Management & Backbone

MPLS - Multi Protocol Label Switching

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MPLS - Multi Protocol Label Switching

MPLS (MultiProtocol Layer Switching) is a layer 2.5 technology that combines the virtues of IP routing and fast layer 2 packet switching. IP packet forwarding is not suited for high-speed forwarding due to the need to evaluate multiple routes for each IP packet in order to find the optimal route, i.e. the route with the longest prefix match. However, Internet Protocol routing provides global reachability through the IP address and through IP routing protocols like BGP or OSPF. Layer 2 packet switching has complementary characteristics in that it does not provide global reachability through globally unique addresses but allows fast packet forwarding in hardware through the use of small and direct layer 2 lookup addresses. MPLS combines IP routing and layer 2 switching by establishing layer 2 forwarding paths based on routes received through IP routing protocols like BGP or OSPF. Thus the control plane of an MPLS capable device establishes layer 2 forwarding paths while the data plane then performs packet forwarding, often in hardware. MPLS is not a layer 2 technology itself, i.e. it does not define a layer 2 protocol but rather makes use of existing layer 2 technologies like Ethernet, ATM or Frame Relay.

QoS - Quality of Service Protocols

Slide Presentation

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QoS - Quality of Service Protocols

Slide Presentation

QoS (Quality of Service) collectively denotes technologies and methods for assuring a defined level of service quality in a data network. Prioritization is a core function of QoS, but QoS is much more than simply giving packets different priorities. In fact, QoS is about ensuring that different properties of the packet transmission meet pre-defined criteria like packet loss rate, delay, delay variation called jitter and error rate. A QoS-enabled router in the transmission path must enforce the defined QoS through appropriate queueing strategies like priority queueing, round robin and weighed fair queueing. Additional algorithms like random early discard improve a router's performance in case of congestion. Commonly used QoS protocols are DSCP / TOS (DiffServ) for IP layer QoS, MPLS and 802.1p (VLAN) for layer 2 QoS and RSVP for IntServ based scenarios. Active queue management algorithms (AQM) are employed to avoid congestion in routers along the transmission path.

SSH - Secure Shell

Slide Presentation

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SSH - Secure Shell

Slide Presentation

SSH (Secure SHell) is a secure replacement for TELNET, rcp, rlogin, rsh (for login, remote execution of commands, file transfer). Security-wise SSH provides confidentiality (nobody can read the message content), integrity (guarantee that data is unaltered in transit) and authentication (of client and server). This provides protection against many of the possible attack vectors like IP spoofing, DNS spoofing, Password interception and eavesdropping. SSH exists in 2 versions. SSH-2 fixes some of the shortcomings of SSH-1 so it should be used in place of SSH-1. SSH also comes with features that in itself raise security concerns like tunneling and port forwarding.