Transcript Analysis of Reliable Multicast Protocols

ITEC4610
Network Switching and Routing
ดร. ประวิทย์ ชุมชู
หัวหน้าสาขาวิชาวิศวกรรมสารสนเทศและการสื่ อสาร(ICE)
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Email: [email protected]
ห้องทางาน: F402
เบอร์โทรศัพท์ที่ทางาน: (02)9883655 ต่อ 220
เบอร์โทรศัพท์เคลื่อนที่: 065343850
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Class XI
MPLS (Multiprotocol Label Switching)
ดร. ประวิทย์ ชุมชู
หัวหน้าสาขาวิชาวิศวกรรมสารสนเทศและการสื่ อสาร(ICE)
MUT
Email: [email protected]
ห้องทางาน: F402
เบอร์โทรศัพท์ที่ทางาน: (02)9883655 ต่อ 220
เบอร์โทรศัพท์เคลื่อนที่: 065343850
MUT
Outlines
Motivation
MPLS Overview
MPLS Operation and Components
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Motivation
• IP
The first defined and used protocol De facto the only protocol for
global internet working
… but there are disadvantages
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Motivation
• IP Routing disadvantages:
– Connectionless
e.g. no QoS
– Each router has to make independent forwarding decisions based on the IPaddress
– Large IP Header At least 20 byte outing in Network Layer
– Slower than Switching
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Motivation
• ATM
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connection oriented
Supports QoS
fast packet switching with fixed length packets(cells)
integration of different traffic types (voice, data,video)
…
but there are also disadvantages
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Motivation
• ATM disadvantages
– Complex
– Expensive
– Not widely adopted
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Motivation
• Traditional Routing and packet switching
– A simple-software-based router platform
– L2 switching (Hardware) for local network
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Motivation
Combine the forwarding algorithm used
in ATM with IP.
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Outlines
Motivation
MPLS Overview
MPLS Operation and Components
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MPLS Overview
Layer 3
IP
MPLS
Layer 2
ATM, FR, Ethernet, PPP
Layer 1
SDH, ODH,WDM,CSMA
MPLS is arranged between Layer 2 and Layer 3
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MPLS Functions
• Specified mechanisms to manage traffic flows of various granularities,
such as flows between different hardware, machines, or even flow
between different applications
• Remains independent of the Layer-2 and Layer-3 Protocols
• Provides a means to map IP addresses to simple, fixed-length labels
used by different packet-forwarding and packet-switching technologies
• Interfaces to existing routing protocols such as resource reservation
protocol (RSPV) and open shortest path first (OSPF)
• Supports the IP, ATM, and Frame-relay Layer 2 protocols
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MPLS Example
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MPLS Example
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Outlines
Motivation
MPLS Overview
MPLS Operation and Components
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MPLS Operation
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Label Creation and Distribution
Table Creation at each router
Label-switched path creation
Label insertion/table lookup
Packet forwarding
MPLS components
• LSRs (Label Switching Router) & LERs (Label Edge Routers)
• FEC (Forward Equivalence Class)
• Label &Label Blinding
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MPLS components
• LER (Label Edge Router)
– Resides at the edge of an MPLS network and assigns and removes the labels
from the packets.
• LSR (Label Switching Router)
– Is a high speed router in the core on an MPLS network.
– ATM switches can be used as LSRs without changing their hardware. Label
switching is equivalent to VP/VC switching.
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Label
• The labels are used to forward the packets on their way ( switching).
• The labels change during transmission.
• Hardware can be used to switch packets quickly between links.
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Label Format
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Label Details
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Label Creation
• Topology-based method
– Uses normal processing of routing protocol (such as OSPF and BGP)
• Request-based method
– Uses processing of request-based control traffic (such as RSVP)
• Traffic-based method
– Uses The reception of a packet to trigger the assignment and distribution of a
lable
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Label Distribution
• LDP (Label Distribution Protocol)
– Maps unicast destination into labels
• RSVP, CR-LDP
– Used for traffic engineering and resource
• PIM (Protocol-Independent multicast (PIM))
– Used for multicast states label mapping
• BGP
– External Label (VPN)
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Label-Switched Path (LSPs)
• Hop-by-hop routing
– Each LSR independent selects the next hop for a given FEC. This
methodology is similar to that currently used in IP networks. The LSR uses
any a viable routing protocols, such as OSPF, ATM private network-tonetwork interface (PNNI), etc.
• Explicit routing
– Explicit Routing is similar to source routing. The ingress LSR specifies the
list of nodes through which the ER-LSP traverses. The path specified could
be nonoptimal, as well.
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LSP Details
• MPLS provides two options to set up an LSP
– hop-by-hop routing:
– Each LSR independently selects the next hop for a given FEC. LSRs support
any available routing protocols ( OSPF, ATM …).
– explicit routing: Is similar to source routing. The ingress LSR specifies the
list of nodes through which the packet traverses.
– The LSP setup for an FEC is unidirectional.
– The return traffic must take another LSP!
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LSP
A path is established before the data transmission starts.
A path is a representation of a FEC.
FEC
The Forward Equivalence Class is a representation of a group of packets that
share the same requirements for their transport.
 The assignment of a particular packet to a particular FEC is done just once
(when the packet enters the network).
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Label Space
• Per Platform
– The label values are unique across the whole LSR. The Label are allocated
from a common pool. No two labels distributed on different have the same
value.
• Per Interface
– The label ranges are associated with interfaces. Multiple label polls are
defined for interface, and the labels provided on those interfaces are allocated
from the separate polls. The label values provided on different interfaces
could be the same.
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Label Merging
• The incoming Streams of traffic from different interface can be merged
together and switched using a common label if they are traversing the
network toward the same final destination. This is known as strem
merging or aggregation of flows
• If the underlying transport network is an ATM networks, LSRs could
employ virtual path (VP) or virtual channel (VC) merging
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Label Retention
• Conservative
– The binding between a label and an FEC received from LSRs that are not the
next hop for a given FEC are discarded. This mode requires an LSR to
maintain fewer Lables.
• Liberal
– The binding between a label and an FEC received from LSRs that are not the
next hop for a given FEC are retained. This Mode allows for quicker
adaptation to topology changes and allows for the switching of traffic to
other LSPs in case of changes
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Label Control
• Independent
– An LSR recognizes a particular FEC and makes the decision to bind a label
to the FEC independently to distribute the binding to its peers. The new
FECs are recognized whenever new routes become visible to the router
• Ordered
– An LSR binds a label to a prticular FEC if and only if it is the egress router
or it has received a label binding fro the FEC from its next hop LSR.
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Signaling Mechanisms
• Label Request
– An LSR requests a label from its downstream neighbor so that it can bind to
a specific FEC
• Label Mapping
– In response to a label request, a downstream LSR will send a label to the
upstream initiator using the label mapping mechanism
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Label Distribution Protocol
• Discovery Messages
– Announce and maintain the presence of an LSR in a network
• Session Messages
– Establish, maintain and terminate sessions between LDP peers
• Advertisement Messages
– Create, change and delete label mapping for FECs
• Notification Messages
– Provide advisory information and signal error information
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Label Stack
• The label stack mechanism allows for hierarchical operation in the
MPLS domain. It basically allows MPLS to be used simultaneously for
routing at the fine-grain level
• Each level in a label stack pertains to some hierarchical level. This
facilitates a tunneling mode of operation in MPLS
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CR (Constraint-based routing)
• CR takes into account parameters such as link characterisitcs
(bandwidth, delay, etc. ), hop count and QoS
• The LSP that are established could be CR-LSPs, where the constraints
could be explicit hops or QSOS requirements
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Advantages of MPLS
 Routing takes place only in the LERs (Label Edge
Router)
 Label switching increases speed
 Provides Quality of Service
 It hides the link layer and the differences between
different Layer 2 protocols
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Disadvantages of MPLS
 An additional layer is added
 The router has to understand MPLS
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Network engineering
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โครงสร้างหลักสู ตรใหม่
C, C+, Script( perl, bash, etc.)
Transmission
system+Data
Communication (L1->L2)
Computer Network
(L3->L7)
Term 2
Network Switching and
Routing
Operating System
Term 3
Wireless Networks
Wireless Network Lab
Term 4
Network Management
Telecommunication
Networks
Term 1
Information Technology for
CCNA1-2
11
CCNA3-4
8
Organization Management
Network security
Project I
10
Project II
8
11+8+10+8=37
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