Final Presentation on the Network layer

Topic
Network Layer
Introduction
And
Its procols:

Presentation by:
Zulfqar Ali Chishti
(Bssit.11.14)
Authors of
Presentation:

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

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

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.

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

Contents of data field for the error message:

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 versions:
 IGMP v1
• Membership query
• Membership report
 IGMP v2
• V2 Membership report (Fast Leave)
• Leave group
• V1 Membership report
 IGMP v3
• V3 Membership report (Explicit Host
Tracking)
• V2 Leave group
• V2 Leave group

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 :
• 192.168.1.1
In Above IP Address:
192 is
168 is
1 is
1 is
• IPv4 is Easy to remember by
using DNS. i.e
localhost 127.0.0.1

Apr 2005 IIT Kanpur 45
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 options
Exception: 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
Unicast Address 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 bits
BC84 : 25C2 : 0000 : 0000 : 0000 : 55AB : 5521 : 0018
• leading zero suppression
BC84 : 25C2 : 0 : 0 :55AB : 5521 : 18
• Compressed format removes strings of 0s
BC84 : 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 NLA
3 13 32
SLA
64 bits
Interface ID
1111111010
10 bits
0
54 bits
Interface ID
64 bits
Public Topology Site
Topology
Interface Identifier
1111111011 0 Interface IDsubnet ID
10 bits 38 bits 16 bits 64 bits
16

Multicast Address
Flags 000T 3 bits reserved
T= 0 permanent
T= 1 transient
Scope 2 link-local
5 site-local
8 org-local
E global
Permanent groups are formed independent of scope.
11111111 flags scope Group ID
8 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 Possibilities
Manual Address configured by hand
Autonomous 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 ServerHost 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

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/IP
Peer Connection
Peers in different AS’s
are called External Peers
Note: eBGP Peers normally should be directly connected.
E
B D
220.220.8.0/24 220.220.16.0/24
220.220.32.0/24

AS 100 AS 101
A C
BGP speakers are
called peers
BGP Peers
iBGP TCP/IP
Peer Connection
Peers in the same AS
are 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
D
220.220.8.0/24 220.220.16.0/24
220.220.32.0/24
E
B
BGP Peers exchange
Update messages
containing Network Layer
Reachability Information
(NLRI)
BGP Update
Messages

Configuring BGP Peers
interface Serial 0
ip 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
interface Serial 0
ip address 222.222.10.1 255.255.255.252
router bgp 101
network 220.220.16.0 mask 255.255.255.0
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 101
222.222.10.0/30
.2
interface Serial 1
ip address 220.220.16.2 255.255.255.252
router bgp 101
network 220.220.16.0 mask 255.255.255.0
B
interface Serial 1
ip address 222.220.16.1 255.255.255.252
router bgp 101
network 220.220.16.0 mask 255.255.255.0
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
iBGP TCP/IP
Peer Connection
AS 100
A
B
C

• Loopback interface are normally used as
peer connection end-points
AS 100
215.10.7.1
215.10.7.2
215.10.7.3
A
B
C
iBGP TCP/IP
Peer Connection

iBGP TCP/IP
Peer Connection
AS 100
A
215.10.7.1
215.10.7.2
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 update-source loopback0
A

AS 100
A
215.10.7.1
215.10.7.2
215.10.7.3
C
A
ip address 215.10.7.2 255.255.255.255
router bgp 100
network 220.220.5.0
B
iBGP TCP/IP
Peer Connection

AS 100
A
215.10.7.1
215.10.7.2
215.10.7.3
A
B
ip address 215.10.7.3 255.255.255.255
router bgp 100
network 220.220.1.0
C
iBGP TCP/IP
Peer Connection

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)

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

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.

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

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

Final Presentation on the Network layer

Final Presentation on the Network layer

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