Learning IOS and JUNOS

Appendix A. IS-IS Packet Formats IS-IS Packet Fields (Alphabetical Order) ATT— Attachment Bits (Flags attachment to other areas) Checksum— Checksum of contents of LSP from source ID field to the end Circuit Type— Defines whether link is Level-1 and Level-2 End LSP— LSP ID of last LSP in CSNP Holding Time— Defines how long to wait for a hello from this system before clearing the adjacency ID Length— Length of the System ID field in an NSAP(NET) Intradomain Routing Protocol Discriminator— Network layer protocol identifier IS Type— Defines type of router, Level-1 or Level-2 LAN ID— LAN Identifier, Consists of the System ID of the designated intermediate system plus a unique number Length Indicator— Length of the fixed header of the packet in bytes Local Circuit ID— Unique identifier for a link LSP ID— Identifier for router's LSP, consisting of the System ID of the router, fragment number, and a nonzero octet for pseudonode number in case of pseudonode LSP Maximum Area Addresses— Numbe...

A primary component of the Cisco Systems ® IP over Dense Wavelength-Division Multiplexing (IPoDWDM) solution for the IP Next-Generation Network (IP NGN) is the simplification of end-to-end control between IP and DWDM networks. To alleviate high operational expenses (OpEx), increase speed for carrier service activations, and eliminate cumbersome and disparate manual provisioning methods at the transport layer, Cisco ® has introduced a new cost-effective and efficient solution based on Generalized Multiprotocol Label Switching (GMPLS). This solution enables both optical and IP devices to dynamically find, identify, and provision optimal paths based on user traffic requirements. Called the Segmentation model of GMPLS (S-GMPLS), this new GMPLS model is a hybrid of current approaches that overcomes several daunting obstacles by allowing both IP and optical networks to maintain their existing segmented administration environments. S-GMPLS allows providers to keep the topology o...

Multicast VPNs (mVPNs) provide a scaleable architecture to enable multicast in an RFC2547 Layer 3 Multiprotocol Label Switching (MPLS) VPN environment. Originally derived from tag switching, MPLS uses labels to combine the intelligence of routing with the high performance of switching. MPLS VPNs are a natural extension of MPLS and are often by service providers to offer VPN services over a shared infrastructure. MPLS VPNs operate based on label stacks. Despite the advantage of label stacking and the ability to decouple routing from forwarding for unicast traffic, MPLS VPNs did not address how to handle multicast traffic. As a result, the only available solution for delivery of IP multicast video, voice, and data over a deployed Layer 3 MPLS VPN was to statically configure point-to-point GRE tunnels between Customer Edge (CE) routers. As the number of CE routers increased, the number of point-to-point GRE tunnels required to maintain a full mesh of CEs quickly became unmanageable. A mor...

...(略) Understanding AToM Operations In Chapter 3, you learned how AToM achieves a high degree of scalability by using the MPLS encoding method. You also read an overview of LDP in the previous section. Reading through this section, you will develop a further understanding of how MPLS encapsulation, LDP sig-naling, and pseudowire emulation work together. The primary tasks of AToM include establishing pseudowires between provider edge (PE) routers and carrying Layer 2 packets over these pseudowires. The next sections cover the operations of AToM from the perspectives of both the control plane and the data plane as follows: Pseudowire label binding Establishing AToM pseudowires Control word negotiation Using sequence numbers Pseudowire encapsulation Pseudowire Label Binding An AToM pseudowire essentially consists of two unidirectional LSPs. Each is represented by a pseudowire label, also known as a VC label. The pseudowire label is part of the label stack encoding that encapsulates Layer...

...(略) RFC 3270 presents three modes of MPLS/DiffServ marking for service providers: 1) Uniform Mode : SP can remark customer DSCP values ...(略)

...(略) SPD State Check The IP process queue on the RP is divided into two parts: a general packet queue and a priority queue. Packets put in the general packet queue are subject to the SPD state check, and those that are put in the priority queue are not. Packets that qualify for the priority packet queue are high priority packets such as those of IP precedence 6 or 7 and should never be dropped. The non-qualifiers, however, can be dropped here depending on the length of the general packet queue depending on the SPD state. The general packet queue can be in three states and, as such, the low priority packets may be serviced differently: NORMAL : queue size RANDOM DROP : min FULL DROP : max In the NORMAL state, we never drop well-formed and malformed packets. In the RANDOM DROP state, we randomly drop well-formed packets. If aggressive mode is configured, we drop all malformed packets; otherwise, we treat them as well-formed packets. In FULL DROP state, we drop all well-formed and malfo...

...(略) 3)Short Pipe Mode (shown below): SP does not remark customer DSCP values (SP uses independent MPLS EXP markings); final PE-to-CE policies are based on customer’s markings ...(略)