Interconnection Protocols Flashcards
VoIP
Ethernet Phones
Not paying to send email, why pay for digitalised voice traffic.
Common all over now.
VoIP advantages
-To reduce the cost
-A single infrastructure
-To gain extended capabilities
-Avoid excess delivery delay
-Provide good QoS
VoIP Risks
Ethernet telephones and gateways between LAN based and legacy telephone networks.
Risk is the quality of connection.
Wireless devices can become out of range of an Ethernet Connection.
SIP
Session Initiation Protocol.
- An Application Layer Protocol
- Signalling protocol for real-time sessions
- Provides a single infrastructure for voice, video, instant messaging.
SIP Group Categories
User location – real-time local discovery
User availability – is user available to communicate
User capability – choice of media and coding scheme
Session set up – establishing the session
Session management – transferring sessions; modifying parameters,
SIP is very similar to HTTP, request response connection.
Session Initiation Protocol (SIP) started as a way to:
- Establish
- Modify
- Terminate calls
The Internet and NAPs, hierarchy of ISP sizes:
Tier 1: International ISPs
Tier 2: National ISPs
Tier 3: Regional ISPs
Tier 4: Local ISPs
The Internet and NAPs
-Network Access Points are Internet Exchange Points (IXPs)
-They interconnect public peering ISPs to exchange traffic.
-They exchange routing information using BGP-4
Selective private peering with direct inter-ISP links
Naps are layer 2 switches
- Typically using ATM switching
- With support for ISO-provided routers
NAPs are interconnected by high-speed backbones
Router Capabilities
Routers may be any of several types:
Access routers – Edges of the internet
Enterprise routers – Organisation network
Core routers – Handling Heavy Data flow
Router may also have Layer 2 switching capabilities
May have hardware or software routing capabilities
Routers may be table top or chassis based
- Multiple plug-in router modules
Modern Router Capabilities
Routers may be embedded into other multi-feature network devices, which also include
- Wireless Access Point
- A small (e.g. 4-port) wired switch
- Firewall (hardware device)
What is MPLS
Multi-protocol label Switching (MPLS)
MPLS philosophy is to “route at the edges, and switch in the core”
Provides the best parts of both Layer 3 routing control and Layer 2 switching
Layer 3 is “multi-protocol” since the switching is done at Layer 2
MPLS
A merger of Layer 3 (e.g. IP) routing protocols and Layer 2 switching.
Intended for use in the core portion of
Intranets/Internet
- Useful for carriers, ISPs and enterprise WAN networks
MPLS router in the core is called a label-switching router (LSR)
Why use MPLS
-MPLS specifications allow many options.
-Route the first packet when an MPLS label path doesn’t exist to the destination network
-When first packet processed at each LSR, the Layer 2 switched connection is set up between those LSR.
-Subsequent packets are handled by switching at Layer 2 (e.g. ATM)
-Swapping the label at each LSR
-Label switching is also label swapping
A specific MPLS Approach
Benefits of MPLS include:
-Traffic engineering capabilities (explicit path other than that selected by routing)
- MPLS-based VPNs with simpler provisioning
Service differentiation (QoS)
- Improved performance (switching instead of routing at each hop)
- Scalability
- Many benefits of connection-oriented forwarding to connectionless intranets and their routing protocols.
QoS with IP
QoS usually refers to providing support for time-sensitive delivery
-Such as voice and/or compressed video
Much of the work in this area is now showing up in products
-Usually involves prioritisation of traffic based on the type of data being carried
Effort Include
-Various forms of IP switching
-Differentiation services (using the IP TOS byte)
-Multiprotocol label Switching (MPLS)
