Module 10 IP Traffic Management, ARP, RARP, ICMP, IGMP

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Module 10 IP Traffic Management, ARP, RARP,
ICMP, IGMP
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• Textbook sections
• LG Section 7.7 Traffic Management and QoS
• BF Chapter 8 ARP and RARP
• BF Chapter 9 Internet Control Message Protocol
  (ICMP)
• BF Chapter 10 Internet Group Management Protocol
  (IGMP)
• Topics
• IP Traffic Management
• ARP RARP
• Internet Control Message Protocol (ICMP)
• Internet Group Management Protocol (IGMP)

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1.IP Traffic Management

• Congestion Overview
• Congestion can occur anytime the amount of data
  that needs to be transmitted by a particular
  media exceeds the bandwidth of that media.
• Congestion anywhere in the path results in delays
  for user applications
• Periodic congestion often occurs due to the busty
  nature of todays network applications and some
  temporary congestion is to be expected in each
  network. Continual congestion or slowness is not
  normal and the causes should be determined.

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1.IP Traffic Management

• Traffic in an IP Network
• Data Examples are
• File transfer FTP and TFTP protocols
• e-mail SMTP protocol
• Overhead Examples are
• Routing protocol updates
• Broadcast requests, such as for a Domain Name
  Server (DNS)
• The use of Address Resolution Protocol (ARP) to
  resolve logical-to-physical addressing issues.
• Traffic Congestion is Caused by the Following
• Bursts of user application traffic
• Multicast and broadcast traffic
• Over-utilized low bandwidth links
• Network design issues

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1.IP Traffic Management

• Network Congestion Can be Controlled in the
  Router Through the Use of
• Adjusting timers on periodic announcements
• To lengthen the interval between the broadcast by
  adjusting timers reduces the overall traffic load
  on the link.
• Providing static entries in routing tables.
• The use of static entries in a routing table can
  obviate the need to dynamically advertise network
  routes across that link. This technique is very
  effective for serial lines.
• Applying standard access lists
• Standard access lists usually filter traffic
  based upon source addressing characteristics. It
  can prevent irrelevant traffic from reaching
  critical links.
• Priority and queues
• Reorder application traffic flowing across a
  serial link in a priority queue so that all
  traffic of a particular type gets through first,
  or in a queue where traffic gets a certain
  percentage of the bandwidth.

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1.IP Traffic Management

• Access List
• An access list is a series of rules that control
  the traffic that flows into or out of an
  interface of a router. An access list is a
  sequential collection of permits and deny
  conditions that apply to IP addresses.
• The router tests addresses against the conditions
  in an access list one by one.
• The first match determines whether the router
  accept or rejects the address.
• Because the router stops testing conditions after
  the first match, the order of the conditions is
  critical.
• If no condition match, the router reject the
  address.

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1.IP Traffic Management
Inbound Access List Processing
No
Incoming packet
Access list?
Yes
Does source address match?
Next entry in list
Yes
No
More entries?
Apply condition
Yes
No
Deny
Permit
Route to interface and forward packet
Issue ICMP Host Unreachable Message
Note For inbound access lists, after receiving
a packet, the router checks the source address of
the packet against the access list If the access
list permits the address, the router continues to
process the packet. If the access list rejects
the address, the router discards the packet and
returns an ICMP Host Unreachable message.
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1.IP Traffic Management

• The syntax of an entry in a standard access list
  (CISCO IOS)
• access-list number action source
• The parameters are
• number A number between 1 and 99, identifying
  the list for future reference
• action The keyword permit or deny, indicating
  whether to allow or block the packet
• source The packets source address
• The following table shows three ways to
  specify the source
• addresses. In most cases, the
  address/mask pairs is used to specify
• blocks of addresses.

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1.IP Traffic Management

• Examples of Access List Processing
• Example 1
• access-list 1 deny 10.10.1.0 0.0.0.255
• access-list 1 deny 10.10.2.0 0.0.0.255
• access-list 1 permit any
• Note
• The router processes each line in order until it
  finds a match. Therefore, if a packet arrives
  from 10.10.2.13, it matches the second rule in
  the list and so is denied.
• Example 2
• access-list 1 permit any
• access-list 1 deny 10.10.1.0 0.0.0.255
• access-list 1 deny 10.10.2.0 0.0.0.255
• Note
• The first line permits all traffic because all
  incoming packets match it. The second and third
  lines are never used. Therefore, access lists
  must be ordered carefully.

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1. IP Traffic Management

• FIFO (first in, first out)
• The first packet received is the first to be sent
  out
• The main problem with FIFO is that it does not
  separate packets according to the queue to which
  they belong. Application, such as telephony,
  could flood the routers with its own packets,
  thereby causing other applications packets to be
  discarded.
• Priority queuing
• A very stringent algorithm that can cause one
  type of traffic to monopolize available
  bandwidth, because as long as there are
  high-priority packets in the queue, theyll be
  processed first. Other traffic is processed only
  when theres available bandwidth left over from
  high-priority traffic.
• Fair queuing
• Share equally with all traffic but gives low
  volume traffic higher priority. Instead of
  assigning priorities to each packet, this
  algorithm tracks the session that a packet
  belongs to. There is no queue list to configure
  or apply to the interface.
• Three different systems
• Ideal fluid flow fair queuing system
• Packet-by packet fair queuing system
• Packet-by-packet weighted fair queuing system

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1. IP Traffic Management

• Quality of Service (QoS)
• A set of metrics used to measure the quality of
  transmission and service available of any given
  transmission system.
• A guaranteed throughput level for critical
  network application. QoS parameters are used in
  traffic engineering to state the level of loss
  (inverse of throughput), latency, and jitter that
  a traffic stream will be guaranteed in a network.
• Queue
• Broadly, any list of elements arranged in an
  orderly fashion and ready for processing.
• In routing, it refers to a backlog of information
  packets waiting in line to be transmitted over a
  router interface.

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LG Figure 7.42 (a) FIFO queuing (b) FIFO queuing
with discard priority
(a)
Packet buffer
Arriving packets
Transmission link
Packet discard when full
(b)
Packet buffer
Arriving packets
Transmission link
Class 1 discard when full
Class 2 discard when threshold exceeded
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LG Figure 7.43 Head-of-line (HOL) priority
queueing
Packet discard when full
High-priority packets
Transmission link
Low-priority packets
When high-priority queue empty
Packet discard when full
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LG Figure 7.44 Sorting packets according to
priority tag
Sorted packet buffer
Arriving packets
Tagging unit
Transmission link
Packet discard when full
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1. IP Traffic Management

• Ideal fluid flow fair queuing system
• Transmission bandwidth is divided equally among
  all nonempty queues. (For example, if the total
  number of flows in the system is n and the
  transmission capacity is C, then each flow is
  guaranteed at least C/n (bits/second)
• One approach could be to service each nonempty
  queue one bit at a time in round-robin fashion

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1. IP Traffic Management

• Packet-by-packet fair queueing system
• One approach could be to service each nonempty
  queue one packet at a time in round-robin
  fashion.
• This approach is not really fair. For example,
  if the packets of one flow are twice the size of
  packets in another flow, then in the long run the
  first flow will obtain twice the bandwidth of the
  second flow.
• A better approach is based on finish tag concept.
  The goal of this approach is to to have each
  packets completion time approximate that of a
  ideal fluid flow fair queuing system
• Each time a packet arrives at a queue, the
  completion time of the packet is derived from an
  ideal fluid flow fair queuing system. The number
  is used as a finish tag for the packet.
• Each time the transmission of a packet is
  complete. The next packet to be transmit is the
  one with smallest finish tag among all of the
  queues.

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1. IP Traffic Management

• Packet-by-packet weighted fair queuing system
• Because different users have different
  requirements, each user flow has a weight that
  determines its relative share of the bandwidth.

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1. IP Traffic Management

• Calculation of finish tags
• Notation
• k k-th packet
• i i-th flow
• C Capacity in bits/second
• P(i,k) length of k-th packet from i-th flow in
  bits
• R(t) the number of rounds at time t in bits
• F(i,k) finish tag of k-th packet for i-th flow
• Case 1 Empty queue Suppose that k-th packet from
  flow i arrives at an empty queue at time tki and
  suppose that the packet has length P(i,k), then
• F(i,k) R(tki ) P(i,k)
• finish tag bits completed at time tki packet
  length in bits

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1. IP Traffic Management

• Calculation of finish tags
• Case 2 Non-empty queue Suppose that k-th packet
  from flow i arrives at an non-empty queue at time
  tki and suppose that the packet has length
  P(i,k), then
• F(i,k) F(i, k-1) P(i,k)
• finish tag finish tag of the previous packet in
  queue packet length in bits
• General case for packet-by-packet fair queueing
  system
• F(i,k) max F(i, k-1), R(tki) P(i,k)

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1. IP Traffic Management

• Calculation of finish tags
• General case for packet-by-packet weighted fair
  queueing system
• F(i,k) max F(i, k-1), R(tki) P(i,k)/wi
• where wi is the weight of i-th flow

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1. IP Traffic Management

• Example (LG Chapter 7 problem 46)
• Problem statement consider a packet-by-packet
  fair queuing system with three logical queues and
  with service rate of one unit per second. Show
  the sequence of transmission for this system for
  the following packet arrival pattern.
• Queue 1 arrival at time t 0, length 2
  arrival at t 4, length 1
• Queue 2 arrival at time t 1, length 3
  arrival at t 2, length 1.
• Queue 3 arrival at time t 3, length 5.

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1. IP Traffic Management
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1. IP Traffic Management

• Round (in terms of ideal fluid flow fair queuing
  system)
• A round consists of a cycle in which all n queues
  are offered service, one bit at a time
• The actual duration of a given round is the
  actual number of queues nactive (t) that have
  information to transmit.
• When the number of active queues is large, the
  duration of a round is large
• When the number of active queue is small, the
  duration of a round is small
• Round is in unit of bit

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1. IP Traffic Management

• Meaning of the equation dR(t)/dt C/nactive(t)
• Given a ideal fluid flow fair queuing system, and
  given the fact that the system started at t 0
• Let R(t) be the number of the rounds at time t,
  that is, the number of cycles of services to all
  n queues. Assuming R(t) is a continuous
  function, then
• dR(t)/dt C/nactive(t)
• Interpretation of the equation above
• For a given duration and number of active queues,
  the higher the transmission capacity in
  bits/second, the more rounds can be completed.
• For a given duration and transmission capacity,
  more active queues means less round can be
  completed.

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LG Figure 7.45 Ideal fluid flow system
Approximated bit-level round robin service
Packet flow 1
Packet flow 2
C bits/second
Transmission link
Packet flow n
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LG Figure 7.46 Ideal fluid flow system and
packet-by-packet fair queuing system (two
packets of equal length)
Queue 1 _at_ t0
Ideal fluid flow system both packets served at
rate 1/2
1
Queue 2 _at_ t0
Both packets complete service at t2
t
0
2
1
Packet from queue 2 waiting
Packet-by-packet queueing system queue 1 served
first at rate 1 then queue 2 served at rate 1.
1
Packet from queue 2 being served
Packet from queue 1 being served
t
0
2
1
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LG Figure 7.47 Computing the finishing time in
packet-by-packet fair queueing and weighted fair
queueing
Generalize so R(t) is continuous, not discrete
R(t) grows at rate inversely proportional to
nactive(t)
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LG Figure 7.48 Ideal fluid flow system and
packet-by-packet fair queuing system (two
packets of different lengths)
Ideal fluid flow system both packets served at
rate 1/2
2
Queue 1 _at_ t0
1
Queue 2 _at_ t0
Packet from queue s served at rate 1
t
2
3
0
Packet-by-packet fair queueing queue 2 served at
rate 1
Packet from queue 2 waiting
1
Packet from queue 1 being served at rate 1
t
1
2
3
0
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LG Figure 7.49 Ideal fluid flow system and
Packet-by-packet weighted fair queuing system
Queue 1 _at_ t0
Ideal fluid flow system packet from queue
1 served at rate 1/4 Packet from queue 1
served at rate 1
Queue 2 _at_ t0
1
Packet from queue 2 served at rate 3/4
t
0
2
1
Packet from queue 1 waiting
Packet-by-packet weighted fair queueing queue 2
served first at rate 1 then queue 1 served at
rate 1.
1
Packet from queue 1 being served
Packet from queue 2 being served
t
0
2
1
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2. ARP RARP

• Address Resolution and Reverse Address Resolution
  
• Physical address (Hardware address)
• local address
• Example MAC address
• Logical address (Protocol address)
• IP address
• Delivery of a packet to a host requires both
  physical address and logical address. Hence,
  mapping between these two address is needed.
• Mapping methods
• Static mapping
• Dynamic mapping
• Address Resolution Protocol (ARP)
• Reverse Address Resolution Protocol (RARP)

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2. ARP RARP
BF Figure ARP and RARP
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BF Figure ARP operation
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BF Figure ARP packet

• Note
• Packet reception When an ARP is received, the
  receiving station will swap hardware and protocol
  addresses, putting the local hardware addresses
  in the sender fields.
• Fig. 8-3 is misleading in describing the length
  of the fields.
• Hardware Type Type of the network (16-bit
  field)
• Protocol Type 16-bit field. For IPv4, the
  value is 080016.
• Target hardware address is not filled in a
  request.

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2. ARP RARP
BF Figure Encapsulation of ARP packet
Note 0x0806 indicates that the data carried by
the fame is ARP
Note Use the physical broadcast address as the
destination address.
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BF Figure Four cases using ARP Part I
Note The selection of the target IP address for
the following four different combinations of
sender and receiver Host -gt Host Host -gt
Router Router -gt Router Router -gt Host
Case2. A host wants to send a packet to another
host on another network. It must first be
delivered to the default router.
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BF Figure Four cases using ARP Part II
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2. ARP RARP
BF Figure Proxy ARP
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2. ARP RARP

• Reverse Address Resolution Protocol (RARP)
• Used for host to dynamically find their IP
  address, when they know only their physical
  address.
• ARP and RARP are different operations
• For ARP, all hosts are equal in status. There is
  no distinction between clients and servers
• RARP requires one or more server hosts to
  maintain a database of mapping from physical
  address to IP address and respond to requests
  from client hosts.

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BF Figure RARP operation
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2. ARP RARP
BF Figure RARP packet
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2. ARP RARP
BF Figure Encapsulation of RARP packet
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3. Internet Control Message Protocol (ICMP)

• Purposes
• IP is a connectionless protocol (best-effort
  delivery service)
• ICMP is to provide feedback about problems in the
  communication environment. ICMP is not meant to
  make IP reliable.
• ICMP message
• ICMP is a network layer protocol.
• However, its message are not passed directly to
  the data link layer as would be expected.
  Instead, the messages are first encapsulated
  inside IP datagrams before going to the lower
  layer.
• Figure 9.2 ICMP encapsulation
• Message Format
• Figure 9.4 General format of ICMP messages
• Table 9.1 ICMP type definition

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3. Internet Control Message Protocol (ICMP)
BF Figure ICMP encapsulation
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3. Internet Control Message Protocol (ICMP)
BF Figure General format of ICMP messages
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3. Internet Control Message Protocol (ICMP)
Table 9.1 ICMP type definition
(a) ICMP types related to error-reporting
(b) ICMP types related to query
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3. Internet Control Message Protocol (ICMP)

• Type 3 Destination unreachable
• Code 0 network unreachable
• Code 1 host unreachable
• Code 2 protocol unreachable
• Code 3 port unreachable
• Code 4 fragmentation needed and DF (do not
  fragment) has been set
• Code 5 Source routing cannot be accomplished

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3. Internet Control Message Protocol (ICMP)

• Type 8 or 0 Echo request or reply
• Can be used by network managers to check the
  operation of the IP protocols
• One of the most frequently used debugging tools
  invokes the ICMP echo request and echo reply
  message.
• A host or router sends an ICMP echo request
  message to a specified destination. Any machine
  that receives an echo request formulate an echo
  reply and returns it to the original sender.
• The echo request and associated reply can be used
  to test whether a destination is reachable and
  responding.
• On many systems, the command users invoke to send
  ICMP echo requests is named ping.

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3. Internet Control Message Protocol (ICMP)

• Type 13 or 14 Timestamp request and reply
• Figure 9.15 Timestamp-request and timestamp-reply
  message format
• Round-trip time calculation
• Sending time value of receive timestamp
  value of original timestamp
• Receiving time time the packet returned
  value of transmit timestamp
• Round-trip time sending time receiving time

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3. Internet Control Message Protocol (ICMP)
BF Figure Timestamp-request and timestamp-reply
message format
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3. Internet Control Message Protocol (ICMP)

• Type 10 or 9 Router solicitation and
  advertisement
• Router discovery
• After a host boots, it must learn the address of
  at least one router on the local network before
  it can send datagrams to destination on other
  networks. ICMP supports a dynamic router
  discovery scheme that allows a host to discover a
  router address.
• Router solicitation
• A host can broadcast a router solicitation
  message. The router or routers that receive the
  solicitation message broadcast their routing
  information using the router advertisement
  message.
• Router advertisement
• Lifetime field It specifies the time in seconds
  a host may use the advertised address. The
  default value is 30 minutes. The default value
  for periodic retransmission of router
  advertisement message is 10 minutes.
• Address preference level field Defines the
  ranking of the router. A host selects a router
  with the highest preference level as the default
  router.

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BF Figure Router solicitation message format
BF Figure 9-18 Router advertisement message
format
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4. Internet Group Management Protocol (IGMP)

• Multicast
• Method of transmitting messages from a host using
  a single transmission to a selected subset of all
  the hosts that can receive the message. A
  message that is sent out to multiple receivers on
  the network by a host.
• Example
• Sending an e-mail message to a mailing list
• Teleconferencing and videoconferencing
• Multicast addresses
• Figure 10.1
• Class D
• Used as destination addresses
• Some addresses are permanently assigned

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4. Internet Group Management Protocol (IGMP)
BF Figure Class D address
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4. Internet Group Management Protocol (IGMP)

• IGMP
• Help a multicast router identify the hosts in a
  LAN that are members of a multicast group
• IGMP messages
• Figure 10.3
• Operation of IGMP in a single network
• Operation of IGMP in an Internet

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BF Figure Four situations of IGMP operation