting special handling by routers.

• Traffic class (8-bit field)Used to mark classes of traffic.

• Payload length (16-bit field)Length of the packet following the IPv6 header, in octets.

• Next header (8-bit field)The type of header immediately following the IPv6 header.


IPv6 Header Fields• Hop limit (8-bit field)

Decremented by 1 by each node that forwards the packet. Packet discarded if hop limit is decremented to zero.

• Source Address (128-bit field)An address of the initial sender of the packet.

• Destination Address (128-bit field)An address of the intended recipient of the packet. May not be the ultimate recipient, if Routing Header is present.


Header Changes from IPv4• Longer address - 32 bits 128 bits• Fragmentation field moved to separate header• Header checksum removed• Header length removed (fixed length header)• Length field excludes IPv6 header• Time to live Hop limit• Protocol Next header• 64-bit field alignment• TOS replaced by flow label, traffic class


Extension Headers• Less used functions moved to extension headers.• Only present when needed.• Processed only by node identified in IPv6 destination field.

=> much lower overhead than IPv4 optionsException: Hop-by-Hop option header

• Eliminated IPv4’s 40-byte limit on options• Currently defined extension headers: Hop-by-hop, Routing,

Fragment, Authentication, Privacy, End-to-end.• Order of extension headers in a packet is defined.• Headers are aligned on 8-byte boundaries.


Address Types

UnicastAddress for a single interface.Multicast Identifier for a set of interfaces.

Packet is sent to all these interfaces.

Anycast Identifier for a set of interfaces.Packet is sent to the nearest

one.


Text Representation of Addresses

• HEX in blocks of 16 bitsBC84 : 25C2 : 0000 : 0000 : 0000 : 55AB : 5521 : 0018

• leading zero suppressionBC84 : 25C2 : 0 : 0 :55AB : 5521 : 18

• Compressed format removes strings of 0sBC84 : 25C2 :: 55AB : 5521 : 18:: can appear only once in an address.can also be used to compress leading or trailing 0s

• Mixed Notation (X:X:X:X:X:X:d.d.d.d)e.g., ::144.16.162.21


IPv6 Addresses

• 128-bit addresses• Multiple addresses can be assigned to an interface• Provider-based hierarchy to be used in the beginning• Addresses should have 64-bit interface IDs in EUI-64

format• Following special addresses are defined :

– IPv4-mapped– IPv4-compatible– link-local– site-local


Unicast Addresses Examples• Global Aggregate Address

• Link local address

• Site-local address

FP TLA NLA3 13 32

SLA64 bits

Interface ID

1111111010

10 bits0

54 bitsInterface ID64 bits

Public Topology SiteTopology

Interface Identifier

1111111011 0 Interface IDsubnet ID10 bits 38 bits 16 bits 64 bits

16


Multicast Address

Flags 000T 3 bits reservedT= 0 permanentT= 1 transient

Scope 2 link-local5 site-local8 org-localE global

Permanent groups are formed independent of scope.

11111111 flags scope Group ID8 bits 4 4 112 bits


IPv6 Routing• Hierarchical addresses are to be used.• Initially only provider-based hierarchy will be used.• Longest prefix match routing to be used.

(Same as IPv4 routing under CIDR.)• OSPF, RIP, IDRP, ISIS, etc., will continue as is

(except 128-bit addresses).• Easy renumbering should be possible.• Provider selection possible with anycast groups.


QoS Capabilities

• Protocol aids QoS support, not provide it.• Flow labels

– To identify packets needing same quality-of-service– 20-bit label decided by source– Flow classifier: Flow label + Source/Destination addresses– Zero if no special requirement– Uniformly distributed between 1 and FFFFFF

• Traffic class– 8-bit value– Routers allowed to modify this field


IPv6: Security Issues

• Provision for– Authentication header

• Guarantees authenticity and integrity of data– Encryption header

• Ensures confidentiality and privacy

• Encryption modes:– Transport mode – Tunnel mode

• Independent of key management algorithm.• Security implementation is mandatory

requirement in IPv6.


Mobility Support in IPv6

• Mobile computers are becoming commonplace.• Mobile IPv6 allows a node to move from one link to

another without changing the address.• Movement can be heterogeneous, i.e., node can move

from an Ethernet link to a cellular packet network.• Mobility support in IPv6 is more efficient than mobility

support in IPv4.• There are also proposals for supporting micro-mobility.


Additional Features

Anycast Addresses• Multiple nodes on link may have this address• All those nodes will respond to an NS message.• Host will get multiple NA messages, but should accept

only one.• The messages should be tagged as non-override.

Proxy advertisements• Router may send NA on behalf of others.• Useful for mobile nodes who have moved.


Address Auto-configuration

The problem• System bootstrap (“plug and play”)• Address renumbering

Addressing PossibilitiesManual Address configured by handAutonomous Host creates address with no external

interaction (e.g., link local)Semi-autonomous Host creates address by combining a priori

information and some external information.Stateless Server Host queries a server, and gets an address. Server does not maintain a state.Stateful Server Host queries a server, and gets an address.

Server maintains a state.


Auto-configuration in IPv6

• Link-local prefix concatenated with 64-bit MAC address. (Autonomous mode)

• Prefix advertised by router concatenated with 64-bit MAC address. (Semi-autonomous mode.)

• DHCPng (for server modes)

– Can provide a permanent address (stateless mode)– Provide an address from a group of addresses, and keep

track of this allocation (stateful mode)– Can provide additional network specific information.– Can register nodes in DNS.


Address Renumbering

• To migrate to a new address– change of provider– change in network architecture

• Methods– router adds a new prefix in RA, and informs that the old

prefix is no longer valid.– When DHCP lease runs out, assign a new address to node.– DHCPng can ask nodes to release their addresses.

• Requires DNS update. DHCPng can update DNS for clients.

• Existing conversations may continue if the old address continues to be valid for some time.


Upper Layer Issues

• Minor changes in TCP– Maximum segment size should be based on Path MTU.– The packet size computation should take into account larger size of IP

header(s).– Pseudo-header for checksum is different.

• UDP checksum computation is now mandatory.• Most application protocol specifications are

independent of TCP/IP - hence no change.• FTP protocol exchanges IPv4 addresses - hence

needs to be changed.


• The pseudo-header is changed in

checksum computation:– Address are 128 bits.– Payload length is 32 bits.– Payload length is not copied from IPv6 header.

(Extension headers should not be counted.)– Next header field of last extension header is used in place of

protocol.

• UDP packets must also have checksum.(Since no IP checksum now.)


Changes in Other Protocols

• ICMPv6– Rate limiting feature added

• Timer based• Bandwidth based

– IGMP, ARP merged– Larger part of offending packet is included

• DNS– AAAA type for IPv6 addresses– A6 type: recursive definition of IP address– Queries that do additional section processing are redefined to

do processing for both ‘A’ and ‘AAAA’ type records

1) IPV6:

IPv6:

• Def:

1) IP_SEC:

IPsec:

• Def:

1) IPX:

IPX :

• Def:

1) MPLS:

MPLS :

• Def:

1) SCCP:

SCCP :

• Def:

1) EGP:

What Is an EGP?

• Exterior Gateway Protocol• Used to convey routing information between

ASes• De-coupled from the IGP• Current EGP is BGP4

Why Do We Need an EGP?

• Scaling to large network– Hierarchy– Limit scope of failure

• Define administrative boundary• Policy

– Control reachability to prefixes

• Interior– Automatic

discovery– Generally trust

your IGP routers– Routes go to all IGP

routers

• Exterior

Specifically configured peers

Connecting with outside networks

Set administrative boundaries

Interior vs. Exterior Routing Protocols

BGP Basics

• Terminology• Protocol Basics • Messages• General Operation• Peering relationships (EBGP/IBGP)• Originating routes

Terminology

• Neighbor– Configured BGP peer

• NLRI/Prefix– NLRI - network layer reachability information– Reachability information for a IP address & mask

• Router-ID– Highest IP address configured on the router

• Route/Path– NLRI advertised by a neighbor

Protocol Basics

• Routing protocol used between ASes

–if you aren’t connected to multiple ASes, you don’t need BGP :)

• Runs over TCP• Path vector protocol• Incremental update

AS 100 AS 101

AS 102

E

B D

A C

Peering

BGP Basics ...• Each AS originates a set of NLRI• NLRI is exchanged between BGP peers• Can have multiple paths for a given prefix• Picks the best path and installs in the IP

forwarding table• Policies applied (through attributes)

influences BGP path selection

AS 100 AS 101

AS 102

A C

BGP speakers are called peers

BGP Peers

eBGP TCP/IPPeer Connection

Peers in different AS’sare called External Peers

Note: eBGP Peers normally should be directly connected.

E

B D220.220.8.0/24 220.220.16.0/24

220.220.32.0/24

AS 100 AS 101

A C

BGP speakers are called peers

BGP Peers

iBGP TCP/IPPeer Connection

Peers in the same ASare called Internal Peers

AS 102

E

B D

Note: iBGP Peers don’t have to be directly connected.

220.220.8.0/24 220.220.16.0/24

220.220.32.0/24

AS 100 AS 101

A C

BGP Peers

AS 102

D220.220.8.0/24 220.220.16.0/24

220.220.32.0/24

E

B

BGP Peers exchange Update messages containing Network Layer Reachability Information (NLRI)

BGP UpdateMessages

Configuring BGP Peers

interface Serial 0ip address 222.222.10.2 255.255.255.252

router bgp 100 network 220.220.8.0 mask 255.255.255.0 neighbor 222.222.10.1 remote-as 101



eBGP TCP Connection

• BGP Peering sessions are established using the BGP “neighbor” configuration command

222.222.10.0/30

B C DA

AS 100 AS 101

.2220.220.8.0/24 220.220.16.0/24.2 .1 .2 .1.1

– External (eBGP) is configured when AS numbers are different

– Internal (iBGP) is configured when AS numbers are same

AS 100 AS 101Configuring BGP Peers

222.222.10.0/30

.2



B



C

iBGP TCP Connection

• BGP Peering sessions are established using the BGP “neighbor” configuration command

D220.220.8.0/24 220.220.16.0/24A .2 .1 .2 .1.1

– External (eBGP) is configured when AS numbers are different


• Each iBGP speaker must peer with every other iBGP speaker in the AS


AS 100

A B

C


• Loopback interface are normally used aspeer connection end-points

AS 100215.10.7.1

215.10.7.2

215.10.7.3

A B

C




AS 100

A

215.10.7.1215.10.7.2

215.10.7.3

C

B

interface loopback 0 ip address 215.10.7.1 255.255.255.255

router bgp 100 network 220.220.1.0 neighbor 215.10.7.2 remote-as 100 neighbor 215.10.7.2 update-source loopback0 neighbor 215.10.7.3 remote-as 100 neighbor 215.10.7.3 update-source loopback0

A


AS 100

A

215.10.7.1215.10.7.2

215.10.7.3

C

A



B



AS 100

A

215.10.7.1215.10.7.2

215.10.7.3

A B



C


BGP Updates — NLRI

• Network Layer Reachability Information• Used to advertise feasible routes• Composed of:

– Network Prefix– Mask Length

Types of BGP Messages

• OPEN– To negotiate and establish peering

• UPDATE– To exchange routing information

• KEEPALIVE– To maintain peering session

• NOTIFICATION– To report errors (results in session reset)

BGP :

• Def:

1) IRP:

IRP :

Interdomain routing is concerned with determining paths between autonomous systems (Interdomain routing)Routing protocols for Interdomain routing are called exterior gateway protocols (EGP)

AS 6 AS 7

AS 4

AS 2 AS 5

AS 1

AS 3

An autonomous system (AS) is a region of the Internet that is administered by a single entity and that has a unified routing policy

Each autonomous system is assigned an Autonomous System Number (ASN).

UofT’s campus network (AS239) Rogers Cable Inc. (AS812)Sprint (AS1239, AS1240, AS 6211, …)

Autonomous System

110

• Intradomain routing– Routing is done based on metrics– Routing domain is one autonomous system

• Interdomain routing– Routing is done based on policies– Routing domain is the entire Internet

EGP (e.g., BGP)

AS 2 AS 2

IGP (e.g., OSPF) IGP (e.g., RIP)

Interdomain vs Intradomain

111

Interdomain Routing • Interdomain routing is based on connectivity between autonomous systems• Interdomain routing can ignore many details of router interconnection

AS 1 AS 2

AS 3

1) FCNP:

FCNP:

• Def.:

1) SMTP:

SMTP :

• Def.:

1) SFTP:

SFTP :

• Def.:

1) POP:

POP :

• Def:

1) PPP:

PPP :

• Def:

Point to Point protocol (PPP)

• Point to point, wired data link easier to manage than broadcast link: no Media Access Control

• Several Data Link Protocols: PPP, HDLC…• PPP (Point to Point Protocol) is very popular: used in dial up

connection between residential Host and ISP; on SONET/SDH connections, etc

• PPP is extremely simple (the simplest in the Data Link protocol family) and very streamlined

PPP requirements• Pkt framing: encapsulation of packets• bit transparency: must carry any bit pattern in the data field• error detection (no correction)• multiple network layer protocols• connection liveness• Network Layer Address negotiation: Hosts/nodes across the link must

learn/configure each other’s network address

PPP non-requirements• error correction/recovery• flow control• sequencing• multipoint links (eg, polling)

PPP Data Frame

• Flag: delimiter (framing)• Address: does nothing (only one option)• Control: does nothing; in the future possible multiple control fields• Protocol: upper layer to which frame must be delivered (eg, PPP-LCP, IP, IP-

CP, etc)

Byte Stuffing• For “data transparency”, the data field must be allowed to include the

pattern <01111110> ; ie, this must not be interpreted as a flag• to alert the receiver, the transmitter “stuffs” an extra < 01111101>

byte after each < 01111110> data byte• the receiver discards each 01111101 after 01111110, and continues

data reception

PPP Link Control Protocol• PPP-LCP establishes/releases the PPP connection; negotiates options• Starts in DEAD state• LCP Options: max frame length; authentication protocol• Once PPP link established, IP-CP (Contr Prot) moves in (on top of PPP)

to configure IP network addresses etc.

1) NNTP:

NNTP :

• NNTP stands for Network News Transfer Protocol

• It delivers news to anyone who has access to the NNTP server

• NNTP give users the post their reply to posted messages on the server thus creating a thread

• News can be organized into categories etc.

Installation of NNTP :

• Open Internet Information Services (IIS)• Right click on server name / new / NNTP Virtual

Server• Type the description of the server• Assign the default port 119• Point to the location of NNTP Server files• Select storage medium to use for NNTP• Select location of the messages to be stored• NNTP Server is now installed

Starting New NNTP Virtual Server Installation

Type the description of the server

Assign the default port 119

Point to the location of NNTP Server files

Select storage medium to use for NNTP

Select location of the messages to be stored

Configuring the NNTP Server

• Open Internet Information Services (IIS)• Click on server name / right click on desired

NNTP Server / click on properties• Click on each appropriate tab to make the

necessary changes• Click “OK” to close the properties box

Internet Information Services (IIS) Console

Selecting the Properties Sheet of the NNTP Server

Properties Sheet of the NNTP Server

Access Tab

Settings Tab

Security Tab

ANY QUESTION

THANKS FOR COORPORATION

final presentation on the network layer

Devices & Hardware